L A N D
M A N A G E M E N T
H A N D B O O K
44
Forest Soil Rehabilitation in British
Columbia: A Problem Analysis
1998
Ministry of Forests
Research Program
Forest Soil Rehabilitation in British
Columbia: A Problem Analysis
C.E. Bulmer
Ministry of Forests
Research Program
Canadian Cataloguing in Publication Data
Bulmer, Charles Ernest, –
Forest soil rehabilitation in British Columbia : a
problem analysis
(Land management handbook ; )
Includes bibliographical references: p.
 ---
. Forest soils – British Columbia. . Forest
site quality – British Columbia. . Soil
productivity – British Columbia. . Forest
productivity – British Columbia. . Soil
conservation – British Columbia. I. British
Columbia. Ministry of Forests. Research Branch.
II. Title. III. Series.
.. 
.’’
©  Province of British Columbia
Published by the
Research Branch
B.C. Ministry of Forests
 Yates Street
Victoria, BC  
Copies of this and other Ministry of Forests
titles are available from
Crown Publications Inc.
 Fort Street
Victoria, BC  
ii
--
SUMMARY
Substantial amounts of money are invested each
year in forest soil rehabilitation, and the amounts
have increased as a result of recent investments
made by Forest Renewal BC. The need for research
on forest soil rehabilitation arises from our desire
to ensure that these funds provide the maximum
possible benefit for the lowest possible cost. Rehabilitation projects are currently being implemented,
or are planned, throughout the province on a wide
range of site and disturbance types. The purpose
of this project was to summarize existing information and assess the need for new information to
improve the results and cost-effectiveness of soil
rehabilitation efforts.
The conclusions presented in this paper arose
from three sources:
• review of the scientific literature;
• field visits with rehabilitation practitioners and
researchers working for industry and government in  forest districts to operational and
research sites representing a wide range of
conditions; and
• consultation with a number of provincial
experts and those from other jurisdictions.
Our knowledge of soil rehabilitation is limited
because few research projects were initiated during
the past decade, the range of site types studied so
far is limited, and many of the questions we ask
about these projects require information on tree
growth response, which can only be collected as
fast as the trees grow. Despite these limitations,
our understanding of how soil processes affect
forest productivity has improved substantially in
the past decade, and much of this information
can be used to solve problems in forest soil
rehabilitation. Sections in this report on soil
physical processes and soil nutrient cycling processes describe how an understanding of growthlimiting conditions can guide rehabilitation
practitioners to strategies for effective and costefficient rehabilitation.
Site-specific rehabilitation plans are an integral
part of modern rehabilitation projects. These plans
provide soil and site information that is used to
develop a cost-effective rehabilitation approach.
The plans also specify the equipment required and
the operating conditions necessary to successfully
restore soil productivity on a particular site. Planning, appropriate equipment, and trained operators
are crucial to successful soil rehabilitation.
People developing rehabilitation plans and implementing rehabilitation projects need information on the effects of various techniques on forest
productivity, and on the potential beneficial effects
of soil rehabilitation on timber supply. Specific
information is needed on the productivity gains
resulting from tillage, topsoil replacement, slope
recontouring, revegetation, reforestation, soil
amendments, and other rehabilitation techniques.
Descriptions of these techniques, and the important information gaps affecting their use are
provided in this report.
iii
ACKNOWLEDGEMENTS
The author wishes to thank all of the people who
contributed information, and those who took the
time to visit field sites. A list of these people is
included in Appendix .
Funding for this project was provided by Forest
Renewal BC.
Lito Arocena, Dave Polster, Paul Sanborn,
Margaret Schmidt, Bob van den Driessche provided
thoughtful reviews of this report.
iv
CONTENTS
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iii
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
iv
 Introduction
........................................................................................................................................

 Forest Soil Rehabilitation in British Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Current Situation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Future Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .




 Productivity of Degraded and Rehabilitated Forest Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Alleviating Growth-limiting Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Restoring Soil Physical Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Processes contributing to soil structure in forest soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Methods for evaluating characteristics of the pore system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Restoration of Nutrient Pools and Soil Nutrient Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Methods for evaluating nutrient pools and nutrient cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .






 Techniques for Forest Soil Rehabilitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Tillage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Extensive tillage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Spot treatments and site preparation equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Information gaps and research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Topsoil Conservation and Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Information gaps: research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Slope Recontouring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Information gaps: research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Reforestation and Revegetation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Coniferous and hardwood crop trees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Grasses, legumes, and native shrubs for soil amelioration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Information gaps: research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Soil Amelioration: Fertilizers, Amendments, and Mulches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Fertilizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Nutrient-poor residues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Nutrient-rich amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Mulches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.. Information gaps: research needs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



















 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References
................................................................................................................................................

People Consulted when Preparing this Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Appendix 
v
TABLES
 Results of studies on tree productivity before and after soil rehabilitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Limiting physical conditions for root growth in forest soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Comparison of organic matter and total N pools on disturbed and rehabilitated sites,
along with nutrient levels in topsoil and other materials having potential as soil amendments . . . . . . . . . . . . . . . .

 Potential contribution of organic matter and nutrients by adding soil amendments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Cost of various implements for extensive tillage of forest soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FIGURES
 The hypothetical trend of the amount of rehabilitation activity in BC, and two possible scenarios
for the future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Winged subsoiler tilling a landing at the Aleza Lake Research Forest, Prince George Forest District . . . . . . . . .

 Rock ripper being used for forest soil tillage in the Penticton Forest District
..........................................

 Excellent growth of lodgepole pine planted in  on a landing tilled with a rock ripper (Kamloops
Forest District, Jamieson Creek Forestry Road, km ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Results of a single pass with a rock ripper on a medium-textured landing in the  Mile House
Forest District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Extensive tillage with an excavator equipped with a site preparation rake (Williams Lake Forest
District) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Excavator with a single-tooth ripper attachment, used for loosening very rocky soils in the
Penticton Forest District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Close-up of the ripper attachment illustrated in Figure , showing the wing attachments to enhance
soil tillage (Penticton Forest District) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Results of partial tillage with an excavator equipped with a silvatiller attachment (Horsefly Forest
District) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Evaluating tillage depth (Morice Forest District, Telkwa River Forestry Road, km ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Topsoil piles commonly found adjacent to bladed areas on level ground (Kalum Forest District) . . . . . . . . . . . .

 Landing rehabilitated as part of EP  in the Williams Lake Forest District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 The right-hand portion of the landing from Figure  (Williams Lake Forest District) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Seedling damaged by cattle trampling in a rehabilitated roadside work area (Moffat Road, Williams
Lake Forest District) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Rehabilitated landing with good pine growth, but poor germination of birdsfoot trefoil because
of delayed seeding (Kispiox Forest District) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Landing rehabilitated in  in the Quesnel Forest District . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

 Surface soil conditions on the landing illustrated in Figure  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

vi
1 INTRODUCTION
This report summarizes issues and problems in forest
soil rehabilitation in British Columbia. It presents an
up-to-date review of the scientific literature and the
activities of rehabilitation specialists and practitioners
working for the forest industry and government. It
is aimed at people who carry out rehabilitation
projects, and those faced with developing and
evaluating cost-effective new techniques for soil
rehabilitation.
The focus of this report is on techniques for
restoring soil productivity, with the implied objective
of re-establishing a productive forest ecosystem on a
site that has suffered degradation. The causes of
forest soil degradation and avoidance techniques are
not addressed in detail, as these are dealt with elsewhere (e.g., Lousier ; Lewis ; and various
Forest Practices Code guidebooks). Also, techniques
for stabilizing slopes, preventing erosion, and for
manipulating and restoring drainage patterns
(i.e., techniques for road deactivation) are not
specifically discussed, as these practices are also
described elsewhere (e.g., Carr ; Chatwin et al.
; Moore ).
Various terms, such as “restoration,” “reclamation,”
and “rehabilitation,” have been used to describe a
range of mitigation activities to counter the effects of
environmental degradation. In this report, the term
“soil rehabilitation” refers to activities that aim to
improve soil productivity to a state where a productive forest can develop on sites that have suffered
some form of soil degradation. This usage reflects
terminology adopted in the Forest Practices Code.
The objectives of this project were:
. to review the literature on techniques for forest
soil rehabilitation;
. to describe the current and projected extent of
forest soil rehabilitation activities in the province
based on consultation with rehabilitation specialists working for industry, government, and other
agencies; and
. to identify gaps in the information base, and the
need for future research.
2 FOREST SOIL REHABILITATION IN BRITISH COLUMBIA
. History
According to Carr (), the Cariboo Regional Policy
was the first to require landing rehabilitation in British Columbia. These policy guidelines resulted from
landing rehabilitation trials in the s initiated as
Project E.P.  (Vyse and Mitchell ). The landing
rehabilitation measures specified in the Cariboo
Regional Policy were:
. ripping or scarification to a depth of  cm, if
deemed necessary;
. burning of slash piles; and
. respreading of topsoil and ash piles on
the landing.
Mitchell (, cited by Carr ) evaluated the
policy’s effect and noted several shortcomings in its
implementation, including excessive site disturbance
associated with landings, lack of topsoil conservation,
ineffective scarification and soil loosening, and poor
performance of planted trees. Mitchell made several
recommendations and a new landing policy was
drafted for the Cariboo Region (Cariboo Forest
Region ). In subsequent years, several forest
regions and districts have developed guidelines and
policies regarding the rehabilitation of landings and
skid roads (e.g., Prince George Forest Region ),
but many of the concerns expressed in Mitchell’s
() report remain valid.
In , a workshop held at the University of
British Columbia (Still and Lousier [editors] )
highlighted the growing awareness among land
managers for increased attention to soil conservation
programs. Utzig and Walmsley () outlined the
costs to the provincial economy associated with forest
soil degradation. By , a more-or-less complete
framework of standards was in effect throughout the
province’s forest regions and districts, which restricted the amount of soil disturbance allowed
1
during timber harvesting and site preparation,
and specified measures for soil rehabilitation.
The degree to which these early policies were
enforced was variable, as was the quality of the
rehabilitation work. In addition, landing rehabilitation objectives were not always clearly stated,
and efforts to produce commercial forests were
often secondary to those aimed at erosion control
or cattle grazing site maintenance. Many landings
had their soil loosened and were grass-seeded, but
a much smaller number were planted to trees. Even
where trees were planted, little follow-up work was
conducted to evaluate survival and growth.
Several forest companies and forest districts in
the interior experimented with road and landing
rehabilitation during the s using brush blades,
rock rippers, and winged subsoilers. By the late
s and early s, substantial landing rehabilitation programs were under way (e.g., Pope and
Talbot, Midway; Weyerhauser, Kamloops; West
Fraser, Quesnel) in several areas. For example,
Crestbrook Forest Industries of Cranbrook began
rehabilitating skid roads in . Several landing
rehabilitation projects that were carried out in the
early s (e.g., Pope and Talbot, Midway; Kispiox
Forest District; Kalum Forest District) used the
winged subsoiler for tilling, followed by seeding
with mixtures of grass and legumes, and planting
with lodgepole pine.
When preparing this report, I became aware of
several other forest companies in the interior and in
coastal regions that were rehabilitating disturbed
lands. It is likely that further contacts with people
working for the Forest Service and forest industry
will reveal additional examples of rehabilitation
projects that were implemented during the past
decade.
Landing rehabilitation during the s and early
s was carried out in a difficult climate, with
rehabilitation practitioners facing widespread
skepticism about the benefits of restoring soil
productivity relative to the costs. Most foresters
and researchers did not consider that the existing
techniques were capable of restoring full site productivity. Currently, however, many foresters and soil
scientists are more optimistic about the potential
productivity of rehabilitated sites. Knowledge and
techniques have improved, and a renewed commitment to restore the forest exists. Consequently,
modern rehabilitation projects are using site-specific
2
techniques that may have been considered impractical only  years ago.
The regional and district policies and procedures,
along with follow-up documents (including Timber
Harvesting Branch  and Vancouver Circular
Letter ), provided the background that led to the
soil conservation requirements in the Forest Practices
Code. The Forest Practices Code Act, regulations, and
guidebooks provide comprehensive, province-wide
standards for soil degradation and rehabilitation. These
instruments supersede most of the regional and
district policies, except where more detail is required.
. Current Situation
The amount of soil disturbance allowed on harvested
areas is now controlled by the Forest Practices Code,
and rehabilitation is required for all temporary access
structures. Even before the Code was fully implemented, the amount of land being degraded each
year as a result of forestry operations was declining.
Key provisions of the Code that affect soil rehabilitation include the following:
. The amount of permanent access (roads and
landings) is limited to that necessary for the
harvest, usually less than % of the area.
. All temporary access structures (roads, landings,
and trails not required for the long-term management of the area) are to be rehabilitated to restore
soil productivity.
. The amount of dispersed soil disturbance in the
net area to be reforested is limited to what is
necessary for the harvest, usually less than %
for coastal sites, and less than % for interior
sites, although on many sites the allowable level
is lower.
Therefore, rehabilitation is required for planned
(temporary) access that is not part of the permanent
access system and for situations where soil is
disturbed excessively during forestry operations.
The amount of rehabilitation that occurs as part of
ongoing operations depends on the logging system
and the site characteristics.
Forest Renewal BC provides funding to rehabilitate degraded areas or those areas at risk because of
past forestry practices. Many of these sites suffer
reduced productivity as a result of equipment traffic
or road construction. However, while soil rehabilitation activities have increased, large areas remain
that require treatment to restore productivity.
Future needs in soil rehabilitation will depend on
numerous factors, including the amount of land suffering degraded productivity, legislation, funding,
and public perception. The short-term trend has
been towards increasing amounts of rehabilitation as
Forest Renewal BC projects reach full implementation, and areas requiring rehabilitation are identified
and treated. A considerable inventory of land in the
province is unproductive because of soil degradation;
the quantity of the unproductive land rehabilitated
will depend on the willingness of the public at large
to fund this activity in view of other demands on
public funds. The availability of funds will inevitably
reflect the perceived benefits of rehabilitation, including increased amounts of fibre, forage, or other
products, improved water quality, and increased
withdrawal of atmospheric carbon, relative to
the costs.
In the long term, when all suitable areas degraded
by past forestry practices are rehabilitated, soil
rehabilitation efforts will involve mainly routine
rehabilitation of temporary access, as specified in the
Code. This situation is illustrated in Figure , which
shows the amount of land being rehabilitated now
compared with the amounts in the past, and the
amounts expected in the future. The increasing, then
decreasing, trend of expected rehabilitation activity
is similar to the trend of road deactivation projected
on U.S. Forest Service lands to the year  (U.S.
Department of Agriculture ). The amount of
rehabilitation of temporary access that occurs in the
future will depend on several factors including access
requirements, site conditions, logging system, success
of the rehabilitation efforts, and relative costs of
rehabilitation compared to the costs of alternatives
that prevent soil degradation.
A comprehensive evaluation of the relative costs
and benefits of various logging systems that incorporate rehabilitation versus those that prevent soil
disturbance has not been carried out. Preventing
soil disturbance will be a preferred option in most
cases, but situations likely exist where creating soil
disturbance followed by routine rehabilitation of the
disturbed area will provide cost advantages or other
benefits such as access to seasonal wood supplies.
For example, cable logging systems produce much
less soil disturbance than ground-based systems, but
Amount of rehabilitation
occurring in ha/yr
. Future Needs
Time –>
  The hypothetical trend of the amount of
rehabilitation activity in British Columbia, and
two possible scenarios for the future. The arrow
points to the situation in 1997, where the
amount of rehabilitation work is increasing in
response to the Forest Practices Code and the
availability of funds from Forest Renewal BC. The
declining portion in the future represents a time
when backlog work is completed and rehabilitation activity is driven mostly by the requirements
of the Code. The diverging lines, in the future,
illustrate that the level of future activity will
ultimately depend on rehabilitation success and
costs relative to alternative strategies for
maintaining productivity.
the cable systems are generally more expensive. Some
forest companies have achieved cost advantages by
employing ground-based systems on steep slopes
(skidding on constructed trails) followed by rehabilitation of the trails. The initial results from this
system are promising, but it is too early to reliably
assess the effects on long-term productivity.
One of the most important considerations
determining the amount of rehabilitation in British
Columbia over the long term is the cost. Obviously,
we would like to reduce the costs while ensuring the
effectiveness of the work. Also, the benefits and costs
of alternative approaches for restoring lost productivity on a landscape scale should be examined. For
example, it may be cost-effective to simply revegetate
degraded areas for erosion control and aesthetics,
while restoring lost productivity through more
intensive management of other, undisturbed areas.
Research aimed at evaluating the costs and benefits of
soil rehabilitation and other alternatives will provide
information to assist decision-makers faced with
such choices.
3
3 PRODUCTIVITY OF DEGRADED AND REHABILITATED FOREST SOILS
Plant productivity on degraded forest soils may be
limited by such factors as: compaction (Greacen and
Sands ; Froehlich and McNabb ); erosion
(Miles et al. ; Carr a); nutrient displacement
(Ballard and Hawkes ); unsuitable moisture,
thermal, and aeration regimes (Standish et al. ;
Sutton ; Day and Bassuk ); and dysfunctional
nutrient cycles (Dick et al. ). These factors also
interact with each other in various ways to produce
conditions unsuitable for tree growth. Utzig and
Walmsley () acknowledged that measurements of
forest productivity on degraded and rehabilitated
soils integrate all of these effects. They used results
from  studies, most conducted in the s and
s, to estimate productivity losses caused by
harvesting-related disturbance. In their calculations
of lost productivity associated with soil degradation
in British Columbia, they used a % reduction in
volume (m/ha) for all types of disturbance, even
though the results from individual studies varied
widely.
Several previous studies (summarized by Andrus
[], cited by Froehlich and McNabb [] and
Andrus and Froehlich []) found that tillage of
forest soil can improve productivity. Most of these
results show the success of tillage, with productivity
gains in both survival (– to %) and height growth
(–%). Some more recent studies are summarized
in Table .
As expected for diverse ecosystems with different
disturbance types and rehabilitation treatments, the
response to machine traffic and rehabilitation
treatments varies widely in these studies. To illustrate
how different initial soil conditions and effect of
treatments on growth-limiting factors influence the
success of rehabilitation, two of the studies are
described in more detail below.
Miller et al. () showed that for skid trails at
coastal sites in Washington State initial increases in
bulk density did not affect eight-year survival of
planted Douglas-fir and Sitka spruce. Tillage
improved survival and early growth of western
hemlock, but tree heights and volumes of hemlock,
Douglas-fir, and Sitka spruce did not differ among
treatments after eight years. The soils at these sites
contained very high amounts of organic matter in the
4
surface  cm, and were generally not adversely
affected by soil disturbance associated with skidder
traffic. The authors concluded that initially
favourable soil conditions, and subsequently
favourable climatic conditions can compensate for
the potentially negative effects of soil disturbance.
These results are likely not applicable to heavily
disturbed roads and landings with low organic
matter levels in surface soil. However, they may be
relevant to studies of isolated ruts and dispersed
disturbances, which occur frequently in wetter
portions of the landscape where surface soils contain
large amounts of organic matter.
Carr (a) reported that seeding a grass and
legume mix and adding  kg/ha of ––
fertilizer to a site with eroded subsoil on Vancouver
Island (CWHdm) increased foliar nitrogen levels
in Douglas-fir and resulted in a % increase in
height growth compared to the untreated control.
The gravelly sandy soil at this site was substantially
eroded by road construction, which left a compacted
nutrient-poor subsoil exposed at the surface. The
rehabilitation treatment obviously alleviated a severe
nitrogen limitation on this site, but the longer-term
effects of soil compaction and loss of organic matter
on trees growing at this site are not known.
Although short-term results are often the only
information available to researchers attempting to
evaluate the effect of management activities on forest
productivity, problems emerge when short-term
results are used to predict long-term changes in
productivity. According to Morris and Miller (),
acceptable evidence for long-term changes in site
productivity must meet three conditions:
. growth differences must be attributable to differences in site conditions, rather than to differences
in resource allocation among target and non-target species or to differences in plant potential;
. growth results must be available for a sufficient
period of time so that the influence of ephemeral
conditions is diminished, and the capacity of the
site to support trees is emphasized; and
. adequate experimental control must exist.
Morris and Miller () considered measures of
site index based on  (fast-growing stands) or more
than  (slow-growing stands) years of data as
  Results of studies on tree productivity before and after soil rehabilitation
Disturbance
type
Productivity of
rehabilitated sites
(% of undisturbed)
Survival Ht
Vol
Productivity of
rehabilitated sites
(% of disturbed)
Survival Ht
Vol
Rehabilitation
treatment
Species/
agea
Seed/fertilize
Fd/9
n.d.b
n.d.
n.d.
n.d.
325
n.d.
Carr 1987a:11
Tillage
Hw Ss Fd/8
101
102
115
111
104
112
Miller et al. 1996c
Winter landings
Auger planting
Pl/5
n.d.
47
n.d.
97
99
n.d.
Arnott et al. 1988d
Winter landings
Auger planting
Pl/5
n.d.
44
n.d.
114
99
n.d.
Arnott et al. 1988e
Deep ruts
In-fill/fertilize
Pe/5
n.d.
107
n.d.
n.d.
158
n.d.
Tiarks 1990
Compact/blade
Skid trails
Source
Medium ruts
In-fill/fertilize
Pe/5
n.d.
107
n.d.
n.d.
125
n.d.
Tiarks 1990
Shallow ruts
In-fill/fertilize
Pe/5
n.d.
121
n.d.
n.d.
110
n.d.
Tiarks 1990
Compact trail
Bed/fertilize
Pt/4
n.d.
108
n.d.
n.d.
227
n.d.
McKee et al. 1985:17f
Site preparation
Shallow till
(rock ripper)
Pp/5
n.d.
n.d.
n.d.
100
97
n.d.
McNabb and Hobbs
1989:244
a
b
c
d
e
f
Tree species: Fd = Douglas-fir; Hw = western hemlock; Ss = Sitka spruce; Pl = lodgepole pine; Pe = slash pine; Pt = loblolly pine; Pp
= ponderosa pine
n.d. = no data
For comparisons of rehabilitated sites with undisturbed, data from one (Central Park) of three locations were used. For comparisons with disturbed sites, data from all three locations were used. Survival data (values for class 2–3 disturbance from Table 5);
height and volume data (values for class 2–3 disturbance from Table 7).
For container seedlings (auger planted = rehabilitated versus dibble planted = control)
For bareroot seedlings (auger planted = rehabilitated versus mattock planted = control)
Data from Table 2.
reasonable criteria for meeting the first two conditions.
For experimental control, they cited requirements
presented in Mead et al. (), which include:
• at least four replications in randomized or
randomized complete-block designs;
• suitable pre-treatment site and crop information
for individual experimental plots;
• measurement plots of at least  m;
• at least  trees left at the end of the experiment;
and
• buffer areas at least  m wide surrounding each
measurement plot.
While some investigations of the changes in longterm productivity that result from soil disturbance
meet, or soon will meet, some of the criteria
described above, a wide gulf exists between the
evidence needed to verify effects of soil rehabilitation
on long-term productivity and the information that
is available now, or is likely to become available in
the near future. Few existing studies (one exception
is described by Sanborn et al. ) meet the criteria
for experimental control outlined above, and only
one study, currently dormant (Vyse and Mitchell
), comes close to meeting the age criteria. For
these reasons, we are left with the use of short-term
studies to evaluate the effectiveness of rehabilitation,
and therefore need to develop other techniques, most
likely based on evaluating soil properties, to predict
the long-term productivity of rehabilitated sites.
Establishing long-term experimental sites where
productivity is assessed for rehabilitated areas is
consequently a high priority. Retrospective studies
of operational projects initiated in the late s and
early s may provide information until the results
of long-term experiments are available.
Estimates of site productivity are needed to
determine the effectiveness of various rehabilitation
treatments, and to evaluate the contributions of these
lands towards timber supply (e.g., Pedersen ).
These calculations would likely involve estimating
the site index based on tree height and age for
rehabilitated areas.
Two methods of determining site index are
commonly used for young stands (B.C. Ministry of
5
Forests ). The biogeoclimatic method predicts
site index based on the subzone and site series, and is
suitable for trees with less than three years growth
above breast height. The biogeoclimatic method is
based on site factors to predict site index (e.g., Wang
et al. ). The growth-intercept method predicts
site index from height and age measurements taken
on selected sample trees. Growth-intercept tables are
available for various coastal and interior species, and
the method is suitable for trees with at least three
years of growth after achieving breast height (. m).
With a few exceptions, the trees growing on most
rehabilitated sites in British Columbia are too young
for reliable site index estimation using the growth-
intercept method. Evaluating the relative success of
rehabilitation treatments should be based on the
survival and early growth of trees on rehabilitated
sites, and the soil conditions, compared to nearby
undisturbed areas. Innovative approaches could be
developed to obtain early estimates of site index for
rehabilitated sites, possibly using some combination
of the existing soil- and site-based approach for
young stands (biogeoclimatic method), and some
evaluation of tree performance relative to expected
performance on nearby undisturbed sites. Such
estimates of site index would be useful to evaluate the
potential contribution of rehabilitated sites to future
timber supply.
4 ALLEVIATING GROWTH-LIMITING CONDITIONS
Soil degradation occurs when machine traffic, or
other types of disturbance, alter the soil physical,
chemical, and biological properties in such a way that
site productivity is reduced (Smith ). A workshop
held in Edmonton, Alberta ( Ziemkiewicz et al. [editors] ) sought to develop guidelines to
characterize desirable characteristics of reclaimed
forest soils after surface mining, and to determine the
depth requirements for reclaimed soils. Workshop
participants concluded that the chemical and physical
characteristics of reclaimed soils could likely be
accurately described by referring to published
reports (some examples are presented by Ballard
), but that soil depth criteria needed to be
developed on a site-specific basis.
Isolating the effect of individual factors or soil
processes that cause reduced productivity may prove
difficult because soil disturbance often results in
changes to more than one soil process. Therefore,
when developing rehabilitation prescriptions to
alleviate growth-limiting conditions, the effect of
numerous interdependent processes on productivity
must be considered. This section describes two major
groups of processes that become dysfunctional in
degraded soils. These processes must be restored to
achieve successful rehabilitation.
Soil physical processes, such as infiltration and
transport of soil water and air, are controlled by soil
porosity and the pore size distribution. The soil pore
system is adversely affected by compaction (an
increase in bulk density) and puddling (a loss of
6
macropores). Soil physical properties also affect the
soil’s thermal regime and the resistance of soil to
plant root growth.
On many degraded sites, nutrient pools are
depleted by the removal of forest floor and surface
soil. Nutrient cycling processes are also impaired by
the removal of nutrients and microbial inoculum.
As well, unsuitable conditions for nutrient cycling
organisms may exist, particularly the altered soil
moisture, aeration, and thermal regimes that result
from soil disturbance. The restoration of nutrient
cycles involves replacing lost nutrients and organic
matter, and providing an environment suitable for
the organisms responsible for nutrient cycling.
. Restoring Soil Physical Processes
On many sites, alleviating compaction and restoring
the pore system so that water and air can move freely
to and from plant roots is the most important requirement for restoring soil productivity. When a soil
is compacted, a number of conditions are created
that inhibit root growth (Bathke et al. ).
Compaction may increase soil strength to the
point where roots cannot penetrate the soil. Also,
compaction and puddling cause soil aggregates to
collapse, destroying the macropores essential for
water and air transport. Excess water drains from
macropores rapidly after a rainfall, leaving them filled
with air. Oxygen transport to growing root tips, and
the movement of physiologically active gases such as
CO and ethylene away from roots to the soil surface,
occurs much more rapidly through air-filled than
through water-filled pores. Low temperatures may
also be an important factor inhibiting root growth on
compacted and puddled soils, which retain water and
therefore warm more slowly in the spring.
Some examples of growth-limiting values for soil
strength (penetration resistance), bulk density, and
aeration porosity (the proportion of the soil volume
occupied by macropores) are presented in Table .
Growth-limiting values provide targets for the
soil conditions needed to restore productivity.
However, some difficulties arise when using critical
values to predict root or shoot growth (Greacen and
Sands ). For example, soil compaction may lead
to compact root systems, which occupy less soil
volume, but shoot growth may be unaffected if air,
water, and nutrient supplies are adequate. Also, a
high degree of spatial variation exists in the strength
of natural soils that are compacted by logging
machinery, especially where traffic is unevenly
distributed over the area. Because roots preferentially
penetrate pockets of lower strength, they may also
penetrate compacted soil layers if sufficient zones
of weakness are present.
Compact soils resist penetration by plant roots.
This may be related to the presence of small pores,
which roots cannot enter, or to rigidity of the pore
system, which prevents growing roots from deforming the soil. Penetrometer resistance measures soil
strength, or resistance to deformation, and is considered to approximate the resistance encountered
by plants roots. Thompson et al. () showed that
penetrometer resistance and bulk density adequately
predicted the performance of hybrid corn on loamy
rehabilitated mine soils. Although bulk density was
slightly better for predicting the effective rooting
depth, penetrometer resistance values were obtained
more quickly and therefore allowed more replication,
which is an advantage in highly variable soils.
Determining a critical value for penetration
resistance is complicated because instrument set-up
(e.g., cone size and shape), operating conditions
(e.g., rate of insertion), and site factors (e.g., soil
moisture content, state of soil aggregation) influence
the values obtained (Atwell ). In many situations,
  Limiting physical conditions for root growth in forest soils (as cited by various sources)
Soil strength (kPa)
Bulk density (kg/m3) Aeration porosity
Soil type
Plant species
Various
Various
Pine
2500
—
—
Zyuz 1968
Sandy
Radiata pine
3000
—
—
Sands et al. 1979
2500a
—
—
—
10%
Source
Greacen et al. 1969
Grable 1971
Sandy
—
—
1350–1600
—
Sands and Bowen 1978
Various
Various
—
1640b
—
Jones 1983
Sandy
Radiata pine
3000–4000
—
—
Greacen and Sands 1980c
—
—
10–12 %d
2000–3000
—
—
Campbell et al. 1988
Brady 1996
Various
Not specified
Loess/tilled Ap horizon
—
3600
—
—
Taylor et al. 1966
Loess/untilled Ap horizon
—
4600–5100
—
—
Taylor et al. 1966
—
Simmons and Pope 1987
—
Tworkoski et al. 1983
Silt loam
Yellow poplar
—
1400e
Clay loam
White oak
—
1500
a
b
c
d
e
Mean value from several studies, range 800–5000 kPa.
Mean value from 10 studies using 20 soils where root growth equaled 20% of optimum.
Extrapolated from a graph of previously unpublished data presented in Greacen and Sands (1980:178).
Individual studies are not cited in the text; this value represents a range described as being commonly accepted by soil physicists.
Average values for trees grown with and without mycorrhizae. The trees were grown at bulk density 1250, 1400, and 1550 kg/m3.
Root length was reduced for the middle treatment; root weight was reduced for the highest level.
7
penetrometer resistance values above  kPa result
in restricted root growth (Table ).
Determining a critical value for bulk density is
not straightforward. Any value will depend on soil
(e.g., texture and organic matter content) and site
(e.g., climate and soil moisture regime) characteristics, and on the criteria used to evaluate when
growth is affected. For example, Jones ()
considered the critical value to be a bulk density level
where root growth was reduced to % of optimum.
Froehlich and McNabb () summarized studies
of the effect of bulk density on growth for six tree
species on a range of soil types. They found that a
linear relationship existed between the percentage
increase in soil bulk density and the percentage
decrease in seedling height growth. According to their
results, for example, a % increase in bulk density
led to a % decrease in height growth. Subsequently,
Miller et al. () showed that even this relationship
did not provide a complete picture of the effect of
bulk density on productivity. For soils near the
Washington coast with surface horizons rich in
organic matter and bulk densities well below critical
values, increases in bulk density of % had little
effect on conifer productivity.
Daddow and Warrington () summarized
several studies and concluded that growth-limiting
bulk density values for sandy loams and loamy sands
were near  kg/m, while clay, silty clay loam, silty
clay, and silt soils had growth-limiting bulk density
values near  kg/m. Lousier () considered
bulk density values of – kg/m to be growthlimiting for most ecosystems. The variable results
described above help to explain why a single critical
value for bulk density is unrealistic for all situations
on all sites.
The relative importance of soil strength and
aeration as growth-limiting factors depends on
soil water content and texture, as well as other site
factors such as climate, plant water demand, and
site drainage characteristics (Froehlich and McNabb
). Root growth in compacted, coarse-textured
soils may be directly related to soil strength, while
aeration is often a more serious problem in compacted, fine-textured soils. Soil strength is also
expected to limit growth in dry soils, while aeration
is more likely to limit growth under wet conditions
(da Silva et al. ).
Seven years after landings were rehabilitated,
Kranabetter and Denham () found that aeration
8
porosity and bulk density were both significantly
correlated with height and height increment of
lodgepole pine, but the relationships were stronger
for aeration porosity. Because of highly variable soil
conditions and tree growth response on these
landings, they used a microplot method to evaluate
soil properties in proximity to groups of six trees. For
aeration porosity, the values (~ %) cited in Table 
are lower than those extrapolated from Kranabetter
and Denham’s () data, which showed that values
near % might be associated with reduced height
growth in lodgepole pine.
Soil temperature is an important factor affecting
root growth in forests (Sutton ). Where compacted soils result in poor drainage and higher
moisture content, lower soil temperatures often
occur because of the high heat capacity of water
relative to soil minerals and organic matter.
.. Processes contributing to soil structure in
forest soils
In undisturbed soils, macropores result when individual sand and coarse silt particles are packed together.
In medium- and fine-textured soils, macropores only
result when silt and clay particles are arranged into
larger structural units called “aggregates.” These
aggregates, and their associated macropores, are
stabilized by organic matter, plant roots, fungal
hyphae, clay binding, and aluminum and iron
hydroxides. Root expansion, soil fauna, and freezethaw and wet-dry cycles are also important to create
and stabilize soil aggregates. Organic matter is a key
ingredient affecting aggregate stability in surface
soils. In clay-rich subsoils with low organic matter
content, fine films of clay that line the pores are
thought to play an important role in stabilizing
structure. In some forest soils, iron and aluminum
hydroxides may also be important.
Processes contributing to aggregate stability are
reasonably well understood for agricultural soils
(Allison ; Tisdall and Oades ), but relevant
information about forest soils is limited. Borchers
and Perry () reported that timber harvesting
reduced forest soil aggregation, and that aggregates in
a medium-textured soil were an important reservoir
of physically protected soil organic matter.
Bartoli et al. () found that organic matter
content was positively correlated with aggregate size
and water stability for a mull A horizon and a
Podzolic B horizon. Oxalate-extractable aluminum
was negatively correlated with aggregate size. Proximity to the roots of -year-old fir trees had no effect
on aggregate size or stability.
In Japan, forest soil aggregates were also stabilized
by organic matter, but soil development resulted in
aluminum hydroxy cation formation, which contributed to aggregate stability (Itami and Kyuma ).
These authors showed that reclaimed subsoils with
low levels of organic matter had lower aggregate
stability and exhibited structural collapse following
forest clearing and land levelling. Soils with clays
dominated by low-charge minerals, such as
aluminum vermiculite and kaolinite, were less
sensitive to dispersion (and structural collapse)
than those with high-charge clay minerals, such
as smectite and illite.
Aggregate stability is probably a factor that controls the phenomenon of resettling, or structural
collapse (puddling), which is implicated as causing
poor soil physical properties after tillage was used to
rehabilitate fine-textured soils in British Columbia
(Carr b). While some resettling and consolidation
is expected after tillage, resettling to the point where
the rehabilitation project fails is of concern. The
conditions under which resettling is likely to cause
failure of the rehabilitation project have not been
documented in any detail.
Subsoils with high clay content are most likely to
experience resettling, but mineral soils with more
than % clay are also subject to plastic behaviour
(Brady ), and may also resettle to unfavourable
physical conditions. Little information exists about
the effects of resettling for the many soils in the
province with intermediate clay contents (–%).
Also, the clay fractions of soils in northeastern
British Columbia are dominated by high-charge
clays, while soils west of the Rocky Mountains
generally have clays with lower charge. Therefore,
resettling might pose more of a problem for soils
in the northeast.
The influence of organic matter on structural
collapse has not received specific attention, but is of
interest, especially because of the possible role of
organic amendments in preserving the benefits of
tillage in fine-textured soils. From another
perspective, Itami and Kyuma’s results ()
suggested that Podzolic B horizons with large
quantities of hydroxy iron and aluminum might
provide a more stable structure and be less likely to
resettle after tillage.
Plant roots and fungal hyphae are important for
stabilizing aggregates, but plants are not equal in
their ability to promote aggregation. For example,
true prairie grasses, which are strongly associated
with mycorrhizae and perennial species of the
Compositae are associated with soils having larger
water-stable aggregates than non-prairie grasses,
such as Agropyron repens and Bromus inermis (Miller
and Jastrow ). Plants with long-lived root
systems, and those more dependent on mycorrhizal
associations will probably promote soil aggregation
to achieve optimal growth. Detailed studies of these
attributes for native forest grasses, herbs, and shrubs
would be of interest to evaluate their potential role in
stabilizing soil structure.
.. Methods for evaluating characteristics of
the pore system
One of the most common measures of soil compaction is bulk density. Core samplers provide a
rapid method to collect bulk-density samples
(Culley ), although excavation methods are more
suitable in rocky soils (Blake and Hartge ). Nuclear methods can provide large amounts of data
quickly, but the reliability is also limited by rocks, and
licensing is costly. Predictions of soil productivity
based on bulk density could be improved if individual bulk-density samples were also analyzed for
organic matter and moisture content. This could
provide a means of isolating the effects of these
important factors on soil bulk density.
While it is possible to calculate total porosity
from bulk density and a knowledge of the density
of individual soil particles, the aeration porosity is
a much more sensitive indicator of soil physical
condition. Aeration porosity is a measure of the large
pores that drain rapidly, and is usually evaluated by
determining the percentage of soil volume occupied
by air-filled pores at low water tension (commonly
.–. MPa).
While determining bulk density and aeration
porosity is reasonably straightforward in principle,
considerable care is required to produce consistent
results, especially for aeration porosity. Also, since
both measurements rely on small samples (< . L),
considerable replication is required to produce
reliable estimates.
Soil strength is measured in several ways, but the
most commonly used measurement relevant to plant
root growth is penetration resistance to a cone
9
penetrometer (e.g., Vepraskas and Miner ). Under good conditions (a major limitation in the use of
penetrometers occurs where soils have high coarse
fragment content), individual measurements of soil
strength taken with a cone penetrometer are more
quickly obtained than bulk density or aeration
porosity values. Penetration resistance was closely
correlated with bulk density for loamy soils in the
British Columbia interior (Smith and Wass a, b),
and was fairly reliable for characterizing various
disturbance types associated with skid road
construction and stumping. Penetration resistance
has potential for more widespread use as an index
of soil physical condition in forest soils in British
Columbia. However, for the method to have predictive ability, the relationships between penetration
resistance, soil moisture content, bulk density,
aeration porosity, and seedling growth need
working out for various forest site types.
Other methods of evaluating soil physical
condition on disturbed and rehabilitated sites may
also have application in studies for evaluating soil
rehabilitation. Air permeability, infiltration rate,
and hydraulic conductivity can be determined and
provide information about the characteristics of
the pore system. Direct measurement of soil air
composition would determine when a soil aeration
problem exists. Image analysis of intact samples
could also prove particularly helpful when evaluating
the factors that affect the stability of soil aggregates
formed by various rehabilitation treatments.
. Restoration of Nutrient Pools and Soil
Nutrient Cycles
Many roads and landings have low nutrient content.
This condition results primarily when topsoil is displaced during construction and levelling. Nutrient
losses associated with removing surface soil and forest floor are well documented (Smith and Wass ;
Carr b, a). Several rehabilitation techniques
have the potential to restore nutrient pools on
degraded sites, including topsoil replacement (Carr
a; Kranabetter and Osberg ), fertilization
(Carr a), establishing nitrogen-fixing plants
(Carr a; Power ), and amending with
nutrient-rich byproducts (McNab and Berry ;
Bauhus and Meiwes ; Rose ).
In general, measures of nitrogen status are more
likely to predict productivity on forested sites than
10
measures for other nutrients (Powers ; Klinka
et al. ). Table  provides examples of organic
matter and nutrient contents that represent typical
values for disturbed, undisturbed, and rehabilitated
ecosystems. The potential to enhance site nutrient
pools with organic amendments is illustrated in
Table .
Forest floor and topsoil removal and other types
of disturbance, and the effects of subsequent soil
rehabilitation techniques on nutrient-cycling
organisms and processes, are more subtle than the
effects on nutrient pools. The effects on forest
productivity are more difficult to evaluate. When
soils are compacted, some studies show that
populations of nutrient-cycling organisms and
biological activity are reduced, but can be restored by
soil rehabilitation treatments. For example, Dick et al.
() observed reduced microbial biomass carbon
and lower enzyme assays on compacted skid roads
compared to undisturbed clay loam soils in Oregon.
Rehabilitation treatments involving subsoiling alone,
or subsoiling and discing, seemed to restore the
biological processes. All of these observations were
made four years after site treatment.
Somewhat different results were obtained by
Smeltzer et al. () for a loamy sand soil under
mixed northern hardwood forest in Vermont. In
this coarse-textured soil, total fungal and bacterial
populations were reduced on compacted plots
compared to control plots, and a surface mulch
applied after compaction had little effect on populations levels. However, in contrast to the results of
Dick et al. (), the effect of compaction was
relatively short-lived—four years after treatment no
differences were evident in populations between the
treatments. The loamy sand soil was apparently less
sensitive to compaction than the clay loam soil.
The effect of compaction on nutrient-cycling
processes is partly related to changes in soil moisture
and aeration. Linn and Doran () showed that
microbial activity in agricultural soils, as indicated by
CO and NO production, was closely related to the
percentage of water-filled pores. Maximum microbial
activity occurred at % water-filled pore space (this
water content represents field capacity for a hypothetical soil with % aeration porosity and bulk density
of  kg/m), and declined rapidly above %
water-filled porosity (this water content represents
field capacity for the same hypothetical soil with %
aeration porosity). These results suggest that soils
with aeration porosity values below % may
experience impaired nutrient cycling for extended
periods after rainfall.
Removing nutrients by disturbing forest floors and
topsoil results in changes to many soil physical and
biological processes. Some of these changes are
possibly similar to those arising from site
preparation, where survival and early growth of
seedlings appears to depend as much on temperature
and moisture changes as on nutrient status. Shortterm results might prove misleading when used to
predict long-term performance, but the short-term
changes observed by Munson et al. () and
Ohtonen et al. () provide insight into the
potential effects of disturbed and rehabilitated soil on
soil nutrient cycles.
Munson et al. () showed that the effects of
controlling vegetation were greater than those of
  Comparison of organic matter (om) and total N (tot N) pools on disturbed and rehabilitated sites, along with
nutrient levels in topsoil and other materials having potential as soil amendments. The organic matter and nutrient
pools presented here strongly depend on the soil depth chosen in the original study. Since the rooting depths vary,
these results should be interpreted as only general trends within a particular row, and are not suitable for comparisons between rows.
Description
Undisturbed kg/ha
om
tot N
Burned windrowsa
90340
Mine
soilsb
1892
Rehabilitated kg/ha
om
tot N
40635
1417
Degraded (kg/ha)
om
tot N
Reference
38340
Ballard and Hawkes 1989
958
—
7600
—
3060
—
1600
Heilman 1990
Fort St. James
—
2311
—
—
—
1760
Carr 1988a
Vanderhoofc
—
—
—
1400
—
1005
Carr 1987a
Koksilahc
—
—
—
1362
—
398
Carr 1987a
a
b
c
Calculated from the authors’ data for forested sites (15 cm depth) at Carp Lake. “Degraded” sites are scalped areas between burned
windrows; “rehabilitated” sites are under the burned windrows. This example relates to a common observation that the best tree
growth near landings is often where debris piles are burned. In the past, rehabilitation often involved simply spreading this material
across the road or landing surface. Concentrations were converted to kg/ha using bulk density values provided in the original text.
Values for mine soils to a depth of 76 cm. The “degraded” sites are recontoured spoils without topsoil; “rehabilitated sites” are
recontoured spoils with topsoil.
Two-year results for the Vanderhoof site after rehabilitation with 300 kg/ha of 19–19–19 fertilizer and seeding with a legume mix
(achieved 65% cover). Two-year results for Koksilah after rehabilitation with 450 kg/ha of 10–30–10 fertilizer and grass-legume seed
mix (achieved 70% cover).
  Potential contribution of organic matter and nutrients by adding soil amendments (the size of the effect depends on
the application rate)
Amendments
Organic matter (kg/ha)
Total N (kg/ha)
75 000
150
55 000
3100
Simpson 1985
75 000
2019
Simpson 1985
Shredded bark (5 cm = 75 dry t/ha)a
Sewage sludge (5 cm = 55 dry
t/ha)b
Wood waste/sewage sludge compost (5 cm = 75 dry
a
b
t/ha)b
Source
Saini and Hughes 1973
Shredded tree bark used to ameliorate potato fields in New Brunswick; an arbitrary depth of 5 cm is presented as an example; the
conversion to weight assumes 150 kg/m3 bulk density (data on bulk density were not provided). In the study, the bark was applied
at 30 t/ha.
Sewage sludges and compost used in a trial of nursery potting mixes; sewage sludge is from the Greater Vancouver Regional District;
assumes bulk density of 100 kg/m3; compost is average value for two composts derived from sewage sludge (Kelowna and the
Greater Vancouver Regional District) and wood waste; assumed bulk density for compost was 150 kg/m3.
11
removing forest floor or fertilizing on four-year
height growth of eastern white pine and white spruce.
As a result of vegetation control, foliar nitrogen levels
increased, even though the site’s nitrogen capital was
depleted by % ( kg/ha) compared to control
plots. Removal of forest floor layers from the sandy
loam Podzolic soil resulted in an initially large nitrogen loss, and reduced nitrate levels in surface mineral
soil after four years, but microbial biomass carbon
and nitrogen, foliar nitrogen levels, and tree growth
were not significantly affected (Ohtonen et al. ).
The long-term effects of nitrogen loss were not
described.
Forest soil nutrient cycles are strongly influenced
by the presence of plant roots and the associated
bacteria and fungi that colonize the rhizosphere.
Mycorrhizae are a major factor affecting nutrient
uptake by forest trees (Read ). Mycorrhizal
colonization increases the nutrient-absorbing surface, and in some cases mycorrhizae may gain access
to organically bound nutrients that are otherwise
unavailable to plant roots.
Perry et al. () described some factors influencing the formation of mycorrhizae on seedlings,
and the subsequent effects on tree performance.
Following disturbance, the number of mycorrhizae
formed might be controlled by the balance of
propagule input to mortality, the rate of recovery
of host plants, and the diversity of fungal species
present. On severely disturbed sites, especially where
topsoil is lost, reduced levels of inocula are probably
present. If unfavourable soil conditions slow the
establishment of hosts on these sites, the rate of
mycorrhizal development would be limited, possibly
establishing a cycle of reduced inocula and poor
seedling performance, which could make
reforestation difficult.
Seedling performance is likely affected both by
the numbers of mycorrhizae and by their diversity.
Kranabetter et al. () evaluated the survival, early
growth, and mycorrhizal colonization of birch seedlings planted in rehabilitated roads in the central
interior of British Columbia. After two growing
seasons, seedling survival and height growth was
not significantly different for seedlings inoculated
at time of planting with fresh soil from a nearby
undisturbed area compared to seedling inoculated
with sterilized soil. Soil conditions remained poor
12
on the rehabilitated site two years after a treatment
that involved respreading a -cm layer of sidecast
topsoil and subsoil onto an untreated roadbed. Frost
heaving was the primary cause of seedling mortality.
Even though mycorrhizal diversity was low for both
treatments after two growing seasons, it was
significantly greater for seedlings inoculated with
fresh soil compared to those inoculated with
sterilized soil, which indicates that some biological
function was restored.
.. Methods for evaluating nutrient pools and
nutrient cycles
Techniques for evaluating site nutrient pools are well
established. Total nutrient concentrations of plant
material and forest floors can be determined by routine procedures that involve dissolving the sample in
acid, followed by analysis of the solution for nutrient
elements. To determine nutrient pools, these concentrations are combined with measures of plant
biomass or forest floor mass, which are calculated on
a unit area basis. Field-based techniques for measuring mass of forest floor, plant material, and mineral
soils are well established, although good measurements require care and patience. For mineral soils,
nutrient content can be determined by combustion
for elements associated primarily with soil organic
matter, such as carbon, nitrogen, and sulphur. For
metals such as calcium, magnesium, and potassium,
and for phosphorus and iron, all-purpose extractants
are suitable (Ballard and Carter ). Combinations
of these techniques were used in many studies to
evaluate changes in site nutrient pools.
A more difficult problem emerges when measures
of plant-available nutrients, and interpretations of
their effects on tree nutrition and growth are required.
In general, soil analysis has proven of limited use for
predicting tree growth on undisturbed soils, and foliar
analysis is much more reliable for evaluating fertilizer
needs. One exception is the use of soil mineralizable
nitrogen, determined by aerobic or anaerobic incubation, which has been used to evaluate site productivity
with considerable success in British Columbia and
elsewhere (Powers ; Klinka et al. ).
The difficulties associated with using measures
of extractable nutrients to explain the effect of soil
disturbance on nutrient cycles may relate to temporal
changes in rhizosphere nutrient cycles. Gosz and
Fisher () discuss a body of evidence that
indicates that plant roots exert considerable control
over microbial activity and nutrient availability
within the rhizosphere. This occurs mostly through
root effects on the availability and quality of organic
substrates, through the inhibiting effect of moisture
and nutrient uptake, and through the production of
allelopathic substances. These authors suggest that
tightly coupled forest nutrient cycles develop in
response to the episodic growth of fine roots and
mycorrhizae, which results in several peaks in root
biomass during a year, followed by periods with
increased mortality. Tree roots absorb more water
and nutrients during periods of root growth, and
release organic substrates during periods of
mortality. Microbial activity is inhibited during
periods of root growth, and enhanced during periods
of root mortality. Therefore, periods of root demand
may coincide with microbial release of nutrients, and
periods of root supply of substrates may coincide
with periods of microbial demand.
Other measures of nutrient cycling and microbial
activity were used by Parmelee et al. (), who
observed that microbial growth rates, biomass carbon
and nitrogen, and faunal populations all increased as
the density of pitch pine roots increased, and that
most of the activity was in rhizosphere soil. Faunal
abundance approached zero for non-rhizosphere soil.
Measurements of mycorrhizal colonization of
seedling roots and other biological attributes may
help to identify and characterize the stock types used
for rehabilitating sites.
Recently, soil scientists from many disciplines
including forestry have tried to define soil quality, or
the soil attributes that provide benefits to society
(Warkentin ). Attempts are under way to define
the minimum data sets required to determine whether
a particular agricultural or forest soil is in a healthy
or a degraded condition (Doran and Parkin ).
Some of the measures proposed include bulk density,
organic matter content, mineralizable nitrogen, and
microbial biomass carbon and nitrogen. These
attempts to quantify soil attributes associated with
quality may guide efforts aimed at quantifying the
effects of soil rehabilitation on nutrient cycles and
soil productivity.
5 TECHNIQUES FOR FOREST SOIL REHABILITATION
In general, soil rehabilitation aims to restore soil
physical, chemical, and biological conditions to a
state where the site’s productivity will mirror that
of undisturbed soils on similar site types in the area.
This section describes current or potential techniques
to restore productivity to soils in various ecosystems
throughout British Columbia.
. Tillage
Tillage involves the mechanical manipulation of soil
to improve soil conditions for plant growth (Hillel
). When rehabilitating forest soil, the primary
goal of tillage is to alleviate compaction, thereby
reducing the resistance of soil to root penetration,
and providing improved drainage and aeration to
enhance seedling establishment and tree growth.
The secondary goal may involve creating a seedbed
for cover crops, or mixing and incorporating
organic amendments.
Many implements are available for tilling forest
soils. The most appropriate implement for a particular area depends on:
• site conditions (e.g., slope, soil texture, moisture
content, organic matter content, presence of
unfavourable subsoil);
• tillage objectives (e.g., depth of tilling based on
a knowledge of natural rooting depth in undisturbed soils, amount of mixing); and
• cost and availability of equipment.
The success of a tillage operation depends on ecologically appropriate objectives, suitable equipment,
and a conscientious and knowledgeable equipment
operator. Therefore, no single prescription or
implement is ideal for all sites.
While the tillage techniques used to rehabilitate
forest soils may be similar to some used in agriculture, forestry tillage is unique in several respects.
Because forest crops have long rotations, tilling forest
soil may occur only once every – years on a
13
particular site. In most situations, tillage must be
completed before the trees are planted. Prescriptions
must rapidly create suitable growing conditions for
tree seedlings, while also restoring growing space that
the roots of mature trees will exploit  or more years
later. Although multiple tillage operations or combinations of different implements and machines are
possible, many degraded forest soils are located in
remote areas. Substantial costs are involved in
transporting equipment and materials to such sites.
Furthermore, degraded forest soils may occur on
steep slopes, they vary more than agricultural soils,
and they may contain large rocks or buried wood,
which hamper tillage operations.
Soil texture and moisture content influence tillage
results. Effective tillage requires that the soil is strong
enough to transfer the energy of the implement
through a substantial portion of the soil profile,
creating numerous fracture planes. Sandy soils derive
their strength largely from internal friction between
grains; strength is not highly dependent on water
content. In contrast, cohesion forces play an important role in binding clay soil particles together. As soil
water content is increased in clay soils, moisture films
weaken inter-particle bonds and reduce internal
friction, thereby reducing soil strength (Hillel ).
Soil strength, therefore, is influenced by moisture
content (Greacen and Sands ), as well as other
soil properties such as clay content and mineralogy
(Barzegar et al. ). Standardized tests describe how
these effects relate to the engineering properties of
soils (McBride ). These tests also help to explain
how individual forest soils are affected by tillage
under changing moisture conditions (McNabb ).
Soil organic matter alters the short-term response of
soils to tillage, but, over the long term, organic matter
stabilizes soil structure. The persistence of macropores (fractures) created by tillage depends on the
stability of the associated clods, which are small
remnants of the compacted soil matrix. Soil organic
matter plays a key role in stabilizing clods and allows
them to transform into soil aggregates that resist
dispersion when wetted.
Our understanding of the effect of different tillage
depths on forest productivity is drawn largely from
results in the United States (Andrus and Froehlich
; McNabb and Hobbs ), where soil and
climatic conditions differ from those in many parts
of British Columbia. For example, many undisturbed
soils in Oregon are derived from volcanic materials
14
and have low bulk densities (<  kg/m) from
the surface to a depth of up to  m (Froehlich and
McNabb ). Although rainfall patterns throughout the region vary tremendously depending on site
location relative to the major mountain ranges,
climates are generally mild, and growing season soil
temperatures encourage deep rooting of forest trees.
While these climatic conditions are similar to south
coastal areas of British Columbia, many areas of the
province have lower temperatures and soils derived
from glacial materials (Lavkulich and Valentine ).
Effective rooting depths (the depth above which %
of the fine roots are located) of only  cm may occur
in glacial-derived soils in the interior because of
naturally dense subsoils and low soil temperatures.
Therefore, tillage of deeper soil layers where rooting
is restricted by low temperatures is unnecessary
unless other factors (e.g., the need for drainage)
are involved.
Two broad strategies for tillage include those that
treat the entire degraded area to a specified depth and
those that attempt to ameliorate only a portion of the
area, perhaps with the intention of creating a planting spot for each tree seedling.
.. Extensive tillage
Extensive tillage, as the term is used here, refers to
techniques that till the entire disturbed area to a
specified depth. Various implements are used, often
pulled by, or attached to, crawler tractors. Excavators
with site preparation rakes and other attachments are
also used to extensively till degraded forest soils. In
general, productivity rates for extensive tillage are
higher and costs are lower for implements that move
in one direction and complete the operation in a single pass. Stopping, reversing direction, and turning all
reduce productivity.
Winged subsoiler The use of winged subsoilers in
forestry tillage was tested in Oregon before .
These implements are either mounted directly to the
back of a crawler tractor or are pulled behind a
crawler. They consist of two or three vertical shanks
with a single wing or “shoe” attached to the bottom
of each shank (Figure ). As the implement is pulled
through the soil at depth, the wings lift the soil,
creating forces that exceed the soil shear strength and
result in fracture.
Several years of experimentation and development
on winged subsoilers in the early s resulted in
a patented design for a self-drafting implement
  Winged subsoiler tilling a landing at the Aleza Lake Research Forest, Prince George Forest District. The implement
illustrated here was designed by Tilth Inc. of Monroe, Oregon, but the attachment to the crawler is not standard.
manufactured by Tilth Inc. of Monroe, Oregon. This
implement, which represents the most advanced subsoiler design currently available, is mounted directly
to a crawler tractor, or mounted to a dolly that is
pulled behind the crawler. This winged subsoiler has
several advantages over other subsoilers lacking the
self-drafting design. First, the self-drafting feature
allows the implement to remain at constant depth
even as the crawler climbs over mounds, logs, and
other irregularities in the soil surface. Also, a constant
amount of force is applied to lift the soil profile regardless of depth, so that fracture patterns and clod size
are more consistent. It also incorporates a tripping
mechanism, which allows the individual shanks to
automatically release, ride over buried wood or rocks,
and then return to position for continued tilling. A
selection of wings is available for use in different soil
types. Generally, wider wings are preferred for deeper
tillage and for fine-textured soils. Several self-drafting
subsoilers are available for use in British Columbia.
Winged subsoilers have proven more effective than
other implements for tilling forest soils (Andrus and
Froehlich ). For example, in a single-pass
operation, a winged subsoiler loosened % of the
compacted volume of a clay loam soil, and –%
of a loam soil. The proportion of compacted soil
loosened by rock rippers and brush blades was much
lower (maximum %), and a disk harrow loosened
only % of the compacted soil volume.
The main advantage of the self-drafting winged
subsoiler is its ability to maintain a lifting and
loosening action when run at depth. Conventional
rock rippers and brush blades produce a desirable
soil condition when used for shallow tillage, but
compress the soil and create well-defined slots when
run below a critical depth especially in moist finetextured soils. Therefore, while the critical depth
varies for different soil conditions and implements,
it is generally near  cm, too shallow to effectively
rehabilitate forest sites in Oregon, for instance
(McNabb and Hobbs ). The disk harrows used
were unable to penetrate the compacted soils below
approximately  cm.
Winged subsoilers have effectively loosened landings (Carr b), skid roads (Andrus and Froehlich
), compacted areas resulting from brush piling
(Davis ), and naturally compact forest soils
(DeLong et al. ).
15
While the research from Oregon suggests that the
winged subsoiler is effective over a range of soil
texture classes, the most consistent results in British
Columbia have occurred on coarse-textured soils.
McNabb () described the winged subsoiler as
only moderately effective for loosening fine-textured
soils in west-central Alberta. Limited shatter was
observed in the surface layers, primarily because
the clay and clay loam subsoils were near field
capacity at the time of tillage, and had low strength,
even though the tillage was carried out after an
extended period of dry weather. In contrast to
the moderate levels of compaction observed for
degraded soils in Oregon, McNabb () showed
that bulk density values in the surface horizons
of the Alberta soils were very near their maximum
attainable values. The tillage operation did not
fracture the very strong surface horizons because
the weak subsoils did not transmit the force of
the subsoiler.
Rock ripper Despite the results of Andrus and
Froehlich (), which showed that winged
subsoilers were favoured for single-pass operations,
conventional rock rippers have been used successfully
for landing rehabilitation in British Columbia. Rock
rippers are tooth-like attachments that are directly
mounted to the rear of a crawler and are lowered into
the soil as the machine moves forward (Figure ).
Preliminary observations made on several sites in
the Kamloops Forest Region (Figure ) indicate that
under appropriate soil conditions (e.g., coarse texture with moderate gravel content) and with careful
operation, satisfactory results are obtained using
rock rippers. A single-pass tillage operation with a
rock ripper may not till the entire soil surface layer
(Figure ). Several passes may be necessary to ensure
that the entire surface layer is loosened. However, the
full range of sites where rock rippers give satisfactory
results is not known, and information on the relative
costs of rock rippers compared to other implements
is not available.
McNabb and Hobbs () found that shallow
tillage ( cm) with a rock ripper did not improve the
growth of ponderosa pine seedlings in compact, fine
loamy soils on a hot, dry site in southwest Oregon.
The techniques reduced the bulk density over only
  Rock ripper being used for forest soil tillage in the Penticton Forest District. The ready availability of rock rippers to
logging operations in the province has encouraged their use in soil rehabilitation.
16
  Excellent growth of lodgepole pine planted in 1990 on a landing tilled with a rock ripper (Kamloops Forest District,
Jamieson Creek Forestry Road, km 33).
  Results of a single pass with a rock ripper on a medium-textured landing in the 100 Mile House Forest District.
Approximately 30% of the surface layer was tilled.
17
% of the area because the rippers were widely
spaced and penetrated to a depth of only  cm.
After five years, seedlings planted in the middle of
the furrow created by the ripper were no larger than
seedlings planted in the compact soil between the
furrows. The authors concluded that the shallow
cultivation depth was not sufficient to provide any
significant advantage to the seedlings.
Brush blade In the Cariboo Forest Region, a landing
rehabilitation project described by Vyse and Mitchell
() used a brush blade to till to a depth of  cm.
The authors’ observations of soil physical properties
are similar to those provided by Andrus and Froehlich (), indicating little effect below that depth.
At least two sites were visited during the summer
of  that were tilled with brush blades. Others
were visited where the tillage method was not documented, but where conditions resembled those
expected when using brush blades. In the Nakusp
area, a landing on coarse-textured soil, which was
rehabilitated with a brush blade in , was observed with good stocking and growth of lodgepole
pine. The use of a brush blade is limited not only by
effectiveness, but also by the expected cost using this
implement. For the operator to avoid travelling over
the tilled surface, the machine must constantly reverse direction to till a small area between the front
of the tracks and the blade. Brush blades are effective
for spreading topsoil piles, however, and will likely
find use in specific rehabilitation situations.
Excavator Extensive tillage is also carried out with
an excavator. Although the costs per hectare tilled are
higher than those for winged subsoilers (Table ),
their use is justified in many situations because of:
• their versatility when equipped with various
attachments;
• their low ground pressure; and
• their ability to gain access to abandoned roads
while causing minimal soil disturbance.
Excavators (Figure ) have rehabilitated landings
(Lawrie et al. ) and roads (Hickling et al. ),
and although little is known of the soil physical
conditions that resulted, depending on the prescription and the amount of money available for
the work, these machines are capable of thoroughly
loosening soil to any reasonable depth. Excavators are
also able to replace topsoil, move debris, incorporate
amendments, and break up large clods to prepare
seedbeds. Compared to a winged subsoiler, more
mixing occurs in surface soil layers that are tilled with
excavators.
A single ripper-tooth mounted on an excavator
was used to till  landings during the summer of
 as part of an Forest Renewal BC–funded project
carried out by Pope and Talbot (Nakusp). Based on
observations of several coarse-textured landings
  Cost of various implements for extensive tillage of forest soils; all figures adjusted to 1996 costs ($140 per hour)
using FERIC’s estimates of machine-ownership costs (Lawrie et al. 1996)
Machine type
Prescription
Productivity
(hr/1000 m2)
Cost
($/1000 m2)
Winged subsoiler
Deep tillage
—
85
Marsland 1994a
Winged subsoiler
Deep tillage
0.39
55
Walker and Horley 1991b
Winged subsoiler
Deep tillage
0.33
45
Lawrie et al. 1996c
Excavator
Shallow till
0.70
71
Lawrie et al. 1996c
Excavator
Till + topsoil
1.24
126
Lawrie et al. 1996c
Rock ripper
Deep tillage
0.42
58
Ellen 1996d
Winged subsoiler
Deep tillage
0.77
107
Fewer 1992e
a
b
c
d
e
Source
1993 program: costs in 1991 ($42) and 1992 ($54) were much lower, but concern was expressed about the quality of the work, so
the 1993 program was carried out at lower machine speeds.
Total costs for the operation.
These costs represent tillage time only, not including delays.
Based on Forest Renewal BC cost estimate for 1994 work, p.17.
Average costs for landings and trails combined in 1991 (Kalum District), including repairs and delays. Costs declined in 1992 to
$87 /1000 m2.
18
  Extensive tillage with an excavator equipped with a site preparation rake (Williams Lake Forest District).
Excavators are often favoured for rehabilitation work because of their suitability for additional tasks such
as culvert installation and removal, topsoil retrieval, and sidecast pullback.
during the summer of , the results appeared
satisfactory. A similar implement (Figures  and )
with wings attached to the ripper-tooth, was in use in
the south Okanagan in .
.. Spot treatments and site preparation
equipment
Spot treatments are applied on their own or as part
of treatment combinations. In British Columbia, applying spot treatments to rehabilitate soil has received
limited use, although a pilot project carried out in the
Cariboo Forest Region during  used some of the
treatments described in this section.
Treatments that create individual planting and
growing spots have potential advantages over extensive tillage methods. First, if only a portion of the
total compacted soil volume is rehabilitated, energy
requirements are reduced, and machines (e.g., excavators) that are expensive when applied to entire
areas may become practical to rehabilitate a wider
range of sites. Second, these types of treatments have
a greater potential to influence surface relief by
creating mounds or trenches. This may benefit sites
where excess moisture, low temperatures, or drought
adversely affect seedling establishment, or backlog
sites where protecting the existing trees is desired.
Throughout British Columbia, various implements
are available to prepare spots, mounds, trenches, and
other features, thereby addressing a range of growthlimiting conditions.
The potential advantages of spot treatments are
only realized, however, if the entire site’s long-term
productivity is returned to a level similar to other
sites in the area. Because spot treatments do not
till the entire degraded soil volume, growing roots
will eventually encounter untreated soil. For most
sites, this would probably reduce overall site
productivity, but two possible mechanisms exist
to maintain productivity. Spot treatments are
successful when:
. tree roots can penetrate the untreated soil when
encountered; or
. aboveground site productivity is unaffected by the
roots’ inability to exploit the untreated soil.
19
  Excavator with a single-tooth ripper attachment, used for loosening very rocky soils in the Penticton Forest District.
  Close-up of the ripper attachment illustrated in Figure 7, showing the wing attachments to enhance soil tillage
(Penticton Forest District).
20
The ability of tree roots to proliferate through
untreated soil depends on the extent to which soil conditions improve during the period after tree planting.
While most authors agree that heavily compacted
soils take several decades to recover (Wert and
Thomas ; Froehlich et al. ), more rapid
recovery is reported on some sites (Corns ;
Reisinger et al. ). For site productivity to be
unaffected by the loss of a significant amount of soil
volume (e.g., case  above), tree roots occupying a
restricted volume of soil must be capable of acquiring
all the water and nutrients required.
The most commonly used machine for spot treatment in British Columbia is an excavator, which can
be equipped with various attachments, including site
preparation rakes, thumbs, and spot-mixing heads
(Figure ). Mounding is commonly used for site preparation in the province, and is used to rehabilitate
degraded soils as well. Mounding is especially
suitable for winter landings, or rutted areas that
occur on wet sites. Some examples of mounding were
observed during visits to sites in the summer of ,
but no information was available about the effects
on productivity. In general, for spot treatments
based on site preparation techniques, rehabilitation
objectives should be based on a knowledge of the
growth-limiting conditions and the effect of the
treatment on those conditions. The effect of site
preparation techniques on soil conditions affecting
seedling growth was described by Orlander et al. ().
Limited rooting volume resulting from spot
treatment would show its effects at a young age for
trees planted in small treated spots. In , the
Canadian Forest Service established a trial that
evaluated auger planting as a method to break up
compacted soils and improve seedling survival and
growth on landings in north-central British Columbia.
Seedlings were planted using a mattock, dibble, or
chainsaw-powered auger, which created  ×  cm
planting holes (Arnott et al. ). Bareroot lodgepole
pine planted with the auger survived better than trees
planted with a mattock, but auger planting had no
  Results of partial tillage with an excavator equipped with a silvatiller attachment (Horsefly Forest District). The
silvatiller mixed the surface soil layers to a depth of approximately 30 cm. The darker strips were tilled, which
loosened the surface soil and disturbed the grass sod. Untilled areas between the strips have a well-developed
grass sod and more compact soils.
21
effect on the survival of container-grown trees.
Auger-planted trees grew no better than those
planted with a dibble or a mattock. Growth of trees
planted on the landings was poorer than growth on
the adjacent portions of the cutover, regardless of
planting method. These results show that ameliorating
approximately . L of soil is insufficient to improve
productivity on compacted and nutrient-deficient
landings.
A site preparation treatment involving shearing,
windrowing, and double discing was effective in
restoring soil physical properties to pre-harvest levels
in the upper – cm of skid roads and cutover areas
that were whole-tree harvested in the United States
(Gent et al. ). Bulk density, aeration porosity, and
saturated hydraulic conductivity were improved in
surface layers (to  cm) where the disk had worked
the soil; minimal improvement occurred below this
depth. The site preparation machinery caused some
additional degradation, but this was thought to have
little effect on productivity. The overall effect of the
treatment on tree growth was not studied, but
reduced productivity may have occurred because of
topsoil losses during windrowing.
.. Information gaps and research needs
Additional research is needed to evaluate tillage techniques and soil physical properties. Tillage is a costly
component of rehabilitation projects, frequently
accounting for one-third to one-half of the overall
project costs. The outcome of subsequent site
investments depend on successful tillage. Therefore,
practitioners need prescriptions based on a good understanding of the effects of tillage on soil conditions;
they must also evaluate tillage operations in the field
so that the technique can be adjusted to meet changing conditions. In British Columbia, there is currently
insufficient expertise to support the tillage activities
in Forest Renewal BC’s land-based programs.
Despite our lack of experience in this area, we can
optimistically expect that research results will flow
quickly and make a significant contribution to
rehabilitation efforts in British Columbia. Two
main aspects of the problem are described below.
Developing and calibrating short-term tillage
evaluation techniques A means of quickly and
reliably assessing the adequacy of tillage for
operational purposes is needed. A rapid method for
evaluating tillage involves the use of a simple probe
made by welding a T-handle onto a  m length of
22
 mm diameter steel rod. By leaning on this probe
at several locations in the tilled area, an operator or
supervisor can obtain a quick estimate of physical
condition and depth of loosened soil (Figure ).
Unfortunately, even this relatively simple technique is
not used on all projects. In addition, interpretations
based on the penetration of such a probe are
qualitative and of little use for sharing information
between projects and regions of the province.
More detailed evaluation of tillage is also required.
For example, approaches are needed based on the use
of cone penetrometers to determine soil strength (e.g.,
Dunker et al. ), as well as approaches to determine
the relationships between measures of penetration
resistance and other indicators of soil physical condition such as bulk density and aeration porosity,
which are useful predictors of forest productivity.
Field staff would benefit from any information
that helps them evaluate tillage effectiveness. In
addition to penetration resistance, the types of
measures that may be of use include:
• depth of tillage;
• minimum clod size and clod size distribution;
• percentage of an exposed profile face with
adequate fracture;
• degree of mixing of soil horizons; and
• amount of organic matter incorporated in the
surface soil layer.
The proportion of tilled soil has been determined
by surveying the area and depth of compacted soil
before and after tillage (Miles and Froehlich )
using penetrometers or excavations.
Percentage of tilled soil proved useful in evaluating
the effectiveness of six tillage implements in Oregon
(Andrus and Froehlich ). Soil structure or clod
size distribution is determined by passing tilled soil
through a nest of sieves. The distribution of clod sizes
immediately after tillage, and in subsequent years,
can provide information about the effectiveness of
tillage and the stability of soil structural units (clods
or peds) created by tillage, although interpretation of
the resulting size distributions presents challenges.
Information on the response of soils to tillage for
various sites would also help in developing methods
to deal with the phenomenon of resettling.
Evaluating the long-term success of various tillage
strategies for a variety of site types More detailed
evaluations of tillage are needed to provide the
foundations for drawing inferences about productivity. The many implements available for forest soil
rehabilitation in British Columbia are being used
under a wide variety of soil and site conditions.
Field visits during the summer of  led to a
preliminary conclusion that a careful and
knowledgeable operator working with a good
prescription is at least as important for a project’s
success as the choice of implement. On many sites,
especially those with coarse-textured soils, several
choices of implement appear to produce good results.
Unfortunately, very few projects exist where the
initial conditions and tillage procedure were
documented well enough to reliably state that this
first impression is correct. The effect of treatments
on long-term plots can be evaluated only if initial
conditions are recorded.
Long-term studies should address the following
questions:
• Depth of tillage: What tillage strategies work best
on a variety of sites and under varying conditions?
Is restoration of a shallow surface layer an effective
technique to restore productivity on sites with
naturally shallow rooting depths?
• Resettling and soil structure stability: Under what
soil/site conditions does resettling cause failure of
the rehabilitation project? What techniques are
suitable to prevent resettling?
• Minimum treatments: What low-cost rehabilitation treatments are effective for a variety of sites,
including those with severe disturbance such as
main roads and landings, and those such as rutted
areas, minor trails, and roadside work areas with
less severe disturbance?
. Topsoil Conservation and Replacement
In forest soil rehabilitation, topsoil is operationally
defined as the upper layer of the soil where most of
the roots are located, with or without the forest floor.
This definition recognizes that forest floor layers have
distinct characteristics and functions compared to
mineral soils, but that separating forest floors from
mineral soil horizons is not usually practical using
heavy equipment (Ballard ; Ziemkiewicz et al.
[editors] ).
  Evaluating tillage depth (Morice Forest District, Telkwa River Forestry Road, km 15). The indicated depth of loosened
soil is approximately 40 cm (total length of probe is 1 m), indicating effective tillage with a winged subsoiler.
23
Replacing topsoil is an effective technique to restore
productivity in degraded soils (e.g., Heilman ,
; Halvorson et al. ). The benefits of topsoil
conservation and replacement are related mostly to
the higher soil organic matter levels present in topsoil
relative to subsoils, and the beneficial effect of the soil
organic matter on physical, chemical, and biological
conditions.
Compared to subsoil materials, topsoils usually
have higher aggregate stability (Itami and Kyuma
), lower bulk density (Smith and Wass ; Carr
a), and more favourable pore size distributions,
which leads to higher hydraulic conductivity, waterholding capacity, and aeration porosity (Potter et al.
; Sharma and Carter ). The loose, open
structure of productive forest soils often depends on
the presence of soil organic matter (Hudson ),
but soil texture also plays a role in topsoils derived
from medium- and fine-textured parent materials. In
many parts of British Columbia, soil development
has resulted in natural topsoils that contain less clay
than subsurface layers (Lavkulich and Valentine
[editors] ), and thus have inherently more stable
macropores than their associated clay-rich subsoils.
Variation in soil texture within the surface layers of
undisturbed soils may result from translocation of
clays in moist climates, or from additions of volcanic
ash or wind-derived material to the soil surface.
Nutrient pools and cycling are also enhanced by
the presence of topsoil on rehabilitated sites. For coal
spoils in Washington, nutrient content of replaced
topsoils was more than twice as high as for subsoils,
even though the levels in topsoil were still well below
those in undisturbed forests (Heilman ). Foliar
nutrient levels in Douglas-fir reflected the soil nitrogen levels. In this study, - to -year-old Douglas-fir
growing in reclaimed soils with topsoil had a similar
site index to reference plantations on undisturbed
soil. A plantation growing on subsoil material had a
lower site index.
Topsoil also acts as a seedbank, which is often an
important resource for revegetation with native
species (Young ), but which also affects the need
for subsequent treatments to control weeds and vegetation competing with crop trees (Heilman ).
According to Young (), seeds are concentrated
in the thin, organic-rich surface layer of soil. The
seedbank layer may represent only a small portion of
a thicker topsoil layer that would be conserved in
many mine reclamation projects, but may closely
24
reflect the types and amounts of materials commonly
found near disturbed forest sites in British Columbia.
Several factors affect the composition and viability of
seed in soil seedbanks, including the composition of
pre-disturbance vegetation and the ecological
strategies (e.g., seed numbers, viability, dormancy
periods, and germination requirements) of the plant
species present. Removing and stockpiling the topsoil
dramatically changes the environmental conditions
that affect the seeds. Some seeds die as stockpiled
topsoil ages, while others have their dormancy
requirements satisfied. For a particular site and
rehabilitation objective, changes in seedbank
composition because of aging may be either
favourable or unfavourable.
Farrish () showed that seedling emergence
was similar for loblolly pine grown in topsoil and
subsoil, but that subsequent survival and early
growth of roots and shoots was significantly higher
for trees growing in the topsoil. Soil organic matter
and nutrient levels were substantially lower for the
subsoil treatments. The growth response was
attributed to soil and plant nutrient status in this
case, but the effects of low organic matter levels on
soil physical properties affecting aeration and root
penetration were not evaluated, and may have
been significant.
When landings and roads are built without the
intention to rehabilitate them, topsoil replacement
simply involves retrieving and spreading any material
piled at the edges of the landing or road (Figure ).
When rehabilitation is anticipated, and on steeper
ground, topsoil is pushed to one side before levelling,
or buried at a known location within the fill. If the
topsoil is pushed to the side, full slope recontouring
is not needed before the topsoil is respread.
In a study of skid site rehabilitation in New Zealand,
Hall () found that ripping and mounding effectively reduced soil shear strength, and the cost of
ripping alone was modest. However, soil nitrogen on
the ripped soils was well below the critical level for
radiata pine, and some amelioration with chemical
fertilizer or legume-derived nitrogen was considered
essential. Respreading topsoil and logging debris was
more expensive (accounting for % of the costs of
a combined treatment that included ripping and
mounding with respreading topsoil and logging
debris) and nutrient limitations were only partially
overcome. The equivalent cost of fertilizing to restore
soil nutrients was not discussed, and comparative
  Topsoil piles commonly found adjacent to bladed areas on level ground (Kalum Forest District). Respreading these
piles should enhance site nutrient conditions and improve productivity.
tree performance on sites with and without topsoil
was not available. Lawrie et al. () showed that
spreading topsoil on landings increased the cost of
shallow tillage with an excavator by approximately
%. Replacing topsoil during rehabilitation raises
practical problems: the replaced topsoil should
retain its beneficial physical properties and detrimental compaction should be avoided. Torbert and
Burger () observed that % of trees planted on
restored mine soils in Virginia survived when planted
on areas with minimal traffic, compared to % survival for trees planted on areas repeatedly travelled
on during topsoil placement. Height growth after two
years was also affected by the traffic. The areas of
extensive traffic resulted from a grading operation
that aimed to produce a uniform surface.
.. Information gaps: research needs
Three aspects of topsoil replacement in forest soil
rehabilitation in British Columbia require further
study. While the effects of topsoil replacement on
productivity could be extrapolated from one disturbance type to another, the evaluation of costs and
machine productivity must be investigated for individual disturbance types.
Quantify the benefits of topsoil replacement, in
comparison to other methods of restoring soil
structure and nutrient cycles Evidence from many
sources indicates that topsoil conservation improves
soil conditions, but the value of such benefits to growing trees is not known for forest soil rehabilitation
situations in British Columbia. Long-term plots are
needed to evaluate tree productivity on areas rehabilitated with and without topsoil replacement. One
approach would include these plots as treatments in
rehabilitation research projects that are evaluating
various methods of restoring productivity.
Investigate biological processes in rehabilitated
surface soils The biological processes that affect
nutrient cycling and their relationship to site productivity are complex. In natural topsoils, populations of
nutrient-cycling organisms are much larger than for
associated subsoils. Studies of nutrient-cycling
processes, such as microbial activity, populations of
soil organisms, and characteristics of soil organic
matter, would provide information about potential
25
indicators of long-term site productivity on a range
of site types.
Determine cost-effective construction methods for
conserving and replacing topsoil Conserving and
stockpiling topsoil for use in rehabilitation projects
will likely become normal construction practice in
forestry operations in the near future because of
Forest Practices Code requirements. However, no
obligation exists to respread topsoil piles that are
adjacent to backlog sites requiring rehabilitation.
Conserving, stockpiling, and replacing topsoil add
significantly to the costs of access construction and
rehabilitation. Many rehabilitation specialists in
British Columbia are either not aware of the potential
benefits, or do not feel that they justify the additional costs associated with the practice. Research,
demonstration, and extension activities are needed
to investigate cost-effective ways to manage topsoil.
For example, studies of machine productivity (e.g.,
Lawrie et al. ) could be carried out to provide
information for a variety of sites.
. Slope Recontouring
Slope recontouring is a method where contour-built
roads and trails are removed and the slope is restored
to its initial shape. It is also called “road debuilding”
on the coast, and in the southeast interior it is an
important technique for skid road rehabilitation.
Slope recontouring is carried out to control surface
erosion, prevent mass wasting, restrict access,
improve aesthetics, and restore soil productivity
(Beese et al. ). The emphasis placed on restoring
productivity depends partly on administrative issues
such as the need for future access, and on site factors
that affect the feasibility of restoring productivity.
Eubanks () described a technique for restoring
slopes that focused on hiding the road from view and
preventing traffic from using the road. Although the
goals were different from those of modern watershed
restoration projects in British Columbia, some of the
recommendations made by Eubanks were similar and
included careful location of road takeoffs, topsoil
stockpiling, and revegetation using seed. The estimated cost for full restoration was about equal to
the initial cost of construction.
In the Nelson Forest Region, logging of steep slopes
often involves construction of contour skid roads.
The amount of land affected by skid roads became a
concern in the early s, after researchers drew
26
attention to degraded soil conditions and reduced
productivity. Soil conditions were especially poor on
the gouged inner portions of skid road surfaces
(Smith and Wass ). In response to the concern,
and initially with the aim of improving visual quality
of cutblocks on steep slopes, Crestbrook Forest
Industries (Cranbrook) developed a system of skid
road construction and rehabilitation that has evolved
for over  years. Objectives of restoring drainage
patterns, slope stability, and soil productivity were
subsequently incorporated into the rehabilitation work.
Currently, skid road construction, use, and
rehabilitation is planned through the entire harvesting operation by Crestbrook. Features of the
operation’s construction phase include consistently
placing topsoil in a small windrow near the outside
of the trail surface, minimizing the cut height, and
avoiding calcareous materials, which are unsuitable
as a growing medium for trees. Rehabilitation
involves loosening and out-sloping the running
surface, replacing the subsoil materials against the
cutbank, replacing the topsoil, and scattering the
slash across the surface. These techniques were
among the most advanced viewed in British
Columbia during site visits in the summer of .
Dykstra and Curran () described an investigation that was recently initiated to evaluate forest
productivity on rehabilitated skid roads. The
objective of the study was to quantify lodgepole pine
and Engelmann spruce growth on rehabilitated skid
road disturbance for various site types. A successfully
rehabilitated site shows no differences in growth
between trees in undisturbed conditions and at all
positions within the profile of the rehabilitated skid
road. On skid roads that have not been rehabilitated,
trees growing on the inner gouged portion of the skid
road are commonly smaller than trees growing on the
outer portions (Smith and Wass ).
In the Vancouver Forest Region, Hickling et al.
() established over  measurement sites to
evaluate the establishment and early growth of trees
growing on rehabilitated roads. Most of the sites were
in the Coastal Western Hemlock (CWH) biogeoclimatic
zone, and trees were planted on roads rehabilitated
with an excavator as part of operational work carried
out by forest companies. Average survival rates after
one year were over %. Preliminary results indicated
that, compared to soils with low organic matter content
(–.%), high levels of organic matter (>␣ %) in
the surface soils were associated with greater height
growth of Douglas-fir and western redcedar (over
% taller). The use of various forms of tea-bag
fertilizer also improved growth, but not to the same
extent that organic matter did. Grass-seeding reduced
height and diameter of Douglas-fir on one site. Deer
browsing affected % of the plots, and was considered a serious problem where deer used the
debuilt road.
Based on their preliminary results, Hickling et al.
() provided a description of what a successful
rehabilitation project might aim for, including:
• a road that takes its place in the natural landscape
(recontoured to natural state);
• organic material that is mixed into the surface,
along with the transplanting of young trees or
brush; and
• stockpiled materials and other available resources
that are used appropriately.
.. Information gaps: research needs
Evaluate conifer growth on recontoured roads and
skid trails We lack reliable information on the productivity of rehabilitated roads and contour-built
skid trails. The work initiated in the Nelson Forest
Region (Dykstra and Curran ) and by Hickling
et al. () illustrates the types of studies that will
gain such information.
. Reforestation and Revegetation Techniques
Numerous strategies can re-establish productive
forests on degraded sites; each approach includes a
range of options for plant species, establishment
methods, and subsequent vegetation management
techniques. On sites with low potential for erosion,
and where soil properties are suitable, a simple and
low-cost strategy involves establishing suitable
conifer or hardwood crop trees and allowing shrub,
herb, and other understory species from nearby areas
to subsequently invade the site. This strategy can
succeed on flat sites (low erosion hazard) with
medium- to coarse-textured soils (rapid infiltration,
limited potential for resettling following tillage), and
where topsoil is respread (seedbank of native species
available). The trees can establish by either natural
regeneration from seed, or by planting suitable container or bareroot stock types. Simple approaches
such as these are likely suitable on many sites, but
additional revegetation techniques are often required,
including those that provide visual cover, control
erosion, restore and maintain soil physical properties,
or enhance site nutrient pools and nutrient cycling.
.. Coniferous and hardwood crop trees
The goal of establishing trees on rehabilitated soils is
the same as that for general silvicultural planting on
undisturbed sites—that is, to achieve high survival
rates and rapid early growth. Early successional
species such as Douglas-fir on the coast and lodgepole pine in the interior have been favoured for
rehabilitation, partly because they are adapted to
the harsh conditions on disturbed areas. As more
experience is gained, however, other species may
prove equally successful, depending on the site conditions. Recently on the coast, plots were established to
evaluate the performance of western redcedar, western hemlock, amabilis fir, yellow-cedar, and red alder
(Hickling et al. ). In the interior, white birch,
white spruce, and western larch were also established
on rehabilitated sites. The unique characteristics of
each of these species, and others including subalpine
fir, aspen poplar, and black cottonwood, will likely
ensure that they are used in rehabilitation work on
some sites.
Successful establishment and early growth of
planted trees requires that a healthy individual of a
suitable seedling stock type is planted in a suitable
microsite. On undisturbed portions of recently
harvested cutovers in British Columbia, this usually
occurs, and plantation failures are rare. For rehabilitated sites, however, seedling mortality rates are
often much higher, and early growth is usually slower
than for undisturbed soils. Each element in this series
of events (i.e., plant, stock type, site) needs evaluation
when developing techniques to establish fast-growing
plantations on rehabilitated sites. Armson ()
described how poor root development, which may
result from low-quality stock or poor soil conditions,
can lead to seedling establishment problems. Armson
also described how root systems, that fail to expand
during periods of rapid growth, can lead to poor
performance and mortality at the sapling, or pole,
stage of stand development. Therefore, along with the
need to restore soil properties to suitable conditions,
the quality of biological material used in rehabilitation is also an important factor affecting success.
Arnott et al. () showed that + bareroot
lodgepole pine outperformed + container seedlings
on landings near Fort St. James. The bareroot stock
type was larger when planted, and maintained
27
consistently larger annual height increments throughout the five-year study. Hickling et al. () also
showed that larger stock types (PSB ) of Douglasfir grew faster on rehabilitated roads in coastal
British Columbia.
Williston and Ursic () recognized the need for
microsite planting, but found that nursery practices
such as fertilization and top pruning had little effect
on success of loblolly pine planted for erosion control
in the United States. Shallow planting was the most
common cause of failure, while auger planting in a
six-inch posthole and carefully selecting the planting
spot improved survival. Some ineffective techniques
included very deep planting, kaolin root dip, wax
coatings to reduce transpiration, fertilizing at  lbs/
acre, and interplanting with legumes.
The range of cultural techniques available in a
modern nursery is much wider than that available in
. In addition, the awareness that mycorrhizae and
other biological partners play an important role in
water and nutrient uptake has led to the development
of various biological inoculants with the potential to
improve seedling performance. Mycorrhizal
inoculation was tested as a means of improving
planted seedling performance, but the results for
undisturbed sites with adequate moisture supplies
were mixed.
Walker et al. () compared the performance
of one-year-old bareroot loblolly pine seedlings
inoculated with the mycorrhizal fungi, Pisolithus
tinctorius, to that of control seedlings colonized
primarily by Telephora terrestris. The seedlings were
outplanted with or without fertilizer on a recontoured coal mine site that was also revegetated with a
herbaceous ground cover. The loam soils had .%
organic matter, a pH of ., and .% total nitrogen.
Survival and growth of loblolly pine after seven years
was improved by the presence of P. tinctorius. The
effect of the P. tinctorius was attributed to improved
water and nutrient uptake evaluated through
measurements of xylem pressure potential and foliar
nutrient analysis. Fertilization with  kg/ha each of
nitrogen, phosphorus, and potassium reduced
survival and had no effect on growth. The effect of
the fertilizer was primarily to enhance the growth of
herbaceous cover, which often overtopped the pine in
the fertilized plots.
Amaranthus and Perry () showed that soil
transfer increased survival and mycorrhizal colonization of Douglas-fir seedlings planted on old
28
clearcuts by up to %. These authors found that the
source of transferred soil was an important factor
affecting success, and believed that the results
demonstrated that ectomycorrhizal fungal inoculum
had been transferred with the soil. Subsequent work
by Colinas et al. (), however, showed that the
situation was more complex—soil that was treated
with fungicide also enhanced the formation of
mycorrhizae on planted seedlings. They suggested
that some aspect of the rhizosphere biology was
altered by the transferred soil, which led to enhanced
ectomycorrhizal colonization of the roots by inoculum already present in the clearcut.
These results might have relevance for rehabilitated sites, where soils would probably have low
amounts of inocula for mycorrhizae and other soil
organisms, and where soil aeration and moisture
conditions are altered compared to undisturbed soils.
.. Grasses, legumes, and native shrubs for soil
amelioration
Various revegetation strategies are available to enhance productivity on degraded soils. Revegetation is
necessary to control surface erosion. Vegetation also
helps to restore the soil by increasing soil organic
matter levels. Techniques for controlling erosion with
grass and legume plantings were the subject of several research projects carried out by the B.C. Ministry
of Forests in the early s. Results were presented in
several reports and the techniques are well developed
to address erosion concerns in forestry (Carr ,
; Homoky , ; Beese et al. ). Although
much was learned, some revegetation issues remain
unresolved and others were raised more recently, including:
• the ecological benefits and hazards associated with
establishing grasses and legumes on rehabilitated
forest soils;
• the potential for improving soil structure through
biological tillage; and
• the enhancement of site nutrient pools through
nitrogen fixation.
Grasses and legumes Agronomic seed mixes are
widely used in soil rehabilitation, and sometimes
the purpose of this work was unclear. For example,
several forest districts developed rehabilitation
policies in the s that required landings on all
cutovers to be loosened and seeded to grass and
legume mixes. In many cases, seeding grasses and
legumes took precedence over planting trees, even on
sites where no erosion hazard existed. While many of
these landings provide valuable forage for cattle, and
soil conditions may have been improved, they are not
yet developing into productive forests.
In , several landings near Williams Lake were
loosened and seeded with combinations of lodgepole
pine and grass seed as part of a trial on the effectiveness of landing rehabilitation techniques (Vyse and
Mitchell ). Although the experiment was
abandoned shortly after it was installed, recent
observations indicate that lodgepole pine was
successfully established from seed on landings not
seeded to grass (Figures  and ). Grass may hamper
germination and subsequent establishment of pine
on sites in this area. Poor germination of pine seed
on the study sites was documented in the first year
of the trial, but in subsequent years more of the seed
germinated. Competition between trees and grass,
and cattle damage to seedlings, may also cause
reforestation problems (Figure ). More recent
evidence from throughout British Columbia
illustrates that, where delayed seeding or other
factors have resulted in poor development of grass
and legume cover crops, growth of pine trees is
satisfactory (Figure ), suggesting that grasses and
legumes are not an essential part of soil rehabilitation
on all sites.
Amaranthus et al. () observed that seeding
annual ryegrass (Lolium multiflorum) in an area
characterized by extended summer drought caused
low soil moisture levels and increased mortality of
sugar pine seedlings planted the following spring. In
the following year, the grass died and the thatch cover
acted as a mulch, which resulted in increased soil
moisture content and improved survival for trees
planted into the thatch. On unseeded plots, bare
mineral soil covered –% of the area, but native
species re-established to cover % of the area after
two growing seasons. Grass covered % of the
seeded areas after one year. Differences in mycorrhizae between seeded and unseeded plots were not
consistent. The authors did not encourage grass
seeding because other studies indicate that grasses
restrict mycorrhizal formation. This can occur
  Landing rehabilitated as part of EP 777 in the Williams Lake Forest District. The entire landing was tilled and
lodgepole pine established from seed. The left-hand portion was not seeded to grasses, and reasonable stocking
and growth of lodgepole pine was observed 20 years after rehabilitation.
29
  The right-hand portion of the landing from
Figure 12 (Williams Lake Forest District), which
was seeded to grasses and legumes. Very few
pine survived.
  Rehabilitated landing with good pine growth,
but poor germination of birdsfoot trefoil
because of delayed seeding (Kispiox Forest
District). Favourable seedbed conditions persist
for only a short time after tillage.
  Seedling damaged by cattle trampling in a
rehabilitated roadside work area (Moffat Road,
Williams Lake Forest District).
30
directly by inhibiting ectomycorrhizae, or indirectly
by slowing the invasion of native shrubs that have
ectomycorrhizae.
In another study of the effects of grass seeding on
tree establishment, Carpenter and Albers ()
showed that moisture stress and mortality were
highest in June for alder seedlings planted into a
dense stand of fescue (Festuca arundinacea Schreb.)
on surface mine soil in Kentucky. Leaf water potential
and soil moisture content were generally lower for
trees planted in plots with fescue and where fescue
was mowed, compared to plots where grass cover was
scalped away or where it was temporarily set back by
herbicide.
Although grass seeding can result in moisture
stress to trees in dry climates, the negative effects of
grass are not well documented in moist climates in
British Columbia. Several examples from various
areas of the province show healthy forests growing on
rehabilitated sites that also support vigorous stands
of grass and legume (Figure ). Grasses and legumes
may provide a cost-effective means of enhancing soil
organic matter and nutrient levels on these sites
(Figure ). In the Interior Cedar–Hemlock (ICH)
and Engelmann Spruce–Subalpine Fir (ESSF)
biogeoclimatic zones of interior British Columbia,
seeding with grasses and legumes is employed to
reduce competition between crop trees and native
vegetation (Steen and Smith ). Early results
suggested that the shorter agronomic grasses and
legumes displaced taller native species, which was the
objective, but had little effect on conifer crop trees.
Hickling et al. () suggested that the growth of
tree seedlings planted in grass-seeded areas was
slightly reduced in coastal British Columbia.
Biological tillage Information in Table  indicates
that the roots of some tree species can penetrate
compacted soils better than others; the same is true
for agricultural crops. This observation has led some
researchers to suggest that such plants could be used
as “biological plows” to penetrate compacted soil
layers, and create channels for the roots of crop
species. Henderson () estimated that this effect
was true of lupine, which improved wheat yields by
 kg/ha, on a sandy soil in Australia that was
compacted by agricultural machinery.
Materachera et al. () evaluated  plant species
for their ability to penetrate a soil medium
compacted to a strength of  kPa (penetrometer
resistance), and found that all species had their root
elongation reduced by over %. The roots of dicotyledonous plants generally had larger diameters and
penetrated the medium better than graminaceous
  Landing rehabilitated in 1987 in the Quesnel
  Surface soil conditions on the landing illus-
Forest District. Excellent pine growth on sandy
soil with organic-rich surface horizon. Excellent
growth of grass and legume. Steel probe
penetrated to 20 cm.
trated in Figure 16 (Quesnel Forest District).
Grasses and legumes contribute soil organic
matter and nutrients to develop a productive
soil.
31
monoctyledons with smaller-diameter roots. The best
species included lupine, medic, and fava bean. In subsequent field tests (Materachera et al. ), lupine
and safflower produced the greatest effect on water
sorptivity of the compacted layers, but sorptivities
were still well below levels for a tilled subsoil. The soil
strength values used in the study by Materachera et
al. () are near the upper limits of values
presented in Table .
The use of biological plows to rehabilitate
compacted forest soils has not been investigated.
However, studies that would be of obvious interest
include evaluating root thickness of forest trees and
shrub species in British Columbia compared to root
thicknesses for species already tested, and using
biological plows to restore severely disturbed sites,
and as additional treatments to stabilize and
maintain soil structure after conventional tillage.
Native shrubs A native shrub program was initiated
in  by the B.C. Ministry of Forests under Project
E.P. . Over  native British Columbia tree and
shrub species were propagated, a propagation manual
was written, and field trials were established between
 and  before funding for the program was
discontinued. The results of this work appear in
several publications including Marchant and Sherlock (), Homoky (, ), and Carr ().
Native woody species are useful in rehabilitation
because they provide deep rooting and long-term
erosion control, although it takes longer for the surface cover to develop than with grasses and legumes.
However, on sites where immediate erosion control is
not a major concern, or where other measures have
been taken to control surface erosion in the short
term, they may provide a method for re-establishing
ecosystem characteristics similar to those of
undisturbed areas. Marchant and Sherlock ()
recommended that the selection criteria for species
be based on the biogeoclimatic subzones. They
presented  criteria that affected rehabilitation
success, which were subsequently grouped into
three major criteria:
. known biological and ecological characteristics of
each candidate species;
. performance in field trials; and
. performance in propagation trials.
Nitrogen-fixing species The potential benefits of
establishing nitrogen-fixing species to restore
nutrients on rehabilitated sites has been known for
some time, but few studies have quantified the
32
nitrogen inputs to rehabilitated soils from seeded
legumes or nitrogen-fixing shrubs. For coastal sites,
considerable information is available about the effects of red alder on soil properties and the potential
rates of nitrogen fixation (e.g., Tarrant et al. ).
For interior sites, use of legumes was investigated in
the Prince Rupert Forest Region on rehabilitated
landings (Marsland ), on blade scarified areas
(Coates et al. ), and on cutovers subject to
various forms of site preparation (Trowbridge and
Holl ). This work has successfully established
species such as birdsfoot trefoil on landings, and
alsike clover on blade-scarified areas. Establishing
legumes to enhance site nitrogen levels resulted in
increased foliar nitrogen levels for lodgepole pine,
but height growth after four years was not affected.
The establishment, growth, and development of
grey alder (Alnus incana) and lupine (Lupinus spp.)
on low-productivity sites in northern Sweden were
studied by Huss-Dannell and Lindmark (). The
sandy soils had been subjected to repeated severe
fires, harvesting, or windthrow, and had thin mor
humus layers, low soil organic matter, pH values near
., and low soil nitrogen. Survival of alder after six
years ranged from very good (–%) to poor (–
%), with better performance indicated for warmer
sites. Survival and growth of alder was similar for
nursery-raised and locally transplanted seedlings, and
for fenced and unfenced plots. Lupinus nootkatensis
was the most successful lupine, either established
from seed or by planting nursery-grown stock.
Liming and scarifying the site improved the success
of sown lupines. A companion experiment, in which
 kg/ha per year of alder leaves were added to the
soil (which represents approximately the amount
expected from established stands of alder or lupine)
showed that the forest floor achieved the properties
of more productive sites after only six years.
For restoration purposes, the authors concluded
that lupin seemed hardier than alder. Lupines are
easier and cheaper to establish because they are sown
from seed, and their high reproductive potential is
useful when complete site occupancy after about four
years is desired. The authors noted, however, that
lupines are toxic to cattle, and that they required
inoculation with Rhizobium. Huss-Dannell and
Lindmark () considered alder as an effective
species for soil restoration.
One strategy for using nitrogen-fixing species
involves planting conifers before lupines are sown.
This is so that the trees do not face severe competition in the first three years after planting; after that
they are likely well established, and begin to shade the
lupine out. When alder is chosen to restore soils,
conifers may be planted at the same time because the
alder does not shade the ground as much as lupine.
Other potential sites of nitrogen fixation in forest
ecosystems is the subject of recent studies. Nitrogen
fixation associated with coarse woody debris
(Graham et al. ) and in the rhizosphere of pine
trees (Bormann et al. ) are of interest as potential
nitrogen sources on degraded soils.
.. Information gaps: research needs
Establishing a productive second-growth forest is the
ultimate test of success for rehabilitation projects.
The renewed focus on rehabilitating soils for conifer
productivity suggests that investment is necessary
in revegetation research. As described previously
(Figure ), the amount of ongoing operational rehabilitation work in British Columbia is increasing
rapidly and the need for information is acute.
The following knowledge gaps were identified.
Testing conifer and hardwood species and stock
types for rehabilitated sites and evaluating
beneficial micro-organisms The range of species
and stock types suitable for use on rehabilitated sites
needs expanding. Large conifer stock types have been
recommended for coastal areas (Hickling et al. )
and in the interior different stock types have shown
varying rates of early growth on degraded sites
(Arnott et al. ). In addition, the potential benefits
of using biological inoculants to enhance rhizosphere
populations of beneficial organisms should be
investigated. Initially, a program of operational
monitoring for survival and early growth of a range
of stock types and species seems a practical approach.
The efforts should expand if an unacceptable rate of
plantation success on rehabilitated sites is observed.
Native plants Native plants can provide many
benefits, but their potential is only starting to
be realized. For example, native species that are
unpalatable to cattle could be used in areas where
cattle damage to crop trees is a problem. The loss
of the B.C. Ministry of Forests native shrub program
in the s has resulted in a significant information
gap at a time when the demand is great. Native species could be used as biological plows, or otherwise
developed as low-cost alternatives for rehabilitating
degraded sites. One research approach would involve
screening of appropriate species and varieties for
desirable characteristics.
Effect of agronomic species on forest
ecosystems Some concern exists that agronomic
grasses and legumes used for rehabilitation could
displace native species. Trials show that grass and
legume seed mixes can control competing vegetation
on cutovers (Steen and Smith ). However, others
feel that native plants quickly invade seeded areas and
restore the natural ecosystem. Once crown closure
occurs, agronomic species can lose their competitive
advantage because of shading. Also, the chances of
agronomic plants displacing native species increase in
dry environments, especially in the southern interior,
and dry sites in other areas where the native vegetation
is dominated by grasses and shrubs. A retrospective
approach could provide useful information on these
topics for select ecosystems in diverse regions of
British Columbia. These studies could, for example,
evaluate vegetation succession on historic sites where
hydroseeding was used to control erosion along road
rights-of-way.
Role of grasses in forest soil rehabilitation Traditionally, grasses have played a dominant role in
road and landing rehabilitation. That role may need
re-examining in light of the information now
available about moisture competition, potential
allelopathic effects on tree seedlings (Amaranthus
et al. ), and cattle trampling damage to seedlings.
Other studies (Walker et al. ) show that seedlings
and herbaceous cover can co-exist on surface-mined
land. The range of site types where competition
between trees and seeded ground cover hinders
rehabilitation success should be determined.
Research could initially focus on evaluating methods
for establishing trees on sites previously tilled and
seeded to grass. In addition, techniques to prevent
cattle trampling damage to seedlings on rehabilitated
sites should be developed further.
. Soil Amelioration: Fertilizers, Amendments,
and Mulches
On many degraded sites, soils are deficient in organic
matter and nutrients, and even after tillage may have
unstable pore structure, low available water retention,
and poor nutrient-retention characteristics. Various
strategies can address limitations on individual sites,
including fertilizer application, application of organic
residues, and mulching.
33
.. Fertilizers
Fertilizer is used in rehabilitation work to enhance
plant establishment, accelerate plant growth, and
maintain productivity (U.S. Department of Agriculture ). Fertilizer use is recommended for erosion
control work and the fertilizer is frequently blended
with the seed mixture in hydroseeding operations
(Beese et al. ). The purpose of initial applications
is to enhance plant establishment and promote early
growth. Subsequent applications are recommended
to maintain the cover of seeded grasses and legumes
(Carr ).
Fertilizing to meet the nutritional demands of tree
seedlings on rehabilitated sites may involve application at time of planting to enhance early growth of
seedlings located on rehabilitated roads (Hickling et
al. ). Broadcast, or single-tree, fertilization after
establishment is an approach used if vegetation
competition is not a problem. For subsequent
fertilizer applications, foliar testing can reliably
indicate tree nutrient status, and should occur before
fertilizing to improve the growth of established trees
(Ballard and Carter ).
While some fertilizer is often required to establish
a productive forest on rehabilitated sites, the possibility
of applying too much fertilizer should be considered.
Fertilizer should not be used alone as a means to reestablish site nutrient pools. Unless vegetation or a
nutrient-demanding organic amendment such as
wood waste is present to utilize the nutrients, much
of the added fertilizer (especially in the form of NO–
and K+) will be lost either to the atmosphere or in
drainage water. Over-fertilization does not affect local
areas alone; the global consequences of profligate
fertilizer use were described by Vitousek ().
.. Nutrient-poor residues
Organic amendments with low nutrient content are
available in all areas of British Columbia, and are perhaps the only practical material to amend soil organic
matter on rehabilitation projects in remote areas.
Depending on the source of the material, C:N ratios
can range from : or higher for wood chips or
fresh sawdust (Arends and Donkersloot-Shouq ),
to : for primary paper mill sludge (Zhang et al.
). Some residues have relatively low values such
as : and : for brown and green needles, respectively (Pluth et al. ). Various organic materials
have been used as soil conditioners (Saini and
Hughes ; Graves and Carpenter ; Schuman
34
and Sedbrook ; Olayinka and Adebayo ).
Various methods are used to process, spread, and
incorporate materials into soil. Woody materials with
high C:N ratios can immobilize soil nitrogen as the
added residue decomposes. Nitrogen fertilizer, sewage
sludge, manure, or other nutrient-rich materials are
usually added with woody residues to prevent nitrogen deficiency in plants.
Saini and Hughes () added  t/ha of shredded
tree bark (C:N = :) to clay loam potato soils in
New Brunswick, along with  kg/ha N. The shredded
material was spread with a manure spreader and
disced into the surface. The bulk density declined to
 kg/m from , and increases were observed for
aggregate stability (.% compared to .), oxygen
diffusion rate (. g /cm compared to .), water
percolation rate (– times faster), and potato
yields (. t/ha compared to .). Assuming a bulk
density of approximately  kg/m for the shredded
bark, the application rate represented a -cm layer.
Ground or chipped woody residues can potentially
improve soil structure and prevent resettling in
fine-textured soils. Schuman and Sedbrook ()
investigated the application of sawmill residues,
which consisted of fresh wood chips, sawdust, and
bark, to abandoned bentonite spoils at rates of , ,
and  t/ha (dry weight basis). Fertilizer was also
added at a rate of , , and  kg N/ha for the
three treatments. This reduced the C:N to :.
Wheatgrasses and other forage species were
established from seed. Over four years, forage
production averaged , , and  kg/ha for the
three treatments. Average soil moisture content was
twice as high in the plots receiving wood waste as in
the controls. Wood waste improved productivity of
these clay soils, and the medium application rate of
 t/ha (a .-cm layer, assuming a bulk density of
 kg/m) achieved a large part of the gain.
Sawdust (initial C:N of :), supplemented with
either inorganic nitrogen (final C:N of :), or dairy
manure (final C:N of :) was evaluated as an
amendment to improve the organic matter content
of a sandy loam soil (Olayinka and Adebayo ).
Two application methods were used: incorporation
and mulching. For maize grown in a greenhouse,
incorporating unamended sawdust reduced dry
matter yield (. g per pot) compared to the control
(. g per pot), but amended sawdust improved
growth (.–. g per pot). In the field experiment,
the amount of amendment added was substantially
lower ( t/ha versus equivalent of  t/ha estimated
for the greenhouse experiment). Untreated sawdust,
whether incorporated to surface soil or applied as a
mulch, reduced dry matter yield (. t/ha) relative to
the control (. t/ha). Amended sawdust improved
growth in the field (.–. t/ha).
These results illustrate the potential for improving
plant growth when woody amendments are used in
rehabilitation work. The use of harvesting residues
and sawmill wastes will likely be encouraged in the
near future, particularly as sawmills adjust to the
loss of burning permits, and seek alternative means
for disposal.
Although a considerable body of knowledge from
other areas is available, applying woody residues to
degraded forest soils is still experimental. The
principles in British Columbia are similar to those
elsewhere, but more experience is needed with specific
materials in local situations so that potential benefits
can be realized (e.g., increased soil productivity,
appropriate use of a waste material), while minimizing environmental consequences (e.g., reduced
site productivity because of over-application or
inappropriate fertilizer regime, toxic leachate
production because of over-application, or fertilizer
leaching because of inappropriate fertilizer regime).
Operational experimentation with these residues in
various situations should be encouraged.
.. Nutrient-rich amendments
Using nutrient-rich byproducts, such as sewage sludge
(McNab and Berry ; Simpson ), urban refuse
(Roldan and Albaladejo ), paper mill biological
waste (Zhang et al. ), and manure (Aoyama and
Nozawa ; Robertson and Morgan ), to improve soil physical properties and nutrient status is
well documented. For many of these materials,
composting before applying helps to control detrimental side effects, such as the introduction of plant
pathogens, weeds, phytotoxic substances, or odors.
A wealth of recent literature exists on the processes
involved in composting and the potential uses of
composts and other nitrogen-rich wastes (e.g.,
Kayhanian and Tchobanoglous ), but local experience still needs developing in British Columbia.
McNab and Berry () described experimental
results in which three species of pine were planted on
a site denuded by air pollution, and subsequently
ameliorated with  t/ha of dried sewage sludge. All
three species of pine grew faster in the presence of
sewage sludge than when inorganic nitrogen was
applied at  kg/ha, a rate intended to match the
one-year release from the sludge. Additional release
of nitrogen (i.e., higher than  kg/ha) from the
sludge might be responsible for the improved
response.
A trial in the Prince George Forest Region
(Kranabetter and Bulmer ) showed that the
particle size of wood waste had a significant effect on
the composting process. Sawdust helped to maintain
an open structure in a well-aerated compost pile that
maintain high temperatures over an eight-week
period. Rapid decomposition occurred initially in a
compost pile with pulp fibre waste and sewage sludge,
but decomposition slowed after three weeks because
of poor aeration. In the sawdust compost after six
weeks, nitrate was the dominant form of mineral
nitrogen, while ammonium was the dominant form
in the pulp fibre compost. Some unexpected results
can occur when using composts and other materials.
Applying high rates of ( t/ha) of urban refuse
(C:N = ) to degraded soils in Spain resulted in
reduced formation of mycorrhizae on pine (Roldan
and Albaladejo ). The major species of fungi
colonizing seedling roots was also affected by changing application rates. A moderate rate ( t/ha)
provided the best results for inoculated seedlings.
The Greater Vancouver Regional District and
other communities in British Columbia have gained
experience in recent years in using sewage sludge, fish
wastes, and other materials to improve forest sites
and to reclaim surface mine sites. Although nutrientrich residues will probably improve soil conditions
and tree growth, many of the field sites that need
rehabilitating are far removed from the urban
centres where these materials are usually produced.
Transport costs are often so high that their use is
justified only on sites in close proximity to the source
of the material.
.. Mulches
Mulches applied to the soil surface control erosion,
preserve water, and moderate soil temperatures. In
hydroseeding for erosion control, thin mulches are
used to stabilize soil surfaces and enhance the establishment of grasses and legumes. Thicker mulches
(approximating the thickness of forest floors on similar sites in the area) derived from logging residues or
other materials may have a unique application to
certain forest soil rehabilitation projects.
35
Graves and Carpenter () showed that as mulch
thickness varied through -, .-, -, and -cm increments, soil moisture content changed significantly
with each increment, while soil temperature changes
were not significant for mulch thickness greater than
. cm. Applying a .-cm layer of bark mulch
improved the stocking levels obtained for three
deciduous tree species established from seed,
compared to control treatments with no bark mulch.
Survival of planted bareroot seedlings was also higher
for plots with either a . or  cm bark mulch layer.
Average leaf water potential for European alder
during the growing season was reduced by applying
the bark mulch, compared to plots with no mulch or
with grasses and herbs.
Although some results show that mulch alone is
ineffective for rapidly improving mineral soil physical
properties (Donnelly and Shane ), mulches are
effective in combination with tillage treatments to
protect soil structure (Luce ). Mulches derived
from woody materials (branches, needles, bark),
which resist decomposition, will probably provide
longer-term effects than material such as straw,
which decomposes rapidly.
.. Information gaps: research needs
Use of woody residues in soil rehabilitation Despite
the potential benefits of using woody residues to
rehabilitate soils, their use is not widespread in
British Columbia. This partly reflects the logistical
problems associated with preparing and delivering
amendments to field sites, but also reflects:
• a poor understanding of their potential benefits;
and
• concern about the risk of degrading site
productivity through inappropriate use.
However, some rehabilitation practitioners are
gaining local experience with their use, and a research
effort is justified to determine the effects of these
materials on productivity. Also, more information
is needed on the specific aspects of using these
amendments, such as identifying potential sources,
developing methods for transport, and monitoring to
document their effects in various ecosystems. Because
these materials alter the soil physical properties as
well as nutrient cycling, their effects should be
evaluated in field trials.
Use of nutrient-rich residues in soil rehabilitation
A large body of knowledge is available concerning
processes of composting and the detailed
36
transformation of organic matter within compost
piles. Sufficient information probably exists (e.g.,
Kayhanian and Tchobanoglous ) for the
successful composting of most materials likely
used to rehabilitate forest soils.
The results of Olayinka and Adebayo ()
illustrate the hazards of relying on greenhouse
experiments to predict field performance. Field
performance of nutrient-poor amendments was
better than would have been predicted from the pot
trial, likely reflecting the effect of residues on soil
organic matter and soil water retention capacity.
Research on the use of nutrient-rich amendments
for soil rehabilitation should focus on high-value
lands close to the source of the waste. Many potential
amendments derived from wastes represent a
problem for the owner of the waste, so research can
also address waste management concerns as well as
environmental restoration.
Use of mulches Evaluating the benefits associated
with the use of mulches should be considered when
developing treatments for field studies of
rehabilitation.
6 CONCLUSION
The primary goal of soil rehabilitation efforts is to
improve soil conditions and establish productive forests on degraded lands. Research is needed to enhance
those efforts by improving our knowledge of how soil
properties and processes affect productivity on rehabilitated soils, and how rehabilitation techniques can
improve soil conditions and tree growth.
Soil rehabilitation research should be focused at
the incremental and strategic research levels (Binkley
and Watts ). Incremental research is required to
provide land managers and rehabilitation practitioners
with information about problems that affect the
success of rehabilitation projects. Strategic research
is required to provide higher levels of management
with information about the benefits associated with
soil rehabilitation investments made in response to
the Forest Practices Code, and the role of soil rehabilitation in maintaining the productivity of our forests.
The following information gaps should be addressed
to meet the information needs of operational
rehabilitation projects that are currently being
implemented by Forest Renewal BC, which are
therefore considered incremental research (Binkley
and Watts ).
• Developing and calibrating short-term tillage
evaluation techniques.
• Determining cost-effective construction methods
to conserve and replace topsoil.
• Testing conifer and hardwood species and stock
types for rehabilitated sites, and evaluating beneficial micro-organisms.
• Using woody residues in soil rehabilitation.
• Using nutrient-rich residues in soil rehabilitation.
• Using mulches in soil rehabilitation.
The following information gaps should be addressed to meet the information needs of forest
management. Results of these projects, which fall
under the category of strategic research (Binkley
and Watts ), could be expected within three to
five years.
• Evaluating the long-term success of various tillage
strategies for various site types.
• Quantifying the benefits of topsoil replacement,
compared to other methods of restoring soil structure and nutrient cycles.
• Investigating biological processes in rehabilitated
surface soils, and evaluating soil quality.
• Evaluating conifer growth on recontoured roads
and skid trails.
• Using native plants in rehabilitation.
• Using agronomic species in forest ecosystems.
• Using grasses in forest site rehabilitation.
37
REFERENCES
Allison, F.E. . Soil aggregation: some facts and
fallacies as seen by a microbiologist. Soil Sci.
:–.
Amaranthus, M.P. and D.A. Perry. . Effect of
soil transfer on ectomycorrhiza formation,
survival, and growth of conifer seedlings on
old, non-forested clearcuts. Can. J. For. Res.
:–.
Amaranthus, M.P., J.M. Trappe, and D.A. Perry. .
Soil moisture, native revegetation, and Pinus
lambertiana seedling survival, growth, and
mycorrhiza formation after wildfire and grass
seeding. Restoration Ecology, Sept. :–.
Andrus, C.W. . Tilling compacted forest soils
following ground-based logging in Oregon.
MSc thesis. Oreg. State Univ., Corvallis, Oreg.
Andrus, C.W. and H.A. Froehlich. . An evaluation
of four implements used to till compacted forest
soils in the Pacific northwest. For. Res. Lab, Oreg.
State Univ., Corvallis, Oreg. Res. Bull. No. .
Aoyama, M. and T. Nozawa. . Microbial biomass
nitrogen and mineralization-immobilization
processes of nitrogen in soils inoculated with
various organic materials. Soil Sci. Plant Nutr.
:–.
Arends, G.J. and S.S. Donkersloot-Shouq. . An
overview of possible uses of sawdust. Tech.
Devel., Devel. Countries, Cent. Int. Coop.
Approp. Tech., Delft, Netherlands.
Armson, K.A. . Tree rooting characteristics. In
Proc. workshop on reconstruction of forest soils
in reclamation. P.F. Ziemkiewicz, S.K. Takyi, and
H. Regier (editors). Alta. Land Conserv. Reclam.
Coun., Edmonton, Alta. Report RRTAC –.
pp. –.
Arnott, J.T., W.W. Carr, and A.C. Waines. . Establishing forest cover on winter landings in the
central interior of British Columbia. For. Chron.
:–.
Atwell, B.J. . Response of roots to mechanical
impedance. Environ. Exp. Bot. :–.
Ballard, T.M. . Tree nutrition. In Proc. workshop
on reconstruction of forest soils in reclamation.
P.F. Ziemkiewicz, S.K. Takyi, and H. Regier
(editors). Alta. Land Conserv. Reclam. Coun.,
Edmonton, Alta. Report RRTAC –. pp. –.
38
Ballard, T.M. and R. Carter. . Evaluating forest
stand nutrient status. B.C. Min. For., Victoria,
B.C. Land Manage. Rep. No. .
Ballard, T.M. and B.C. Hawkes. . Effects of burning and mechanical site preparation on growth
and nutrition of planted white spruce. Can. For.
Serv., Victoria, B.C. Inf. Rep. BC-X-.
Bartoli, F., G. Burtin, R. Philippy, and F. Gras. .
Influence of fir root zone on soil structure in a
 m forest transect: the fractal approach.
Geoderma :–.
Barzegar, A.B., J.M. Oades, P. Rengasamy, and R.S.
Murray. . Tensile strength of dry, remoulded
soils as affected by properties of the clay fraction.
Geoderma :–.
Bathke, G.R., D.K. Cassel, W.L. Hargrove, and P.M. Porter. . Modification of soil physical properties
and root growth response. Soil Sci. :–.
Bauhus, J. and K.J. Meiwes. . Potential use of
plant residue wastes in forests of northwestern
Germany. For. Ecol. Manage. :–.
Beese, W., T. Rollerson, and R.N. Green. . Forest
site rehabilitation for coastal British Columbia
(Interim methods). B.C. Min. Environ., Lands
and Parks and B.C. Min. For., Victoria, B.C.
Watershed Restoration Tech. Circ. No. .
Binkley, C.S. and S.B. Watts. . The status of forestry research in British Columbia. For. Can. and
B.C. Min. For., Victoria, B.C. FRDA Rep. No. .
Blake, G.R. and K.H. Hartge. . Bulk density. In
Methods of soil analysis Part . A. Klute (editor).
Am. Soc. Agron., Madison, Wis. pp. –.
Borchers, J.G. and D.A. Perry. . The influence of
soil texture and aggregation on carbon and nitrogen dynamics in southwest Oregon forests
and clearcuts. Can. J. For. Res. :–.
Bormann, B.T., F.H. Bormann, W.B. Bowden, R.S.
Pierce, S.P. Hamburg, D. Wang, M.C. Snyder,
C.Y. Li, and R.C. Ingersoll. . Rapid N fixation in pines, alder, and locust: evidence from the
sandbox ecosystem study. Ecology :–.
Brady, N.C. . The nature and properties of soils.
 ed. Prentice-Hall, Upper Saddle River, N.J.
British Columbia Ministry of Forests. . Growth
intercept method for silviculture surveys. Silv.
Prac. Branch, Victoria, B.C.
Campbell, R.B., W.J. Busscher, O.H. Beale, and R.E.
Sojka. . Soil profile modification and cotton
production. In Proc. Beltwide Cotton Prod. Res.
Conf., Nat. Cotton Coun. Am., Memphis, Tenn.
pp. –
Cariboo Forest Region. . Cariboo Region operational guidelines. B.C. Min. For. Policy Reference
Vol. III PRO , File –.
Carpenter, S.B. and D.J. Albers. . Establishing
European alder seedlings in fescue covered
surface mine spoil. S. J. Appl. For. :–.
Carr, W.W. . Handbook for forest roadside surface erosion control. B.C. Min. For., Victoria, B.C.
Land Manage. Rep. No. .
.␣ . Access-road related degradation problems in forestry. Paper presented at Soil Degradation Workshop. Harrison Hot Springs, Feb. –,
. Agric. Can. Res. Stn., Vancouver, B.C.
.␣ . Watershed rehabilitation options for
disturbed slopes on the Queen Charlotte Islands.
B.C. Min. For., Victoria, B.C. Land Manage.
Rep. No. .
.␣ a. Restoring productivity on degraded
forest soils: two case studies. For. Can. and B.C.
Min. For., Victoria, B.C. FRDA Rep. No. .
.␣ b. The effect of landing construction
on some forest soil properties: a case study. For.
Can. and B.C. Min. For., Victoria, B.C. FRDA
Rep. No. .
.␣ a. Nutritional and soil compaction
aspects of establishing forest cover on winter
landings in the Fort St. James area. For. Can.
and B.C. Min. For., Victoria, B.C. FRDA Rep.
No. .
.␣ b. The rehabilitation of degraded forest
soil in British Columbia: an overview. In Degradation of forested land: forest soils at risk. Proc.
th B.C. Soil Sci. Workshop, Feb. . G.W. Still
and J.D. Lousier (editors). B.C. Min. For., Victoria, B.C. Land Manage. Rep. No. . pp. –.
Chatwin, S.C., D.E. Howes, J.W. Schwab, and D.N.
Swanston. . A guide for the management of
landslide prone terrain in the Pacific Northwest.
nd ed. B.C. Min. For., Victoria, B.C. Land Manage. Handb. No. .
Coates, K.D., M.J. Douglas, J.W. Schwab, and W.
Bergerud. . Grass and legume seeding on a
scarified coastal alluvial site in northwestern
British Columbia: response of native non-crop
vegetation and planted Sitka spruce (Picea
sitchensis (Bong.) Carr.) seedlings. New For.
:–.
Colinas, C., R. Molina, J. Trappe, and D. Perry. .
Ectomycorrhizas and rhizosphere microorganisms of seedlings of Pseudotsuga menziesii
(Mirb.) Franco planted on a degraded site and
inoculated with forest soils pretreated with
selective biocides. New Phytol. :–.
Corns, I.G.W. . Compaction of forest soils and
effects on coniferous seedling growth on forest
soils in the Alberta foothills. Can. J. For. Res.
:–.
Culley, J.L.B. . Density and compressibility. In Soil
sampling and methods of analysis. M.R. Carter
(editor). Lewis, Boca Raton, Fla. pp. –.
Daddow, R.L. and G.E. Warrington. . Growthlimiting soil bulk densities as influenced by soil
texture. Watershed Systems Develop. Group, U.S.
Dep. Agric. For. Serv., Fort Collins, Colo. Rep.
WSDG-TN-.
daSilva, A.P., B.D. Kay, and E. Perfect. . Characterization of the least limiting water range of
soils. Soil Sci. Soc. Am. J. :–.
Davis S. . Effectiveness of a winged subsoiler in
ameliorating a compacted clayey forest soil. West.
J. Appl. For. :–.
Day, S.D. and N.L. Bassuk. . A review of the effects of soil compaction and ameliorative treatments on landscape trees. J. Arbor. :–.
DeLong, D.L., P.M. Osberg, C. Clarke, and W. Hayes.
. Trial of the Tilth winged subsoiler on
naturally compact soils in north central British
Columbia. FERIC, Vancouver, B.C. Tech. Note
TN-.
Dick, R.P., D.D. Myrold, and E.A. Kerle. . Microbial biomass and soil enzyme activities in compacted and rehabilitated skid trail soils. Soil Sci.
Soc. Am. J. :–.
Donnelly, J.R. and J.B. Shane. . Forest ecosystem
responses to artificially induced soil compaction.
. Soil physical properties and tree diameter
growth. Can. J. For. Res. :–.
Doran, J.W. and T.B. Parkin. . Defining and
assessing soil quality. In Defining soil quality
for a sustainable environment. J.W. Doran,
D.F. Bezdicek, D.C. Coleman and B.A. Stewart.
(editors). Soil Sci. Soc. Am., Madison, Wis. Spec.
Publ. No. .
39
Dunker, R.E., C.L. Hooks, S.L. Vance, and R.G.
Darmody. . Deep tillage effects on compacted
surface-mined land. Soil Sci. Soc. Am. J. :–.
Dykstra, P.R. and M. Curran. . Skid road rehabilitation in the Nelson Forest Region: tech.
rep. to Dec. . Nelson For. Reg., B.C. Min.
For., Nelson, B.C. Unpubl. draft.
Ellen, G. . Clearwater Forest District reclamation/
revegetation guidelines. Training package from
March  Clearwater training session, April .
Eubanks, S.T. . Full restoration method for closing spur roads. J. For. :–.
Farrish, K.W. . Effects of soil loss on emergence
and growth of loblolly pine. J. Soil Water
Conserv. :–.
Fewer, O. . Report on  landing and skid trail
rehabilitation project: Kalum Forest District. B.C.
Min. For., Terrace, B.C.
Froehlich H.A. and D.H. McNabb. . Minimizing
soil compaction in Pacific Northwest forests. In
Forest soils and treatment impacts. Proc. th N.
Am. For. Soils Conf. E.L. Stone (editor). Dept.
Forestry, Univ. Tenn., Knoxville, Tenn. pp. –.
Froehlich, H.A., D.W.R. Miles, and R.W. Robbins. .
Soil bulk density recovery on compacted skid trails
in central Idaho. Soil Sci. Soc. Am. J. :–.
Gent, J.A. Jr., R. Ballard, A.E. Hassan, and D.K. Cassel.
. Impact of harvesting and site preparation
on physical properties of Piedmont forest soils.
Soil Sci. Soc. Am. J. :–.
Gosz, J.R. and F.M. Fisher. . Microbial responses
to ecosystem fluctuations: influence of clearcutting on selected microbial processes in forest
soils. In Current perspectives in microbial ecology. Proc. rd Int. Symp. Microbial Ecology, Am.
Soc. Microb. Ecol., Washington, D.C. M.J. Klug
and C.A. Reddy (editors). pp. –.
Grable, A.R. . Effects of compaction on content
and transmission of air in soils. In Compaction
of agricultural soils. Am. Soc. Agric. Eng., St.
Josephs, Mich. Monogr. No. . K.K. Barnes (editor). pp. –.
Graham, R.T., A.E. Harvey, M.F. Jurgensen, T.B. Jain,
J.R. Tonn, and D.S. Page-Dumbrose. . Managing coarse woody debris in forests of the Rocky
Mountains. U.S. Dep. Agric. For. Serv., Ogden
Utah. Res. Pap. INT-RP-.
Graves, D.H. and S.B. Carpenter. . Use of hardwood bark in stripmine reclamation. In Organic
and fuel uses for bark and wood residues. Annu.
40
Meet. For. Products Res. Soc., Boston, Mass. R.C.
Allen (editor). For. Products Res. Soc., Madison,
Wis. p. .
Greacen, E.L., K.P. Barley, and D.A. Farrell. . The
mechanics of root growth in soils with particular
reference to the implications for root distribution. In Root growth. W.J. Whittington (editor).
Butterworths, London, U.K. pp. –.
Greacen, E.L. and R. Sands. . Compaction of forest soils: a review. Aust. J. Soil Res. :–.
Hall, P. . Skid site rehabilitation. Logging Ind. Res.
Org., Rotorura, N.Z. LIRO Rep. Vol.  ().
Halvorson, G.A., S.W. Melsted, S.A. Schroeder, C.M.
Smith, and M.W. Pole. . Topsoil and subsoil
thickness requirements for reclamation of nonsodic mined land. Soil Sci. Soc. Am. J. :–.
Heilman, P.E. . Effect of surface treatment and
interplanting of shrub alder on growth of Douglasfir on coal spoils. J. Environ. Quality :–.
.␣ . Growth of Douglas-fir and red alder on
coal spoils in western Washington. Soil Sci. Soc.
Am. J. :–.
Henderson, C.W.L. . Lupine as a biological
plough: evidence for, and effects on wheat
growth and yield. Aust. J. Exp. Agric. :–.
Hickling, J., R. Scagell, and J. Charles. . Seedling
survival and productivity on rehabilitated logging
roads: year two results. Contract report prepared
for For. Sci. Sect., B.C. Min. For., Nanaimo, B.C.
Hillel, D. . Applications of soil physics. Academic
Press, New York, N.Y.
.␣ . Introduction to soil physics. Academic
Press, New York, N.Y.
Homoky, S. . Research on grasses, legumes and
shrubs for erosion control (E.P. .). B.C. Min.
For., Victoria, B.C. Res. Rep. RR-HQ.
.␣ . Research on grasses, legumes and
shrubs for erosion control (E.P. .). B.C. Min.
For., Victoria, B.C. Res. Rep. RR-HQ.
Hudson, B.D. . Soil organic matter and available
water capacity. J. Soil Water Conserv. :–.
Huss-Dannell, K. and J.E. Lindmark. . Growth of
nitrogen-fixing Alnus incana and Lupinus spp. for
restoration of degenerated forest soil in northern
Sweden. Studia Forestalia Suecica :–.
Itami, K. and K. Kyuma. . Dispersion behavior of
soils from reclaimed lands with poor soil physical
properties and their characteristics with special
reference to clay mineralogy. Soil Sci. Plant Nutr.
:–.
Jones, C.A. . Effect of soil texture on critical bulk
densities for root growth. Soil Sci. Soc. Am. J.
:–.
Kayhanian, M. and G. Tchobanoglous. . Computation of C/N ratios for various organic fractions.
Biocycle : –.
Klinka, K., Q. Wang, and G.J. Kayahara. . Quantitative characterization of nutrient regimes in
some boreal forest soils. Can. J. Soil Sci. :–.
Kranabetter, J.M. and C.E. Bulmer. . Composting
trial using pulp fiber waste and municipal sewage
sludge. Report prepared for For. Sci., Prince George
For. Reg., B.C. Min. For., Prince George, B.C.
Kranabetter, J.M. and M. Osberg. . Landing
reclamation trials in the Prince George Region.
Report prepared for For. Sci., Prince George For.
Reg., B.C. Min. For., Prince George, B.C.
Kranabetter, J.M. and W.T. Denham. . Soil properties related to lodgepole pine productivity on
reclaimed landings. Report prepared for For. Sci.,
Prince George For. Reg., B.C. Min. For., Prince
George, B.C.
Kranabetter, J.M., H.B. Massicotte, and L. Tackaberry.
. Mycorrhizal limitations of reclaimed forest
soils: a trial using paper birch and soil inoculum.
For. Sci., Prince Rupert For. Reg., B.C. Min. For.,
Smithers, B.C. Unpubl. rep.
Lavkulich, L.M. and K. Valentine (editors). . Soil
landscapes of British Columbia. B.C. Min.
Environ., Victoria, B.C.
Lawrie, D., R.K. Krag, P. Sanborn, and C. Bulmer.
. Reclamation of compacted fine-textured
soils on the Aleza Lake Research Forest using a
winged subsoiler and a hydraulic excavator.
FERIC, Vancouver, B.C. Tech. Note TN-.
Lewis, T. . Developing timber harvesting prescriptions to minimize site degradation. B.C. Min.
For., Victoria, B.C. Land Manage. Rep. No. .
Linn, D.M. and J.W. Doran. . Effect of waterfilled pore space on carbon dioxide and nitrous
oxide production in tilled and nontilled soils.
Soil Sci. Soc. Am. J. :–.
Lousier, J.D. . Impacts of forest harvesting and
regeneration on forest soils. B.C. Min. For.,
Victoria, B.C. Land Manage. Rep. No. .
Luce, C.H. . Effectiveness of road ripping in
restoring infiltration capacity of forest roads.
Restoration Ecology :–.
McBride, R.A. . Soil consistency limits. In
Soil sampling and methods of analysis.
M.R. Carter (editor). Lewis, Boca Raton, Fla.
pp. –.
McKee, W.H., G.E. Hatchell, and A.E. Tiarks. . Managing site damage from logging. U.S. Dep. Agric.
For. Serv., Asheville, N.C. Gen. Tech. Rep. SE-.
McNab, W.H. and C.R. Berry. . Distribution of
aboveground biomass in three pine species planted
on a devastated site amended with sewage sludge
or inorganic fertilizer. For. Sci. :–.
McNabb, D.H. . Tillage of compacted haul roads
and landings in the boreal forests of Alberta,
Canada. For. Ecol. Manage. :–.
McNabb, D.H. and S.D. Hobbs. . Shallow tillage
fails to increase -year growth of ponderosa pine
seedlings. Northwest Sci. :–.
Marchant, C. and J. Sherlock. . A guide to the
selection and propagation of some native woody
species for land reclamation in British Columbia.
B.C. Min. For., Victoria, B.C. Res. Rep. No.
RR-HQ.
Marsland M. . Review of the Kispiox and Kalum
landing and skid road rehabilitation program.
Kispiox Dist., B.C. Min. For., Intern. Rep.
Materachera, S.A., A.R. Dexter, and A.M. Alston. .
Penetration of very strong soils by seedling roots
of different plant species. Plant and Soil :–.
Materachera, S.A., A.M. Alston, J.M. Kirby, and A.R.
Dexter. . Field evaluation of laboratory techniques for predicting the ability of roots to penetrate strong soil and of the influence of roots on
water sorptivity. Plant and Soil :–.
Mead, D.J., A.G.D. Whyte, R.C. Woollens, and P.N.
Beets. . Designing long-term experiments to
study harvesting impacts. In Long-term field
trials to assess environmental impacts of harvesting. Proc. IEA/TA Workshop, Feb. . W.J.
Dyck and C.A. Mees (editors). N.Z. For. Res. Inst.
Bull. No. . pp. –.
Miles, D.W.R. and H.A. Froehlich. . Objectives
and evaluation of forest tillage. In Degradation
of forested land: forest soils at risk. Proc. th
B.C. Soil Sci. Workshop, Feb. . G.W. Still and
J.D. Lousier (editors). B.C. Min. For., Victoria,
B.C. Land Manage. Rep. No. . pp. –.
Miles, D.W.R., F.J. Swanson, and C.T. Youngberg.
. Effects of landslide erosion on subsequent
Douglas-fir growth and stocking levels in the
western Cascades, Oregon. Soil Sci. Soc. Am. J.
:–.
Miller, R.M. and J.D. Jastrow. . Hierarchy of root
41
and mycorrhizal fungal interactions with soil
aggregation. Soil Biol. Biochem. :–.
Miller, R.E., W. Scott, and J. Hazard. . Soil
compaction and conifer growth after tractor
yarding at three coastal Washington locations.
Can. J. For. Res. :–.
Mitchell, W.K. . The construction and rehabilitation of logging landings in the Cariboo Region.
Cariboo For. Reg., B.C. Min. For., Williams Lake,
B.C., Res. Brief No. .
Moore, G.D. . Resource road rehabilitation handbook: planning and implementation guidelines
(Interim methods). B.C. Min. Environ., Lands
and Parks and B.C. Min. For., Victoria, B.C. Watershed Restoration Tech. Circ. No. .
Morris, L.A. and R.E. Miller. . Evidence for longterm productivity changes as provided by field
trials. In Impacts of forest harvesting on longterm site productivity. W.J. Dyck, D.W. Cole and
N.B. Comerford. (editors) Chapman and Hall,
London, U.K. pp. –.
Munson, A.D., H.A. Margolis, and D.G. Brand. .
Intensive silvicultural treatments: impacts on soil
fertility and planted conifer response. Soil Sci.
Soc. Am. J. :–.
Ohtonen, R., A. Munson, and D. Brand. . Soil
microbial community response to silvicultural
intervention in coniferous plantation ecosystems.
Ecol. Appl. :–.
Olayinka, A. and A. Adebayo. . The effect of
methods of application of sawdust on plant
growth, plant nutrient uptake, and soil chemical
properties. Plant and Soil :–.
Orlander, G., P. Gemmel, and J. Hunt. . Site
preparation: a Swedish overview. For. Can. and
B.C. Min. For. Victoria, B.C. FRDA Rep. No. .
Parmelee, R.W., J.G. Ehrenfeld, and R.L. Tate III. .
Effects of pine roots on microorganisms, fauna, and
nitrogen availability in two soil horizons of a coniferous forest spodosol. Biol. Fert. Soils :–.
Pedersen, L. . Rationale for allowable annual cut
(AAC) determination. Okanagan Timber Supply
Area. Timber Supply Br., B.C. Min. For.,
Victoria, B.C.
Perry, D.A., R. Molina, and M.P. Amaranthus. .
Mycorrhizae, mycorrhizospheres, and reforestation: current knowledge and research needs. Can.
J. For. Res. :–.
Pluth, D.J., H. Nommik, G. Wiklander, K. Larsson,
and A. Erikson. . Carbon and nitrogen
42
mineralization of harvesting residues of Pinus
sylvestris L. during aerobic laboratory incubation.
Scand. J. For. Res. :–.
Potter, K.N., F.S. Carter, and E.C. Doll. . Physical
properties of constructed and undisturbed soils.
Soil Sci. Soc. Am. J. :–.
Power, J.F. . Overview of green manures/cover
crops. In Proc. Northeast and Inter-mountain
Forest and Conservation Nursery Assoc. St.
Louis, Mo., Aug –, . T.D. Landis (editors).
U.S. Dep. Agric. For. Serv., Fort Collins, Colo.
Gen. Tech. Rep. RM-. p. –.
Powers, R.F. . Mineralizable soil nitrogen as an
index of nitrogen availability to forest trees. Soil
Sci. Soc. Am. J. :–.
Prince George Forest Region. . Prince George
Forest Region Standard Operating Procedures:
protection manual, Chap. . B.C. Min. For.,
Prince George, B.C.
Read, D.J. . The role of mycorrhizal symbiosis in
the nutrition of plant communities. In Proc.
Marcus Wallenburg Found., No. . Stockholm
Sweden, Sept. , . The Marcus Wallenburg
Found., Falun, Sweden. pp. –.
Reisinger, T.W., P.E. Pope, and S.C. Hammond. .
Natural recovery of compacted soils in an upland
hardwood forest in Indiana. N. J. Appl. For.
:–.
Robertson, F.A. and W.C. Morgan. . Mineralization of C and N in organic materials as affected
by duration of composting. Aust. J. Soil Res.
:–.
Roldan, A. and J. Albaladejo. . Effect of
mycorrhizal inoculation and soil restoration on
the growth of Pinus halapensis seedlings in a
semiarid soil. Biol. Fert. Soils :–.
Rose, R. . An overview of the role of organic
amendments in forest nurseries. In Proc. Northeast and Intermountain Forest and Conservation
Nursery Association. St. Louis, Mo., Aug –,
. T.D. Landis (editor). U.S. Dep. Agric. For.
Serv., Fort Collins, Colo. Gen. Tech. Rep. RM-.
pp. –.
Saini, G.R. and D.A. Hughes. . Shredded tree bark
as a soil conditioner in potato soils of New
Brunswick, Canada. In Soil conditioners. Soil Sci.
Soc. Am., Madison, Wis. Soil Sci. Soc. Am. Spec.
Publ. No. . p.–.
Sanborn, P., D. Coopersmith, and C. Bulmer, .
Methods for reclaiming fine-textured landings
and spur roads in the B.C. Interior. Paper presented to the Coastal Forest Site Rehabilitation
Workshop, Oct. – Nov. , , Nanaimo, B.C.
Sands, R. and G.D. Bowen. . Compaction of
sandy soils in radiata pine forests. II. Effects of
compaction on root configuration and growth
of radiata pine seedlings. Aust. J. For. Res.
:–.
Sands, R., E.L. Greacen, and C.J. Gerard. . Compaction of sandy soils in radiata pine forests. I. A
penetrometer study. Aust. J. Soil Res. :–.
Schuman, G.E. and T.A. Sedbrook. . Sawmill residue for reclaiming bentonite spoils. For. Products
J. :–.
Sharma, P.P. and F.S. Carter. . Reclamation and
compaction effects on soil water retention and
pore size distribution. Paper presented at 
meeting of Soil Sci. Soc. Am. Seattle, Wash, Nov.
–, . Agron. Abstr. p. .
Simmons, G.L. and P.E. Pope. . Using VAmycorrhizae to enhance seeding root growth in
compacted soil. N. J. Appl. For. :–.
Simpson, D.G. . Growing conifer seedlings in
woodwaste-sewage sludge compost. B.C .Min.
For., Victoria, B.C. Res. Note No. .
Smeltzer, D.L.K., D.R. Bergdahl, and J.R. Donnelly.
. Forest ecosystem responses to artificially
induced soil compaction. II. Selected soil
microorganism populations. Can. J. For. Res.
:–.
Smith, R.B. . Soil disturbance, degradation, and
productivity relationships. In Degradation of
forested land: forest soils at risk. Proc. th B.C.
Soil Sci. Work., Feb. . G.W. Still and J.D.
Lousier (editors). B.C. Min. For., Victoria, B.C.
Land Manage. Rep. No. . pp. –.
Smith, R.B. and E.F. Wass. . Tree growth on and
adjacent to contour skid roads in the subalpine
zone, southeastern British Columbia. Can. For.
Serv., Victoria, B.C. Inf. Rep. BC-R-.
.␣ . Some chemical and physical characteristics of skid roads and adjacent undisturbed
soils. Can. For. Serv., Victoria, B.C. Inf. Rep.
BC-X-.
.␣ a. Impacts of skid roads on properties of
a calcareous, loamy soil and on planted seedling
performance. Can. For. Serv., Victoria, B.C. Inf.
Rep. BC-X-.
.␣ b. Impacts of a stump uprooting operation on properties of a calcareous, loamy soil and
on planted seedling performance. Can. For. Serv.,
Victoria, B.C. Inf. Rep. BC-X-.
Soehne, W. . Pressure distribution and soil compaction under tractor tyres. Agric. Eng. :–.
Standish, J.T., P.R. Commandeur, and R.B. Smith.
. Impacts of forest harvesting on physical
properties of soils with reference to increased
biomass recovery. a review. Can. For. Serv.,
Victoria, B.C. Inf. Rep. BC-X-.
Steen, O. and A. Smith. . Grass and legume
seeding for vegetation control on blade scarified
sites in the ICH and ESSF zones in the central
interior of British Columbia. For. Can. and B.C.
Min. For., Victoria, B.C. FRDA Rep. No. .
Still, G.W. and J.D. Lousier (editors). . Degradation of forested land: forest soils at risk. Proc.
th B.C. Soil Sci. Workshop, Feb. . B.C. Min.
For., Victoria, B.C. Land Manage. Rep. No. .
Sutton, R.F. . Soil properties and root development in forest trees: a review. For. Can., Sault Ste.
Marie, Ont. Inf. Rep. O-X-.
Tarrant, R.F., D.E. Hibbs, and D.S. DeBell (moderators). . Biology and management of red
alder: course notes presented on Nov. –, .
Oreg. State Univ., Corvallis, Oreg.
Taylor, H.M., G.M. Robertson, and J.J. Parker. .
Soil strength: root penetration relations for
medium- to coarse-textured soil materials. Soil
Sci. :–.
Thompson, P.J., I.J. Jansen, and C.L. Hooks. .
Penetrometer resistance and bulk density as
parameters for predicting root system performance in mine soils. Soil Sci. Soc. Am. J. :–.
Tiarks, A.E. . Growth of slash pine planted in soil
disturbed by wet weather logging. J. Soil Water
Conserv. :–.
Timber Harvesting Branch. . Soil conservation
guidelines for timber harvesting: Interior British
Columbia. B.C. Min. For., Victoria, B.C.
Tisdall, J.M. and J.M. Oades. . Organic matter and
water stable aggregates in soils. J. Soil Sci. :–.
Torbert, J.L. and J.A. Burger. . Tree survival and
growth on graded and ungraded minesoil. Tree
Plant. Notes :–.
Trowbridge, R. and F.B. Holl. . Legumes in reforestation: field screening trials. B.C. Min. For.,
Victoria, B.C. Res. Rep. -PR.
Tworkoski, T.J., J.A. Burger, and D.W. Smith. . Soil
texture and bulk density affect early growth of
white oak seedlings. Tree Plant. Notes :–.
43
United States Department of Agriculture. . User
guide to vegetation: mining and surface mining
in the west. Intermount. For. Range Exp. Stn.,
Ogden, Utah. Gen. Tech. Rep. INT-.
.␣ . The Forest Service program for forest
and rangeland resources: a long term strategic
plan (Draft). Available on the internet at http:://
www.fs.fed.us/land/RPA.
Utzig, G.F. and M.E. Walmsley. . Evaluation of
soil degradation as a factor affecting forest productivity in British Columbia: a problem analysis. Phase I For. Can. and B.C. Min. For., Victoria,
B.C. FRDA Rep. No. .
Vancouver Circular Letter. . Pre-harvest silviculture prescription procedures and guidelines for
the Vancouver Forest Region, pp. –.
Vepraskas, M.J. and V.P. Miner. . Effects of
subsoiling and mechanical impedance on tobacco root growth. Soil Sci. Soc. Am. J. :–.
Vitousek, P.M. . Beyond global warming; ecology
and global change. Ecology :–.
Vyse, A. and W. Mitchell. . Rehabilitating landings
in the Cariboo Forest District. B.C. Min. For.,
Williams Lake, B.C. Res. Brief No. .
Walker, L. and G. Horley. . Quesnel Forest District landing rehabilitation plan. B.C. Min. For.,
Quesnel, B.C.
Walker, R.F., D.C. West, S.B. McLaughlin, and C.C.
Amundsen. . Growth, xylem pressure potential, and nutrient absorption of loblolly pine on a
reclaimed surface mine as affected by an induced
Pisolithus tinctorius infection. For. Sci. :–.
44
Wang, Q., G.G. Wang, K.D. Coates, and K. Klinka.
. Use of site factors to predict lodgepole pine
and interior spruce site index in the sub-boreal
spruce zone. B.C. Min. For., Victoria, B.C. Res.
Note No. .
Warkentin, B. . The changing concept of soil
quality. J. Soil Water Conserv. :–.
Wert S. and B.R. Thomas. . Effects of skid roads
on diameter, height, and volume growth in
Douglas-fir. Soil Sci. Soc. Am. J. :–.
Williston, H.L. and S.J. Ursic. . Planting loblolly
pine for erosion control: a review. Tree Plant.
Notes ():–.
Young, J.A. . Population-level processes: seed and
seedbed ecology. In Evaluating reclamation success: the ecological consideration. Proc. symp.
sponsored by Am. Soc. Surface Mining and Reclamation. J.C. Chambers and G.L. Wade (editors). U.S. Dep. Agric. For. Serv., Broomall, Penn.
Gen. Tech. Rep. NE-. pp. –.
Zhang, X., A.G. Campbell, and R.L. Mahler. .
Newsprint pulp and paper sludge as a soil additive/amendment for alfalfa and bluegrass greenhouse study. Commun. Soil Sci. Plant Anal.
:–.
Ziemkiewicz, P.F., S.K. Takyi, and H. Regier (editors)
. Proc. workshop on reconstruction of forest
soils in reclamation. Alta. Land Conserv. Reclam.
Coun., Edmonton, Alta. Rep. RRTAC –.
Zyuz, N.S. . Bulk density and hardness of the
Hillocky sands of the Middle Don. Sov. Soil Sci.
:–.
APPENDIX 1 PEOPLE CONSULTED WHEN PREPARING THIS REPORT
Name
Agency/Company
Address
Bill Chapman
B.C. Min. For., Cariboo Region
Williams Lake
Lorne Walker
B.C. Min. For., Quesnel District
Quesnel
Rita Cassavant
B.C. Min. For., Quesnel District
Quesnel
Jeff Alexander
Lignum Ltd.
Williams Lake
Derek Hodgkins
Inland Timber Management
Williams Lake
Graeme Hope
B.C. Min. For., Kamloops Region
Kamloops
Geoff Ellen
Consultant
Clearwater
Ed Collen
Weyerhauser Ltd.
Armstrong
Don Brimacombe
Weyerhauser Ltd.
Kamloops
Kelly Fay
Riverside Forest Products
Kelowna
Shayne Brown-Clayton
Riverside Forest Products
Kelowna
Stephen Homoky
Consultant
Logan Lake
Mike Curran
B.C. Min. For., Nelson Region
Nelson
Lawrence Redfern
Crestbrook Forest Industries
Cranbrook
George Delisle
Pope and Talbot
Midway
Doug Lang
Pope and Talbot
Nakusp
Sue Harris
Pope and Talbot
Nakusp
Paul Sanborn
B.C. Min. For., Prince George Region
Prince George
Richard Kabzems
B.C. Min. For., Prince George Region
Fort St. John
Eric Ravnaas
B.C. Min. For., Dawson Creek District
Dawson Creek
Graeme Anderson
B.C. Min. For., Prince George Region
Fort St. John
Dan Lousier
University of Northern B.C.
Prince George
Marty Kranabetter
B.C. Min. For., Prince Rupert Region
Smithers
Margaret Marsland
B.C. Min. For., Kispiox District
Hazelton
Rod Meredith
B.C. Min. For., Kalum District
Kispiox
Lance Loggin
Skeena Sawmills
Terrace
Phil Burton
Consultant
Smithers
Jim Dunkley
B.C. Min. For., Port McNeill
Port McNeill
Terry Rollerson
B.C. Min. For., Nanaimo
Nanaimo
Milt Holter
B.C. Min. For., Mid-Coast District
Hagensborg
Neil Oborne
Interfor Ltd.
Hagensborg
Al Barber
Canadian Forest Products
Woss
John Senyk
Canadian Forest Service
Victoria
Bill Carr
Carr Environmental Consulting
Cloverdale
Dave McNabb
Alberta Environmental Centre
Vegreville, Alberta
Ed Fields
Tilth, Inc.
Monroe, Oregon
Lisa Lewis
U.S. Dep. Agric. Forest Service
Olympia, Washington
Richard Miller
U.S. Dep. Agric. Forest Service
Olympia, Washington
45