_____________________________________________________________________
Review of the relationship between light
availability and growth of understory
pine
_____________________________________________________________________
Report produced by
Rasmus Astrup
[email protected]
Report produced:
November 1, 2005
1
Abstract
This report compiles all available literature regarding the relationship between light
availability and growth of understory and suppressed pine trees. The term growth is
defined as a change in any of: height, diameter, biomass, or crown dimensions. Pine
refers to lodgepole pine (Pinus contorta Dougl. Ex Lound. var. latifolia Engelm.) and
jack pine (Pinus banksiana Lamb.).
A total of 23 studies with measurements of both light availability and pine growth were
identified. The majority of these studies have measures of diameter and/or height
increment available in the publication. In terms of other growth measures, the available
information was found to be sparse.
Under field conditions in conifer-dominated stands, the majority of the reviewed
literature indicated that the relationship between light availability and height increment is
approximately linear (slightly asymptotic or slightly exponential). In two shadehouse
experiments and in two other cases more asymptotic relationships have been observed.
There is insufficient information to judge the relationship between light availability and
height increment in aspen-dominated stands.
The reviewed literature indicates that pine diameter increment increases throughout the
full light spectrum. Additionally, all sources seem to indicate that this relationship is
approximately linear under conifer-dominated canopies. There is insufficient information
to judge if this also is the case under aspen canopies.
Table of Contents
Introduction................................................................ 4
Objectives and scope of this report............................................................................. 4
Approach to the literature search ................................................................................ 4
Structure of this report and associated databases........................................................ 4
Literature summary section ....................................... 6
Introduction................................................................................................................. 6
Table 1 & 2 column headings and definitions ............................................................ 6
Summary tables........................................................................................................... 8
Outline of main findings.......................................... 16
Introduction............................................................................................................... 16
Height and diameter increment................................................................................. 16
Above-ground biomass, leaf area, and crown allometry .......................................... 19
References................................................................ 23
Introduction
Objectives and scope of this report
The objective of this report is to compile all available information regarding the
relationship between light availability and growth of understory and suppressed pine
trees. The term growth is defined as change in any of: height, diameter, biomass, or
crown dimensions. In this report, pine refers to lodgepole pine (Pinus contorta Dougl. Ex
Lound. var. latifolia Engelm.) and jack pine (Pinus banksiana Lamb.).
The available data is compiled to assist in further development and parameterization of
the process-based growth and yield model TASS (Mitchell 1975). Consequently, the
compilation of the available information focuses on studies with a strong quantitative
component. More specifically, only literature that includes both measures of light
availability and growth is included in this report. There is a substantial amount of
literature that does not include light measurements but focuses on competition and
growth of mixed stands of aspen and pine (e.g. Brockley and Sanborn 2003; DeLong and
Tanner 1996; Longpré et al. 1994; Navratil and MacIsaac 1993; Navratil et al. 1990;
Newsome et al. 2003; Newsome et al. 2004a; Newsome et al. 2004b). As these
references did not explicitly measure light, they are not included in the remainder of this
review.
Approach to the literature search
To compile the best available information a comprehensive literature search was
undertaken. The literature search was performed with literature databases (Agricola and
CAB Abstracts), and an internet-based search-engine (Google).
Structure of this report and associated databases
This report consists of an introduction, a literature summary section, and a brief outline of
the main findings. The literature summary section consists of two tables. Table 1
summarizes all identified references that include both measures of light and pine growth.
Table 2 provides a brief summary of the references included in Table 1. This report is
produced in conjunction with two Excel databases. These databases (A and B) were
produced to compile the best available quantitative information to form the basis for
meta-analysis. Database A includes regression models that predict height or diameter
increment as a function of light availability. Database B includes paired observations of
height or diameter increment and light availability. Originally, it was also the intent to
compile a database of other growth measures in addition to height and diameter
increment. Unfortunately, the amount of available information is too sparse to create a
meaningful database.
5
Literature summary section
Introduction
This section contains two summary tables. Table 1 includes references that have paired
measurements of pine growth and light availability. Table 2 includes a brief summary for
each of the references in Table 1. The summaries in Table 2 illustrate how each reference
is related to the relationship between light and pine growth.
Table 1 & 2 column headings and definitions
The definitions and explanations for selected column headings used in Table 1 & Table 2
are outlined below:
Location: Indicates geographic location. In British Columbia (B.C.) this column refers to
BEC zone (Meidinger and Pojar 1991). In the rest of Canada this column refers to
province. In the USA this column refers to state, and in other countries this column refers
to country.
Species: Indicates the species (lodgepole pine = Pl, jack pine = Pj).
Database entry: Indicates whether the reference is included in one of the associated
databases. “A” indicates that the reference is included in the database for height and
diameter increment regression models. “B” indicates that the reference is included in the
database for discrete observations of height and diameter increment.
Quantitative usefulness: Indicates a subjective judgment of the quantitative usefulness
of the data for parameterization of a process-based forest growth model. It must be
emphasized that this is not a judgment of the scientific merit of a paper. The quantitative
usefulness is judged in two categories. The first category refers to the actual information
that is available in the publication. This information is judged on the following scale from
1 – 5:
1. The data is not accessible through the publication (e.g. ANOVA table with pvalues) and the data is not fully relevant.
6
2. The data is not accessible through the publication (e.g. ANOVA table with pvalues) or the data is somewhat relevant (e.g. herbaceous competition).
3. The data is relevant but is not easily accessible (e.g. graphic representation).
4. The data is accessible through the publication (discrete data points or regression
model) and is collected under conifer-dominated stands. Alternatively, the data
comes from a controlled experiment with artificial shade.
5. The data is accessible through the publication (discrete data points or regression
model) and is collected in aspen-dominated stands.
The second category refers to the usefulness of the data given it was obtained from the
owner. This data is judged on the following scale from 1 – 5:
1. The data is not fully relevant.
2. The data is somewhat relevant.
3. The data is relevant but has a low sample size or is of questionable quality.
Alternatively, the data-set is large but of lesser relevance or the data comes from a
controlled experiment with artificial shade.
4. The data is relevant and has a large sample size. The data is collected under
conifer-dominated canopies.
5. The data is relevant and has a large sample size. The data is collected under
aspen-dominated canopies.
7
Summary tables
Table 1. Literature that includes paired measurements on pine growth and light availability.
Life-stage1
SBS,
Ontario
Pl,
Pj
Planted
seedlings
(2 g.s.f.p.)
Herbaceous
No
Burton (2002)
SBS
Pl
Seedlings,
Saplings,
Matures
Variable age
conifers
No
1
4
Height,
Diameter
Transects
ANOVA,
Regression
Chen et al.
(1996)
IDF
Pl
Saplings
(0.8 –
1.3m)
Variable age
conifer-dominated
A
4
4
Height,
Branch
increments,
Specific leaf
area
Transects
Regression,
ANOVA
Claveau et al.
(2002)
ICH,
Quebec
Pl,
Pj
Seedlings,
Saplings
(0.3 – 4m)
Mixed conifers,
Mixed hardwoods
No2
3
5
Height,
Diameter,
Crown
allometry,
Branch
increments
Sampling/remeasurement
ANCOVA
Species
Brand (1991)
Quantitative
usefulness
In
If data
publication is
obtained
1
1
Location
Source
Cover type
Database
entry
Data
Analysis
Measurements
Sampling/
Treatment
Height,
Diameter,
Biomass
components,
Leaf surface
area
Treatments
ANOVA
Table 1. Continued.
Location
Species
Source
Life-stage
Cover type
Database
entry
Claveau et al.
(2005)
ICH,
Quebec
Pl,
Pj
Seedlings,
Saplings (0.3
– 4m)
Mixed conifers,
Mixed hardwoods
No1
Quantitative
usefulness
In
If data
publication is
obtained
3
5
Coates and
Burton (1999)
ICH
Pl
4
4
Maine
(greenhouse)
Pj
Mixed conifers
(Approximately
150 years)
Artificial shade
A
Day et al.
(2005)
Planted
seedlings
(4 g.s.f.p.)
Seedlings (0-3
years)
No
1
1
Eis (1970)
SBS
Pl
Seedlings,
Saplings
(1-15 years)
Mature forest
No3
4
4
Data
Analysis
Measurements
Sampling/
Treatment
Height,
Diameter,
Crown
allometry,
Branch
increments,
Total needle
area,
Specific needle
area ,
Biomass
components
Height,
Diameter
Destructive
sampling
ANCOVA
Sampling/remeasurement
Regression
Greenhouse
experiment
ANOVA
Sampling
Descriptive
analysis
Height,
Diameter,
Specific leaf
area,
Biomass
components
Height,
Diameter,
Root growth,
Biomass
components
9
Table 1. Continued.
Location
Species
Source
Greenhouse
Pj
Seedlings
Artificial shade
No
Quantitative
usefulness
In
If data
publication is
obtained
1
1
SBS
Pl
Natural
regeneration
(1-1.5 m)
Coniferdominated
A
4
4
Landhausser
and Lieffers
(2001)
Alberta
Pl
Mature mixed
stand of aspen
and balsam
poplar
No
2
2
Logan (1966)
Ontario
Pj
1-year old
seedlings
grown in pots.
Measurements
after second
growing
season
Seedlings (6
years old)
Artificial shade
B
4
3
MacDonald
and
Thompson
(2003)
Ontario
Pj
Planted
seedlings (5
g.s.f.p)
Mixedwood
(70 years)
No
1
1
Hoddinott
and Scott
(1996a)
Hoddinott
and Scott
(1996b)
Kayahara et
al. (1996)
Life-stage
Cover type
Database
entry
Data
Analysis
Measurements
Sampling/
Treatment
Height,
Diameter,
Biomass
components,
Physiological
parameters
Greenhouse
experiment
ANOVA
Height,
Diameter,
Specific leaf
area
Height,
Total leaf area,
Specific leaf
area,
Photosynthesis,
Biomass
components
Height,
Diameter,
Number of
needles,
Biomass
components
Sampling
Regression
Measurements
of plots
Several
approaches
Annually
measured
experiment
Descriptive
analysis
Height,
Leader
diameter
Measurements
of plots
ANOVA
10
Table 1. Continued.
Wisconsin
Pj
Planted
seedlings
(4 g.s.f.p)
Mixed hardwoods
No
Morris and
Forslund
(1991)
Noland et al.
(1997)
Ontario
Pj
Mix of shrubs and
young hardwoods
No
1
1
Ontario
Pj
Planted
seedlings (4
g.s.f.p.)
Seedlings
(<1 year)
Artificial
No
1
1
Reich et al.
(1998a)
Minnesota
Pj
Seedlings
(<1year)
Artificial
No
1
1
Shirley
(1945)
Minnesota
Pj
Planted
seedlings
(4 g.s.f.p)
B
5
5
Williams et
al. (1999)
IDF
Pl
Seedlings,
saplings
(0.1-6.0m)
Artificial shading,
Aspen canopy
(43 years),
Pine canopy
(55 years)
Pine (90 – 120
years) mixed with
few Douglas-fir
(300-350 years)
No1
3
4
Species
Machado et
al. (2003)
Quantitative
usefulness
In
If data
publication is
obtained
2
2
Location
Source
Life-stage
Cover type
Database
entry
Reich et al.
(1998b)
Data
Analysis
Measurements
Sampling/
Treatment
Height,
Specific leaf
area,
Biomass
components,
Leaf area ratio
Diameter
Measurements
of plots
ANOVA,
Regression
Sampling
Regression
Greenhouse
experiment
ANOVA
Greenhouse
experiment
Growth
analysis
Mixed
NA
Sampling
ANOVA
Root growth,
Shoot
elongation
Biomass
components,
Root growth,
Specific leaf
area,
Total leaf area
Height,
Diameter,
Biomass
components
Height,
Diameter,
Lateral branch
increments,
Crown
allometry
11
Table 1. Continued
Northern
B.C.
Species
Wright et al.
(1998)
Location
Source
Pl
Life-stage
Seedlings,
Saplings
(0.5-8.6m)
Cover type
Conifer-dominated
Database
entry
A
Quantitative
usefulness
In
If data
publication is
obtained
4
4
Data
Analysis
Measurements
Sampling/
Treatment
Height,
Diameter
Sampling
Regression
Data also
presented in
Wright et al.
(2000)
1. Growing seasons from planting is abbreviated as “g.s.f.p”.
2. Data is mainly graphically represented.
3. Not included as results are not fully represented in the publication.
12
Table 2. Short summaries of references.
Source1
Short summary of contents related to pine growth
Brand (1991)
Investigated the effect of different environmental factors on the growth of seedlings. Light was measured for a small
portion of these seedlings. The shading was caused by non-tree competitors. Relative growth rates were found to be
positively related to light intensity and nitrogen availability.
Burton (2002) Investigated the effects of edges on overstory and understory lodgepole pine growth. Height and diameter growth of
understory trees were found to be correlated with light availability. The publication contains two equations. The first
predicts height increment as a function of distance from the edge, and the second predicts the light level as a function
of proximity to the edge. Potentially these two equations could be combined.
Chen et al.
Investigated how lodgepole pine saplings perform at a gradient of light levels under a conifer overstory. Height and
(1996)
lateral branch increments were found to increase with light availability. The increase can be described as slightly
exponential. Specific leaf area was found to decrease linearly with light availability.
Claveau et al. Investigated the interactive influence of tree size and light availability on above-ground biomass distribution in
(2005)
lodgepole pine and jack pine. All investigated biomass traits varied with light availability and tree size. Additionally,
interactions between light availability and tree size were found to influence biomass distribution. Consequently, it
was concluded that not all functional responses can be scaled between trees of different sizes.
Claveau et al. Investigated the effect of a light gradient on lodgepole pine and jack pine growth in Quebec and B.C. Strong
(2002)
correlations between light availability and growth were observed. At very low light levels tree size was not found to
increase growth, while at higher light levels tree size was found to increase growth.
Coates and
Investigated the effect of light availability on growth of planted seedlings in mixed-conifer stands that had undergone
Burton (1999) partial cutting. For lodgepole pine, height and diameter increments were found to increase approximately linearly
with light availability.
Day et al.
Greenhouse experiment that investigated the effect of seedbed, light environment, and elevated night temperatures
(2005)
on growth and carbon allocation in jack pine seedlings. Seedlings were grown in full light and at 40% light. Growth
was found to be higher in full light.
Eis (1970)
Investigated the effect of light availability on carbon allocation and growth of lodgepole pine. Compared to trees
grown in full light, height growth, shoot weight, needle weight, root weight, root spread, and root depth were found
to be between 48-68% of full light growth in 50% light availability. In 25% light availability the growth was between
12-35% of the maximum.
13
Table 2. Continued.
Source
Short summary of contents related to pine growth
Hoddinott and
Scott (1996a)
Hoddinott and
Scott (1996b)
Investigated the effect of light quality (red/far-red quantum flux ratio) on growth and physiological responses of jack
pine seedlings. Seedling above-ground growth was found to generally increase with lower red/far-red quantum flux
ratios. Red/far-red quantum flux ratios were also found to influence several physiological parameters.
Kayahara et al. Investigated the effect of light availability on height increment of lodgepole pine. Height increment was found to
(1996)
increase slightly exponentially (almost linearly) with light availability. Specific leaf area was found to increase with
decreasing light availability.
Landhausser
Investigated the growth, carbon allocation and photosynthesis of 1-year old lodgepole pine seedlings grown in pots
and Lieffers
under open conditions and in the shade of a mixed stand of aspen and balsam poplar (21.5% light availability). Pine
(2001)
height increment was found to be similar in the shaded and full light condition. Shoot mass and root mass growth
were larger in full light. Total leaf area was larger in open conditions while specific leaf area was larger in the shade.
Logan (1966)
Experiment that investigated the effect of artificial shade on jack pine growth. Tree growth was found to increase
with light intensity. Height increment was maximized at 100% light but the relationship appears asymptotic.
Diameter increments were found to increase to 100% light availability. The increase in diameter increment as a
function of light availability occurred at a slightly decreasing rate.
MacDonald
Investigated the growth of jack pine planted under different overstory densities. Seedling height and diameter
and Thompson increments were found to increase with site openness and thus with light availability.
(2003)
Machado et al. Investigated the effect of root competition and light availability on growth of jack pine in deeply shaded
(2003)
understories. Both root competition and light availability were found to limit seedling growth. Biomass production
and height growth were found to increase with site openness.
Morris and
Investigated the effects of a competition index (Shade Index) on the diameter growth of planted jack pine seedlings
Forslund
in 4-year old plantations. The diameters of the sampled jack pine were linearly correlated to the Shade Index.
(1991)
Noland et al.
Investigated the root growth of young jack pine seedlings at 4 different light levels. Decreased light levels decreased
(1997)
root growth.
14
Table 2. Continued.
Source
Short summary of contents related to pine growth
Reich et al.
(1998a)
Reich et al.
(1998b)
Shirley (1945)
Williams et al.
(1999)
Wright et al.
(1998)
Wright et al.
(2000)
Investigated the growth and photosynthesis of jack pine seedlings (<1year) grown in a greenhouse under 5% and
25% light availability. Relative growth rates were higher in 25% light than in 5% light, while specific leaf area
increased with decreasing light availability.
A three part study that investigated the effect of light availability and root competition on growth of planted jack
pine. The first part of the study was carried out with artificial shade. The second part of the study was carried out in
an aspen stands. The third part of the study was carried out in a pine stands. Growth was found to be restricted by
both light availability and root competition. In the greenhouse experiment, jack pine height and biomass increments
were found to peak at 46% light. In the aspen and the pine stands, both height and biomass increment increased to
full light.
Investigated the influence of light availability and sapling size on crown morphology and growth of understory
lodgepole pine. Height increment, crown depth, and number of branches per whorl were found to increase with light
availability. At higher light levels larger saplings outgrew smaller individuals, while their growth was similar at very
low light levels. For lodgepole pine, tree size was found to have little effect on crown morphology.
Investigated the effect of light availability on lodgepole pine growth. Regression models for several biogeoclimatic
zones in the northwestern B.C. were developed. For lodgepole pine, the relationship between light availability and
growth was found to vary between different climatic regions. Both height and diameter increments were found to
increase with light availability. The shapes of the regression curves varied between approximately linear and slightly
asymptotic.
Investigated the effect of suppression and release on the growth of lodgepole pine in several biogeoclimatic zones in
northwestern B.C. The utilized data was previously analyzed by Wright et al. (1998).
15
Outline of main findings
Introduction
A total of 23 studies with measurements of both light availability and spruce growth were
identified (Table 1 & Table 2). The majority of these studies have information on
diameter and/or height increment available in the publication. A sizable portion of the
studies have measures of biomass production. Three studies that directly study the
interactions between light, tree size, and crown allometry were identified (Claveau et al.
2005; Claveau et al. 2002; Williams et al. 1999). The following sections will summarize
the relationships between light availability and each of the following: height, diameter,
biomass, and crown allometry.
Height and diameter increment
Introduction
Figure 1A illustrates all compiled regression models (Database A) that predict height
increment as a function of light availability. Figure 1B illustrates all compiled regression
models (Database A) that predict diameter increment as a function of light availability.
Figure 2A illustrates a scatter plot of all complied paired observations of height increment
and light availability (Database B). Figure 2B illustrates a scatter plot of all compiled
paired observations of diameter increment and light availability (Database B).
Figure 1 and Figure 2 illustrate that there is large variability in both: (1) the increment
observed at a given light level (horizontal distribution of graphs), and (2) the general
shape of the light-growth response curve (non-parallel graphs).
Diameter:height ratios
Primary growth (height increment) generally has higher priority than secondary growth
(diameter increment) (Oliver and Larson 1996). Consequently, height increment should
generally be saturated at lower a light level than diameter increment. This implies that
larger height:diameter ratios should be observed for understory trees than for tree grown
in open conditions. In Figure 1 and Figure 2, the graphs generally comply with this
expectation.
The effect of tree size on height and diameter increment
In the majority of reviewed papers, the range of tree heights is 0.1 – 7 meters. In this
range, pine height and diameter increments (at a given light level) generally increase with
tree size (e.g. Claveau et al. 2005; Claveau et al. 2002; Williams et al. 1999). At very low
light levels this might not be true. Williams et al. (1999) found that below 15% light
availability tree height did not increase height or lateral branch growth. At very low light
levels, larger trees might even be at a disadvantage due to higher respiration rates
associated with non-photosynthetic matter (see Messier et al. 1999).
Sources of variation for the observed height and diameter increments
In Figure 1 and Figure 2 some of the variation in predicted diameter and height
increments can be attributed to different tree sizes. None of the reviewed regression
models explicitly take tree size into account. The observations in Figure 2 also originate
from trees of different sizes. Consequently, comparison of the predicted or observed
diameter and height increments is difficult. The variability of diameter and height
increments is also caused by the different climatic conditions and site conditions in which
the trees were grown.
Height increment
The overwhelming majority of reviewed sources indicate that pine height increment
increases with light availability throughout the full light gradient. The shadehouse
experiment of Logan (1966) indicates that the light-height increment relationship is
asymptotic. This pattern is also supported by the shadehouse experiment by Shirley
(1945) who found that jack pine height increment was maximized at 46% light. An
asymptotic pattern was also observed by Wright et al. (1998) for lodgepole pine sampled
in the ESSFvw and ESSFmc. In the ICHmc2, SBSmc2, BWBSdk1, and BWBSdk2,
Wright et al. (1998) found approximately linear light-height increment relationships for
lodgepole pine. Coates and Burton (1999) also found an approximately linear light-height
17
increment relationship for lodgepole pine in the ICH. This pattern is additionally
supported by slightly exponential light-height increment relationships observed by Chen
et al. (1996) in the IDF and Kayahara et al. (1996) in the SBS (Figure 1A & Figure 3A).
All of these field studies were carried out under conifer-dominated canopies. Only one
identified study (Shirley 1945) investigated the light-height increment relationship under
an aspen-dominated canopy. This study only has observations below 40% light
availability and at 100% light availability, thus it is hard to infer much about the shape of
the observed light-height increment response. Consequently, there is insufficient
information to judge if pine light-height increment responses differ between aspendominated canopies and conifer-dominated canopies.
The majority of the reviewed literature indicates that under field conditions the
relationship between light and height increment for pine grown under conifer-dominated
canopies is approximately linear (slightly exponential or slightly asymptotic). There is
insufficient information to judge if this also is the case under aspen-dominated canopies.
Diameter increment
All reviewed sources indicate that pine diameter increment increase with light availability
throughout the full light spectrum1. Additionally, all sources seem to indicate that the
increase is approximately linear (slightly asymptotic or slightly exponential). Slightly
asymptotic light-diameter increment relationships were observed by Logan (1966) and
Coates and Burton (1999). Linear or slightly exponential relationships were observed by
Wright et al. (1998).
In conclusion, the relationship between light and diameter increment for pine grown
under conifer-dominated canopies is approximately linear (slightly exponential or slightly
asymptotic). There is insufficient information to evaluate the shape of the light-diameter
increment relationship under aspen-dominated canopies.
1
Shirley (1945) reported that biomass production of jack pine is optimized at 46% light in a shadehouse
experiment. The diameter increment was not reported but it must be assumed that diameter increment also
is maximized at this low light level.
18
Above-ground biomass, leaf area, and crown allometry
Introduction
The available information regarding growth measures besides height and diameter
increment is limited. Consequently, the following will briefly outline the references that
are relevant to each of above-ground biomass and crown allometry.
Above-ground biomass
Above-ground biomass production is well correlated to diameter increment. Thus, similar
conclusions ought to apply for above-ground biomass and diameter increment. Under
field conditions, Shirley (1945) found that jack pine biomass production was maximized
in full light. On the other hand, Shirley (1945) also reported that biomass production for
jack pine was optimized at 46% in a shadehouse. Eis (1970) found that the lodgepole pine
shoot mass, needle weight, root weight, and height growth were maximized in full light.
This is also supported by Landhausser and Lieffers (2001) and Claveau et al. (2005). In
conclusion, the majority of the available information indicates that biomass production of
pine increases with light level throughout the full light spectrum.
Crown allometry
For understory pine the main sources of crown allometry information are Chen et al.
(1996), Claveau et al. (2005), Claveau et al. (2002), and Williams et al. (1999). The data
from Claveau et al. (2005), Claveau et al. (2002), and Williams et al. (1999) are mainly
graphic and better information could be achieved by obtaining this data through a data
use agreement. Claveau et al. (2002) found that crown morphology of both jack pine and
lodgepole pine was less responsive to changes in light availability than in more shade
tolerant species. Lodgepole pine live crown ratio and number of branches per whorl was
found to decrease with light availability (Williams et al. 1999). Specific leaf area has
been found to decrease with increasing light availability (Chen et al. 1996; Kayahara et
al. 1996).
19
A. Annual height increment (cm/year)
90
Chen (1996)
80
Coates and Burton (1999)
Annual height increment (cm/year)
70
Kayahara et al. (1996) MD
Kayahara et al. (1996) SD
60
Kayahara et al. (1996) FM
50
Wright et al. (1998) ESSFwv
40
Wright et al. (1998) ESSFmc
30
Wright et al. (1998) ICHmc2
20
Wright et al. (1998) SBSmc2
Wright et al. (1998) BWBSdk1
10
Wright et al. (1998) BWBSdk2
0
0
20
40
60
80
100
120
Light (%)
B. Annual diameter increment (mm/year)
20
Coates and Burton (1999)
Annual diameter increment (mm/year)
15
Wright et al. (1998) ESSFwv
Wright et al. (1998) ESSFmc
10
Wright et al. (1998) ICHmc2
5
Wright et al. (1998) SBSmc2
Wright et al. (1998) BWBSdk1
0
0
20
40
60
80
100
120
Wright et al. (1998) BWBSdk2
-5
Light (%)
Figure 1. Graphs of height and diameter increment as a function of light availability. Some graphs have
been transformed from their original units to facilitate comparison. Each model is graphed in the
approximate range of light conditions represented in the given study.
20
Annual height increment (cm/year)
25
Logan (1966)
Height increment (cm/year)
20
15
Shirley (1945) pine site
10
5
Shirley (1945) aspen site
0
0
20
40
60
80
100
120
Light (%)
Annual diameter increment (mm/year)
7
Annual diameter increment (mm/year)
6
5
4
Logan (1966)
3
2
1
0
0
20
40
60
80
100
120
Light (%)
Figure 2. Annual height and diameter increment as a function of light availability. Some observations have
been transformed from their original units to facilitate comparison
21
A. Relative annual height increment
1.2
Chen (1996)
Coates and Burton (1999)
1
Relative annual height increment
Kayahara et al. (1996) MD
Kayahara et al. (1996) SD
0.8
Kayahara et al. (1996) FM
Wright et al. (1998) ESSFwv
0.6
Wright et al. (1998) ESSFmc
0.4
Wright et al. (1998) ICHmc2
Wright et al. (1998) SBSmc2
0.2
Wright et al. (1998) BWBSdk1
Wright et al. (1998) BWBSdk2
0
0
20
40
60
80
100
120
Light (%)
B. Relative annual diameter increment
1.2
Coates and Burton (1999)
1
Relative annual diameter increment
Wright et al. (1998) ESSFwv
0.8
Wright et al. (1998) ESSFmc
0.6
Wright et al. (1998) ICHmc2
0.4
Wright et al. (1998) SBSmc2
0.2
Wright et al. (1998) BWBSdk1
0
0
20
40
60
80
100
120
Wright et al. (1998) BWBSdk2
-0.2
Light (%)
Figure 3. Graphs of relative height and diameter increment as a function of light availability. At a given
light level the annual relative increment is calculated as the predicted increment divided by the predicted
increment at full light (100%).
22
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