follow a relativelygood seedyear, whichwe experienced.Earlyindications
are that thistechniquecould
achieve at least a degree of conversionto pine.
Considerablework will undoubtedlybe required to
obtainpure standsof pine,but laterobservations
are
neededto estimatethe type and extentof treatment.
Literature
Cited
BELANGER,
R. P. 1979.Stumpmanagement
increases
coppiceyield
of sycamore.
South.J. of Appl. For. 3:101-103.
Boycs,STSP}•SN
G., andJos P. McCLURE.1975.How to keeponethird of Georgiain pine. USDA For. Serv. Res. Pap. SE-144.
Southeast.For. Exp. Stn.,Asheville,NC. 23 p.
Boycs,STSPHSN
G., andJoEP. McCLuRE.1976.Actionsto capture
the biologicalpotentialfor loblollypine in Virginia and the
Carolinas.In Proc.55thAnnualMeetingof AppalachianSection,
SocAmer. Foresters,February4-6, Asheville,NC. 43-45.
BoYcs,STSPHSN
G., and HERBSRT
A. KNIGHT.1979.Prospective
ingrowthof southernpinebeyond1980.USDA For. Serv.Res.
Pap. SE-200.Southeast.For. Exp. Stn., Asheville,NC. 50 p.
LANGDON,
O. GORDON.
1981.Naturalregenerationof loblollypine:
a soundstrategyfor manyforestlandowners.
South.J. of Appl.
For. 5:170-176.
LoTto, T. 1961. The casefor natural regeneration.In Crow, A.
B., ed. Proc. 10th Ann. For. Symp.LouisianaSt. Univ. Press,
Baton Rouge,LA. 16-23.
McGsE,C. E. 1980. Expandingoptionsfor reforestationof the
CumberlandPlateau.South.J. of Appl. For. 4:158-162.
McM•NN,JAMES
W. 1983.Pineregenerationvia fuel chip utiliza-
tion. Ga. For. Res.Pap.41. Ga. For. Cornmiss.,
Macon,GA. 7
p.
McM•NN,JAMESW., and WADSL. NuT'rsm 1981. Energywood
harvesting:a studyof promises
and pitfalls.Ga. For. Res.Pap.
17. Ga. For. Commiss.,Macon,GA. 6 p.
NUTTEg, WADE L., and JAMSSW. McMINN. 1980. Total-tree
chipping:what aboutnutrientdrain?In Total-treechips:harvesting,transporting,storingand processing.
Proc.Ann. Meet.,
Southeast. Section, FPRS, November 19-21, Savannah, GA. 37.
SoclEanc
os AMEmCAN
FORESTEgS.
1979. Improvingoutputsfrom
non-industrial
privateforests:studyreportof a taskforceof
the Societyof AmericanForesters,Washington,DC. 11 p.
VAN LEAR,D. H., J. E. DOUGLASS,
S. K. Cox, M. K. AUGSPURGER,
and S. K. NODINE.1983.Regeneration
of loblollypine standsin
the Piedmontby clearcuttingwith seedin place.In Jones,E. P.,
Jr., ed. Proc. SecondBiennialSouth.Silvic.Res.Conf. USDA
For. Serv. Gen. Tech. Rep. SE-24. Southeast.For. Exp. Stn.,
Asheville, NC. 87-96.
Jamesw. McMinnisprincipalresearch
forester,USDA
ForestService,Southeastern
ForestExperimentStation,
Forestry
Sciences
Laboratory,
Athens,Georgia30602.
Yield Relationshipsin Unthinned
Loblolly Pine Plantationson
Cutover, Site-PreparedLands
Harold E. Burkhart, DeborahC. Cloeren,and Ralph L. Amateis
wereno significant
differences
between
sitepreparation
classes
theregions.
l
(Pinustaeda)plantations
oncutover,
site-prepared
landsacross within
much
ofthesouthern
United
States.
Initialmeasurement
datafrom
these
permanent
plotswereusedto(1) develop
regression
relationExtensive
plantings
ofloblolly
pinehave
been
esships
between
yieldof theplanted
loblolly
pineandmeasurements tablishedthroughoutthe South. During the 1950s
of theplanted
pineandcompeting
vegetation,
and(2) assess
reand early 1960smostplantingswereon abandoned
lationships
between
yieldandsitepreparation
methods
andphysio- agriculturallands.These old-fieldplantationshave
graphicregions
(Coastal
Plain andPiedmont).
These
analyses
and a voluminousquanshowed
thatyieldoftheplanted
pinecomponent
couldbepredicted beenthoroughlyresearched
tity
of
growth
and
yield
information
hasbeendeveladequately
fromage,average
height
ofdominant
andcodominant
oped from them (Burkhart et al. 1981). For more
trees,and numberof survivingplantedtreesperunitarea.Measurements
onthecompeting
vegetation
didnotsignificantly
reduce than a decade, the vast majority of loblolly pine
theerrorsumofsquares
afteraccounting
for theplanted-pine
variables.
An analysis
of covariance
showed
thatmeanyields(after
bytheLoblolly
PineGrowth
andYield
adjusting
for theeffects
ofplantation
age,siteindex,andnumber • Thisstudywassponsored
Research
Cooperative
at VPI & SU. Supportfrom BowaterInc.,
ofsurviving
trees)werenotsignificantly
different
for sitepreparationclasses
or physiographic
regions.
Furtheranalyses
showed ChampionInternationalCorp., ChesapeakeCorp., Continental
ForestIndustries,CrownZellerbachCorp., FederalPaperBoard
thatsurvivalrelationships
weresimilarfor thephysiographic
reInternationalPaperCo., PotlatchCorp.,UnionCampCorp.,
gionsandsitepreparation
classes
included.
Although
theheight- Co.,
WestvacoCorp., WeyerhaeuserCo., North CarolinaDivisionof
agerelationships
for anamorphic
siteindexcurveconstruction
were
Forestry,Virginia Divisionof Forestry,and the USDA Forest
significantly
different
for theCoastal
PlainandPiedmont,
there
Service(bycooperative
agreement)
is acknowledged.
ABSTRACT. Data were collected
in unthinnedloblollypine
84
SOUTHERNJOURNALOF APPLIEDFORESTRY
plantationshavebeenestablished
on cutoverareas
that havebeensite preparedprior to planting.Differencesin siteand competitive
relationships
between
old-fieldand site-preparedareasare likelyto affect
yieldrelationships.
Oldfieldstypically
contained
little
competing
woodyvegetation,
showedmodifiedsoil
physical
properties
asa resultof agricultural
activity,
and had some residual fertilizer effects.
The objectives
of thisstudywereto: (i) determine
what variablesare importantfor predictingyieldsof
loblollypine plantationson cutover,site-prepared
areas,and (2) investigatethe effectsof sitepreparation methodsand geographic
locationon yieldrelationshipsin theseplantations.
Table1. Summaryof plot locationsby stateandphysiographicregion.
Physiographic
region
Coastal
State
Alabama
Arkansas
treatment
for the site conditions
and time at which
the plantationwasestablished.
The locationand standhistorywere recordedfor
eachplot. Standhistoryincludedtypeof standprior
to the current plantation,whenclearcut,type of site
Other
13
1
1
--
-9
14
10
8
Total
7
--
15
Louisiana
23
--
--
23
Maryland
Mississippi
3
13
---
---
3
13
North Carolina
Oklahoma
South Carolina
Tennessee
Texas
17
-10
1
6
19
-11
2
--
-1
-3
--
36
1
21
6
6
2._•7
=
68
13
TOTAL
During the 1980-81 and 1981-82 dormant seasons,permanentplots were established
in cutover,
site-prepared plantations throughout the native
range of loblollypine (Figure 1 and Table i). The
initialmeasurement
datafrom thesepermanentplots
were usedin thisstudy.To be includedin the sample,
the plantationshad to meet the followingspecifications:at least8 yearsin age (definedasyearssince
planting),unthinned,free of evidenceof heavydiseaseor insectattack,not heavilydamagedby ice or
wind storms,free of interplanting,unpruned, not
fertilizedwithin the last 4 years,not plantedwith
geneticallyimproved stock,containa minimum of
200 to 300 plantedpine stemsper acrewhichappear
free to grow,not more than 25% of the maincanopy
composedof volunteer pines, and establishedon a
cutover area that receivedtypical site preparation
Piedmont
Georgia
Virginia
DATA
Plain
11
105
3___•8
186
preparation,
whenplanted,whetheror notreleased,
and other pertinentinformation.In addition,number of treesplantedand ageweredetermined.
The followingdatawererecordedfor all planted
pines:dbh to the nearest0.i in, totalheightto the
nearestfoot, height to the baseof the live crown,
crownclass,and a stemqualityassessment.
In addition to the data recordedon the planted
pine, the followinginformationwasrecordedfor
naturalpinesandhardwoods
whichwerein themain
canopy:dbhto the nearest0.i in, totalheightto the
nearestfoot,andspecies.
Naturalpineandhardwood
treesnot in the maincanopy,but greaterthan0.5 in
dbh,weretalliedby 1-indbh classes
only.
Measurementdata from the plots were used to
computesiteindex,numberof trees,basalarea,and
volume per acre. Tables 2 and 3 showsummary
statistics
for the 186sampleplots.Whencomputing
siteindex, an equationfor combinedCoastalPlain
and Piedmont data from old fields was used (Devan
Table2. Summarystatistics
for the 186sampleplots.
Variable
Age (yearsfrom
planting)
Numberof planted
Ioblollysurviving
(trees/acre)
Arithmetic mean dbh of
planted Ioblolly (in)
Total overstorybasal
area (sqft/a--all
taggedtrees)
PlantedIoblollybasal
area (sq ft/a)
Volume planted Ioblolly
Minimum
8
275
Mean
15.2
558
Maximum
25
950
2.7
5.7
9.4
26.2
110.4
231.3
22.9
105.1
230.9
229.3
2125.2
7589.2
44.6
65.7
87.6
(cu ft/a oh)
Site index (ft, baseage
Figure1. Map showing
thelocationof sample
plotsby
county.
Eachdarkened
countycontains
oneor moreplot
installations.
SOUTHERNJOURNALOFAPPLIEDFORESTRY
25)4
• ComputedusingequationfromDevanandBurkhart(1982)withcoefficients from combined Coastal Plain and Piedmont data,
85
Table 3. Classificationof 186 sampleplots by age,
site index, and numberof trees per acre of planted
Ioblollypine.
Age
Site
index
class
class
Years
8-12
13-17
Feet
40-55
56-65
66-75
76 +
Total
Treessurvivingper acre
0-300
..........................
I
1
40-55
56-65
66-75
76+
40-55
56-65
66-75
76 +
Total
Grand
Total
501-700
Number
1
2
13
4
20
2
3
6
6
17
Total
8-25
301-500
1
701 +
Total
..........................
8
2
22
2
3
33
1
5
1
13
37
8
59
8
21
25
5
1
12
16
6
3
3
36
1
11
10
4
7
5
23
1
3
10
7
6
24
6
1
35
4
7
63
61
104
20
186
64
33
13
tion in the residual variation after accountingfor
both plantedpinesand natural pinesand hardwoods
in the main canopy that could be ascribedto the
understorydensitywascomputed.
Independentvariablesusedin the regressionequationsto predictplantedpine yield from the planted
standmeasurements
only were plantationage,averageheightof dominantsand codominants,
and number of survivingstemsper acre.In all trial regressions,
yield was subjectedto logarithmic transformation,
and age wasenteredas a reciprocal.Variousexpressionsfor the heightof dominantsand codominants
were evaluated,includingheightdividedby age and
the logarithmof height. Numbersof treesper acre
plusreciprocaland logarithmictransformations
were
entered. The following regressionequation accountedfor a relativelyhigh proportionof the variation in yield and resultedin residualplotswith no
discernabletrendsover the independentvariables:
In Y = - 1.00184+ 0.97745/A
Re -- 0.9597
and Burkhart 1982). The region-widetree volume
equationfrom Van Deusenet al. (1981) for old-field
loblollypine plantationswasusedto computetotal
cubic-footvolume (outsidebark). Site preparation
treatmentsvaried widely from locationto location;
many areas received a combinationof treatments
(Table 4).
(1)
+ 2.14146 In Ha + 0.00105 N•
Sy.x= 0.1310
where
Y = total cubic-footvolume,outsidebark, per
acreof plantedloblollypine
A = plantationage(yearssinceplanting)
Ha = averageheightof dominantand codominant plantedloblollypines(feet)
N• = numberof plantedloblollypinessurviving
(per acre)
ANALYSES
Yield Equations
Initial measurement
datafrom the permanentplots
were usedto explore relationshipsbetweenyield of
planted loblolly pine and measurementsof the
planted pine and competingvegetation,both in the
main canopyand in the understory.
Sitepreparationmethodswerehighlyvariableand
often not well documented,thus it was necessaryto
use the result of treatment--as indicated by stand
parameters--inregression
analyses.
Regression
analyseswith successively
increasinginformation were
performed. First, the proportion of variation in
planted pine yield accountedfor by measurement
dataon the plantedpine only wasdetermined.Next,
the proportionof the residualvariationafter accounting for plantedpinevariables
thatcouldbeattributed
to volunteerpinesand hardwoodsin the maincanopy
wasascertained?And finally,the additionalreduc-
Plottingresiduals
for equation(1) overthenumbers
of naturalpinesand hardwoodsin the overstoryand
numbersin the understoryshowedlittletrend except
that all residualswere negativefor all observations
in whichnumbersof volunteersin the overstorywere
greaterthan 350 stemsper acre(or about20 sqft of
basalarea per acre).
Equation(1) wasacceptedfor predictingplanted
pine yield from measurementdata on only the
plantedpine component.Numbersof naturallyoccurring pine and hardwoodstemsin the overstory
were then addedto the equation.Althoughthe sign
of the coefficientfor numbersof nonplantedtrees
in the overstorywas negative,as expected,the addition of thisvariabledid not bring abouta significant
reductionin the error sumof squares?Additional
s All testsof hypotheses
wereperformedat the0.01levelbecause
to separatethe competitorsin the main canopyinto pinesand
hardwoods;
consequently
all competingtreesin the maincanopy
werelumpedtogetherfor theseanalyses.
(1) a largenumberof testswereplannedand useof the 0.01 level
for eachindividualtestguardedagainsta greatlyinflatedoverall
Type I error rate,and (2) unlessthe testsof interestin thisstudy
showedstatistical
significance
at the 0.01 levelthere wouldlikely
be little practicalimpacton predictedvalues.
86
SOUTHERN JOURNAL OF APPLIED FORESTRY
2Therewerenotsufficient
numbers
of plotswithvolunteer
pines
Table4. Summaryof plantingmethods,sitepreparation,andintermediatetreatmentsby physiographic
regionfor 186locations.
Planting
method
Site preparation and intermediate treatments
Burn
Chop
Drain
Bed
Shear
Disc
Windrow
Spray
Other
Release
Fert.
Coastal Plain
Hand
40
24
Machine
Combination
27
2
15
1
Hand
Machine
Combination
22
10
1
8
5
6
13
10
9
14
7
12
2
8
1
10
1
8
1
4
1
20
2
12
10
22
11
4
1
14
1
1
9
4
Piedmont
11
8
Other
Hand
10
Machine
8
Combination
1
TOTAL
111
53
6
15
1
8
1
2
1
2
1
2
49
44
67
7
30
58
expressionsfor numbers in the overstorywere entered but none wassignificant.
Next, numbersof naturally occurringstemsin the
understorywereaddedto equation(1). When adding
numbersin the understory,the signof the coefficient
was positive,an unexpectedresult, but the variable
wasnot significant.Various transformationsof numbers in the understorystill showeda positiverelationship with yield after accountingfor the age,
averageheight of dominantsand codominants,and
number of survivingplanted stemsper acre. However, none of the variablesexpressingunderstory
densitywassignificant.
Finally,both numbersin the overstoryand numbers in the understorywere added to equation(1)
but no significant reductions in the error sum of
squaresresulted.In additionto the equationswhich
used numbers per unit area, analogousequations
were computed with basal area per acre and with
crowncompetitionfactor(Krajiceket al. 1961) asthe
measureof stand densityand the conclusions
were
10
5
Effectsof Site Preparation
and Physiographic
Region
on Yield
After determiningan appropriateyield equation,
relationshipsbetweenyield and sitepreparationand
physiographicregion were explored. As there was
wide variation in site preparation treatments,the
data were groupedin classes.
The followingdefinition of site preparationclasses,
usedby Clutter et al.
(1976) in an analysisof the relationshipsbetween
soilsand site preparationin slashpine plantations,
wasapplied:
Site PreparationClass1: Bedded--debrismoved
Site Preparation Class 2: Bedded--debris not
moved
Site Preparation Class 3: Not bedded--debris
moved
Site PreparationClass4: Not bedded--debrisnot
moved.
the same.
Regressionanalysesindicated that equation (1),
with age,heightof the dominantstand,and numbers
of survivingplantedpine, is adequatefor predicting
total cubic-footyield of planted pines for cutover,
site-preparedareas,exceptthat overpredictionbias
mayresultfor standswith a relativelylargehardwood
componentin the overstory(above350 stemsor 20
sq ft of basalarea per acre). It is possiblethat the
effectsof competingwoodyvegetationare indirectly
expressedthrough modificationsin height of dominants and codominants
and numbers
of trees surviv-
ing.Althoughthe measurements
of competingwoody
vegetationwere not significantlyrelated to yield of
the plantedpine, future growthof thesepermanent
plotsmay be significantlycorrelatedwith the density
of nonplantedpine competitors.
SOUTHERN JOURNAL OF APPLIED FORESTRY
Table
5 shows the distribution
of actual treatments
by theseclasses.
When testingfor the effectsof physiographic
region, the data were groupedinto two classes:(1)
Piedmont and (2) CoastalPlain. There were insufficient data (only 13 plots)in the "other"categoryto
retainit for anyof thesecomparisons
(Table6). Eight
plotshad inadequate
recordsto placetheminto the
defined site preparationclasses
and were omitted
from further analyses.
Thus, 165 plotsremainedfor
the analysesof effectsof site preparationand physiographicregion on yield. Comparisonsinvolving
the CoastalPlainphysiographic
provinceincludedall
sitepreparationclasses,
whereascomparisons
for the
Piedmont included only site preparation classes3
and 4 (classes
1 and 2 involvedbedding,and there
87
Table5. Frequencyof treatmentsby site preparation
classes.•
Treatment
Frequency
Sitepreparationclass1: bedded--debrismoved
Bed, shear
Bed, shear, windrow
1
1
Bed, shear, windrow, disk
Bed, windrow, burn
Bed, windrow, burn, KG
2
1
3
TOTAL
8
Sitepreparationclass2: bedded--debrisnot moved
Bed
1
Bed,chop
1
Bed, burn
2
Bed,chop,burn
Bed,chop, burn, drain
1
2
TOTAL
7
Sitepreparationclass3: not bedded--debrismoved
Shear
Windrow
1
9
Shear, windrow
11
Shear,windrow, ripped
1
Shear, windrow, disk
Windrow, burn
Windrow, disk, burn
6
4
5
Windrow,burn, kg
1
Shear, burn
Shear, windrow, burn
Shear, windrow, burn, bulldozed, rootraked
Shear, windrow, disk, burn
4
14
1
2
Shear,windrow, disk, burn, inject
Windrow,chop, burn
Windrow,disk, chop, burn
Shear,windrow,disk, pile, burn
Push,pile
Shear,windrow, disk, inject
2
1
1
1
1
1
Shear, windrow, disk, burn
1
TOTAL
67
Sitepreparationclass4: not bedded--debrisnot moved
Spray
Burn, disk, spray
4
1
Disk
15
Chop, burn
38
Burn
17
Chop, spray
Burn, chop, disk
1
2
Burn, disk
3
Burn, chop, drain
Chop
Chop, burn, spray
Injected
3
1
1
4
Burn, tractor mist blown
1
Wildfire
3
Burn, injected
2
TOTAL
96
by sitepreparationclasses
and physiographic
region
An analysisof covariance(withcovariatesl/A, In Ha,
and Ns, and responsevariable In Y) showedno
significantrelationshipbetweenadjustedobserved
yield and site preparationclassesor physiographic
regions.Thus the conclusion
wasthat, giventhe age,
averageheightof dominantsand codominants,
and
numberof survivingplantedpine stemsper acre,a
single yield equation can be applied for all site
preparationclasses
and physiographicregions.Clutter et al. (1976) reachedthe sameconclusionfor the
site preparationclassesand soilsgroupsthat were
included in their analysesof slashpine plantation
data.
Althoughthe sameyield equationcan apparently
be used for all site preparationclasses
and physiographicregions,it ispossible
thatdifferentsiteindex
equationsor survivalfunctionsare needed. As an
initial look at siteindex relationships,it wasassumed
that anamorphicsite index curveswould be appropriate and the guide curve
In Ha = bo + bJA
wasfitted to the plot data in eachsite preparationphysiographicregion class with sufficient data
(CoastalPlain--site preparationclasses
1, 2, 3 and 4;
Piedmont--sitepreparationclasses
3 and 4). Analysis
of varianceshoweda significantdifferencebetween
the Coastal Plain and Piedmont, but there were no
differencesbetween site preparation classeswithin
physiographic
regions.
The logarithmof height-reciprocal
of age model
fitted to the data from eachsite preparation-physiographicregionwasusedto estimatemean siteindex
for each class.Mean site index values were (Table
6):
Site preparationclass
Coastal Plain
Piedmont
I
2
3
4
76.3
63.6
61.3
57.0
59.8
55.8
Analysisof varianceproceduresshowedsignificant
differences
between mean site indexes for the Coastal
Plain; there were no significantdifferencesfor the
Piedmont.Further, there were no significantdifferences in mean site index between the Coastal Plain
• Eightplotswereomittedfromthistabulationbecause
of inadequate
recordson site preparationtreatmentsapplied.
and Piedmont for site preparationclasses3 and 4
Becausethe treatmentswere not assignedat random
(that is,the sitepreparationmethodsemployedwere
subjectivelydetermined based on knowledgeand
were no data from beddedplantationsin the Piedmont).
availabilityof techniquesplus conditionson the site
at the time of treatment),it is not possibleto make
Comparisonsof averageyieldsby site preparation
validinferencesfrom theseresults(e.g.,differentsite
classes
and physiographicregion were adjustedfor
preparationtechniquesdo or do not affectsiteindex).
the effectsof age, site index, and stemsper acre,
because the level of these variables varied from class
If one assumes,however,that there was no strong
to class.Table 6 showsthe sampleplot characteristics associationbetween inherent site quality prior to
88
SOUTHERNJOURNALOF APPLIEDFORESTRY
Table 6. Mean valuesfor selectedcharacteristics
of the sampleplots by site preparationclassesand physioõraphicreõions.
Site
preparation
class
Site
Plots
•
^õe
index
No.
Yrs.
Ft.
I
2
3
4
8
7
20
62
11.6
11.4
14.7
15.8
76.3
63.6
61.3
59.8
Combi ned
97
14.9
61.8
Yield
N•
Cu ft/a
No
Nu
BA•
................. No/a.................................
Coastal Plain
2092.6
555.5
1299.7
601.4
2289.6
536.3
2184.3
2134.6
BAo
B,%
ScI ft/a...............
524.7
23.6
22.6
57.3
73.3
391.0
521.9
485.7
880.9
103.8
78.8
108.9
104.6
1.96
1.04
5.27
6.41
3.99
5.04
6.35
10.91
535.2
62.3
733.1
103.6
5.42
8.97
54.6
80.0
66.5
1297.3
1481.2
1383.8
109.9
111.2
110.5
4.27
6.68
5.40
12.77
16.22
14.40
Piedmont
2
..........
3
4
Combined
36
32
68
15.5
16.5
16.0
57.0
55.8
56.4
2136.0
2149.3
2142.2
611.2
572.2
592.9
Other
2
..........
3
4
Combined
11
2
13
9.1
14.5
9.9
57.6
61.0
58.2
664.0
2347.2
923.0
576.2
677.0
591.7
49.9
49.0
49.8
433.7
785.5
487.8
53.2
121.4
63.7
1.70
2.35
1.80
3.46
5.95
3.85
8
7
67
96
11.6
11.4
14.2
16.0
76.3
63.6
58.4
58.5
2092.6
1299.7
1940.1
2176.0
Combined
555.5
601.4
583.1
543.7
23.6
22.6
54.6
75.0
391.0
521.9
913.2
1079.0
103.8
78.8
100.3
107.2
1.96
1.04
4.15
6.42
3.99
5.04
9.33
12.57
178
15.0
59.5
2049.0
561.4
63.0
963.8
103.3
5.15
10.67
I
2
3
4
Combined
• E•õhtplotswereomittedfromthistabulation
because
of inadequate
records
on sitepreparation
treatments
applied.
treatmentand site preparationmethod,then these
results,althoughinconclusive,
indicatethat sitepreparationmethodhasnot greatlyaffectedsiteindex.
Relationships
betweensitepreparationtechniques
and physiographicregionsand survivalwere also
•nvesti.gated.
In the survival
analyses,
theeffectsof
Ha = averageheight of dominantsand codominantsat ageA.
The covariateswere thus defined as (A)(log Np),
(A)(Ha) and (A)(X/-•a).After adjustingfor the covariates,there were no significantdifferencesin the
survivalattributableto site preparationmethod or
physiographic
region.Thisresultmustbeinterpreted
age, s•te index, and initial number planted were
removedascovariates
andthentestswereperformed
with caution, however. All data used were from stands
to determineif the mean numberssurvivingwere
8 to 25 years.The analysisused the only two data
s•gnificantlyaffectedby site preparationtreatment
available--one at time of planting (N•) and
or physiographic
region.Asin the previousanalyses, points
the other at the time of observation in an established
data from site preparation classes1, 2, 3, and 4 were
available for the Coastal Plain, while data from site
preparation classes3 and 4 were availablefor the
P•edmont.Only 69 plotscontaineddataon the number of treesplanted;thus,the survivalanalysiswas
based on a reduced data set. The form of the survival
function of Feducciaet al. (1979) wasused to define
the covariates. Their
survival function is
log(Np/N)= A[bxlogNt, + beHa+ b•X/-ff•a]
where
Np = numberof seedlings
plantedper acre
A = age (yearsfrom planting)
N = numberof survivingstemsper acreat
age A
SOUTHERNJOURNAL OF APPLIED FORESTRY
plantation(N). It is possiblethat mortalitypatterns
(especially
in the earlyyears)couldbe differentacross
sitepreparationmethodsandphysiographic
regions.
If suchdifferencesexist,theycouldhavebeenmissed
in thisanalysis,
dueto the natureof thedataat hand.
Furthermore,sampleplotswere established
only in
plantationswith reasonablygood survival,possibly
eliminatingsomeof the variationbetweensitepreparation methodsand physiographicregions.This
analysisdoespresentsomeevidence,however,that
mortalityrelationships
may not be drastically
different for differingsitepreparationclasses
and physiographicregions.
As another examinationof relationships
between
yield, site index, and survivaland site preparation
89
classesand physiographicregion, the data in each
physiographic
region were regroupedaccordingto
the followingclasses:
Site PreparationClass1: Tilled--debris moved
SitePreparationClass2: Tilled--debris not moved
Site PreparationClass3: Not tilled--debris moved
Site Preparation Class 4: Not tilled--debris not
ß Although the nature of the sample data precludes firm conclusions, indications are that survival
is not greatlyaffectedby sitepreparationmethodor
physiographicregion.
In similaranalyses
with data from slashpine plantationson site-preparedlandsin the flatwoods,Clutter et al. (1976) found (1) averagesiteindicesto be
moved
quite homogeneousfor soil seriesgroupsand site
where tilled is either disked or bedded or both. This
preparation classes,(2) no differencesin average
groupingof the data resultedin four sitepreparation
yield (adjustedfor variationin age, site index, and
classes
in eachregion.The analyses
describedprestemsper acre) by seriesgroup or site preparation
viouslywererepeatedwiththesedatagroupings.The
classes,
and (3) no significantdifferencesin average
resultsdid not change.That is, no significantrelapercentsurvivalor averagenumberof survivingtrees
tionshipswere found between adjusted observed by either seriesgroup or site preparationclass.The
yield and site preparationclasses
or physiographic analysesreported here for loblollypine plantations
regions.There was a significantdifference in the
corroboratethe findingsof Clutter et al.
height of dominantsand codominantsversusage
Results and conclusionsof this study must be
relationshipbetweenthe CoastalPlain and Piedmont
interpretedcautiouslyand in light of the type of data
physiographic
regions,but therewasnot a significant analyzed.Data from both studiesdid not comefrom
differencebetweensite preparationmethodswithin
designedexperimentsbut rather from a surveyof
each region. No significantdifferencesin mean surexistingplantations.In the presentstudy,standhisvivalwerefound betweensitepreparationclasses
or
tory data were limited and there were no measurephysiographic
regions.
ment data on the standsprior to plot installation
The sitepreparationtreatmentswere not appliedat
randombut weresubjectively
chosen,basedon methDISCUSSION
AND CONCLUSION
odsin useand conditionson the groundat the time
of plantation establishment.These resultsdo show,
For the populationof plantationssampledin this
however,that for loblollypine plantationsof the type
studyit wasconcludedthat:
sampledon cutover, site-preparedlands, a single
yield equationbasedon age, averageheight of the
ß Yield of the planted loblolly pines can be predominants and codominants, and number of survivdicted from age, averageheight of dominantsand
ing planted pines,is applicableacrossa wide range
codominants,
and numberof survivingplantedpines
of sitepreparationmethodsand a broadgeographic
only. For thesedata, it wasnot necessary
to include
area. Preliminary indicatorsare that different site
measurements
from volunteerpinesand hardwoods
index curvesmay be needed for the CoastalPlain
to obtain adequatepredictions,but there was eviand Piedmontregions,but that within each region
dence that inclusionof the densityof volunteersin
the samecurveappliesto all sitepreparationmethods
the overstorymay be necessary
at high levels(more
And, finally, there is evidencethat survivalrelationthan 350 stemsor 20 sq ft of basalarea per acre of
shipsare similaracrosssitepreparationmethodsand
volunteers).
physiographicregions.
ß A singleyieldequationisadequatefor predicting
total cubic-footvolume yield acrossall site preparation methodsand physiographicregionssampled.
Literature
Cited
ß The height of dominantsand codominantsversusagerelationshipdoesn'tseemto be alteredby site
BURKHART,
H. E., Q. v. CAO,and K. D. WARE.1981.A comparison
preparationmethod,but it wassignificantly
different
of growthand yield predictionmodelsfor loblollypine. Sch.of
between the Coastal Plain and Piedmont physioFor. and Wildl. Resour., VPI and State Univ., Publ. FWS-2-81
59 p.
graphicregions.
ß No
firm
conclusion
can be drawn
from
these
data regarding sitepreparation effectson siteindex.
Mean site index was significantlydifferent for the
four site preparationclasses
in the CoastalPlainbut
it wasn't different
for the two classes in the Piedmont.
This result doesnot provide strongevidencefor or
againstsitepreparationaffectingsiteindex,because
site preparationmethodswere not assignedat random in theseplantations.
90
CLUT•rER,
J. L., j. c. FoRysoN,and B. D. S•IVER. 1976. Some
relationships
betweensoilsand site preparationin flatwoods
slashpineplantations.
In Proc.,SixthSouth.For.SoilsWorkshop,
Charleston,SC. p. 28-41.
DEVA•,J. S. and H. E. BVRK•AR•r.1982. Polymorphicsiteindex
equationsfor loblollypine basedon a segmentedpolynomial
differential
model. For. Sci. 28:544-555.
FEDUCCIA,D. P., T. R. DELL, W. F. MANN, T. E. CAMPBELL,and
B. H. POLMER.
1979.Yieldsofunthinnedloblollypineplantations
on cutoversitesin the WestGulf Region.USDA For. Serv.Res
Pap.SO-148.88 p.
SOUTHERNJOURNAL OF APPLIED FORESTRY
KRAJ•CgK,
J. E., K. A. BR•N}•MAN,
and S. F. G•N(;R•cn.1961.Crown
competition--ameasureof density.For. Sci.7:35-42.
V^N DErSEN, P. C., A.D.
Sv•.•.•v^•, and T. G. M^-r•E¾. 1981. A
predictionsystemfor cubicfootvolumeofloblollypineapplicable
through muchof its range.South.J. Appl. For. 5:186-189.
HaroldE. BurkhartisThomas
M. Brooks
professor,
DeborahC. Cloeren,
formergraduate
research
assistant,
and
RalphL. Amateis,
research
associate,
Department
of Forestry,VirginiaPolytechnic
Instituteand StateUniversity,
Blacksburg,
Virginia24061.
Economic Aspectsof the Forest
Regeneration Delay Decision
ThomasJ. Strakaand JamesE. Hotvedt
ABSTRACT.Regeneration
lag,thecostresulting
froma delayin
reestablishment
of a foreststand,represents
an important
opportunitycost--the
cost
oftheforegone
opportunity
togrowtimber
over
theperiodof thedelay.Thelandexpectation
value(Le)criterion
•susedtoevaluate
thecosts
associated
withone-time-only
andperpetuallags.Significantdecreases
in wealth,or barelandvalue,
werefoundusinga simplified
example
withreal-world
costand
pricedata.Changes
in required
landbases
resulting
fromregeneration
delays
werealsoreviewed.
Theadditional
landrequirements
resulting
fromscheduled
delays
in regeneration
canbecostly.
ing a timber saleconsiderregenerationlag? In the
caseof proposedwholesalepostponements
of regeneration after harvest,corporateofficersimplicitly
assumethat savingsin short-terminterest on borrowedmoneyand the benefitsof maintainingdesired
levels of liquidity offset the costsof regeneration
delay. In this case,thesecostsalso include higher
costsof sitepreparationsincethe sitewill havebeen
left asis after a harvest,resultingin higherlevelsof
Regeneration
isdefined
astheactofreplacing
old
This paper is concernedwith deliberatedelaysin
regeneration.The regenerationlag problemcan be
analyzedbystudyingfour affectedfactors:cashflows,
forest structureand allowablecut, land expectation
values,and land requirementsfor mill furnish.Brodie and Tedder (1982) discussed
the impactof regenerationdelayon the harvestvolumelossfor the
forest as a whole, stressingthe impact of different
allowablecut constraints.We stressthe managerial
implications
of regenerationlag, mainlyits impact
on land expectationvaluesand land requirements.
trees,either naturallyor artificially.While prompt
regenerationisusuallyassumed
in managementplanning,it is not alwayssotimely.Timber salesare often
extended for up to a year in order to clean up a sale,
1.e.,to harvesta few marginalcordsof wood.Another
causeof regenerationlag is businessdownturnsand
their resultantcashflow problems.In the lastrecessionfor example,somecompanies
considered
wholesalepostponement
of regenerationafter harvestto
saveon cashoutflow,often to the chagrinof woodlandsmanagers.In the caseof deliberatepostponement, it may well be that improvementsin shortterm
cash flows are considered
sufficient
to offset
lossesin land expectationvalues,increasedland
requirements,and disturbances
in the optimalforest
structure(or a delay in achievingit).
Regenerationlag refersto the costof delayin reestablishment of a forest stand (Davis 1966). It is
often ignoredin forestinvestmentanalyses.Regeneration lag representsan opportunitycost,or the
costof the foregoneopportunityto growtimber over
the period of the delayand the costof postponing
future rotations.The decisionto delay regeneration
means
that
the value
of future
rotations
will be
deferredby the lengthof the delayor, alternatively,
that harvestsof delayed standswill be conducted
beforethe ageof financialor of biologicalmaturity.
How often doesthe foresterresponsible
for extendSOUTHERNJOURNAL OF APPLIED FORESTRY
brush control.
ANALYTICAL
MODEL
Land expectation
value(Le), or bare land value,
can be used to measurethe changein forestland
valueresultingfrom regeneration
lag. The formula
used to calculate L, is often called the Faustmann
formula. The calculationis relatively simple and
involvescompoundingeachcostand revenueat a
given interestrate to derive net incomeat some
specified
rotationage.Sincethe formulacalculates
bare land value,regenerationcostis included,but
land cost is not. It is assumedthat the specified
rotationwilloccurin perpetuityandthattheperiodic
cashflow will not changeover time. Thus, we are
dealingwitha perpetualperiodicpayment.
The net
valueof compounded
incomelesscompounded
costs
91