Application of Growth Models in Thinning

7/27/2019 Application of Growth Models in Thinning

1/60

APPLICATIONS OF GROWTHMODELS FOR THINNING

Makrand Gujar

11-661-003

I. Ph.D


2/60

Thinning

Thinning is defined as a felling made in an

immature stand for the purpose of improving

the growth and form of the trees that remain,after thinning without permanently breaking

the canopy.

Thinning consist of series of successive

felling operations for a number of times

before crop matures.

The interval between two successive felling

may be fixed but it is dependent on time

required for canopy closure.

Thinning is carried from sapling stage and is

continued upto the beginning of the

regeneration period

Thinning is applicable to pure and even agedor nearly even aged crop.


3/60

Objectives of Thinning

To improve the hygieniccondition

To create best condition of

growth

Salvage the anticipated lossesof the mercantable volume

To obtain desirable

composition of crops

Improvement in wood quality

To obtain intermediate yield

and increase net yield and

financial out turn

To reduce risk of pest and


4/60

Thinning cycle

Planned number of years whichelapses between succesive orconsecutive thinning in the samecrop.

Thinning cycles are not regular

They are shorter during earlyperiod of growth and longer whenthe crop is middle aged to mature.

Eg.

The teak plantation in M.P & Mah.Are thinned at 5th , 10th,20th,30th,45th and 60th year.

Upto 10 th year, thinning cycle isfive year,from 10th to 30th year it is

ten year and afterwards it is fifteen


5/60

Thinning reduces mortality (or salvages it before it occurs) by reducing the number of trees

per acre.

The remaining trees then have more site resources to draw from and typically grow faster

and healthier.

By thinning at regular intervals, one can be assured that stress due to overcrowding is

avoided.

Thinned trees can then develop stronger root systems and be less prone to windthrow.

The species composition of a stand can also be influenced by thinning, e.g., depending on

which tree species are cut and which are retained.

If sawlogs or veneer logs are sought, thinnings would focus on developing large and high

quality stems. Thus thinning can improve growing conditions, species composition, tree

quality, and the economic value of the stand.

Importantly, poor thinning choices can reduce quality and economic values (e.g., high

grading or always taking the best trees and leaving the worst).

However, well planned thinning can provide increases in timber values and economic

returns. Specific recommendations for thinning are provided in the tree specific guide

sections.

ADVANTAGES OF THINNING


6/60

Growth Models..

Models estimating growth and yield of forest stands provideimportant tools for forest management.

It is useful to distinguish between

models for prediction, and(intended for management)

models for understanding(e.g. physiological, process models)

(Bunnell 1989).

Typical applications are in

forecasting for forest planning purposes,

in the comparison and

evaluation of silvicultural (pruning, thinning) regimes,and

in the updating of stand description databases.

Thinning models comes under models for prediction category


7/60

Survival pattern of tree Three distinct survival patterns found during the life of a plantation which must be recognized if the total

survival pattern is to be modelled.

The first pattern occurs during the first year after planting.

Survival during the first year is highly variable and depends on many factors including care of the planting

stock at the nursery and at the planting site, time of seedling storage, planting crew practices and first year

climatic factors (such as the amount and distribution of rainfall during the growing season).

The second easily identifiable survival pattern occurs from year one to some time beyond crown closure.

Mortality during this period is random and can be attributed to factors other than intra-specific competition

(although intra-specific competition, i.e. crown closure, may begin during this period). Important factors here

which may influence survival include levels of inter-specific competition (both woody and herbaceous), stand

establishment practices and certain stochastic elements such as insect, rodent or disease attacks.

The third survival pattern occurs from the onset of intra-specific competition induced mortality to rotation.

During this period, the effects of intra-specific competition are the dominant forces affecting survival (although

random mortality can still occur). Two important factors which must be considered when modeling survival

during this period include stand density and site index.

Amateis et al.,1996


8/60

These factors will also affect when competition induced mortality

begins(obviously, denser stands on better sites will enter this stage of stand

development sooner). In addition, intermediate silvicultural treatments applied to

plantations during this period may also affect survival patterns.

Thinning, in particular, has a direct effect on stand survival because it alters the

amount and distribution of the growing stock.

It also changes the overall vigor of the stand by removing smaller, slower growing

trees (if the thinning is from below) and providing additional growing space for the

residual stand.

Therefore, appropriate survival models for this period of intra-specific competition

should be sensitive to natural changes in stand density due to self-thinning as well

as artificial changes due to thinnings applied as silvicultural treatments


9/60

Growth models used for thinning

FORECASTis a management-oriented, stand-level, forest-growthand ecosystem-dynamics model. The model was designed to

accommodate a wide variety ofsilvicultural and harvesting systems

and natural disturbance events (e.g., fire, wind, insect epidemics) in

order to compare and contrast their effect on forest productivity,stand dynamics, and a series of biophysical indicators of non-timber

values.

COMMIX :A mechanistic model, COMMIX, whichsimulates growth of mixed-species forest stands

(Bartelink 1998b),

TADAM

SILVA

BWINPRO SORTIE
http://en.wikipedia.org/w/index.php?title=Stand-level_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_growth_modelling&action=edit&redlink=1http://en.wikipedia.org/wiki/Ecosystemhttp://en.wikipedia.org/wiki/Silviculturehttp://en.wikipedia.org/w/index.php?title=Forest_stand_dynamics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_stand_dynamics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_stand_dynamics&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_stand_dynamics&action=edit&redlink=1http://en.wikipedia.org/wiki/Silviculturehttp://en.wikipedia.org/wiki/Ecosystemhttp://en.wikipedia.org/wiki/Ecosystemhttp://en.wikipedia.org/wiki/Ecosystemhttp://en.wikipedia.org/w/index.php?title=Forest_growth_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_growth_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Forest_growth_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Stand-level_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Stand-level_modelling&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Stand-level_modelling&action=edit&redlink=1


10/60

Thinning effects

Thinning causes reduction of density and associatedreduction in resource use and competition, whichincrease the growth of the remaining trees and reducestheir mortality rate.

On the stand scale this effect can be divided into twoeffects.

First, the total stand production (NPP) is reduced(although very slightly for light thinning) because of thereduced resource capture (Zeide, 2004).

Second, the self-thinning (density dependent) mortalityis reduced, which is linked to the improved growth of theremaining trees.


11/60

3/2 Law of Self-Thinning

The most famous and most controversial of hypotheses

is the

3/2 Law of Self-Thinning(Hutchings 1983, Weller 1987,

Lonsdale 1990), which says that

stands of plants reach a limiting density such that the

average plant mass w =W/N is proportionalto N3/2, i.e.,


12/60

CASE STUDIES


13/60

Effects of stand composition and thinning in mixed-

species forests: a modelling approach applied to

Douglas-fir and beech

A mechanistic model, COMMIX, which simulates growth of mixed-speciesforest stands (Bartelink 1998b), was used to estimate the response ofmixed-forest growth and development to specific silvicultural treatmentsand stand compositions.

COMMIX(COMpetition in MIXed stands)

The model was also used to analyze effects of thinning regimes and stand

composition on productivity.

To investigate model performance, simulation estimates were comparedwith field data.(yield tables) (Jansen et al. 1996).

Thinning regimes included in the yield tables (in terms of basal area to beremoved) were applied in the model runs.

In the present study, COMMIX was used to investigate the effects of standcomposition and thinning regime on growth and yield.

In this study, thinning from above (crown thinning or high thinning) wasapplied: to benefit the best trees, the strongest competitors are removed,H. H. BARTELINK,2000


14/60

The relative yields of Douglas fir and beech were defined

as:

RYD =YDmix / YDmono

RYB =YBmix / YBmono

where YDmixand YBmix are the yields of Douglas-fir and beech in

the mixture (m3 ha1), and

YDmono and YBmono are the yields in monoculture (m3 ha1),

The relative total yield was defined as:

RYT = RYD + RYB.


15/60

Two thinning regimes were also defined.

In Thinning Regime I, thinning intensity (expressed as a fraction of the standing basal area) was

the same as used in the yield table (the default thinning regime). High thinning was the

method of thinning applied.

Beech is generally believed to be at a disadvantage in this mixture type,

Thinning Regime II was defined so that the thinning intensity in beech was fixed at only 5% of

the standing basal area, whereas for Douglas-fir the thinning fraction increased from 1.0 times

the default fraction (i.e., the yield table values) at Age 20, to 1.5 times the default fraction at Age

70.

Simulated stands comprised 400 (20 20) trees.

Initial planting distance was 2.5 m, based on Douglas-fir stand densities.

The model was set to simulate 50 years of stand growth, from age 20 to 70.


16/60

Table 2. Tree components distinguished in the COMMIX

model and the initial values of the variables. Biomass

amounts are dry weights.

Foliage area is one-sided (i.e., projected area). Tree

diameter (dbh) is measured at breast height (1.30 m

above the forest floor).

Main species-specific parameters used COMMIX

(after Bartelink 1998b). In addition, empiricalparameters are applied to describe the allometry

between tree diameter at breast height (dbh; 1.30 m

above the forest floor), dbh and branch biomass,

dbh and coarse root biomass, dbh and crown

dimensions, and dbh, height and bole volume.


17/60

RESULTS


18/60

Figure 1. Simulated LAI development over time for stands with

different shares of Douglas-fir and beech, for Thinning Regime

I. Abbreviations: %dg indicates percentage of Douglas-fir.

Figure 2. Simulated development over time of the total stand

biomass for stands with different proportions of Douglas-fir and

beech, for Thinning Regime I. Abbreviations: %dg indicates

percentage of Douglas-fir.

Figures 1 to 3 show only the results obtained under Thinning Regime I, because relatively little variation between the two

thinning regimes were apparent in the stand-level results.

Figure 3. Simulated development over time of the root/shoot ratio for

stands with different shares of Douglas-fir and beech, for Thinning

Regime I. Abbreviations: %dg indicates percentage of Douglas-fir.

Figure 4. Simulated stand volume increment for stands with different

proportions of Douglas-fir and beech, for Thinning Regimes I (a) and

II (b). Abbreviations: % indicates percentage of Douglas-fir.

Th l ti i ld (RYB RYD d


19/60

The relative yields (RYB, RYD, and

RYT) of beech and Douglas-fir in the

two scenarios.

The yield of Douglas-fir in the mixedstand is higher than the yield of a

monospecific Douglas-fir stand.

However, when thinning intensities in

beech are lower than the default-thinning regime (Figure 5b), the RY of

Douglas-fir in mixtures with a low

proportion of Douglas-fir is less than 1.0,

and the RYT exceeds 1.0. Figure 5. Estimated relative yield (RY) for the stands, based onthe stem volume production over a 50-year period, for Thinning

Regimes I (a) and II (b).

The lower-left to upper-right solid line represents the yield of the

Douglas-fir trees in the mixture (RYD), the upper-left to lower-rightsolid line represents the beech yield (RYB),

the horizontal solid line is the (mixed) stand total yield (RYT).

The dashed lines show the expected yield if intra- and inter-

specific interactions were equivalent, i.e., no advantage of mixing

would exist.

The position of the individual stands on thex-axis depends on

their proportion (in terms of basal area) of Douglas-fir.


20/60

Figure 7. Relative diameter frequencydistributions of beech (open) and Douglas-

fir(solid), for Thinning Regime I. Relative

diameter frequency distributions after 50 years

of growth (Age 70), for the five initial stand

conditions (ae). The x-axis shows the dbh

class(cm), and the y-axis shows the relative

frequency in the stand.

Figure 8. Relative diameter frequencydistribution of beech (open) and Douglas-fir

(solid), for Thinning Regime II. Relative

diameter frequency distributions after 50 years

of growth (Age 70), for the five initial

stand conditions (ae). The x-axis shows the

dbh class (cm), and the y-axis shows the relative

frequency in the stand.


21/60

The model was validated with field data from yield tables.

For douglas fir, For Douglas-fir, the yield table data conformed well to the

results of simulated low thinning in the first decades. However, there were differences between table and model estimates in

older stands.

The higher estimates with the model compared with the yield table in older

stands are in accordance with the findings of Schoonderwoerd and Daamen

(1995),who reported that the yield table underestimates growth rates instands older than approximately 40 years.

The simulated beech stand initially grew faster than described by the yield

table, but slowed down with increasing stand age.

Simulated stand productivity decreased as stand age increased, which couldbe attributed to the opening up of the canopy.

The thinning intensity indicated by the yield table is large compared with the

estimated basal area increment

Conclusion


22/60

Comparing Thinning Regimes I and II reveals that,

For Douglas-fir, increased thinning intensity of Douglas-fir(Thinning Regime II) results in

(1) larger diameters in stands with a low share of beech;

(2) smaller diameters in mixtures with a large share of

beech, compared with the stand structures arrived at inThinning Regime I.

For beech, the reduced thinning intensities in both beech and

Douglas-fir (Thinning Regime II) lead to a higher stem

number and consequently, a lower mean dbh and asmaller dbh range.


23/60

TAUYIELD: A STAND-LEVEL GROWTH AND YIELD

MODEL FOR THINNED AND UNTHINNED LOBLOLLY

PINE PLANTATIONS

TAUYIELD can be used for a variety of purposes including inventory

updating, evaluating thinning as a silvicultural alternative and as input to

management decision-making.

The light-thin and heavy-thin plots used in developing TAUYIELD

received primarily selection thinnings from below with a few plots first

receiving a row thinning to provide access followed by a selection

thinning.

Trees were selected for removal based on size, vigor, quality and

spacing. All plots were thinned once and allowed to grow for twelve years.

Amateis et al.,1996


24/60

Basal area and survival for each of four thinning treatments at plot

establishment, five years, ten years and eighteen years.


25/60

The thinning response function developed by Liu et al. (1995)

was incorporated into each dynamic equation of the system. The

general form of the function is:

where: T = thinning response

Ga, Gb = stand basal area after

and before thinning, respectively

A = stand age

TA = age of thinning

r, k = parameters to be estimated


26/60

Equation (1) has certain desirable biological properties.

The first is that when no thinning has occurred, the before to after thinning basal arearatio is 1 which means T has no effect on the equation of which it is a part.

Second, at time of thinning the response is also conditioned to be 1 which means

there is no immediate response at the time of thinning.

Third, response to thinning begins at zero and, depending on the magnitudes andsigns of r and k, affects the equation into which it has been incorporated to an

increasing degree up to some maximum effect and then diminishes over time

.

The duration of thinning response (in years) is determined by the value of the duration

parameter, k.

The rate parameter, r, is dimensionless and along with G , G , A and TA defines the

shape of the response function.


27/60

In order to project stand basal area, it is necessary to provide TAUYIELD

with an initial basal area. When one is not available, the following basal area

prediction equations can be used:

where: N = number of trees removed in the thinning operation tN = number of trees remaining after thinning a

G = basal area removed in the thinning operation t

b - b = parameters to be estimated

BASAL AREA PREDICTION EQUATIONS


28/60


29/60

Total yield prediction

In order to predict total cubic foot volume, a multiple linear

regression equation was formulated:

where: b - b = parameters to be estimated


30/60

Thinned-unthinned

Figures 11a 11d compare some basic stand development relationships

for the average unthinned, light thinned and heavy-thinned stand in theregion-wide plantation data set.

At plot establishment, the average stand conditions were age 15, siteindex 60, 566 trees per acre and 110 square feet per acre of basal area.

Following thinning, the average light-thinned conditions were 315 treesper acre and 80 square feet per acre of basal area. For the averageheavy-thinned stand, the mean residual number of trees per acre was238 and the mean residual basal area was 65 square feet per acre.

These figures present projections to age 35 which, for the average stand,is 20 years following thinning.

(1) Unthinned control plot,

(2) Lightly thinned plot from

which approximately

one-third of the basal

area was removed, and,

(3) Heavily thinned plot from

which approximately

one-half of the basalarea was removed.

Comparison of TAUYIELD projected growth and yield data for unthinned


31/60

MIC Stand Age

10 15 20 25 30

Ft3/ac

MIC 1:

traditional309 1,121 2,004 2,716 3,158

MIC 2:

genetics396 1,353 2,355 3,135 3,605

MIC 3:

MIC2 + F396 1,353 2,637 3,433 3,912

MIC 4: MIC

3 + H518 1,670 3,139 4,033 4,502

MIC 5: MIC

4 + 2nd

F&H

641 2,170 3,645 4,587 5,057

SRTS-FIA 568 1,138 1,708 2,361 3,013

1993 RPA 310 1,136 1,892 2,382 2,824

1997 FIA

Georgia

Survey

420 912 1,540 1,969 2,625

(Ft3/ac to a 4 in.

diameter outside

bark top)

MIC=management

intensity class;F=fertilization;

H=herbicide

application.

TAUYIELD assumes

SI 60 at base age 25

and planting densityis 600 trees per ac;

SRTS-FIA, 1993

RPA, and 1997 FIA

Georgia survey data

p p j g y

MICs with FIA data and modeling assumptions. Merchantable wood

volume

Thinning Response and Thinning Bias


32/60

Thinning Response and Thinning Bias

in a Young Scots Pine Stand The study analyses the annual post-thinning response and thinning bias of a young Scots pine

stand as a function of tree size, competition faced by the tree, and competition that is removed

around the tree in the thinning treatment.

The thinning response of a tree was defined as the change of tree growth due to a thinning

treatment. The thinning bias was defined as the difference between the true growth and model

prediction.

A distance-dependent (spatial) and a distance-independent (non-spatial) growth model were

used in the calculations.

The distance-dependent growth model was (Miina and Pukkala 2000; Equation 8):

(id)0.5 = 2.7432 3.0645/(d + 5) + 0.3332d/(age + 5) 0.3115ln(age) 0.1160ln(G) 0.0411CIp

0.0358CIs

where id is the future 5-year increment in overbarkdiameter (cm),

d is the tree diameter (includingbark) at breast height (cm), age is the tree age at breast

height (years),

G is the stand basalarea (including bark) (m2ha1),

CIp and CIs are the competition indices computed from pine and spruce competitors, resp.Timo Pukkala, Jari Miina and Marc Palah,2002


33/60

The distance-independent growth model was (Nyyssnen and Mielikinen 1978;

Equation 4):

ln(pd) = 5.4625 0.6675ln(T) 0.4758ln(G) + 0.1773ln(D)

0.9442ln(Hdom) 0.3631ln(d) + 0.7762ln(h) wherepd is the future annual increment in overbark

diameter growth in the next 5-year period, as a compound interest percentage

(%),

T is the stand age (years),

G is the stand basal area (including bark) (m2ha1), D is the diameter(including bark) of the median basal area tree (cm),

Hdom is the dominant height (m),

d is the tree diameter (including bark) at breast height (cm) and

h is the tree height (m)

The empirical data were measured from a thinning experiment consisting of ten plots,

each 40 30 m in size, which were thinned to different stand densities.

The ten-year post-thinning growth of every remaining tree was measured.


34/60

Table . Stand characteristics of plots after thinning in 1986/87 and in 1997.

N = number of stems per ha,

G before and G = stand basal area before and after thinning, respectively,

D = mean diameter at breast height,

H = mean height, T = mean breast height age, and g = weighted by tree basal area.


35/60

Where Cij is competition index for tree j

nj is the number of neighbour nearer than 6m

ij is vertical angle defined by the predicted height of the tree j

The following competition index was computed for every

tree :


36/60

The annual thinning response in

different classes of (A) diameter, (B)

retained competition and (C)

harvested competition Diameter

growths are predicted with thedistance-dependent model.

The annual thinning response in

different classes of (A) diameter, (B)

retained competition and (C)

harvested competition. Diameter

growths are predicted with thedistance-independent model.


37/60

Conclusion

The results indicated that the highest thinning response is among medium-sized

and co-dominant trees.

The thinning response is quite small, and even negative for some trees, for two

years after thinning but it becomes clearly positive from the third year onwards.

The spatial model underestimated the growth of small trees (which usually face

high competition) while the non-spatial model overestimated the growth of treesthat are small or face much competition.

The spatial model used in this study overemphasized the effect of competition while

the non-spatial model underestimated this effect. Both growth models

overestimated the growth of trees in heavily thinned places, but this bias

disappeared in two years.

The negative bias was more pronounced with a spatial growth model because the

tendency of the non-spatial model to underestimate the growth of trees facing little

competition partly compensated for the negative bias.


38/60

A generic model of thinning and stand density effects on forest

growth, mortality and net increment

The model is based on the relationship between the self-

thinning limit, i.e. the maximal number of trees that can

coexist on a fixed area (Nmax; cf. symbols in Tab. I) and

the mean tree size (b).

To model the number of trees and the effects of thechanges in forest stand density during the development

of a stand, a self-thinning equation is used.

For stands growing at maximum density (closed stands)

b = k Nmax

Where, Nmax is number of trees and b is the biomass of

the average tree

(Oskar et al.,2009)


39/60

Closure (c) after a thinning. The figure shows thinning removal

ofN0 Nt trees, which are smaller than the average tree (thinning

from below). This leads to an increase in mean tree size (b)

from b0 before thinning to bt after the thinning. c after the thinning is

given by N after thinning (Nt) divided by the Nmax (solid line) corresponding

to bt (Nmax t). The dashed line shows the development after

thinning.


40/60

The response of growth rate (ug) and mortality (um) tostand closure (c). Dotted straight lines show the responses

immediatelyafter thinning before the trees have utilized the

new growing space available. The solid lines show the

acclimated responses and the dashed lines show the effect

of a thinning to c = 0.5 followed byacclimation.


41/60

All values are means for each species. 1 Number of observations, 2mean stand age during experiment, 3 duration over which mean

responses were

estimated, 4 adjusted value, measured value was 1.27

q is mean tree size,


42/60

Examples of the development of un-

thinned (solid line) and a thinned stand(dashed line) simulated with a forest

growth model for un-thinned stands

(Franklin et al., 2009) combined with the

thinning scenario presented here, including

the effect of competition

un-related mortality (Eq. (7)).

Thinnings that reduce closure (c) to

c = 0.6 are triggered when c > 0.85. The

stand is Scots pine planted

at 3000 trees per ha. Net increment (C) isgross biomass growth

mortality.


43/60

In conclusion, introducing a generic thinning framework

as presented in this study in large scale scenario

analyses of forest resource development could

significantly increase their realism with regard to the

silvicultural decision space in forest management.


44/60

Thinning Impacts on Even-aged

Stands

of Eucalyptus in Brazil

E i t l D i


45/60

Experimental Design

-Replicated randomized complete block with repeated measures

-6 blocks (two in each installation), each one involving two repetitions;

- 4 treatments, corresponding to different basal area percentages removed in each thinning :

Treatment 1: 20% without pruning;



Treatment 4: 35% with pruning up to 6.0 meters;

- Each block contained 8 permanent rectangular plots, with an area of 2,600 m2, totaling 48

plots (6 blocks x 2 repetitions x 4 treatments)

Eff t i di i t f t t l h i ht


46/60

Effect on periodic increment of average total height

A B C

A: only thinning 35% and thinning 35% + pruning were equal

B and C : Only thinning 20% was different from the other treatments

There is thinning effect

Effect on periodic increment of basal area per


47/60

ect o pe od c c e e t o basa a ea pe

hectare

A B C

A, B and C: only thinning 35% and thinning 35% + pruning were equal


Eff t i di i t f l h t


48/60

Effect on periodic increment of volume per hectare

A B C



Eff t i di i t f l t


49/60

Effect on periodic increment ofvolume per tree

A



B C

Conclusion


50/60

Conclusion

Thinning affected the growth of total height, diameter, basal area per hectare, total

volume per tree and total volume per hectare, but did not affect the growth of

dominant height

Thinning prevented regular tree mortality

Prunning did not affect the growth trend of the variables analyzed


51/60


52/60

THANK YOU

Using a Density Management Diagram to Develop


53/60

Using a Density-Management Diagram to Develop

Thinning

Schedules for Loblolly Pine Plantations

A density-management diagram is a stocking chart

based on natural stand development expressed as

changes in average tree size and trees per acre

overtime.

(Dean and Baldwin, 1993)


54/60

Thinning s equence for a hypoth etical s tandplot ted on

the lob lo l lyp ine dens i ty -manugement

diagram. Dotted l ines denote upp er and low er

grow ing stock l imi ts for th isexample.


55/60

Thinning is an important means to pursue silvicultural

objectives(e.g. selection of desired tree species,

promotion of stability and stem quality) that generates

income opportunities during the long rotation periods in

temperate and boreal forest ecosystems. As acentrepiece in stand level forest management, thinning

has received considerable attention in forest research


56/60

WHY THINNING?

Thinning removes surplus trees and concentrates the

potential wood production of the stand on the selected crop

trees. By thinning your plantation, you are essentially

salvaging trees which would eventually die naturally.However, by thinning, you can control which trees survive.

When the average height of the trees in the forest plantation

is greater than 10 feet, it is time to ask a professional forester

about thinning.

Crown closure, or when the crowns of the trees in the

plantation begin to crowd each other, is another clue that the

plantation requires thinning.

Modeling Diameter Growth and Self-Thinning


57/60

g g

in Planted Sugi

(Cryptomeria japonica) Stands

The objectives of this study were to analyze diameter

growth in relation to natural thinning in high-density

stands in even-aged, pure plantation forests and to

develop a growth prediction system based on Japanese

permanent plot data. the diameter growth rate was formalized as a function of

DBH, stand density and stand age, using parameters

derived from full density curves

Tohru Nakajima*,1, Mitsuo Matsumoto2

and Norihiko Shiraishi3

ON STAND DENSITY MANAGEMENT


58/60

ON STAND DENSITY MANAGEMENT

DIAGRAM


59/60

Figure 6. Estimated absolute yield of the stands over a 50-

year period for Thinning Regimes I (a), and II (b).

The dashed lines show the expected yield if intra- and inter-

specific interactions were equivalent; i.e., no advantage of

mixing would exist.

Solid lines represent the model estimates: deviations from

the dashed lines indicate that interaction between thespecies occurs.


60/60

CROWN COMPETITION FACTOR Foresters base the rules for thinning plantations on

the crown competition factor (CCF), a measure ofcompetition that integrates tree size and the

number of trees per acre.

A plantation with a CCF = 100 indicates that thesum of the tree crown areas equals the area of theplantation.

A CCF less than 100 indicates an understockedplantation; a CCF greater than 100 indicatescrowding.

Determine the CCF of plantation by measuring anytwo of the following:

the average tree size in the plantation, the basalarea of the plantation, and the number of trees per

acre.

The number of trees per acre to thin from theplantation will depend on the CCF of the stand andthe upper and lower CCF levels between whichplantation stocking will be maintained.

Documents

Application of Growth Models in Thinning