Lecture 12FORE 3218

Forest Mensuration IIForest Mensuration II

Lecture 12Lecture 12

Tree-Growth and Stand-Table ProjectionTree-Growth and Stand-Table Projection

Avery and Burkhart,Avery and Burkhart,

Chapter 16Chapter 16

Lecture 12FORE 3218

Increase in Tree Diameter Increase in Tree Diameter

Adding wood just under the barkAdding wood just under the bark– In temperate forests, a growing tree adds a yearly layer. In temperate forests, a growing tree adds a yearly layer.

What about trees in tropical forests? What about the trees What about trees in tropical forests? What about the trees growing under a very stressful environment?growing under a very stressful environment?

Annual ring width decreases as tree age increases, Annual ring width decreases as tree age increases, but basal area and volume may increasebut basal area and volume may increase

Diameter growth are influenced by spacing (stand Diameter growth are influenced by spacing (stand density), climate, site characteristics, disturbancesdensity), climate, site characteristics, disturbances

Lecture 12FORE 3218

How tree height How tree height growth is growth is accomplished? accomplished?

Tree height typically Tree height typically grows in a sigmoid grows in a sigmoid fashionfashion

Increase in Tree Height Increase in Tree Height

Tree Age (Years)0 10 30 40 5020

0

10

20

30

Tot

al H

eigh

t (m

)

Cumulative Growth

Lecture 12FORE 3218

Defining Periodic and Mean Annual GrowthDefining Periodic and Mean Annual Growth

Current annual growth (current annual increment)Current annual growth (current annual increment)– The increase in tree size (measured by dbh, height, volume, The increase in tree size (measured by dbh, height, volume,

or biomass) for one yearor biomass) for one year

Periodic annual growthPeriodic annual growth– Average annual growth over a period of 5 or 10 yearsAverage annual growth over a period of 5 or 10 years

Mean or average annual growth Mean or average annual growth – Total tree size at any point in time divided by total ageTotal tree size at any point in time divided by total age

Lecture 12FORE 3218

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80 100

Age (year)

DB

H G

row

th (

cm/y

ear)

Relationships between Periodic and Mean Relationships between Periodic and Mean Annual GrowthAnnual Growth

What if the growth is measured by tree height, volume or biomass?

Lecture 12FORE 3218

Growth from Stem AnalysisGrowth from Stem Analysis

Diameter growthDiameter growth Height growth Height growth Volume or biomass growth Volume or biomass growth

Lecture 12FORE 3218

Absolute and Relative Growth RateAbsolute and Relative Growth Rate

Absolute volume growth rate (mAbsolute volume growth rate (m33/year)/year) Relative volume growth rate (growth percent/year)Relative volume growth rate (growth percent/year)

1

12percent Growth vn

vv

Lecture 12FORE 3218

Stand GrowthStand Growth

““The basic elements of stand growth are The basic elements of stand growth are accretion, mortality, and ingrowth”accretion, mortality, and ingrowth”

AccretionAccretion is the growth on all trees that were is the growth on all trees that were measured at the beginning of the growth period, measured at the beginning of the growth period, including the growth on tree that were cut plus including the growth on tree that were cut plus those tree died and were utilizedthose tree died and were utilized

Mortality Mortality is the volume of trees initially measured is the volume of trees initially measured that died during a growth period and were not that died during a growth period and were not utilizedutilized

Growth Growth – Gross: Gross: change in total stand volume including mortality change in total stand volume including mortality – Net: Net: change in total stand volume excluding mortalitychange in total stand volume excluding mortality

Lecture 12FORE 3218

Characteristics of Stand-Table ProjectionCharacteristics of Stand-Table Projection-Procedure-Procedure

1.1. Develop a present stand table showing number of Develop a present stand table showing number of tree in each dbh classtree in each dbh class

2.2. Determine past periodic growth by dbh classes by Determine past periodic growth by dbh classes by increment borings or measurement of PSPincrement borings or measurement of PSP

3.3. Apply past diameter growth rates to the present Apply past diameter growth rates to the present stand to derive future stand tablestand to derive future stand table

4.4. Apply local volume equation to estimate both Apply local volume equation to estimate both present and past stand volumepresent and past stand volume

5.5. Obtain periodic stand volume growth as the Obtain periodic stand volume growth as the difference during the growth perioddifference during the growth period

Best suited to uneven-aged, low-density, and Best suited to uneven-aged, low-density, and immature timber stands, why?immature timber stands, why?

Lecture 12FORE 3218

How to determine diameter growth with How to determine diameter growth with increment boringsincrement borings

Measure Measure dobdob Obtain wood growth in Obtain wood growth in

diameter from an diameter from an increment boring (e.g., increment boring (e.g., 10 years)10 years)

Develop a relationship Develop a relationship between bark thickness between bark thickness and and dibdib

Calculate Calculate dobdob from from dib dib and the above and the above relationship for any relationship for any previous yearsprevious years

Lecture 12FORE 3218

Stand Mortality and IngrowthStand Mortality and Ingrowth

Mortality and ingrowth can be obtained reliably from Mortality and ingrowth can be obtained reliably from consecutive reinventories of PSPs. consecutive reinventories of PSPs.

Year 1990 Year 2000

Lecture 12FORE 3218

Elements of Reliable Stand-Table Elements of Reliable Stand-Table ProjectionProjection

Growth-index ratio by dbh classes estimated Growth-index ratio by dbh classes estimated from surviving treesfrom surviving trees

Mortality by dbh classesMortality by dbh classes IngrowthIngrowth