Brief History of Site Quality Estimation from a Forest Mensuration Perspective

Eric C. Turnblom

ESRM 410 - Forest Soils and Site Productivity - Autumn 2009

Site Quality metrics should be …

highly correlated with potential maximum wood volume or biomass for the standindependent from stand density or stockingindependent from thinning regime (or other stand manipulation)independent from species compositionapplicable to other species

Primary focus on primary products

Choices in methods …Could borrow the agricultural model: bushels [bales, tons, etc.] ac-1

Historical yield records Average the yields over several rotations Issues ?

Current yield Volume at a particular age Issues ?

The trouble with density …

Choices in methods …

Height in relation to age Advantages over ag. model

For a given age, high correlation between volume yield and stand height

Average height of Dominants is little affected by density (Unlike DBH)

Not affected by thinning (except thinning of dominants)

Site index (avg. ht of dominants at “base” or “index” age) adopted by SAF in 1923 as the cornerstone for productivity estimation in US

H - Age (McArdle, Meyer 1930)

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Based on Temporary Sample Plots

H - Age (King 1966)

Based on StemAnalysis

Offers new opportunity for using curves to predict H development into the future

H - Age (Monserud 1985)

H - Age (Flewelling, et al 2001)Permanent Sample PlotMethod

Solid (pink) linesare King’s curvesdashed (blue) linesare new curves

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H - Age (Flewelling, et al 2001)Permanent Sample PlotMethod

Solid (red) linetracks 300 TPA stand,dashed (blue) lineTracks 1200 TPA

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Advantages of Site Index …

Height growth is highly correlated with volume growth so height at index age should be with max potentialFor most species, dominant height growth is unaffected by densityHeight growth of species of interest is unaffected by species composition

Disadvantages of Site Index …

Most Site Index equations do not perform well in young stands, say < 20 years-old

Site Index in very young stands

Periodic stand height growth Growth-intercept (or height-intercept)

method estimates site index from height growth measured over a short interval SBH20 = 4.9 + 14.23 (GI) SBH20 = Site index of red pine (m at 20 years breast

height age), GI = 5-year growth intercept (avg. of 3

doms., meters) starting above 1.5 m

Site Index in very young stands

Disadvantages of Site Index …

Site Index cannot be determined when no trees of the species of interest can be found on the site Might use so-called Overstory Interspecies

Relationships or Site Index Conversion Eq’s

Site Index Conversion Eq’s …

Disadvantages of Site Index …

Site Index cannot be determined when no trees are present on the site Might use so-called Soil Site Index

Equations

Soil Site Index Equations …

Steinbrenner (1979) found the following relationship for Douglas-fir in Western WA

S = 78.3 + 0.7649 ED + 2.811 DA – 0.0304 (DA x ED) – 1.018 EL

S = King's (1966) site index,

ED =Effective soil depth (inches)

DA =Depth of A horizon (inches)

EL = Elevation (100’s of feet)

Disadvantages of Site Index …

Site Index is best used in Even-aged stands, i.e., it is very difficult to find trees in uneven-aged stands that have been “free to grow” their entire lives, without sustaining top damage Might adopt the concept of Site Form as

measure of site quality Avg. height of trees at index DBH

Site Form …

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Uneven-aged Red Spruce foresttype in Maine (McLintock & Bickford 1957)

Huang & Titus (1993)also found this systemto be useful in boreal stands in Alberta, as have otherresearchers for otherspecies elsewhere

Disadvantages of Site Index …

Site Index, usually thought of as constant for a given locale, actually may change over time due to changing climate, to treatments such as fertilization, or with the introduction of genetically improved trees

Age 5 Height - 2005 reps

5.4

5.6

5.8

6

6.2

6.4

6.6

6.8

7

15x 10x 7xSpacing (ft)

Mean Height (ft)

Woods run Intermediate Elite

Genetically improved DF trees …

Intermediate, Elite gain trees are 6.5%, 8% taller, resp.

Disadvantages of Site Index …

While Site Index itself for a particular species is unaffected by species composition, yield can be greatly affected by compositionSite Index may not be correlated with potential yield in heterogeneous stands or stands with stockability problems, i.e., stands with highly variable soils, say, peppered with rocky outcrops, wet areas, dry areas, …

Other “hybrid” approaches …

Using habitat classification schemes to augment Site Index estimation Habitat Classification uses potential climax

vegetation to group areas into similar site types, presumed then to be similar in most respects

Difficult to apply in highly disturbed areas, such as in cases where vegetation has been burnt, plowed areas, roadside edges, etc.

Site Index - Habitat Class

Monserud(1985)

Other “hybrid” approaches …

Developing process model-based estimates It has been suggested that a good process

(or mechanistic) model might be “fit” to local stand data by adjusting its internal site parameter and using that as an index to productivity 3PG (Physiological Principles Predicting Growth) Forest-BGC (BioGeochemical Cycles)

Productivity … Other issues

What exactly is productivity ?Should it be some measure of biomass?Challenges remain in the estimation of tree biomass

Biomass estimation issues

T r e a t m e n t

1 9 7 8 / 9 8

g r o w t h

t m t v s

c o n t r o l

1 9 7 8 / 9 8

g r o w t h

t m t v s

c o n t r o l

h n b k v s

a c t u a l

1 9 7 8 / 9 8

g r o w t h

t m t v s

c o n t r o l

G h o l z v s

a c t u a l

t m t v s

c o n t r o l

t m t v s

c o n t r o l

J e n k i n s

v s

a c t u a l

C o n t r o l 1 5 2 0 % 1 3 6 0 % 8 9 % 8 4 0 % 5 5 % 7 2 0 % 4 8 %

T h i n n e d 1 4 9 - 2 % 1 2 8 - 6 % 8 6 % 1 2 4 4 7 % 8 3 % 1 0 6 4 7 % 7 1 %

B i o s o l i d s 1 4 3 - 6 % 1 3 8 2 % 9 7 % 1 0 8 2 9 % 7 6 % 9 2 2 9 % 6 5 %

T h i n n e d x B i o s o l i d s 1 7 1 1 2 % 1 6 6 2 3 % 9 7 % 2 0 8 1 4 8 % 1 2 2 % 1 7 6 1 4 8 % 1 0 3 %

C o n t r o l 7 5 0 % 6 7 0 % 8 9 % 4 1 0 % 5 5 % 3 6 0 % 4 8 %

T h i n n e d 7 3 - 2 % 6 3 - 6 % 8 6 % 6 1 4 7 % 8 3 % 5 2 4 7 % 7 1 %

B i o s o l i d s 7 0 - 6 % 6 8 2 % 9 7 % 5 3 2 9 % 7 6 % 4 5 2 9 % 6 5 %

T h i n n e d x B i o s o l i d s 8 4 1 2 % 8 2 2 3 % 9 7 % 1 0 2 1 4 8 % 1 2 2 % 8 6 1 4 8 % 1 0 3 %

C o n t r o l 0 n a 0 n a n a 0 n a 0 n a

T h i n n e d 2 0 n a 1 9 n a 9 6 % 1 6 7 7 % 1 4 7 1 %

B i o s o l i d s 0 n a 0 n a n a 0 n a 0 n a

T h i n n e d x B i o s o l i d s 2 0 n a 1 9 n a 9 6 % 1 6 7 7 % 1 4 7 1 %

C o n t r o l 7 5 0 % 6 7 0 % 8 9 % 4 1 0 % 5 5 % 3 6 0 % 4 8 %

T h i n n e d 9 3 2 5 % 8 2 2 3 % 8 8 % 7 6 8 5 % 8 2 % 6 6 8 6 % 7 1 %

B i o s o l i d s 7 0 - 6 % 6 8 2 % 9 7 % 5 3 2 9 % 7 6 % 4 5 2 7 % 6 5 %

T h i n n e d x B i o s o l i d s 1 0 4 3 9 % 1 0 1 5 2 % 9 7 % 1 1 8 1 8 5 % 1 1 3 % 1 0 1 1 8 3 % 9 7 %

d . C o m b i n e d f o r e s t g r o w t h & p r o d u c t p o o l s

W o o d H a n d b o o k G h o l z E q .A c t u a l J e n k i n s E q .

c . P r o d u c t c a r b o n , 1 9 7 7 T h i n

b . s t e m w o o d c a r b o n

a . s t e m w o o d b i o m a s s , d r y w e i g h t

Actual vs. predicted 20-year stem wood dry weight and carbon storage by treatment, tonne ha -1

You have just witnessed aBrief History of Site Quality Estimation from a Forest Mensuration Perspective

Eric C. Turnblom

ESRM 410 - Forest Soils and Site Productivity - Autumn 2009