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Special LectureStand Structural Diversity

Forest Mensuration II

Special lectureFORE 3128

Biological Diversity

• Genetic diversity • Stand level diversity () • Local landscape diversity () • Regional diversity ()

Species richness

Evenness

Structure

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Objectives

• Concepts• Classification of stand structure• Measures of stand structural

diversity

Special lectureFORE 3128

Stand structure attributes

• Living trees• Snags, CWD• Age• Composition

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Stand structure

• Arrangement of trees in space

– Vertical– horizontal

Stand structural diversity-Variability among trees vertically and horizontally within a stand

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Why stand structural diversity?

• Ecological– A measure of biodiversity– Wildlife habitat– Ecosystem process (e.g., productivity)

• Social– Visual quality

• Management - structure based

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Vertical structure

Single-storied/normal

Multi-storied/irregular

Multi-storied/inverse J

Two-storied/bimodal

Smith et al. 1997

Frequency (stems/ha)

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Special lectureFORE 3128

Special lectureFORE 3128

Special lectureFORE 3128

Special lectureFORE 3128

Special lectureFORE 3128

Measures of vertical structural diversity

• Shannon-Weiner index (H´) • Variance of tree size (S2)

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Shannon-Weiner index (H´)

i

n

ii pp

1

ln

0.330.69

H’Stand A

Stand B

P1 P2

0.9 0.10.5 0.5

Example

1.10Stand C 0.33 0.33 0.34

P3

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Shannon-Weiner index (H´)

i

n

ii pp

1

ln

DBH

Proportion (Freq.)

DBH

Proportion (BA)

Frequency(stems/ha)

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Variance of tree size

1

)(1

2

2

n

xxn

ii

S

x

DBH

Frequency

Frequency(stems/ha)

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Horizontal structure

Random Clumped (aggregate)

Uniform

Stand 1 Stand 2 Stand 3

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Random

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Clumped

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Clumped

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Uniform

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Measure of horizontal structure

Clark and Evans’ test (C)

se

obs

DDD

C exp

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Observed mean distance

n

dD

n

ii

obs

1

= (1.5+1.8+1.5+,,,)/15= 1.493 m

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Expected mean distance

Random (Poisson) distribution

AnD

/21

exp

Standard error

nADse

07.0

291.1100/152

1 m

176.015

10007.0

m

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Clark and Evans’ test

se

obs

DDD

C exp 147.1

176.0291.1493.1

Clumped Random Regular

0-1.96 1.96

C

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Three-dimensional structure

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x

y

z

x

y

z

Structural complexity index (SCI)

n

ii

n

ii

A

ATSCI

1

1

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Problem with SCI

Stand 1 Stand 2 Stand 3

Tree heights = 5 m Tree heights = 10 m Tree heights = 20 m

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Summary• Concepts• Classification of stand structure

– Vertical– Horizontal

• Measures of stand structural diversity– Vertical

• Shannon-Weiner index • Variance of tree size

– Horizontal: Clark and Evans test– Three-dimensional: SCI

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Possible research topics

• Does increasing structural diversity affect

Stand productivity?

Silvicultural feasibility?

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Special lectureFORE 3128

Special lectureFORE 3128

How do we measure landscape structural diversity?

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Criteria for Sustainable Forest Management

• Conserving Biological Diversity• Maintenance and enhancement of Forest Ecosystem

Condition and Productivity• Conservation of Soil and Water Resources• Forest Ecosystem Contributions to Globe Ecological

Cycles• Multiple Benefits to Society• Accepting Society’s Responsibility for Sustainable

Development