bohl.pdf · created date: 12/19/2006 11:57:24 am

Evaluating trends in structural diversity of forest ecosystems … a Swiss case study

Porto, Dezember 2006J�rgen B�hl

Outline

- Definition and suitable Index

-The case study

-Estimator

-Are there enough sample plots?

-How to detect significant trends.

- Pro and Contra



Magurran:

"a suitable measure of diversity should be chosen by means of evaluating whether it fulfillscertain functions or criteria"



If a system contains only one characteristic, the diversity equals zero

If by a given number of charcteristics n all charcteristicsare equally frequent, the maximum diversity in a system occurs

Nagel:

4 criterions for a diversity index



If there are multiple independent varying characteristics, the diversity of a pool of characteristics must equal the sum of the characteristics’ diversity

Given two systems with equal distribution of characteristics and number of characteristics n and n-1, the diversity of the system with n characteristics must be higher



1 21

'( , ,..., ) ln( )k

k i ii

H p p p p p

Shannon - Index

1,21 1

' ln( )n m

ij iji j

H p p

Pielou's hierarchical diversity



H'species = 0.69

H'heightclass = 0.69

H'species = 0.69

H'heightclass = 0.69

H'spec/height = 0.69 H'spec/height = 1.38

1 21

'( , ,..., ) ln( )n

n i ii

H p p p p p

1/ 21 1

' ln( )n m

ij iji j

H p p

1 2 1/2' ' 'T H H H

1 2

2' 'TK

H H

T = 0.69

K = 1

T = 0

K = 0

(Nagel, Weber)



The case studyData from the Swiss National Forest Inventory

3 inventory occasions(20 Years)



'1,2

1 1

ˆ ˆˆ ln( )ˆ ˆ

n mij ij

i j

N NH

N N

Char. 1: Tree speciesChar. 2: BHD classes

N = Basalarea

First Step: The Estimator



Second Step: Are there enough sample plots?

"pooled quadratmethod"

or

"randomized sample accumulation curve"



Third Step: Jackknife pseudovalues

ˆ( ') ( 1)( )i iVP nH n VJ

VJi = Jackknife Value when missing out the i-th sample plot

VPi= Jackknife pseudovalues



Fourth Step: Analysis of Variance

K

NFI3 (2003-2006)

NFI1(1982-1986)

NFI2 (1993-1995)

H'species/DBH

H'DBHH'species



pro

-can beestimated withbasic NFI data

-olderinventory's canbe used

contra

-abstract index-values

-only trend canbe interpreted



Outlook

Are observed trends relevant to Forest Politics and Ecologists?



Thank you for your attention ...



Fourth Step: Analysis of Variance and TukeyGroupings

1004521.82111AA

2104521.85405AA

3104521.87048AinvnrNMeanTukey Grouping

Means with the same letterare not significantly different.H'species




1004521.55254C

2104521.64056B


Means with the same letterare not significantly different.H'DBH




1004523.32779BB

2104523.44163ABA


Means with the same letterare not significantly different.

H'species/DBH

bohl.pdf · created date: 12/19/2006 11:57:24 am

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