Formalized reproduction of an expert-based phytosociological classification



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- Formalized reproduction of an expert-based phytosociological classification -

601


Journal of Vegetation Science 14: 601-610, 2003

© IAVS; Opulus Press Uppsala.

Abstract. Delimitation of vegetation units in phytosociology

is traditionally based on expert knowledge. Applications of

expert-based classifications are often inconsistent because cri-

teria for assigning relevés to vegetation units are seldom given

explicitly. Still, there is, e.g. in nature conservation, an increas-

ing need for a consistent application of vegetation classification

using computer expert systems for unit identification.

We propose a procedure for formalized reproduction of an

expert-based vegetation classification, which is applicable to

large phytosociological data sets. This procedure combines

Bruelheide’s Cocktail method with a similarity-based assign-

ment of relevés to constancy columns of a vegetation table. As

a test of this method we attempt to reproduce the expert-based

phytosociological classification of subalpine tall-forb vegeta-

tion of the Czech Republic which has been made by combina-

tion of expert judgement and stepwise numerical classification

of 718 relevés by TWINSPAN. Applying the Cocktail method

to a geographically stratified data set of 21 794 relevés of all

Czech vegetation types, we defined groups of species with the

statistical tendency of joint occurrences in vegetation. Combi-

nations of 12 of these species groups by logical operators

AND, OR and AND NOT yielded formal definitions of 14 of

16 associations which had been accepted in the expert-based

classification. Application of these formal definitions to the

original data set of 718 relevés resulted in an assignment of 376

relevés to the associations. This assignment agreed well with the

original expert-based classification. Relevés that remained un-

assigned because they had not met the requirements of any of

the formal definitions, were subsequently assigned to the asso-

ciations by calculating similarity to relevé groups that had

already been assigned to the associations. A new index, based

on frequency and fidelity, was proposed for calculating similar-

ity. The agreement with the expert-based classification achieved

by the formal definitions was still improved after applying the

similarity-based assignment. Results indicate that the expert-

based classification can be successfully formalized and con-

verted into a computer expert system.

Keywords:  Braun-Blanquet approach; Cocktail; Czech Re-

public; Expert system; Matching;  Mulgedio-Aconitetea;

Species group; Vegetation survey.

Nomenclature: Kubát et al. (2002).

Abbreviations:  FDI  = Fidelity Index; FFI  = Frequency-

Fidelity Index; FQI = Frequency Index.



Introduction

In the last decade, phytosociological classification

of vegetation (Westhoff & van der Maarel 1978) has

been increasingly applied in nature conservation and

landscape planning (Ostermann 1998). Nature manag-

ers are in urgent need of consistent systems of vegeta-

tion classification that would be valid over large areas

and that would provide unequivocal criteria for assign-

ment of vegetation stands to the classification units. An

ideal tool for nature conservation authorities would be

computer expert systems (Noble 1987) for identifica-

tion of vegetation units.

Traditional expert-based vegetation classifications,

which are widely accepted in many countries, suffer

from several inconsistencies. Vegetation units accepted

in these classifications have usually been defined by

many different researchers who have used variable and

in most cases not explicitly stated classification criteria.

Frequently there are considerable overlaps in delimita-

tion of vegetation units by different researchers. Exten-

sive national revisions of vegetation units (e.g. Ober-

dorfer 1977-1992; Mucina et al. 1993; Schaminée et al.

1995-1999; Valachovič 1995 et seq.; Dierschke 1996 et

seq.) eliminated these inconsistencies only incompletely.

The advent of numerical classification methods since

the 1960s (Mucina & van der Maarel 1989) and the

availability of large electronic databases of vegetation

relevés since the 1990s (Ewald 2001; Hennekens &

Schaminée 2001) made it possible to develop highly

formalized, consistent and repeatable classifications as

an alternative to the traditional expert-based approaches.

However, even sophisticated combinations of several

formalized methods (e.g. Wildi 1989) so far have not

received universal acceptance especially in those Euro-

pean countries where phytosociological tradition is firmly

established. In our opinion, the main reason is that the

results of commonly used agglomerative or divisive

classification algorithms strongly depend on the geo-

graphical or ecological extent and stratification of the

data sets (Bruelheide & Chytrý 2000). Confronted with

multiple solutions of numerical classifications, many

Formalized reproduction of an expert-based phytosociological

classification: A case study of subalpine tall-forb vegetation

Kočí, Martin

1,2


; Chytrý, Milan

1,*


 & Tichý, Lubomír

1,3


1

Department of Botany, Masaryk University, Kotlářská 2, CZ-611 37 Brno, Czech Republic; 



E-mail koci@sci.muni.cz;

3

tichy@sci.muni.cz; 

*

Corresponding author; Fax +420541211214; E-mail  chytry@sci.muni.cz





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