Classification of relevé data aims to present the best possible explanation of the vegetation
within a specific study area. The variety of multivariate techniques available to classify
vegetation into ecological communities has developed in recent years, which contributes to
uncertainty among vegetation scientists as to which methods and computer software to select
for optimum classification results. The wide application of the classical TWINSPAN algorithm
along with the Braun-Blanquet approach of plant community descriptions and diagnostic
species identification in southern Africa prompted a comparison of classification results
between these classical approaches and a modern approach. The modern approach, as
being referred to in this study, entails the recent improvement on the classical TWINSPAN
algorithm, namely the Modified TWINSPAN algorithm in combination with statistical measures
of species fidelity. Comparisons between classification end-results were undertaken at
various spatial scales to test whether discrepancies between results obtained from the
different approaches are similar when applied to a broad-scale synthesis, an intermediate
synthesis and a local-scale classification within a similar vegetation type, the Mopaneveld.
Such a comparative study is envisaged to present insight on the credibility of the use of
classical approaches in phytosociology at various spatial scales.
A modern approach was tested upon three previous vegetation classification studies which
followed the classical approach. These vegetation classification studies were all undertaken
at different spatial scales and are being referred to as the reference classifications. The data
that were subjected to the modern approach were analogous to those used in the reference
classifications. The computer package JUICE 7.0 was used in which the Modified
TWINSPAN algorithm was applied in combination with statistical measures of species
fidelity, which was obtained as a function directly in the JUICE program. Classification
hierarchies were constructed for both the classical and modern approach results to compare
and describe similarities and discrepancies between the different hierarchical dendrograms.
Fidelity syntables were constructed to assist in the grouping of diagnostic species according
to highest fidelity values. Such diagnostic species groups were compared with the lists of
diagnostic species in the reference classifications.
At the broadest spatial scale, comparisons revealed discrepancies between classification
results from the classical and the modern approach. The modern approach presented a
more robust synthesis of the Mopaneveld in southern Africa since the vegetation units and
their associated diagnostic species are ecologically better expressed. The intermediate scale synthesis comparison revealed similar discrepancies, which again question the
credibility of the classical approach at broader spatial scales. The application of the modern
approach to the local scale classification, however, revealed little difference with the results
obtained through the classical approach. Although more alternative classification techniques
need to be applied to report on the most robust technique for vegetation classifications
across spatial scales, it could be reported that the classical TWINSPAN algorithm is not
favorable for vegetation classifications and syntheses beyond the local scale.
The ecological reliability of the modern approach at the intermediate scale prompted its
application in a synthesis of the riparian vegetation within the Mopane Bioregion of South
Africa, which was not achieved in any previous study. Riparian vegetation plays an important
role in maintaining good water quality and also provides habitat for many species. Riparian
vegetation therefore needs to be classified and described. The synthesis of the riparian
vegetation in the Mopane Bioregion of South Africa revealed six distinct plant communities
which are described and discussed in terms of diagnostic, constant and dominant species
along with variance in plant species diversity. / Thesis (Ph.D. (Botany))--North-West University, Potchefstroom Campus, 2012
| Identifer | oai:union.ndltd.org:NWUBOLOKA1/oai:dspace.nwu.ac.za:10394/8488 |
| Date | January 2012 |
| Creators | Siebert, Frances |
| Publisher | North-West University |
| Source Sets | North-West University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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