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THE EFFECT OF HERBICIDES ON VEGETATION DYNAMICS: A MULTIVARIATE STUDY

Klára VIRÁGH
Abstracta Botanica
Vol. 10, No. 2 (1986), pp. 317-340
Published by: Akadémiai Kiadó
Stable URL: http://www.jstor.org/stable/43519137
Page Count: 24
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
THE EFFECT OF HERBICIDES ON VEGETATION DYNAMICS: A MULTIVARIATE STUDY
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Abstract

Major floristic changes induced by some leaf-herbicides in an old perennial grassland community were studied using permanent quadrats from 1979 to 1984. Clustering methods and principal coordinates analysis were applied to characterize vegetation pattern and to reveal trends of temporal variation. The results indicate a tendency of forming a new stable state rather than the recovery of the pre-disturbance state of the community. The multivariate techniques demonstrate that the different coenostates developed after the treatments were more or less sensitive to drought and were much influenced by the amount of herbicide applied. The expression of seasonality is also apparent especially in the ordinations. It must be noted that pure seasonal fluctuations can be detected unambiguously only in the intact community. In some treated plots, seasonal changes are also present but less clear, and in the other cases they cannot be distinguished at all from regeneration and other processes. Principal coordinates analysis reveals underlying trends in vegetation dynamics and facilitates the interpretation of factors primarily responsible for the changes. The first two axes seem to correspond to fluctuations in the control experiment or a secondary successional trend initiated by herbicide treatment, whereas the third axis reflects either seasonality or dry periods in the climate. It is concluded that the joint application of classification and ordination methods is very useful in detecting vegetational changes. The analyses confirm the findings obtained previously by different similarity indices and provide new information as to the "group-structure" of the sampling units and the temporal trajectories throughout the study.

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