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RELATIVE INFLUENCE OF OBSERVER ERROR AND PLOT RANDOMIZATION ON DETECTION OF VEGETATION CHANGE

Neil E. West and Thomas J. Hatton
Coenoses
Vol. 5, No. 1 (Spring 1990), pp. 45-49
Published by: Akadémiai Kiadó
Stable URL: http://www.jstor.org/stable/43461022
Page Count: 5
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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.
RELATIVE INFLUENCE OF OBSERVER ERROR AND PLOT RANDOMIZATION ON DETECTION OF VEGETATION CHANGE
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Abstract

A study was conducted in sagebrush-steppe vegetation, near Kemmerer, Wyoming, U.S.A., to separate the effects of observer error and plot randomization on the estimation of interannual changes in plant species richness, evenness, diversity and total cover. Multiple observers of the same set of quadrats produced significantly different estimates of diversity due to differences in the length and composition of species lists and cover estimates. A single observer's estimates of different sets of quadrats had equivalent diversities and reflected the same community. Changing observers, introduced less variability in floristic richness, in a relative sense, than did plot randomization. However, when species presence was combined with ocular estimates of cover, changing observers introduced more error into the estimation of diversity incorporating evenness and the characterization of the trajectory of change than did spatial randomization of plots. The desirability of using permanent plots and the same competent observer over time to detect vegetation change was reconfirmed as was the need to objectify estimates of abundance.

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