ASSESSING CHANGES IN BIOLOGICAL DIVERSITY OVER TIME

Data from remeasured permanent plots were used to determine if composi tional biodiversity was changing over time within a research natural a rea in southern Indiana. To extend the time period over which change c ould be evaluated, we used subsets of the permanent plot data for comp arison to three independently published data sets collected before the permanent plots were established. The statistical technique of jack-k nifing provided a means of attaching statistical significance to calcu lated differences in Shannon-Weiner diversity. Diversity decreased sli ghtly during the 11-year period covered by the permanent plot data. Fo r two of the three published data sets, it was possible to obtain comp arative subsets of the permanent plot data. These data indicated that diversity had been increasing during the 37 years before the establish ment of the permanent plots. Although remeasured permanent plot data w ill provide the best information on change over time, it does appear t hat additional data from other sources can be used to extend the time series when long-term permanent plot data are not available.