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Jurasinski, G*: Biodiversity and Disturbance in a Semi-Arid Ecosystem – Patterns and Scale
Talk, European Vegetation Conference, Galway, Ireland: 2005-06-21 - 2005-06-23

Abstract:
We lack quantitative and comprehensible methods to assess spatio-temporal changes in biodiversity of landscapes. Even more we are missing methods to determine the amounts of change. The shifting of land-use (changing disturbance regimes) is a major cause for these changes. We develop a widely applicable method to reveal spatio-temporal changes in vegetation patterns and to relate them to ecosystem processes. Especially if one wants to find patterns in landscapes ecological monitoring should be spatially and temporally explicit. We use a systematic grid of hexagonal plots in a spatially nested design (three spatial scales and levels) to examine these patterns. The hexagonal grid, as well as the hexagonal plot provides several advantages compared to other methods. Most import in the context of evaluating patterns is the equidistant nature of the grid. This facilitates data analysis and circumvents statistical overdub and logical problems (compared to squared or circle plots). Correlations between structural data assessed with the Line-Intercept-Method and assessed with digitized reality are very strong (r=0,88***) and show that the lines which are used to mark out the plots provide an easy and feasible method to assess quantitative data on structure and disturbance. Furthermore we found that the patterns of vegetation relate to disturbance and structure, but we found different relationships on the different scales and levels. After three years of working with the equidistant grid in different ecosystems we think that they are optimised concerning the ratio between amount of work involved in marking, area-perimeter-ratio, accuracy, consistency of analysis and grid consistency. The method is widely applicable to find and ecologically analyse patterns of floristic diversity.

last modified 2006-04-26