Spatial and Temporal Heterogeneity of Species Diversity in a Mediterranean Ecosystem Following Fire

Abstract

This study examines species richness, species diversity (H'-Shannon-Weiner Index) and species dominance (C- Simpson-Index) in a Mediterranean ecosystem as a function of time elapsed since fire and the extent to which micro-climate regulates these indexes after wildfire occurrence. The study was conducted in an eastern Mediterranean ecosystem (Israel) over three consecutive years. About 400 ha of a mixed oak - pine forest burned in the summer of 1983 and part of it also suffered from a repeat fire in the summer of 1989. Different trends for each parameter and for each slope aspect (north and south) were observed indicating different fire intensities and frequencies, and different physical conditions characterizing each of the slope aspects. Species richness on the northern slope was the highest 2 - 4 years after fire followed by a decrease with time elapsed since fire. A recurrent fire on the southern slope caused a decrease in species richness two years after fire, which increased a year later to the level observed in the unburned forest. Species diversity, however, increased after fire on both aspects, reaching lower values 10 years later and then increased again, but still to values lower than those obtained 2 - 4 years after fire. The rate of change is higher on the southern slope than that on the northern one. The different trends following fire indicate that high temporal and spatial variability both in the micro- and macroscales exist in this region.