Vegetation response to possible scenarios of rainfall variations along a Mediterranean-extreme arid climatic transect

The vegetation response to variation in rainfall totals along a climatic transect extending from a Mediterranean region to an extreme arid region was studied. A curvilinear relationship was suggested between annual rainfall, species richness, species diversity and dominance. The maximum number of species was calculated to be in the range of 900-950 mm, the maximum diversity between 750 and 800 mm, and the minimum dominance in the range of 600-700 mm. Annual species decrease logarithmically from the extreme desert to the Mediterranean region with a parallel increase of perennial herbaceous and woody plants. Wet and dry scenarios are considered as a framework to evaluate future vegetation responses to possible climate change. (C) 2000 Academic Press.