- Changes in plant cover, species richness and spe- cies diversity were recorded over a 2-year period along a climatic gradient running from a Mediterranean region (Judean Mountains) to the Dead Sea desert area. Changes along the climatic gradient were found not to be gradual. A narrow belt exists in which a drastic decline in all plant parameters occurs. This belt divides the research area into two main systems- the Mediterranean and the arid. The belt shifts eastwards and westwards depending on rainfall. The shifting range is limited to the area between the xeric Mediterranean and the arid regions.