Spatial variations in vegetation as related to the soil moisture regime over an arid limestone hillside, northern Negev, Israel.

A detailed study of the distribution of plant communities was conducted in an experimental site, located in the arid northern Negev of Israel, where the spatial variation in rainfall, runoff and soil moisture regime are currently being studied. Phytogeographical methods of analysis usually used for studies on a regional scale were applied for a small area extending over 11,325 m2 of a north-facing hillside. Data obtained indicate that the best water regime and a high diversity of plant species are characteristic of a massive limestone rock unit; whereas worse water regimes characterize densely jointed and thinly bedded limestones. Over slopes, developed in a uniform lithology, whose lower part is composed of a colluvial mantle, a gradual downslope worsening of the soil moisture regime is recorded within the colluvium. These changes are well expressed in the distribution of the plant communities and their phytogeographical affinities along the slopes.