The content and contributions of deposited aeolian organic matter in a dry land ecosystem of the Negev Desert, Israel

The northern Negev desert in Israel has a mosaic of two types of plant community patches. One is dominated by vascular plants (shrub patches) and the other by a nonvascular crust community (crust patches) consisting of cyanobacteria, bacteria, algae, mosses and lichens. The crust patches are sources of soil material and sediment – laden runoff water while the shrub patches are the sinks and function as ‘islands of fertility’ in the desert environment. Accumulation of resources is often a limiting factor in this ecosystem. The aim of this study was to investigate the contribution of high nutrient organic residues that are readily decomposable, to the aeolian deposition on the crust patches. During the five years of the study, three dominant groups were found in the organic matter: plant material, insect and snail residue (feces). The average accumulation of the aeolian deposition of the organic matter showed significant spatial and temporal differences. Similar quantities were found on the north and the south-facing slopes of the watershed with a minimum in the wadi. A significant difference in average accumulated organic matter for the five years was found. The maximum was for the third year (1995) and the minimum for the fifth year (1997). This may be due to the variations in the annual rainfall amount. The results showed that the origin of most of the organic matter content is from native sources. The highest and most significant amount was registered during the spring season, which is the flowering season in the northern Negev. This may explain the high quantity of plant material obtained and the great amounts of insect and snail (feces) residue that were also found during this season. Since the crust patches serve as a source of water and nutrients in this ecosystem, the organic residues that are of high nutrient quality and readily decomposable, contribute to the productivity of the shrub patches and thus of the overall ecosystem.