Possible role of biogenic crusts in plant succession on the Sharon sand dunes, Israel

Sand dunes in the coastal plain are subjected to stabilization processes du e to the increase of vegetation cover of both vascular and non-vascular pla nts (e.g., mosses, lichens, fungi, and cyanobacteria). The non-vascular pla nts form intimate associations with surface soils known as biogenic crusts. These crusts play a major role in pedologic and overland geomorphic proces ses. The spatial distribution of biogenic crusts on semi-stabilized and sta bilized sand dunes of the Sharon coastal plain, and their effect on organic matter content and water regime in the soil, were analyzed. Results indica ted that a small and discontinuous area of the semi-stabilized sand dunes w as covered by biogenic crusts. This crust was mainly composed of mosses and was concentrated beneath shrubs. Nevertheless, 88% of the stabilized sand dunes were covered with biogenic crusts composed mainly of cyanobacteria. T he levels of organic matter and the water content in the upper soil layer ( 0-2 cm) of the crusted sand were significantly higher than levels in the un crusted sand. The water regime in the upper soil layer covered with mosses was higher than that covered by cyanobacteria crust. The water regime in th e soil determined by the biogenic crust may play an important role in the v ascular plant succession of the sand dunes.