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 due to the increase of vegetation cover of both vascular and non-vascular plants (e.g., mosses, lichens, fungi, and cyanobacteria). The non-vascular plants form intimate associations with surface soils known as biogenic crusts. These crusts play a major role in pedologic and overland geomorphic processes. The spatial distribution of biogenic crusts on semi-stabilized and stabilized sand dunes of the Sharon coastal plain, and their effect on organic matter content and water regime in the soil, were analyzed. Results indicated that a small and discontinuous area of the semi-stabilized sand dunes was 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. The 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 uncrusted sand. The water regime in the upper soil layer covered with mosses was higher than that covered by cyanobacteria crust. The water regime in the soil determined by the biogenic crust may play an important role in the vascular plant succession of the sand dunes.