Biocrust‐induced extracellular polymeric substances are responsible for dune stabilization in the Negev

Abstract

AbstractThere is no consensus over the factors responsible for dune stabilization in arid regions, with some scholars maintaining that dust (i.e., silt and clay) plays a major role in dune stabilization. Aiming to explore the principal driving factor responsible for dune stabilization in the Negev, we compared various biocrusts having different biomass and compressive strength, and performed surface degradation and illuviation experiments with dust in the presence or absence of biocrusts in order to assess the crust role in impeding wind erosion and dust illuviation. We show that dust cannot be regarded as the primary driving factor for crust strength and subsequently for dune stabilization in the Negev, as suggested in some publications. This function is however fulfilled by extracellular polymeric substances (EPS, mostly polysaccharides), which are excreted by the biocrust (mainly cyanobacteria), and serve as a cementing agent for the establishing crust and therefore for the dust. Exhibiting high water absorption and strong adhering properties, EPS is responsible for granting strength to the crust, impeding wind erosion and dust illuviation, thus providing the necessary cementing agent, which facilitates dune stabilization in the Negev. Global warming which may result in frequent droughts and high input of dust may not contribute to dune stabilization as suggested by some scholars, but rather will negatively affect dune stabilization, as it may result in EPS degradation and subsequently in dune mobilization.