Sand dunes mobility and stability in relation to climate

Sand dunes form an important and unique system that can be mobile or fixed by vegetation. The common mobility indices of sand dunes, which are related to the wind and the amount of precipitation and potential evaporation, do not work in many dune fields around the world. The reasons for that lie in the singular physical characteristics of the sandy soil. Sand has high hydraulic conductivity causing a high rate of infiltration of rain water to the groundwater. Sand particles lack cohesion and that makes wind erosion the main limiting factor for vegetation. Hence, wind power, manifested by the drift potential (DP), is a good index for the limiting factor of plants on sand. The physical-biological interaction is further developed by hysteresis, which shows that a dune can become vegetated when the wind power is sufficiently low. Once vegetated, a much higher wind stress is needed to destroy the vegetation and re-activate the dunes. (c) 2005 Elsevier B.V. All rights reserved.