Wind speed determines the transition from biocrust-stabilized to active dunes

Abstract

Abstract We examine the hypothesis that above a certain height, crusted, stabilized dunes become non-crusted with a mobile crest. Toward this end, twelve plots, 10 × 10 m, were demarcated along a 1 km-long transect in the Nizzana research site (NRS), western Negev, Israel, extending along a ridge of a dune from the crusted interdune up to a height of 22 m above the interdune, characterized by a non-crusted mobile crest. Within each plot, a 4 × 4 m subplot was established where the upper 3 cm of all surfaces was removed. Surface stability was monitored using six erosion pins from March 2010 to February 2012. In addition, data from a nearby meteorological station were analyzed. The data indicated that drift potential (DP) was the highest during winter and spring. A good correlation (with r2 = 0.73) was found between the monthly DP and the absolute change in pin height. Also, a good correlation (with r2 = 0.85) was found between altitude and the absolute change in pin height. A monthly change in pin height of ∼0.3 cm marked the threshold between the crusted and the non crusted sections of the dune, which corresponds to 8 m above the interdune. The findings imply that as long as the absolute monthly change in pin height is