Spatial distribution of soil surface coverage on north and south facing hillslopes along a Mediterranean to extreme arid climatic gradient

Four research sites were established along a climatic gradient in Israel representing Mediterranean, xeric Mediterranean, arid and extreme arid climate conditions. The cover percentage of eight soil surface components [vegetation (annual and perennial forms), biogenic crust (mosses, lichens, cyanobacteria, and dwarf grass), stones and bare soil patches] were measured. Transects along hillslopes on each of two opposite aspects (south and north facing slopes) were established at each site (altogether eight transects). Dominance and soil surface cover diversity indices, and similarity coefficients between the transects were calculated. High similarity values in soil surface cover were found between the south facing slopes located in the xeric. Mediterranean, arid, and extreme arid areas. These hillslopes are dominated by stones and bare soil patches. In contrast, lower similarity values were found between the northern slope aspects dominated by biotic components (vegetation and biogenic crusts). The study along a climatic gradient together with the comparison between northern and southern aspects provide useful information that can be utilized for evaluation of changes in soil surface cover characteristics given various scenarios of future climate regimes in that region.