Effects of land use and eventual fire on soil erodibility in dry Mediterranean conditions

The Mediterranean countries of Europe have suffered deep land-use transformations during this century and the expansion of wildfires after generalized land abandonment in the marginal uplands. Differences in soil properties due to land use may lead to different responses of the ecosystem in case of fire. We analyze how soil erodibility in a cropland and oldfields of different age after abandonment (bushland, shrubland and pine forest) would be affected by wildfire. Soil samples taken in each land use were analyzed to characterize soil erodibility. From fuel load measures, the range of temperatures to be attained in case of a fire were estimated for the topsoil. From these temperatures and from the information available in the literature, we predicted the changes in soil properties produced by the fire and estimated soil erodibility for the burned lands. Changes in soil erodibility were slight in the field crop with low fuel load, and increased according to biomass and forest floor accumulation. As the initial soil erodibility was inversely related to fuel load, the fire would increase the values of soil erodibility of the different land uses up to close to those of the field crop. In addition, the fire would produce very similar soil erodibility values for the different land uses, and therefore a homogenizing post-fire soil response in the landscape.