The erosional response of calcareous soils along a climatological gradient in southeast Spain

The erosional response of calcareous soils along a climatological gradient in Alicante, SE Spain was studied. The erosional response was defined in terms of indicators obtained from field rainfall simulation experiments and laboratory studies of soil aggregation. Measurements were made at seven sites on limestones and marls between Benidorm with an annual average rainfall of 400 mm yr^-1 and Coll de Rates (annual rainfall 900 mm yr^-1). The sites were on matorral vegetation affected to varying intensities by grazing and fire. At the seven locations, soil aggregation was studied by sieving, by the single water drop test and by a Microscan particle-sizer. Rainfall simulation experiments were made on circular 55-cm diameter target area plots using the Calvo simulator at an intensities between 35 and 50 mm h^-1. On limestone, it was found that on bare surfaces, the coarse soil aggregation increases with depth at the highest sites and decreases at the lower sites. The Benidorm Surface soil has the highest erodibility. The least stable soils are at the lower intermediate sites. On marls, the aggregate stability is generally high in contrast to those under cultivation. Simulated runoff from the wetter limestone sites is very low. The driest areas have the highest runoff and sediment yields. Trends with climate suggest that the erosional responses of the soils indeed increase with aridity and temperature but local factors have a large effect, particularly at intermediate altitudes. A clear relationship like that found in Israel by Lavee on a similar lithology does not exist.