Climatic and altitudinal effects on soil aggregation in slopes of mediterranean environment

Abstract

Two slopes with similar characteristics (lithology, soils and aspect), but with contrasting climatological conditions were chosen in the North of the province of Alicante (South East of Spain) in order to study the aggregation of the soil surface. The influence of climatic conditions at the local scale and microclimatic conditions at the slope scale were evaluated. Soil temperature and moisture, organic matter and clay content at different sampling points on each slope were measured. The soil aggregation was studied at two levels: firstly, the aggregate size distribution and stability of macroaggregates (4-4.8 mm); secondly, the water stable microaggregation in the fraction <105 μ. At the local scale, soil aggregation on the most arid slope seems to be positively influenced by the biological activity, the clay content and periods of high soil moisture. On the most moist slope the aggregation is negatively influenced by the restrictive temperatures and the lower clay content. At the slope scale, aggregation under plants, especially due to better microclimatic conditions (more water availability and moderate temperatures), is better than in the bare patches.