Validation of RUSLE K factor using aggregate stability in contrasted mediterranean eco-geomorphological landscapes (southern Spain)

Mediterranean mountains are facing great environmental and socioeconomic challenges in the current framework of Global Change. One of these is soil degradation, which is one of the major threats in those territories. Soil degradation is more dramatic where eco-geomorphology and land uses with less vegetation cover promote soil erosion. Soil erosion is influenced by soil erodibility, which can be assessed by different methodologies, e.g. RUSLE K factor and aggregate stability of soils. This study deals with the validation of RUSLE K factor by means of soil aggregate stability analysed in two-contrasted watersheds from one Mediterranean mountainous region in South of Spain, under sub-humid and semiarid climatic conditions. In both of them, landscape dynamic from 1956 to 2016 was analysed in order to characterize the modifications in land uses. A total of 361-soil samples was also taken covering all land uses for analysing aggregate stability of soils as well as those soil properties needed to calculate the RUSLE K factor. The results indicated that: i) landscape dynamic was influenced by changes in land uses contributing mainly to an increment in vegetation cover in the rainiest watershed; ii) the analysed soil properties showed very few significant differences between watersheds and between land uses, especially regarding organic matter content; and iii) the validation of K Factor using aggregate stability was better in the rainiest watershed and, within this one, in the natural land uses and irrigated cultivations, meaning where the biotic factors were more influential. These results implicated more researches are necessary, principally, focussed on the validation of the RUSLE K parameter using different fractions of aggregates as well as considering other eco-geomorphological parameters. •Two watersheds differing in climate and eco-geomorphology were analysed.•Land use changes were characterized from 1956 to 2016.•Aggregate stability and K Factor were calculated to assess soil erodibility.•K Factor was validated by comparison with aggregate stability.•Validation results were better achieved in the sub-humid watershed.