Erodibility and hydrology of arid burned soils:: Soil type and revegetation effects

A set of experiments with a rainfall simulator was performed in the field to evaluate the efficiency of parallel contour seeding as a post-fire restoration strategy in the arid central Ebro Valley (NE Spain). Rainfall simulations were conducted in spring, after seeded plant development, on calcareous and gypsiferous soils, with the same experimental design (two-soil treatments-seeded and nonseeded-per two soil types and per nine replicates). The parallel contour seeding treatment increases soil cover and soil surface roughness, which significantly ameliorates the hydrological and erosional response of both calcareous and gypsiferous burned soils. Seeding decreased soil loss, both in calcareous (23- fold) and gypsiferous soils (4- fold). In addition, it decreased the sediment concentration of runoff for calcareous (6- fold) and gypsiferous soils (2- fold) and the runoff coefficient for calcareous (3.5- fold) and gypsiferous soils (1.5- fold). On the other hand, seeding increased the steady state infiltration rate (3- fold), as well as surface soil moisture (1.2- fold) and wetting front depth (2- fold), with a similar order of magnitude for both soils. Time to runoff and runoff quality (electrical conductivity [EC] and pH) were not affected by seeding. Gypsiferous soils had a higher soil loss, runoff coefficient, and EC flow and a lower time to runoff, steady state infiltration rate, and wetting front depth than calcareous soils. Some of these differences were directly related to differences in soil gypsum and carbonate content (i. e., EC and pH of water runoff) and others are related to the proportion of surface soil protection, an indirect effect of soil characteristics. The results suggest that parallel contour seeding is an effective restoration measure with a short-term response that allows conservation of water and soil on recently burned arid lands, especially in situations of high erosion risk as occurs with soils with low plant cover.