Características de las costras físicas y biológicas del suelo con mayor influencia sobre la infiltración y la erosión en ecosistemas mediterráneos

Physical soil crusts and biological soil crusts occupy a wide extension in arid and semiarid areas all over the world. In these regions, soil crusting has a very strong influence on local hydrologic regimes and erosion. The main purposes of this paper are: 1) to examine how crust characteristics influence infiltration and erosion and 2) to identify the most influential crust characteristics on runoff and erosion processes. Two semiarid areas in the province of Almería were chosen and the most representative physical and biological soil crusts were identified at both sites. For each crust type, physical and chemical characteristics of the crust and the soil underneath the crust were analysed, as well as other crust properties like roughness, hydrophobicity, resistance to penetration and cover. To analyse the influence of the crust on infiltration and erosion, rainfall simulations were conducted on plots with the intact crust, and in order to examine the influence of the soil underlying the crust, rainfall simulations were conducted on plots after removing the crust. The hydrological response of the studied encrusted areas is affected, not only by the characteristics of the crust itself, but also by the characteristics of the soil in where the crust is developed and specially by the slope gradient that appears like a highly predictive variable for infiltration and erosion. Among the properties of the soil material below crusts, it is remarkable the influence of soil texture, organic carbon content and electrical conductivity, and among the properties of the crust, cover and roughness are the most predictive variables explaining the differences in infiltration and erosion between sites. Las costras físicas (CFS) y biológicas (CBS) del suelo ocupan una gran extensión en zonas áridas y semiáridas de todo el mundo. En estos medios, el encostramiento del suelo tiene una gran influencia sobre los procesos hidrológicos y erosivos. Los objetivos que se persiguen en este trabajo son: analizar las características de las costras que influyen en la infiltración y en la erosión e identificar cuáles de estas características tiene una mayor influencia sobre estos procesos. En dos áreas semiáridas representativas en la provincia de Almería se identificaron los principales tipos de costras físicas y biológicas. Para cada tipo de costra, se analizaron las características físicas y químicas de la propia costra y del material subyacente, así como su rugosidad, hidrofobia, resistencia a la penetración y cobertura de diferentes comunidades de organismos. Para analizar la influe