Biocrusts positively affect the soil water balance in semiarid ecosystems

Abstract

Biocrusts play crucial roles in hydrological processes by controlling soil water availability and regulating water redistribution from source to sink areas. Most studies have examined the influence of biocrusts on isolated components of the soil water balance, but few have addressed this matter from an integrated point of view, involving their influence on all components together. Such integration is crucial to elucidate the overall effects of biocrusts on the soil water balance. The aim of this study was to review the role of biocrusts in the soil water balance, by examining their influence on infiltration, evaporation and soil moisture at plot scale, in two contrasting ecosystems of SE Spain. Our results show that biocrust infiltration was higher in flat soils with sandy loam texture than in steep soils with silty loam texture. The influence of biocrusts on infiltration depended on rainfall intensity. Biocrusts increased infiltration with respect to biocrust-removed soils during low intensity rainfalls but showed similar or even lower infiltration than biocrust-removed soils during high-intensity events. As a result of the increase in infiltration and a decrease in evaporation during wet cold periods, biocrusts increased soil moisture when compared with biocrust-removed soils. However, during warm periods, biocrusts and biocrust-removed soils lost water very quickly, thus resulting in similar water losses and moisture content under both types of surfaces. We conclude that biocrusts increase water input by increasing infiltration and soil moisture, and reduce water output by reducing soil evaporation, thus eventually enhancing the available water to plants.