Biocrust reduced soil water retention and soil infiltration in the alpine Kobresia meadow

Abstract. Biocrust is a key component of ecosystems and plays a vital role in altering hydrological processes in terrestrial ecosystems. The role of biocrust on hydrological properties in arid and semi-arid ecosystems has been widely documented; however, the effects and mechanisms of biocrust on soil hydrological properties in alpine ecosystems are still poorly understood. In this study, we selected two meadow types from the northern Qinghai-Tibet Plateau: normal Kobresia meadow (NM) and biocrust meadow (BM). Both the soil hydrological and physicochemical properties were examined. We found that in the 0–30 cm soil layer, soil water retention and soil water content in NM were higher than those in BM, whereas the 30–40 cm layer’s soil water retention and soil water content in NM were lower than those in BM. The topsoil infiltration rate in BM was lower than that in NM. Furthermore, the physicochemical properties were different between NM and BM. The 0–10 cm soil layer’s clay content in BM was 9 % higher than that in NM, whereas the 0–30 cm layer’s soil capillary porosity in NM was higher than that in BM. In addition, the 0–20 cm layer’s soil total nitrogen (TN) and soil organic matter (SOM) in NM were higher than those in BM, implying that the presence of biocrust did not favor the formation of soil nutrients owing to its lower soil microbial biomass carbon and microbial biomass nitrogen. Overall, soil water retention was determined by SOM by altering soil capillary porosity and bulk density. Our findings revealed that the establishment of biocrust did not improve soil water retention and infiltration, which may be more vulnerable to runoff generation and consequent soil erosion in biocrust meadows. These results provide a systematic and comprehensive understanding of the role of biocrust in the soil hydrology of alpine ecosystems.