Abstract

The occurrence of biocrusts and its disturbance alters infiltration in the Mu Us Desert. Knowledge of the hydrological properties of biocrusts and estimation of soil hydraulic parameters are crucial to improve simulation of infiltration and soil water dynamics in vegetation-soil-water models. Infiltration experiment was conducted to evaluate the effects of biocrust development and its disturbance on soil infiltrability in Mu Us Desert, northwest of China. A combined Wooding inverse approach was used for the estimation of soil hydraulic parameters. The results showed that both lichen- and moss-covered biocrusts had a negative influence on infiltration in comparison with the bare soil. Moreover, moss-covered biocrusts had much lower soil infiltrability compared to the lichen-covered biocrusts. Biocrust disturbance alters infiltration, but its effect differs depending on the biocrust and disturbance types. For high pressure heads, water retention on the moss-covered soils was higher than on the lichen-covered soils. Moreover, trampling caused a higher water retention at high pressure heads. However, opposite was observed at low pressure heads. In addition, moss-covered soils had lower hydraulic conductivity than the lichen-covered soils. Additionally, for each biocrust-covered soil, both trampling and scraping resulted in a higher hydraulic conductivity when compared with the undisturbed soils. The occurrence of biocrusts and its disturbance influenced van Genuchten parameters, and subsequently affected the water retention curve, and thus altered the plant-available water. The findings about the parameterization of soil hydraulic properties have important implications for the simulation of eco-hydrological processes in arid and semiarid ecosystems.