Biocrusts and its disturbance controls on soil infiltrability in a semi-arid ecosystem

The biocrust occurrence and its disturbance alters infiltration in the Mu Us Desert. Knowledge of the hydrological properties of biocrusts and parameterization of soil hydraulic properties 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 biocrusts and its disturbance on soil infiltrability in the 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. 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 water condition in the biocrust layer. The findings about the parameterization of soil hydraulic properties are crucial for the simulation of eco-hydrological processes in arid and semi-arid ecosystems.