Abstract: As an important part of desert ecosystems, biological soil crusts (BSCs) play an extremely important role in the stability and function of desert soils. We analyzed the influence of BSCs on soil multifunctionality (SMF) in different soil layers and main driving factors. This study was carried out in the Gurbantunggut Desert, and two types of BSCs (algal-lichens and mosses) were used as research objects (with bare sand as the control). Soil organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), inorganic nitrogen (IN) and soluble organic nitrogen (DON) were selected to calculate the SMF index by the mean method. Each functionality such as TOC, TN, TP, IN and DON increased with the development of BSCs and decreased with soil depths. The SMF of bare sand ranged from -0.96 to 0.55, showing an increasing trend in the 0-5 cm soil depth and a decreasing trend in 5-20 cm soil depth. The SMF of mixed algal-lichen crusts and moss crusts was at -0.53 to 1.33 and -0.43 to 2.05, respectively, and showed a decreasing trend in the 0-20 cm soil depth. The SMF of the three types of BSCs tended to be stable in the 20-100 cm soil layer. The SMF showed an overall trend of moss crusts > mixed algal-lichen crusts > bare sand in the 0-20 cm and 0-100 cm soil layer. Soil pH, soil water content, and soil urease activity were closely related to the vertical changes of SMF. Soil pH and soil water content had significant negative effects on SMF, while soil urease activity had significant positive effects. Soil particle size was one of the main factors affecting SMF, with negative relationship between medium-sized sand contents and SMF, and positive relationship between coarse sand contents and SMF. Therefore, the development of BSCs significantly improved soil single functionality and soil multifunctionality. The influence of BSCs on soil multifunctionality was mainly concentrated in the range of 0-20 cm in the surface soil, with little effect on the deeper soil. While BSCs affected soil multifunctionality, other functions also changed.

Key words: biological soil crusts, soil multifunctionality, soil depth, Gurbantunggut Desert, driving factor