Research Data

Biological soil crusts (BSCs) are indispensable components for maintaining the stability of desert ecosystems. To date, most studies on the functions and environmental responses of BSCs have focused on desert lowlands, whereas the patterns and drivers of BSC functional traits and biocrust multifunctionality (BMF) on sand-covered mountain slopes remain largely unexplored. In this study, we selected a sand-covered mountain on the northern slope of the central Kunlun Mountains, Hotan County, Xinjiang, where BSCs are widely distributed along a pronounced altitudinal gradient (2,300–3,400 m, eight altitude levels). We conducted field measurements of BSC physical properties (biomass per unit area, thickness, and surface roughness), and laboratory analyses of chemical properties, nutrients, and extracellular enzyme activities. Using linear and nonlinear regression, variance partitioning, and structural equation modeling (SEM), we investigated the altitudinal patterns of BSC functional traits and their potential drivers. The results showed that total phosphorus (TP), soil organic carbon (SOC), and urease activity (S-UE) exhibited significant unimodal trends with increasing altitude (P < 0.05), while hydrolyzable nitrogen (AN), available phosphorus (AP), pH, electrical conductivity (EC), and catalase activity (S-CL) displayed significant U-shaped patterns (P < 0.01). The inflection points of nutrient contents generally occurred between 2,700 and 3,000 m. Ecoenzymatic stoichiometry analysis represented that carbon limitation of BSCs weakened first and then strengthened with altitude, and the nutrient limitation regime shifted gradually from phosphorus limitation to nitrogen limitation. Climatic factors were the dominant drivers of BMF (relative explanatory power: 38%), and also exerted the strongest influence on SOC (34.6%) and total nitrogen (TN, 30.4%). Both climate and BSC physical properties played key regulatory roles on TP, whereas total potassium (TK), available potassium (AK), and AP were primarily driven by geographic factors. Alkaline phosphatase (S-ALP) and S-UE were jointly explained by climate and geography, while AN was mainly regulated by pH and EC. SEM further revealed that climate, BSC physical traits, and soil chemical conditions directly affected BMF, while geographic factors influenced BMF indirectly through climate. Among these, the effects of climate (0.614), pH (−0.573), and geography (0.370) were most pronounced. This study provides the first evidence of the altitudinal variation in the physicochemical properties and multifunctionality of BSCs on the northern slope of the Kunlun Mountains, highlighting the crucial regulatory role of altitude in shaping the ecological functions of desert mountain BSCs. Our findings have important implications for land management and ecological conservation in desert mountain ecosystems, offering a scientific basis for sustainable resource utilization and ecosystem restoration.