古尔班通古特沙漠不同坡位地衣结皮土壤磷组分分布特征

s the fundamental terrain of deserts, sand ridges play a crucial role in shaping the surface water and thermal environment at different slope positions, which profoundly influences how biological soil crusts develop and their spatial distribution patterns. Lichen crusts are widely distributed on the desert surface. However, issues such as how lichen crusts at different slope positions affect the soil phosphorous cycle and what factors play keyroles in influencing this remain unclear. Against this background, this study was conducted in Gurbantunggut Desert, involving a systematic analysis of the changes in phosphorus fractions and related enzyme activities in the lichen crust and 0-5 cm soil layer beneath the crust at different slope positions. The results showed that stable phosphorus in the soil (HCl-Pi, HHCl-Po, HHCl-Pi, and Residual-P) accounted for over 75% of the total phosphorus (TP) content, followed by medium labile phosphorus (NaOH-Pi and NaOH-Po) and labile phosphorus (Resin-P, NaHCO3-Pi, and NaHCO3-Po). The slope position had a significant impact on stable phosphorus, and the soil layer had a significant impact on medium labile phosphorus (P<0.05). The data on the contents of stable phosphorus, TP, organic phosphorus (Po); and inorganic phosphorus (Pi) all revealed that, in the crust layer, the values at the bottom of the slope were significantly higher than those on the east and west slopes, while in the 0-5 cm soil layer, the values on the west slope were significantly lower than those at the bottom of the slope and on the east slope (P<0.05). However, the content of NaOH-Pi was significantly higher on the east and west slopes than at the bottom of the slope in the crust layer, and it was significantly higher on the west slope than on the east slope and at the bottom of the slope in the 0-5 cm soil layer. In terms of soil enzymes, the east slope exhibited the lowest activity of alkaline phosphatase activity (ALP) and -glucosidase activity (GC) in the crust layer, but the highest in the 0-5 cm soil layer. Random forest model analysis showed that the changes in moisture and temperature broughtabout by the slope position were the most important factors affecting the levels of labile phosphorus and stable phosphorus in the crust soil, respectively. This provides scientific support that enriches the theoretical framework of soil phosphorous cycling in desert ecosystems.