Soil microbial functional profiles of P-cycling reveal drought-induced constraints on P-transformation in a hyper-arid desert ecosystem

Soil water conditions are known to influence soil nutrient availability, but the specific impact of different conditions on soil phosphorus (P) availability through the modulation of P -cycling functional microbial communities in hyper -arid desert ecosystems remains largely unexplored. To address this knowledge gap, we conducted a 3 -year pot experiment using a typical desert plant species ( Alhagi sparsifolia Shap.) subjected to two water supply levels (25 % -35 % and 65 % -75 % of maximum field capacity, MFC) and four P -supply levels (0, 1, 3, and 5 g P m( -2) y( -1) ). Our investigation focused on the soil Hedley-P pool and the four major microbial groups involved in the critical phases of soil microbial P -cycling. The results revealed that the drought (25 % -35 % MFC) and no P -supply treatments reduced soil resin -P and NaHCO3 -Pi concentrations by 87.03 % and 93.22 %, respectively, compared to the well -watered (65 % -75 % MFC) and high P -supply (5 g P m (-2) y( -1) ) treatments. However, the P -supply treatment resulted in a 12 % -22 % decrease in the soil NH 4(-)(+)N concentration preferred by microbes compared to the no P -supply treatment. Moreover, the abundance of genes engaged in microbial Pcycling (e.g. gcd and phoD ) increased under the drought and no P -supply treatments ( p < 0.05), suggesting that increased NH 4(-)(+)N accumulation under these conditions may stimulate P-solubilizing microbes, thereby promoting the microbial community's investment in resources to enhance the P -cycling potential. Furthermore, the communities of Steroidobacter cummioxidans , Mesorhizobium alhagi , Devosia geojensis , and Ensifer sojae , associated with the major P -cycling genes, were enriched in drought and no or low -P soils. Overall, the drought and no or low -P treatments stimulated microbial communities and gene abundances involved in P -cycling. However, this increase was insufficient to maintain soil P-bioavailability. These findings shed light on the responses and feedback of microbial -mediated P -cycling behaviors in desert ecosystems under three-year drought and soil P -deficiency.