Microbial Life‐History Strategies and Functional Gene Regulation Drive Soil Nitrogen and Phosphorus Bioavailability During Succession in an Arid Valley Ecosystem

Arid valley ecosystems are highly vulnerable to environmental change and face accelerating degradation due to climate warming and anthropogenic disturbance. Although soil microorganisms are known to drive nutrient cycling during succession, their adaptive strategies under persistent nutrient limitation remain poorly understood. This study integrated metagenomics, enzymatic stoichiometry and co-occurrence network analysis to investigate microbial community composition, life-history strategies, and nitrogen (N) and phosphorus (P) cycling functional genes along a successional gradient in an arid valley on the southeastern Tibetan Plateau. We found that microbial communities experienced consistent N limitation throughout succession, which shaped their functional potential and biogeochemical roles. Notably, during the transition from bare soil to biological soil crusts (BSCs), shifts in microbial life-history strategies towards resource acquisition (A-strategy) were accompanied by increased network complexity. Key functional genes, particularly those involved in nitrification (nxrB, amoC), dissimilatory nitrate reduction (nirB, nifH, nirD), inorganic P solubilization (gcd, ppk) and organic P mineralization (phnJ, phoA, phnM, phnI), were significantly upregulated during the BSCs stage. These genetic traits facilitated the transformation of organic and mineral nutrients into bioavailable forms, thereby supporting ecosystem development. This is manifested as a higher bioavailability of DON (+110%) and Bio-P (+97%) in the BSCs stage compared to bare land. Our results demonstrate that microbial communities adapt to resource constraints through trait-based strategies and functional gene regulation, highlighting the BSCs stage acts as a critical biogeochemical trigger in early succession. These insights advance our understanding of microbial-mediated nutrient cycling in arid ecosystems and inform restoration strategies under global change.