Carbon–Phosphorus Limitation Is Associated With Shifts in Microbial Life‐History Strategies Across Vegetation Restoration Modes in Alpine Sandy Land on the Tibetan Plateau

Alpine sandy land on the Tibetan Plateau is fragile, with poorly developed soils, low nutrient availability, and weak biological resilience. Vegetation restoration is widely used to improve soil functioning, yet how microbial nutrient limitation and life‐history strategies vary among restoration modes remains unclear. We compared bare sandy land (BL) with herbaceous (H), shrub–herb (SH), and tree–shrub–herb (TSH) restoration modes by assessing soil nutrients, extracellular enzyme stoichiometry, microbial communities, and life‐history strategies. SOC, TN, and TP were higher in SH and TSH than in BL and H, whereas soil pH decreased and approached neutrality, especially under TSH. Ecoenzymatic vector analysis indicated stronger relative C limitation but weaker relative P limitation in restored plots than in BL, with TSH showing the greatest C limitation. Thus, increased nutrient pools did not necessarily alleviate microbial resource limitation, possibly because complex plant‐derived C inputs and plant–microbial demand exceeded readily available C supply. Microbial diversity and composition also differed among modes, with fungal α‐diversity responding more clearly than bacterial α‐diversity. Restored plots showed greater dominance of oligotrophic K‐strategist taxa and lower abundance of copiotrophic r‐strategist taxa. Fungal K/r peaked under TSH, whereas bacterial K/r peaked under SH, suggesting contrasting bacterial and fungal responses. Correlation analyses linked enzyme vector parameters to microbial K/r patterns, while random forest modeling identified VA and VL as important predictors of bacterial K/r. These findings reveal associations among soil resource limitation, microbial community structure, and life‐history patterns, providing a microbial perspective on nutrient cycling during restoration in fragile alpine drylands.