关键词: 增雨, 氮沉降, 土壤酶活性, 养分限制

Abstract: Aims Quantify how increased summer precipitation and nitrogen deposition, alone and in combination, affect soil extracellular enzyme activities and stoichiometry. Identify the resulting shifts in microbial nutrient limitations in a Caragana microphylla-encroached grassland. Methods Conducted a factorial field manipulation in Inner Mongolia with summer precipitation addition (PA) and nitrogen addition (NA, simulating deposition). Measured activities of carbon-, nitrogen-, and phosphorus-acquiring extracellular enzymes. Assessed microbial nutrient limitation using vector analysis based on enzyme stoichiometry. Important findings PA increased carbon- and nitrogen-acquiring enzyme activities but decreased phosphorus-acquiring enzyme activity. NA increased phosphorus-acquiring enzyme activity and shifted enzyme stoichiometry. Vector analysis indicated predominant co-limitation by nitrogen and phosphorus. NA alleviated phosphorus limitation by increasing nitrogen-acquiring enzyme activity and altering N:P enzyme ratios. PA intensified microbial carbon and phosphorus limitations, likely via soil moisture effects on microbial biomass and enzyme production. Overall, increased precipitation and nitrogen deposition reconfigured microbial nutrient constraints by modulating extracellular enzyme activities and stoichiometry in shrub-encroached grasslands.

Key words: increased precipitation, nitrogen deposition, soil enzyme activity, nutrient limitation