How does grassland degradation affect soil enzyme activity and microbial nutrient limitation in saline‐alkaline meadow?

Abstract

Soil enzyme activity and its stoichiometry are excellent representatives of soil microorganisms' response to changing conditions, and act as a good indicator of microbial energy and nutrient demands. However, how soil enzyme activity and microbial nutrient limitation will be modified by grassland degradation is not well understood, especially in the saline‐alkaline meadow. Here, we presented how soil enzyme activity and microbial nutrient limitation shifted along a well‐characterized gradient of salinized degraded grasslands (non‐degraded, moderately degraded, and severely degraded). Our results showed soil enzyme activity was the highest in moderately degraded grasslands, which was mainly regulated by soil bacterial diversity. Soil microbial community metabolism in alkali‐saline meadow grasslands was limited by both carbon and phosphorus. Microbial carbon limitation showed a hump‐shaped pattern along the grassland degradation gradient, while microbial phosphorus limitation showed a gradually decreasing trend. Soil bacterial diversity is a key regulator of soil microbial carbon limitation, but the structure of the soil bacterial and plant community determines microbial phosphorus limitation. Taken together, our findings, taken together, provide evidence that soil bacteria are direct drivers of soil enzyme activity and microbial nutrient limitation along a grassland degradation gradient with salinization and suggest that these changes are regulated by soil salinity.