Land conversion from cropland to grassland alleviates climate warming effects on nutrient limitation: Evidence from soil enzymatic activity and stoichiometry

Abstract

Climate warming and land conversion are key factors affecting ecosystem functions. Investigating the effects of these two factors on soil enzyme activity and stoichiometry will provide insights into soil nutrient limitation in terrestrial ecosystems. However, how climate warming and land conversion affect soil nutrient limitation remains poorly understood. Here, we investigated the effects of climate warming and land conversion on soil enzyme activity and stoichiometry. An 8-year mesocosm experiment was set up with climate warming in soil transplants from a temperate gradient region and land conversion from cropland to grassland. The results showed that land conversion from cropland to grassland increased the activity of C- and N-acquired enzymes but decreased the activity of P-acquired enzyme. Moreover, the enzyme stoichiometry of C:P and N:P increased under grassland over cropland. The changes in soil enzyme activity and stoichiometry suggested that land conversion from cropland to grassland increased C and N limitation but decreased P limitation. In cropland, climate warming did not significantly affect soil enzyme activity and stoichiometry. In grassland, as temperature increased, C-acquired enzyme, enzyme stoichiometry of C:P and N:P, and vector length decreased, but P-acquired enzyme and vector angle increased. This result suggested decreased C limitation and increased P limitation with climate warming. Additionally, redundancy analysis demonstrated that soil pH, soil dissolved nutrients, and soil stoichiometry were important factors for soil enzymes in grassland. Our findings suggested that long-term climate warming could alter C and P limitation of soil microbes following land conversion.