Warming effects on C:N:P stoichiometry and nutrient limitation in terrestrial ecosystems

Carbon (C): nitrogen (N): phosphorus (P) stoichiometry in terrestrial ecosystems largely determines nutrient cycling in plant-soil-microorganism systems. However, a comprehensive evaluation of the effects of warming on plant-soil-enzyme C-N-P stoichiometry has not been well documented. Here, a global meta-analysis of 603 pairwise observations was conducted to reveal the impacts of experimental warming on C:N:P stoichiometry in plant-soil-microorganism systems across different warming duration (0-5, 5-10, and >10 years), magnitudes (<2 and >= 2 C), and ecosystem types (cropland, grassland, shrub, and forest). Overall, results show that warming increased soil N:P and vector angle (reflecting the P limitations of soil microbes) by 4.2 % and 2.0 %, but decreased plant shoot N:P and enzyme N:P by 15.1 % and 2.1 %, respectively. The percentage changes of soil N:P and enzymes N:P increased but the vector angle and length (reflecting the C limitations of soil microbes) decreased with warming duration. The soil N:P, vector angle, and length increased but plant shoot N:P decreased with warming magnitudes. Warming increased microbial P limitation but decreased the microbial C limitation in the forest. MAP negatively affected the shoot N:P in areas with a range of 400-800 mm. In conclusion, our results indicated that both plants and microorganisms are more likely to be limited by P than by N under warming. These effects were influenced by warming duration, magnitudes, ecosystem type, and soil depths. The results deepened our understanding of C, N, and P cycling processes in terrestrial ecosystems. Simultaneously, warming duration, magnitudes, ecosystem type, and soil depths should be incorporated into the C and N cycle model under global warming.