The response of ecosystem carbon and nitrogen pools to experimental warming in grasslands: a meta-analysis
Junliang Zou, Juying Wu, Bruce Osborne, Yiqi Luo
Abstract
Abstract Carbon (C) and nitrogen (N) coupling processes in terrestrial ecosystems have the potential to modify the sensitivity of the global C cycle to climate change. But the degree to which C–N interactions contribute to the sequestration of terrestrial ecosystem C (Cseq), both now and in the future, remains uncertain. In this study, we used a meta-analysis to quantitatively synthesize C and N responses from field experiments on grasslands subjected to simulated warming and assessed the relative importance of three properties (changes in ecosystem N amount, redistribution of N among soil, litter and vegetation, and modifications in the C:N ratio) associated with grassland Cseq in response to warming. Warming increased soil, litter and vegetation C:N ratios and approximately 2% of N shifted from the soil to vegetation and litter. Warming-induced grassland Cseq was the result of the net balance between increases in vegetation and litter C (111.2 g m−2) and decreases in soil C (30.0 g m−2). Warming-induced accumulation of C stocks in grassland ecosystems indicated that the three processes examined were the main contributors to Cseq, with the changes in C:N ratios in soil, litter and vegetation as the major contributors, followed by N redistribution, whilst a decrease in total N had a negative effect on Cseq. These results indicate that elevated temperatures have a significant influence on grassland C and N stocks and their coupling processes, suggesting that ecological models need to include C–N interactions for more accurate predictions of future terrestrial C storage.