Significantly more carbon (C) is stored in deep soil than in shallow horizons, yet how the decomposition of deep soil organic C (SOC) will respond to rising temperature remains unexplored on large scales, leading to considerable uncertainties to predictions of the magnitude and direction of C-cycle feedbacks to climate change. Herein, short-term temperature sensitivity of SOC decomposition (expressed as Q10) from six depths within the top 1 m soil from 90 upland forest sites (540 soil samples) across China is reported. Results show that Q10 significantly increases with soil depth, suggesting that deep SOC is more vulnerable to loss with rising temperature in comparison to shallow SOC. Climate is the primary regulator of shallow soil Q10 but its relative influence declines with depth; in contrast, soil C quality has a minor influence on Q10 in shallow soil but increases its influence with depth. When considering the depth-dependent Q10 variations, results further show that using the thermal response of shallow soil layer for the whole soil profile, as is usually done in model predictions, would significantly underestimate soil C-climate feedbacks. The results highlight that Earth system models need to consider multilayer soil C dynamics and their controls to improve prediction accuracy.
Bibliographical noteFunding Information:
They thank Eric A. Davidson and Chao Liang for insightful discussions during the preparation of the manuscript; they also thank Zhen Li, Hui Guo, Xiao Xu, and Huimin Sun for the help with measurements and analyses; they also appreciate two anonymous reviewers for their valuable comments on the manuscript. This work was supported by the National Science Foundation of China (Nos. 91951112 and 31930070), the Postdoctoral Science Foundation of China (2020M670975), and the Australian Research Council (No. DP170102766).
© 2020 The Authors. Published by Wiley-VCH GmbH
- carbon decomposition
- deep soil
- forest ecosystems
- global warming
- temperature sensitivity