Stable isotopic constraints on global soil organic carbon turnover

Wang, Chao; Houlton, Benjamin Z.; Liu, Dongwei; Hou, Jianfeng; Cheng, Weixin; Bai, Edith

Carbon dioxide release during soil organic carbon (SOC) turnover is a pivotal component of atmospheric CO 2 concentrations and global climate change. However, reliably measuring SOC turnover rates on large spatial and temporal scales remains challenging. Here we use a natural carbon isotope approach, defined as beta ( β), which was quantified from the δ13C of vegetation and soil reported in the literature (176 separate soil profiles), to examine large-scale controls of climate, soil physical properties and nutrients over patterns of SOC turnover across terrestrial biomes worldwide. We report a significant relationship between β and calculated soil C turnover rates ( k), which were estimated by dividing soil heterotrophic respiration rates by SOC pools. ln( −  β) exhibits a significant linear relationship with mean annual temperature, but a more complex polynomial relationship with mean annual precipitation, implying strong-feedbacks of SOC turnover to climate changes. Soil nitrogen (N) and clay content correlate strongly and positively with ln( −  β), revealing the additional influence of nutrients and physical soil properties on SOC decomposition rates. Furthermore, a strong ( R2 = 0.76; p < 0.001) linear relationship between ln( −  β) and estimates of litter and root decomposition rates suggests similar controls over rates of organic matter decay among the generalized soil C stocks. Overall, these findings demonstrate the utility of soil δ13C for independently benchmarking global models of soil C turnover and thereby improving predictions of multiple global change influences over terrestrial C-climate feedback.

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Wang, Chao / Houlton, Benjamin Z. / Liu, Dongwei / et al: Stable isotopic constraints on global soil organic carbon turnover. 2018. Copernicus Publications.

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