Articles | Volume 15, issue 4
Biogeosciences, 15, 987–995, 2018
Biogeosciences, 15, 987–995, 2018

Research article 20 Feb 2018

Research article | 20 Feb 2018

Stable isotopic constraints on global soil organic carbon turnover

Chao Wang1, Benjamin Z. Houlton2, Dongwei Liu1, Jianfeng Hou1,3, Weixin Cheng1,4, and Edith Bai1,5 Chao Wang et al.
  • 1CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China
  • 2Department of Land, Air and Water Resources, University of California, Davis, CA, 95616, USA
  • 3College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, 100049, China
  • 4Department of Environmental Studies, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064, USA
  • 5School of Geographical Sciences, Northeast Normal University, Changchun, 130024, China

Abstract. Carbon dioxide release during soil organic carbon (SOC) turnover is a pivotal component of atmospheric CO2 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.

Short summary
Soil contains a large amount of organic carbon and plays a crucial role in regulating Earth's C cycle and climate system. In this study, we collected soil-carbon isotope data within a 1 m depth globally and provided an isotope-based approach for understanding soil carbon decomposition rate. Compared with other methods, utilization of C isotope composition ratios in the soil profile provides an independent approach that does not rely on disruption of plant-soil-microbe interactions.
Final-revised paper