Global subsoil organic carbon turnover times dominantly controlled by soil properties rather than climate

Zhongkui Luo,Enli Wang,Guocheng Wang

doi:10.1038/s41467-019-11597-9

Abstract

Soil organic carbon (SOC) in the subsoil below 0.3 m accounts for the majority of total SOC and may be as sensitive to climate change as topsoil SOC. Here we map global SOC turnover times (τ) in the subsoil layer at 1 km resolution using observational databases. Global mean τ is estimated to be 1015_{729}^{1414} yr (mean with 95% confidence interval), and deserts and tundra show the shortest (146_{114}^{188} yr) and longest (3854_{2651}^{5622} yr) τ respectively. Across the globe, mean τ ranges from 9 (the 5% quantile) to 6332 years (the 95% quantile). Temperature is the most important factor negatively affecting τ, but the overall effect of climate (including temperature and precipitation) is secondary compared with the overall effect of assessed soil properties (e.g., soil texture and pH). The high-resolution mapping of τ and the quantification of its controls provide a benchmark for diagnosing subsoil SOC dynamics under climate change.

Highlights

May be as sensitive to climate change as topsoil Soil organic carbon (SOC)
Using Earth system models (ESMs), for example, global average SOC turnover times in the top 1 m soil were estimated to be in the range of 10.8–39.3 yr[11]
Analysis of radiocarbon data sets from 157 soil profiles down to 1 m across the globe challenged the estimates by ESMs and found that ESMs underestimate SOC turnover times by a factor of more than six[21]

Summary

Introduction

We map global SOC turnover times (τ) in the subsoil layer at 1 km resolution using observational databases. The high-resolution mapping of τ and the quantification of its controls provide a benchmark for diagnosing subsoil SOC dynamics under climate change. By assessing the underlying drivers of SOC turnover time, we can gain insights into the dynamics of SOC under climate change and other soil disturbances, which otherwise are difficult to be obtained by conducting manipulation experiments. Several studies have estimated ecosystem carbon turnover times at the global scale[13], subsoil SOC turnover times have not been explicitly quantified based on observational data, nor the mechanisms controlling the turnover. A detailed observation-based quantification of subsoil SOC turnover times and their association with climate and soil properties represents a key step towards reliable predictions of carbon cycle-climate feedbacks

Methods

Results

Conclusion