Global patterns of soil organic carbon dynamics in the 20–100 cm soil profile for different ecosystems: A global meta-analysis

Abstract

Abstract Determining the dynamics of organic carbon in subsoil (SOC, depth of 20–100 cm) is important with respect to the global C cycle and warming mitigation. However, there is still a huge knowledge gap in the dynamics of spatiotemporal changes in SOC in this layer. We developed a new method to spatially resolve soil β values for global ecosystems (cropland, grassland, and forestland) and SOC dynamics at high resolution. We first quantified the spatial variability characteristics of these values and driving factors by analyzing 1221 soil profiles (0–1 m) of globally distributed field measurements and mapped the grid-level soil β values. Then we evaluated the SOC dynamics in different soil layers to determine the subsoil C stocks of various ecosystems. The subsoil SOC density values of cropland, grassland, and forestland were 63.8, 83.3, and 100.4 Mg ha–1, respectively. SOC density decreased with increasing depth, ranging from 5.6 to 30.8 Mg ha–1 for cropland, 7.5 to 40.0 Mg ha–1 for grassland, and 9.6 to 47.0 Mg ha–1 for forestland. The global subsoil SOC stock was 912 Pg C, in which an average of 54% resided in the top 0–100 cm of the soil profile. Our results provide insights into subsoil dynamics and the untapped potential to enhance global SOC sequestration in terrestrial ecosystems toward climate neutralization.