Significant loss of soil inorganic carbon at the continental scale

Abstract

Widespread soil acidification due to atmospheric acid deposition and agricultural fertilization may greatly accelerate soil carbonate dissolution and CO2 release. However, to date, few studies have addressed these processes. Here, we use meta-analysis and nationwide-survey datasets to investigate changes in soil inorganic carbon (SIC) stocks in China. We observe an overall decrease in SIC stocks in topsoil (0￢ﾀﾓ30ￂﾠcm) (11.33ￂﾠg C m￢ﾀﾓ2 yr￢ﾀﾓ1) from the 1980s to the 2010s. Total SIC stocks have decreased by ￢ﾈﾼ8.99ￂﾠￂﾱￂﾠ2.24% (1.37ￂﾠￂﾱￂﾠ0.37ￂﾠPg C). The average SIC losses across China (0.046 Pg C yr￢ﾀﾓ1) and in cropland (0.016 Pg C yr￢ﾀﾓ1) account for ￢ﾈﾼ17.6%￢ﾀﾓ24.0% of the terrestrial C sink and 57.1% of the soil organic carbon sink in cropland, respectively. Nitrogen deposition and climate change have profound influences on SIC cycling. We estimate that ￢ﾈﾼ19.12%￢ﾀﾓ19.47% of SIC stocks will be further lost by 2100. The consumption of SIC may offset a large portion of global efforts aimed at ecosystem carbon sequestration, which emphasizes the importance of achieving a better understanding of the indirect coupling mechanisms of nitrogen and carbon cycling and of effective countermeasures to minimize SIC loss.