Climate and anthropogenic activities control spatiotemporal dynamics of topsoil inorganic carbon in China

Soil inorganic carbon (SIC) comprises nearly half of terrestrial carbon storage and is vital for climate regulation. While previous studies focused on SIC’s size, composition, and distribution, its temporal dynamics and drivers remain understudied. Here, we analyzed SIC spatiotemporal changes (1980–2020) across China using 2526 soil samples and a digital soil mapping framework. In 2020, China’s top 30 cm SIC stock was 15.15 Pg C, with the highest density in desert. Spatial patterns followed a northwest-to-southeast gradient shaped mainly by climate and soil properties. Temporal trends were primarily driven by anthropogenic factors. Increased nitrogen deposition, fertilizer-induced acidification, and reduced calcium supply from declining base-cation deposition contributed to an annual SIC loss of 0.03 Pg C. These changes alter carbon fluxes among soil-atmosphere-hydrosphere system, with implications for climate. Our findings highlight the need for sustainable nitrogen management and base cation supplementation to mitigate SIC loss and support long-term carbon retention. Spatial variability of topsoil inorganic carbon is influenced by climate and soil properties, whereas nitrogen deposition, fertilizer-induced acidification, and reduced calcium supply contribute to the temporal trends, according to an analysis of 2526 soil samples across China from 1980 to 2020.