A new Nature Geoscience paper based on an 8-year semi-arid grassland experiment and a meta-analysis of 44 observations finds that warming and nitrogen input together reduce soil inorganic carbon by about 9.1%, while altered precipitation alone had no measurable effect. Nitrogen input on its own did not shift inorganic carbon, but when combined with warming, the loss appeared alongside enhanced nitrification, suggesting that proton production from nitrification drives carbonate dissolution. The same global change drivers pushed soil inorganic and organic carbon in opposite directions, creating a trade-off that dryland carbon models often ignore. Most soil carbon monitoring and credit protocols focus on organic carbon, but this study is a reminder that drylands store large amounts of inorganic carbon too. If warming and nitrogen deposition continue to rise, projects that only track organic carbon could report gains while total soil carbon actually falls. Data and code are available on Zenodo.
