ABSTRACT Nitrogen (N) addition can increase soil organic carbon (SOC) in some grasslands, however, it is unknown whether N addition may enhance SOC in a warmer climate at broad spatial scales. We conduct a field experiment to test how N addition and warming interactively influence SOC in a temperate semiarid grassland. N addition significantly increases SOC by 14%, while simultaneous N addition and warming significantly decreases SOC by 25% relative to N‐only addition. This result is further supported by a global meta‐analysis, which shows that N addition (1 g N m −2 yr −1 ) increases SOC content by 0.2% relative to ambient conditions in grasslands, but the positive effect of N on SOC significantly declines at a rate of 0.06% per °C of increased mean annual temperature. Our field experiment and meta‐analysis suggest that warming may reduce or even eliminate the positive effect of N addition on SOC in grasslands.
Shi et al. (2026) studied this question.