The positive effect of plant diversity on soil carbon (C) stocks is well documented, yet its role in shaping persistent C components essential for long-term soil C stability remains unclear. Using a 3,000-km transect survey of natural grasslands, we found that both bacterial and fungal necromass C increased with plant species richness, with more pronounced effects in the topsoil than in the subsoil and a steeper increase in fungal-derived necromass. Plant C inputs emerged as the primary driver of this response, exerting a stronger influence than soil nitrogen, pH, microbial attributes or mineral properties. These findings indicate that plant diversity promotes persistent soil C accumulation primarily through substrate supply that enhances microbial residue production. Our study underscores the importance of maintaining and restoring plant diversity in grasslands as a nature-based strategy to enhance stable soil C storage, thereby facilitating soil C sink capacity and contributing to climate change mitigation. Soil bacterial and fungal necromass carbon is linked with plant species richness with a stronger positive correlation in the topsoil than in the subsoil, according to observations along a 3,000 km transect in grasslands on the Tibetan plateau.
Yan et al. (2026) studied this question.