Global change reshapes glomalin-mediated soil carbon sequestration by influencing plant inputs

Glomalin-related soil protein (GRSP), a by-product of arbuscular mycorrhizal fungi (AMF), plays a crucial role in stabilizing soil organic carbon (SOC). Global change factors (GCFs) such as elevated atmospheric carbon dioxide (CO₂), climate warming and anthropogenic nitrogen (N) input strongly affect soil AMF activity, consequently influencing GRSP formation. However, the impacts of these GCFs on GRSP dynamics remain poorly understood despite their critical role in SOC accumulation and stability. Through a systematic search of publications, we synthesized 529 observations from 122 primary studies worldwide. We conducted a meta-analysis to reveal general patterns and drivers of the effects of N, phosphorus (P), their co-addition, warming, elevated [CO₂], drought and forest restoration on easily extractable (EE-GRSP) and total GRSP (T-GRSP), and quantitatively assessed the role of GRSP in SOC sequestration. Results showed that N, P, their co-addition and forest restoration increased EE-GRSP by 12%, 3.1%, 13.4% and 49%, and T-GRSP by 13%, 10%, 11% and 65%, respectively, because reduced nutrient limitation stimulated plant inputs and AMF growth, promoting the formation of GRSP. In contrast, elevated [CO₂], warming, and drought had negligible effects on GRSP. Machine learning identified plant inputs (partly proxied by plant biomass) as the primary mediator of GRSP changes along with AMF activity. The increases in GRSP were positively correlated with the soil aggregate stability (e.g. mean weight diameter [MWD] of soil aggregates) and SOC, which itself was positively related to the MWD of soil aggregates. Structural equation modelling further validated that GRSP changes, mainly influenced by altered plant inputs and AMF activity, directly enhance SOC accumulation and indirectly contribute to soil aggregate formation and SOC stability. These findings provide insights into the positive role of mycorrhizal fungal metabolites in SOC sequestration and highlight the potential to improve GRSP production to promote carbon sequestration under global environmental change. Read the free Plain Language Summary for this article on the Journal blog.