Temporal Variation of Arbuscular Mycorrhizal Fungi and Glomalin‐Related Soil Proteins in Citrus Orchards of Different Planting Durations

ABSTRACT Glomalin‐related soil proteins (GRSPs) play a vital role in the stabilization of soil organic carbon (SOC); however, their long‐term dynamics under intensive cultivation remain poorly understood in citrus orchard ecosystems. In this study, we studied GRSP contents and arbuscular mycorrhizal fungi (AMF) communities in natural forest soils and citrus orchards cultivated for 10, 20, and 30 years. The results showed that natural forest soils had the highest content of total GRSP (T‐GRSP), significantly exceeding that in citrus orchard soils irrespective of planting duration. AMF Shannon and Simpson indices in the 20‐ and 30‐year‐old citrus orchard soils were markedly lower than that in the 10‐year‐old orchards and natural forest soils. Hierarchical clustering further indicated a distinct gradient in AMF community composition across different land‐use types and cultivation years, with the AMF community in natural forest soils being clearly separated from that in citrus orchards. Paraglomus and Glomus dominated the AMF genera, showing opposite trends of variation with increasing planting years. The relative abundance of Paraglomus increased significantly with planting duration and stabilized in the 20‐ to 30‐year‐old soils, whereas Glomus was more abundant in the 10‐year‐old soils than in the older orchards. Variation partitioning analysis revealed that T‐GRSP content was jointly regulated by AMF and basic soil properties. Soil factors (pH and SOC) alone explained 29.3% of the variation in T‐GRSP, while AMF diversity, community composition, and the dominant genus Paraglomus and Glomus together explained 21.6%. These findings highlight the pivotal role of T‐GRSP in enhancing SOC storage and stabilization under long‐term, intensive citrus cultivation. Moreover, this integrative study provides new insights into the ecological mechanisms driving AMF community assembly and their functional contributions to soil carbon processes.