Synergistic Mechanisms of Plant Phosphorus (P) Resorption and Microbial P-Limitation Affecting Soil P During Grassland Vegetation Succession

Phosphorus (P), a crucial element for all life forms on Earth, is often insufficiently available in terrestrial ecosystems. The interaction and feedback between plants and soil microorganisms are crucial links integrating above- and below-ground ecosystems. However, changes in soil P fractions in response to plant-microbe interactions during vegetation succession remain poorly understood. This study investigated the trends and relationships between plant resorption, microbial properties, and soil P fractions in the transformation interface soil layer (TIS) and underlying topsoil layer (UTS) during grassland vegetation succession. The results point to a combination of soil properties, alongside microbial and plant factors driving soil P changes. However, the TIS and UTS layers differ, with phosphorus dynamics in the TIS layer primarily influenced by microorganisms. Microorganisms are co-limited by C and P in both the TIS and UTS layers. Under microbial P-limitation, microorganisms produce alkaline phosphatases (AP), while C deficiency stimulates the production of C-acquiring enzymes, subtly regulating soil P dynamics through organic matter decomposition. Plant P resorption efficiency and microbial P-limitation exhibit synergistic variations, reaching their lowest levels during the mixed Bothriochloa ischaemum and Stipa bungeana Trin (Bo.I + St.B) stage. This study emphasizes that P cycling is influenced by plant-microbe-soil interactions and feedback. Plants and soil microorganisms jointly regulate soil nutrient effectiveness and partitioning in the ecosystem.