Heterogeneity of phosphorus sources invokes distinct niche partitioning pathways of ectomycorrhizal fungi in forest soils

Ectomycorrhizal (ECM) fungi are pivotal in acquiring phosphorus (P) in nutrient-deficient soils, especially beyond the rhizosphere. However, the extent to which ECM community structure and function affect the utilization of various P-containing substrates in forest soils is not fully understood. This study explored the influence of different P substrates — calcium orthophosphate, phosphate-saturated goethite, fluorapatite, and wheat bran—on the release of plant-available P using hyphal in-growth mesh bags. Our results show that these substrates released comparable amounts of plant-available P to the Pinaceae hosts. A significant correlation was observed between the relative abundance of Tylospora (Atheliaceae) and Hourangia (Boletaceae), and their extracellular enzyme activities involved in P acquisition and trivalent iron reduction. This correlation was particularly evident in fungal taxa characterized by long/medium-distance hyphal exploration types. These findings underscore the ECM fungi's distinct preferences for different P-containing substrates, emphasizing the importance of recognizing these preferences to enhance forest management in low P environments.