Soil phosphorus dynamics and its correlation with ectomycorrhizal fungi following forest conversion in subtropical conifer (Picea asperata) forests

Ectomycorrhizal (ECM) fungi or their associated microbes play key roles in mobilizing phosphorus (P) from soil organic matter. Forest conversion often alters soil P availability. However, the correlation between P dynamics caused by forest conversion and changes in ECM fungi is not clear. To dress this issue, we create ECM-reduction (trenched) and ECM-intact (untrenched) conditions in the natural forest and plantation. We then measured soil microbial properties, fungal communities, and P fractions. Our results showed that the natural forest exhibited a higher proportion of inorganic phosphorus (Pi) and a lower proportion of organic phosphorus (Po) compared to the plantation, indicating that forest conversion resulted in a decrease in P mineralization. Under ECM-reduction conditions, resin-Pi contents increased in both forest types. ECM-reduction led to an increase in NaOH-Pi and a decrease in NaOH-Po in both forest types. However, ECM-reduction decreased the 1 M HCl-Pi content in the natural forest while increasing it in the plantation. Structural equation modeling revealed that in the natural forest, trenching directly affected the reads number of ECM fungi, which subsequently influenced 1 M HCl-Pi and resin-Pi contents. In the plantation, trenching impacted NaOH-Po and ECM reads number, which were associated with changes in residual-P and resin-Pi contents. These findings highlight that ECM fungi differ in their utilization of resin-Pi and their ability to mobilize primary mineral Pi (1 M HCl-Pi) and poorly-available P, depending on the soil quality of natural forests and plantations.