Evidence for involvement of keystone fungal taxa in organic phosphorus mineralization in subtropical soil and the impact of labile carbon

Soil organic carbon (SOC) derived from manure increase phosphorus (P) availability by increasing the proportion of organic P (Po) in total P. However, what role SOC plays in the process of converting Po to available P (AP) and who modulates Po mineralization are still poorly understood. In this study, we collected three soil samples under long-term filed treatment with different organic (no carbon, straw, and manure) inputs. By comparing bacterial and fungal lecithin-enrichment liquid cultures, we observed that the lecithin-enriched fungal community showed higher capability for Po mineralization. Using high-throughput sequencing of the field and lecithin-enriched microbial communities, we identified Po-mineralizing taxa in the soil. Co-occurrence network analysis revealed that the keystone fungal taxa Geastrum sp. and Chaetomium sp. in the fungal network negatively associated with Po-mineralizing fungal taxa, whereas keystone bacterial taxon was not directly related to Po-mineralizing bacteria. We found labile C limits the growth of keystone fungal taxa and that the addition of lactose enhanced Po mineralization by increasing the abundance of Po-mineralizing fungal taxa. Our results emphasize the importance of soil fungi for Po mineralization in acidic soil from a community perspective and provide evidence that easily degradable C drives Po mineralization and influences P availability through limitation of keystone fungal taxa. Our study gives insight into the biological mechanisms underlying specific organic carbon-induced interactions between fungal taxa and provides crucial information for the facilitation of P cycling.