Synergistic effects of AMF and Trichoderma longibrachiatum on reshaping fungal communities to promote nutrient release and plant uptake from fore-rotating crop straw in albic soil

Straw return is considered an effective strategy for its improvement. However, in regions where albic soil is predominantly distributed, low temperatures severely hinder straw decomposition and nutrient release. Arbuscular mycorrhizal fungi (AMF) and Trichoderma longibrachiatum (TH) are important functional soil microorganisms for improving soil conditions and promoting organic matter decomposition. However, the synergistic mechanisms between them are still unclear. This research investigated the regulatory effects of AMF and TH co-inoculation on fungal communities during straw decomposition and nutrient cycling in albic soil. Our study revealed that: (1) TH inoculation enhanced the responsiveness of the host root system to AMF, increasing the mycorrhizal colonization rate by 6.67%. Meanwhile, AMF modulated the ecological function of TH, directing its functions toward organic matter decomposition and nutrient release; (2) AMF synergistically enhanced the activities of key decomposing enzymes with TH and increased soil pH by 0.13 units. These changes accelerated straw decomposition and nutrient release, thereby increasing the aboveground and underground fresh weights of soybeans increased by 36.71% and 40.95%, respectively; (3) AMF synergized with TH to reshape the rhizosphere fungal community, significantly increasing the abundance of TH and enriching dominant microbial taxa involved in organic matter decomposition. This synergistic interaction further enhanced straw degradation and nutrient transformation by improving the soil nutrient profile. Overall, AMF synergized with TH through multiple pathways to significantly enhance straw decomposition efficiency and nutrient use efficiency, providing a valuable strategy for improving crop productivity in Albic soil fields.