[Effects of Long-term Corn Stover Return on Fungal Communities and Enzyme Activities in Brown Soil]

Based on a 31-year consecutive long-term positioning trial of stover return to field， including four different corn stover return methods： stover not returned to field （CK）， stover overgrown （CM）， stover crushed and directly returned to field （SC）， and stover mulched （SM）； the soil nutrient content， extracellular enzyme activity， fungal community structure， and mycorrhizal functional activity were comprehensively analyzed using high-throughput sequencing technology， FUNGuild functional prediction， and ecological network approach. We investigated the effects of different straw return modes on the nutrient content of brown soil farmland， analyzed the characteristics of soil extracellular enzymes and functional activities of fungal communities， and provided a theoretical basis for efficiently improving the soil fertility of brown soil farmland. The results showed that： ① Long-term different straw return treatments （SM， SC， and CM） significantly increased soil fertility， maize yield， and extracellular enzyme activities， and soil organic carbon （SOC）； total nitrogen （TN）； total phosphorus （TP）； total potassium （TK）； alkaline dissolved nitrogen （AN）； effective phosphorus （AP）； quick-acting potassium （AK）； cumulative yield of maize； and the contents of soil glucosidase （β-GC）， cellobiose hydrolase （CBH）， and dehydrogenase （DHA） contents were elevated from 17.0%-42.9%， 3.0%-50.0%， 2.3%-27.9%， 4.4%-11.5%， 11.2%-71.0%， 14.1%-320.8%， 17.1%-153.6%， 6.4%-23.0%， 35.6%-190.7%， 41.9%-58.6%， and 28.8%-773.8%； among them， the CM treatment had the most significant enhancement effect. ② Long-term different straw return treatments changed the structural composition of the soil fungal community， and the relative abundance of fungi in the phylum Periphyton decreased by 29.05%-31.12%， and the phylum Stachybotrys was enhanced by 24.76%-481.10%. The soil pH was an important influencing factor affecting the composition of the fungal community. ③ The results of network analysis showed that the indicator species of different straw return treatments in the long term belonged to different modules， which were significantly correlated with soil nutrient content and enzyme activity， among which Phaeoacremonium and Conocybe enriched in the CM treatment formed specific functional microbial clusters through a strong symbiotic relationship. ④ Functional prediction based on FUNGuild found that long-term different straw return treatments both increased the relative abundance of pathogenic and saprophytic trophic fungi and decreased the relative abundance of saprophytic-symbiotic trophic fungi. Long-term straw return can improve soil fertility and extracellular enzyme activity， increase the abundance of beneficial flora， significantly change the structure and composition of fungal communities， and favor carbon and nitrogen cycling， thus promoting the formation of a suitable environment for crop and fungal growth in brown soils.