马尾松林土壤真菌生物量及酶活性季节变化特征OACHSSCD

Plants and soil microorganisms have established intimate relationships in the flow of carbon and nutrients,which exerts a significant impact on the nutrient cycling of ecosystems.The seasonal dynamics of soil fungal communities,biomass,and enzyme activity in Pinus massoniana forests in Chongqing,China,are investigated,with a focus on the seasonal complementarity of nitrogen utilization between soil fungi and plants.Soil samples were collected during the plant active growing season(summer)and the dormant season(winter)from 22 forest plots.The contents of soil dissolved organic carbon(DOC),ammonium(NH4+-N),and nitrate(NO3--N)were measured.Fungal communities were analyzed using high-throughput sequencing of fungal ITS regions,and fungal biomass was quantified through phospholipid fatty acid analysis.Soil enzyme activities were also measured to assess microbial metabolic activity.Significant seasonal variations in soil DOC,NH4+-N,and NO3--N contents were observed(P＜0.001),with higher DOC and lower nitrogen availability in winter,and a significant increase in ammonium and nitrate levels in summer.Fungal community structure showed distinct seasonal differences(P＜0.001),with saprotrophic fungi dominating in summer(P=0.016),and ectomycorrhizal fungi significantly increasing in winter(P＜0.001).Fungal biomass was significantly higher in winter(P＜0.001).Enzyme activity analysis revealed higher carbon and nitrogen hydrolytic enzyme activities in summer(P＜0.01),but with a significantly lower enzyme carbon to nitrogen ratio in summer(P＜0.001),indicating that microbial growth in summer was more limited by carbon availability.The findings suggest that soil fungi and plants in P.massoniana forests exhibit seasonal complementarity in nitrogen utilization:in winter,fungi immobilize nitrogen into their biomass,reducing the availability of nitrogen in the soil to plant.In summer,due to carbon limitation,fungal biomass declines,and nitrogen previously immobilized in fungal biomass is mineralized and released back into the soil for plant uptake.This seasonal dynamic reduces direct competition for nitrogen between fungi and plants.This provides a conceptual framework for understanding the seasonal nutrient dynamics in forest ecosystems,advancing our understanding of soil microbial and plant nutrient cycling.