Effects Of Different Carbon And Phosphorus Addition On Soil Carbon,Nitrogen And Phosphorus Nutrients And Microbial Activities In Subtropical Forests

Carbon（C）,nitrogen（N）and phosphorus（P）are the main energy and nutrient sources absorbed and utilized by plants and microorganisms,which have important effects on maintaining forest productivity and stability.C,N,and P exist widely in the biogeochemical cycle of forest ecosystems,which affect the ecological stoichiometry of soil microorganisms and are crucial to the growth and development of plants.C and P,as important nutrients in subtropical forest soil,will change the soil environment,and then change the soil microbial activity,and significantly affect the soil nutrient cycling process.Simple organic matter and inorganic matter are the most easily absorbed and utilized by soil microorganisms.Therefore,this study,based on sanming Forest Ecosystem and Global Change Research Station of Fujian Province,took the soil under cunninghamia lcunninghamia and Schima superba forests as the research object and carried out a 21-day indoor culture experiment:Set up the control（CT）,carbon addition(C:C₆H₁₂O₆),phosphorus addition（P:Na H₂PO₄）,carbon and phosphorus simultaneous addition(C+P:C₆H₁₂O₆+Na H₂PO₄)carbon and phosphorus compound addition(CP:C₆H₁₂O₉PNa₂)To study the effects of different types of carbon and phosphorus addition on soil carbon,nitrogen and phosphorus nutrients and microbial activities in subtropical forest soil.The main conclusions are as follows:（1）P-related addition can improve acidic soil,increase soil soluble organic carbon（DOM）content,and make soil DOM more stable.CP addition has the largest increase in soil p H value.C supplementation may reduce the release of soil soluble organic nitrogen（DON）and mineral nitrogen,P supplementation may promote the release of N-related available nutrients,and carbon and phosphorus mixed supplementation can promote the release of DON,especially CP compound supplementation greatly increased THE DON content.C addition had no significant effect on available P,and when CP compound was mixed,C might have a negative effect on the accumulation of P in soil.（2）CP supplementation had a significant effect on soil microbial biomass,and the microbial biomass PHOSPHORUS（MBP）increased significantly at the initial stage due to the P limitation of SCHba superba.There was no P limit in Cunninghamia lanceolata,so MBP content increased slowly.Soil microbial biomass carbon and microbial biomass PHOSPHORUS（MBC:MBP）in p.superba soil were lower than those in CT.However,C+P and CP additions in Chinese fir soil were higher than those in CT at 3 d,which may be due to the possible C limitation in Chinese fir soil.Chinese fir soil has a more urgent demand for C,and C will be prefered to be used when C and P are added simultaneously.（3）The DOM composition of C+P addition in Chinese fir soil was more similar to that of CP addition,and the composition of C+P addition,C+P addition and CP addition were more consistent.Chinese fir soil needed C source nutrient more.P addition in SCHima superba soil is more similar to THE DOM composition of C+P addition,and the composition of P addition,C+P addition and CP addition is more similar and obviously different from CT and C addition.Schima superba more uses CP compound as P source.（4）Carbon supplementation significantly increased MBC:MBN and MBC:MBP at the initial stage of culture,while MBC:MBN decreased rapidly during culture.Schima superba MBC:MBP also decreased rapidly,while Cunninghamia lhamia rose rapidly after reaching the lowest level on the 14th day.P supplementation promoted soilβG:ACP,while carbon supplementation had no effect on soilβG:ACP.Soil quantitative ratio was positively correlated with microbial quantitative ratio,but negatively correlated with microbial enzyme activity.（5）CP and C+P supplementation decreased the abundance and even-average of communities,but significantly increased the abundance of Proteobacteria and basidiomycetes.The main bacterial communities of Chinese fir and Schima superba are Proteobacteria,Actinobacteria and Acidobacteria.The fungal communities were Basidiomycota and Ascomycota.The p H values of the two treatments were higher than those of the other treatments.The fungi in Cunninghamia lense soil were not sensitive to the difference of nutrients,and the fungi in Schima superba soil had different responses to easily decomposed carbon and CP compounds.