Effects Of Phosphorus Addition On Soil Carbon,Nitrogen And Phosphorus Stoichiometry And Microbial Diversity In Cunninghamia Lanceolata Plantations

As one of the main fast-growing timber species in China,Cunninghamia lanceolata has been directly affected in terms of its sustainable development,due to the phenomenon of pure forest management and multi-generation continuous planting of Cunninghamia lanceolata,which resulted in the increasingly prominent problems of soil fertility decline and primary productivity decline of Cunninghamia lanceolata plantation.This has become a recognized fact that the soil in low latitudes lacks phosphorus,which is an important factor restricting the high yield of Cunninghamia lanceolata forest and affecting the stability of the ecosystem.With taking Cunninghamia lanceolata plantations of different forest ages at the National Field Science Observation and Research Station of Lutou Forest Ecosystem in Hunan Province as the research object,activating phosphate fertilizer with biological enzyme,and laying out four phosphorus addition levels:P1(P2O5,2g·m-2·a-1),P2(P2O5,5g·m-2·a-1),P3(P2O5,10g·m-2·a-1)andPO(P2O5,Og·m-2·a-1)inatotalof 4 treatments and 3 repeated field in-situ experiments conducted,this study is to measure SOC,TN,TP contents and microbial community diversity of Cunninghamia lanceolata plantation soil at different forest ages under different phosphorus addition levels,and to reveal the responses of soil stoichiometry characteristics of Cunninghamia lanceolata plantation at different forest ages to bio-enzyme activated phosphorus addition,in order to provide theoretical basis for nutrient maintenance and sustainable management of Cunninghamia lanceolata plantation.The main study results are as follows:(1)The application ofbio-enzyme to activate phosphate fertilizer has changed the stoichiometry characteristics of C:N,C:P,N:P in Cunninghamia lanceolata forest soil to varying degrees to improve the availability of soil nutrients and ease the phosphorus limitation.(2)The results of correlation analysis and redundancy analysis among SOC,TN,TP,C:N,C:P,N:P of the soil in Cunninghamia lanceolata plantations show that:in the juvenile stage Cunninghamia lanceolata plantation,the response of soil C:N to phosphorus addition is mainly affected by soil SOC,while the response of soil C:P,N:P to phosphorus addition is mainly affected by TP,which indicates that juvenile stage Cunninghamia lanceolata plantations are greatly limited by phosphorus;in the Fast-growing stage Cunninghamia lanceolata plantation,the response of soil C:P to phosphorus addition is mainly affected by soil SOC,while the response of soil C:N,N:P to phosphorus addition is mainly affected by soil TN,which indicates that Fast-growing stage Cunninghamia lanceolata plantations are mainly limited by nitrogen.(3)Misep high-throughput sequencing shows that the Soil microbial dominant bacteria of Cunninghamia lanceolata forest at the phylum levels are Acidobacteria and Proteobacteria,at the genes levels are Candidatus Solibacter and Acidibacter.The response trend of Acidobacteria and Proteobacteria to phosphorus addition was consistent with that of nitrogen to phosphorus addition and their changes in relative abundance indicating changes in nutrient strategies of soil bacterial communities.(4)The results of RDA analysis show that:the response of soil microbial community to phosphorus addition in Fast-growing stage Cunninghamia lanceolata forest is mainly affected by soil N:P ratio,while the response of soil microbial community to phosphorus addition in juvenile stage Cunninghamia lanceolata forest is mainly affected by Soil organic carbon content which indicates that the diversity of soil microorganisms shows strong response to fertilization treatment.