格氏栲幼苗根系性状的生长权衡对氮磷添加的响应

[Objective]Due to the long-term impact of nitrogen deposition in subtropical regions of China,plant growth is mainly limited by phosphorus.To understand the underground growth trade-off strategy of Castanopsis kawakamii seedlings in subtropical areas with severe phosphorus limitations,and to explore the response of root traits of Castanopsis kawakamii seedlings to nitrogen and phosphorus addition,in order to provide theoretical reference for the sustainable development of Castanopsis kawakamii populations.[Method]Taking Castanopsis kawakamii seedlings as the research object,nitrogen(low nitrogen(N1),medium nitrogen(N2),high nitrogen(N3)),phosphorus(low phosphorus(P1),medium phosphorus(P2),high phosphorus(P3))were set according to the local nitrogen and phosphorus levels,and interaction experiments were set up based on the nitrogen phosphorus ratio,namely N0P0,N1P1,N1P2,N1P3,N2P1,N2P2,N2P3,N3P1,N3P2,and N3P3 totaling 16 treatments,Among them,N0P0(non nitrogen and phosphorus addition treatment)was used as a control to determine the response strategies of root traits such as total root length,root surface area,root biomass,specific root length,root volume,and average root diameter of seedlings to different nitrogen and phosphorus concentrations.The effects of nitrogen and phosphorus addition on the root traits of Castanopsis kawakamii seedlings were analyzed.[Result]1)The addition of nitrogen and phosphorus nutrients significantly promoted the growth of morphological indicators such as total root length,average root diameter,and root surface area of Castanopsis kawakamii seedlings,and the response of each root indicator to different nitrogen and phosphorus concentrations was different.2)There is a highly significant positive correlation between total root length,specific root length,number of root tips,number of branches,and root surface area(p<0.001);There is a significant positive correlation between root biomass and root volume in the root system(p<0.001),and a highly significant negative correlation with root specific surface area(p<0.001).3)The principal component results showed that the root morphology indicators were basically distributed on two orthogonal axes,with a total cumulative variance interpretation rate of 55.1%.The first principal component axis had a significant correlation with root surface area,root tip number,branch number,total root length,specific root length,root specific surface area,and root volume.The second principal component axis has a strong correlation with the average root diameter,root biomass,and root nitrogen content.4)Hierarchical clustering analysis divided 16 treatments into 3 groups,in which N0P3,N1P3 and N2P1 were divided into the same group,N1P0,N1P2,N2P3,N0P1 and N1P1 were divided into the same group,and other treatments were divided into the same group separately.[Conclusion]The addition of nitrogen and phosphorus nutrients significantly promoted the root growth of Castanopsis kawakamii seedlings,among which the comprehensive effects of various root indicators of Castanopsis kawakamii seedlings under N0P3,N1P3,and N2P1 treatments were the best.In the future forest management process,the rapid growth and development of the root system of Castanopsis kawakamii seedlings can be promoted through the interactive addition of nitrogen and phosphorus.