'泓森槐'幼苗生理生态特性对模拟氮沉降的响应研究

[Objective]The response and coexistence mechanism of urban atmospheric nitrogen deposition and plants reflect the ability of urban plants to provide ecosystem services to a certain extent.The good species of Robinia pseudoacacia'Hongsen'is a new variety suitable for urban landscaping,with the characteristics of thornless,fast-growing,and strong resistance,and it is of certain practical significance to explore the physiological and ecological characteristics of nitrogen deposition in response to it.[Method]Through the simulated nitrogen deposition control test,NH4NO3 was used as the nitrogen source,and R.pseudoacacia'Hongsen'was used as the nitrogen addition object,and three simulated nitrogen deposition levels of low nitrogen(LN,5 g·m-2·a-1),medium nitrogen(MN,10 g·m-2·a-1)and high nitrogen(HN,15 g·m-2·a-1)were set up,and the nitrogen application amount of each nitrogen treatment was evenly divided into six parts,and the nitrogen fertilizer required for different nitrogen treatment was sprayed as a solution at the beginning of each month,and the clean water spraying was the control(CK).The TC,TN,and TP contents of roots and soil,and soil enzyme activity were determined at 30 d,58 d,89 d,119 d,152 d,and 180 d after nitrogen application.[Result]:(1)simulated nitrogen deposition promoted the growth of the root system of R.pseudoacacia'Hongsen'to a certain extent,and with the extension of nitrogen application time,the promotion effect gradually weakened and even inhibited growth;(2)Nitrogen deposition increased the contents of nitrogen(N)and phosphorus(P)in stems,leaves,and roots of R.pseudoacacia'Hongsen',decreased the content of organic carbon(C)in leaves,and significantly increased the C content of stems and roots under LN treatment(P<0.05),which decreased under HN treatment.Nitrogen deposition reduced the C:N,C:P,N:P ratio of leaves to roots and C:Nand C:P of stems;(3)Nitrogen deposition improved the coordination degree between root-soil nutrient systems,medium nitrogen treatment was not conducive to the improvement of root-soil nutrient system coupling;and the comprehensive evaluation index of root nutrients reached a maximum value under low nitrogen treatment,which was 496.68%higher than that of the control,which was more conducive to the coordinated development of root-soil nutrients;(4)Nitrogen deposition led to soil acidification,and the soil acidity was the largest under HN treatment;With the increase of nitrogen concentration,the contents of C,N,P,microbial biomass carbon(MBC),microbial biomass nitrogen(MBN)and soil urease(Ure),acid phosphatase(Acp)and catalase(Cat)activities in soil increased first and then decreased.The soil C,N,and P contents were the highest under MN treatment,and MBC,MBN,Ure,App,and Cat were the highest under LN treatment.The activity of soil sucrase(Suc)continued to increase,and the activity under HN treatment was higher than that of LN and MN.Nitrogen deposition increased soil C:N,C:P,N:P,and decreased MBC:MBN.The contents of soil C,N,P,MBC,MBN and Ure,Acp,Cat,and Suc decreased with the deepening of soil depth.With the extension of nitrogen application time,the soil C,P,MBC,and MBN contents reached the maximum values of 152d,119d,89d,and 89d,respectively.[Conclusion]Therefore,exogenous nitrogen input is conducive to the growth of seedling roots,which has a promoting effect on the productivity of R.pseudoacacia'Hongsen',and low nitrogen input can better maintain the stability of the ecosystem.In addition,the results of the comprehensive evaluation index of coupling coordination degree in this study showed that the comprehensive evaluation index of root nutrients was higher than that of soil nutrients,indicating that the nutrient development of the root system of R.pseudoacacia'Hongsen'was better than the development of soil nutrients under the simulated nitrogen deposition environment.