亚热带常绿阔叶林林下灌木光合荧光特性对长期氮磷添加的响应特征

[Objective]To understand how photosynthetic properties and fluorescence parameters of understorey shrubs in subtropical broadleaved evergreen forests respond to long-term nitrogen(N)and phosphorus(P)additions,and to provide basic data on plant photosynthetic physiological properties in response to global climate change with long-term N deposition.[Method]In this study,based on an 11-year field experiment with N and N+P additions,the photosynthetic characteristics,fluorescence and fluorescence of four dominant understory shrubs,Machilus thunbergia,Maesa japonica,Symplocos sumuntia and Ardisia crenata,were measured in the field.By analyzing the changes in leaf net photosynthetic rate(Pn),transpiration rate(Tr),water use efficiency(WUE),stomatal conductance(Gs),intercellular carbon dioxide concentration(Ci)and water vapour pressure deficit(VPD)of different dominant tree species,the actual photosynthetic efficiency(Y(II)),maximum photochemical efficiency(Fv/Fm),and potential activity(Fv/Fo),photochemical quenching coefficient(qP),non-photochemical quenching coefficient(NPQ),and quantum yield of PSⅡ non-regulated energy dissipation(Y(NO))were determined using fluorescent probe technique.The photosynthetic nutrient use efficiency of shrub leaves was combined with a comprehensive analysis of the way in which photosynthetic fluorescence characteristics of dominant shrub species respond to long-term N and N+P additions.[Result]It was found that N and N+P addition had significant effects on Pn,WUE,qP and Y(NO)of the leaves.In photosynthetic characteristics,Pn of Ardisia crenata was significantly higher than other species,and compared to CK,Ardisia crenata Ci was significantly higher and Ci of Machilus thunbergii was significantly lower than it in N addition.Fluorescence parameters varied significantly between species,with Y(II)of Symplocos sumuntia significantly higher than other dominant species,and Y(II)of Symplocos sumuntia,Machilus thunbergii and Maesa japonica all showed a decreasing trend in N addition compared to CK,but the decrease was mitigated by N+P addition.The qP of both Machilus thunbergii and Maesa japonica was significantly higher after N+P addition compared to N addition.Fv/Fm was significantly higher in Maesa japonica than in the other species under the different treatments,while Fv/Fm was lowest and significantly lower in Ardisia crenata than in the other dominant species.Y(NO)increased significantly after N addition in leaves of all dominant species except Ardisia crenata.PNUE of Machilus thunbergii and viburnum increased significantly in N+P addition.[Conclusion]The photosynthetic characteristics and fluorescence parameters of different tree species in response to N and N+P addition have different characteristics.Among them,all dominant species,except viburnum,activated photoprotection mechanisms to prevent damage to PSII in N addition.By studying the photosynthetic and fluorescence characteristics of the dominant tree species in the understory,the physiological response strategies of understory shrubs to long-term N and P addition can be observed more accurately.