Effects Of Simulated Nitrogen Deposition And Biochar Amendment On Physiological Characteristics Of Moso Bamboo

In order to understand the effects of nitrogen?N?deposition and biochar amendment on photosynthesis of new and old leaves of Moso bamboo?Phyllostachys edulis?,we investigated the effects of the N addition with different amounts(N0:0 kg·hm^-2·a^-1,N30:30 kg·hm^-2·a^-1,N60:60kg·hm^-2·a^-1,N90:90 kg·hm^-2·a^-1)and three different biochar amendment(BC0:0 t·hm^-2 BC20:20t·hm^-2,BC40:40 t·hm^-2)on photosynthesis,chlorophyll fluorescence characteristics and ecological stoichiometry in Moso bamboo leaves.The results showed that:?1?N deposition significantly increased the maximum net photosynthetic rate?Pmax?,stomatal conductance?Gs?and transpiration rate?Tr?of 1-,2-,3-and 5-years-old Moso bamboo leaves?P<0.05?,while significantly decreased the actual quantum yield Y???of 1-,3-and 5-years-old Moso bamboo leaves?P<0.05?,as well as significantly decreased the maximum photochemical efficiency?Fv/Fm?,potential activity of PS??Fv/F0?and Y???of 2-years-old Moso bamboo new leaves?P<0.05?.N deposition had no significant difference in chlorophyll content?SPSD?in leaves of Moso bamboo at 4 ages?P>0.05?.At the same time,N deposition significantly increased foliar N concentrations and foliar P concentrations of 1-,3-and 5-years-old Moso bamboo leaves?P<0.05?,With the increase of nitrogen intensity,the foliar C and soluble protein concentrations of 1-,3-and 5-years-old Moso bamboo,the foliar N,P concentrations of 3-and 5-years-old Moso bamboo,and foliar C:N,N:P and C:P in1-years-old Moso bamboo increased first and then decreased,these parameters increased significantly under low nitrogen?N30?and reached their maximum values?P<0.05?.?2?Biochar amendment significantly increased Pmax of new and old leaves of 2-year-old bamboo?P<0.05?,increased the Tr of new leaves and Fv/F0,Fv/Fm and Y???of old leaves?P<0.05?,significantly reduced the Ci of old leaves?P<0.05?,but had no significant effect on the Gs and chlorophyll content of new and old leaves of 2-year-old bamboo?P>0.05?.?3?The combination of N deposition and biochar amendment significantly impacted the Photosynthesis and chlorophyll fluorescence parameters?P<0.01?except Gs of 2-year-old bamboo old leaves.Biochar amendment in combination with N depositions?N30?significantly decreased the Pmax of 2-year-old bamboo old leaves compared with the old leaves without biochar?BC0??P<0.05?.While biochar amendment in combination with both N depositions?N60 and N90?significantly increased Pmax of 2-year-old bamboo old leaves compared with the N depositions alone?P<0.05?,and increased Pmax of 2-year-old bamboo old leaves under biochar amendment in combination with both N depositions?N30 and N90?.BC20 in combination with both N depositions?N30 and N60?significantly decreased the SPAD of old leaves compared with the N depositions alone.The SPAD of new leaves in N60-BC20 was significantly lower than that in the N60-BC0.Both biochar amendments in combination with both N depositions?N30 and N60?significantly increased Fv/Fm,Fv/F0 and Y???of new and old leaves than the N depositions alone?P<0.05?.However,biochar amendments in combination with both N90 significantly decreased Fv/Fm and Fv/F0 of new and old leaves compared with the N depositions alone.?4?Compared with1-year-old bamboo,Pmax,Gs,Tr,non-photochemical quenching coefficient?qN?,foliar N,P concentrations of 3-year-old and 5-year-old bamboo leaves significantly decreased?P<0.05?,while chlorophyll content,foliar N:P and C:P increased significantly?P<0.05?.It is concluded that N deposition promotes the photosynthetic rate of Phyllostachys pubescens,but long-term high concentration of nitrogen deposition will damage the photosystem?of Phyllostachys pubescens.In conclusion,this study demonstrated that biochar amendment promoted photosynthesis of leaves and thus increased productivity of Moso bamboo forest under the background of globally increasing N deposition.