Effects Of Precipitation Amount Changes Changes And Nitrogen Addition On Leaf Photosynthesis Of Quercus Variabilis Carruth

Earth system models have predicted an intensification of the global hydrological cycle in the future,resulting in the shift on global precipitation regime changes,especially precipitation amount.The changes in precipitation patterm have profound impacts on regulating ecosystem processes.The abilities of plants to obtain carbon(C)through photosynthesis and to regulate water loss through transpiration are highly sensitive to precipitation pattern.The changes of precipitation amount will directly affect plant growth,nutrient acquisition,and subsequently ecosystem functioning.In addition,with increases of fossil fuel combustion and artificial fertilization,atmospheric nitrogen(N)deposition is exacerbated.Atmospheric N deposition alters original N nutrition state in soil and affects plant growth.Given the importance of precipitation change and increased N deposition to C and N cycles in forest ecosystems,a manipulative experiment with six treatments(control,increased 50%of mean annual precipitation,decreased 50%of mean annual precipitation,N addition,increased precipitation plus N addition,and decreased precipitation plus N addition)was conducted to examine the effects of precipitation amount change and N deposition on specific leaf area,foliar stoichiometry,and photosynthesis of Quercus Variabilis in a deciduous broadleaved forest ecosystem of the Transition Zone Forest between subtropical and warm temperate regions in Central China.Across 2017 to 2018,soil moisture was reduced by 2.03 V/V%(absolute change)under the decreased precipitation treatment.Decreased precipitation reduced foliar C,N,and phosphorus(P)contents by 11.28%,10.08%,and 13.78%,respectively,but stimulated foliar N:P by 12.84%.Increased precipitation elevated N:P by 11.73%.Soil total inorganic N content was decreased by 19.53%under the N addition treatment.Decreased precipitation reduced net photosynthetic rate(P_n)and leaf stomatal conductance(G_s) by 14.52%and 29.09%,respectively.Increased and decreased precipitation suppressed leaf transpiration(T_r)by 12.49%and 29.41%,respectively.The N addition treatment decreased P_n and G_s by 3.52%and14.35%,respectively.Foliar N:P ratio linearly increased with specific leaf area.The reductions of foliar C,N,and P contents under the decreased precipitation treatment were attributed to stimulating the specific leaf area of Q.variabilis and led to the increases of foliar N:P ratio.Leaf P_n showed a positive relationship with G_s.Decreased precipitation reduced G_s,resulting in the reduction of P_n.Precipitation amount changes and nitrogen addition had different effects on leaf photosynthesis of Q.Variabilis.Leaf photosynthesis was more sensitive to decreased than increased precipitation.In addition,the leaf photosynthesis was sensitive to N deposition.Our findings facilitate the understanding and projections of plant leaf level physiology and its impact on plant individual growth and ecosystem productivity of the Transition Zone Forest under future climate change scenarios.