Photosynthetic Characteristic Of The Dominant Plants In Subalpine Treeline Compound Community And The Response To Simulated Temperature

It is true that the global climate be becoming warmer.The alpine treeline are the most sensitive areas to climate change because it's located in special geographical places,and is thought to the ideal areas in which we study the correlation between vegetation and climate change.In this article,we have determined the photosynthetic performances of dominant plants in subalpine treeline compound community.Otherwise,we have set up the Open-Top Chamber(OTC),which imitates the International Tundra Experiment(ITEX), have explored the response of alpine treeline to the simulated temperature(2.9±0.5)℃,and have researched for the acclimation of the photosynthetic performances,leaf nitrogen content(Nmass) and leaf mass per area(LMA) to the simulated temperature.The results show that:(1) In the natural environment,the photosynthetic performance of the dominant plants in subalpine treeline compound community is poorer than other places,but its photosynthetic potential is great.In the condition of saturated CO₂ concentration and illumination,the plants perform bigger photosynthetic capacity.Because of low temperature,air pressure and photoinhibition arose by strong photosynthetic active radiation(PAR),the apparent quantum yields(AQY) are lower.(2) With the added PAR,the net photosynthesis rate(P_n) increase rapidly at first,and then decrease slowly.At the same time,stomatal conductance(Cond) and vapor pressure deficient(VPD) increase,and water utilization efficiency(WUE) increase firstly,then decrease.In the process of added CO₂ concentration,P_n and WUE increase slowly,by contrary,both Cond and stomatal limitation(Ls) decrease.(3) The plants' carboxylation efficiency(CE) and dark respiratory rate(R_d) are both slower in the natural environment,probably because of less quantity of Rubisco enzyme and lower photosynthetic activity in blade cell.In the saturated illumination,the P_n becoming slow with added CO₂ concentration result from the non-stomatal factor and are related with the capacity of P_i regeneration.(4) There is a remarkable linear relation between N in leaf and P_mass,but a marked difference of photosynthesis nitrogen utilization efficiency(PNUE) exists among the plants. Furthermore,herbaceous plants' PNUE are higher than arbor and shrub plants.(5) With the temperature becoming higher,the photosynthetic capacities of the plants have improved,but too much illumination leads to photoinhibition.On one hand,AQY,R_d,Ls,WUE and photorespiration(R_p) quicken in the simulated temperature.On the other hand, Cond and Tr reduce.(6) In the simulated temperature environment,N in leaf has increased by 9.6%and PNUE has improved.Moreover,the higher temperature leads to LMA to increase by 8.9% averagely.There is a comparability of N_mass in the same environment.