短期CO_2浓度升高对黄土高原刺槐光合日变化的影响

Effects of short-term elevated CO_2 concentration on diurnal dynamics of photosynthesis of Robinia pseudoacacia on the Loess Plateau

以黄土高原19年生刺槐(Robinia pseudoacacia)人工林为对象,比较研究刺槐在环境CO_2浓度(350μmol/mol)和倍增CO_2浓度(700μmol/mol)下的净光合速率(Pn)、气孔导度(G_s)、胞间CO_2浓度(C_i)、蒸腾速率(T_r)、水汽压亏缺(VPD)和水分利用效率(WUE)的日变化动态及日均值差异.结果显示:刺槐P_n、G_s、C_i、WUE的日变化在短期CO_2浓度升高条件下并未发生明显改变,但T_r、VPD的日进程在环境CO_2浓度下呈"双峰"曲线,而在倍增CO_2浓度下呈"单峰"曲线.短期CO_2浓度升高使刺槐G_s和T_r平均降低10.01%和8.71%,但其P_n和WUE显著提高107.47%和135.40%.本研究表明刺槐人工林在黄土高原具有较强的光合潜力与水分利用能力.(图1表2参38)

Diurnal dynamics and daily-mean value differences of net photosynthetic rate （Pn）, stomatal conductance （Gs）, intercellular CO2 concentration （Ci）, transpiration rate （Tr）, vapor pressure deficit （VPD） and water use efficiency （WUE） of 19-year-old black locust （Robinia pseudoacacia） plantations on the Loess Plateau were compared and analyzed under ambient CO2 concentration （350 ？mol/mol） and elevated CO2 concentration （700 ？mol/mol）. Diurnal dynamics of Pn, Gs, Ci, and WUE did not change obviously under short-term elevated CO2 concentration, however diurnal variations of Tr and VPD presented ＂double peak＂ curves under ambient CO2 concentration, but ＂single peak＂ curves under elevated CO2 concentration. Short-term elevated CO2 concentration caused reduces in Gs and Tr of R. pseudoacacia by 10.01% and 8.71%, respectively, but significant increases in Pn and WUE by 107.47% and 135.40%, respectively. The results indicated that black locust plantations have strong photosynthetic potential and water utilization ability on the Loess Plateau.