Effects of short-term elevated CO2 concentration on diurnal dynamics of photosynthesis of Robinia pseudoacacia on the Loess Plateau
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 μmol/mol) and elevated CO2 concentration (700 μmol/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.
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