Effects of water stress on growth characteristics and water use efficiency of Populus euphratica and Populus pruinosa

In order to improve the irrigation water utilization efficiency of farmland shelterbelt and select the appropriate tree species in the Tarim basin, the growth characteristics, the photosynthetic and chlorophyll fluorescence kinetics parameters, transpiration and water use efficiency (WUE) of Populus euphratica and Populus pruinosa were investigated with pot-culture experiment.The results showed that the photosynthetic and fluorescence kinetics parameters (except non-photochemical quenching coefficient, qN), water consumption and intensity, biomass and WUE declined with water stress, with the least values of these parameters occurring at the severe water stress. Compared with parameters under normal water irrigation, the reductions of photosynthetic and fluorescence parameters, water consumption and biomass of Populus euphratica were all lower than those of Populus pruinosa under different water stress, however, the reductions of Populus euphratica were higher than those of Populus pruinosa under severe water stress. The whole water use efficiency (WUEM), intrinsic water use efficiency (WUEP), instantaneous water use efficiency (WUEL) of Populus euphratica and Populus pruinosa were the highest under moderate stress and light stress respectively. For both poplar species, the water-consumption intensity and periodic consumption ratio reached maximum in July. Based on these findings, Populus euphratica was the preferred tree species than Populus pruinosa in establishing shelter forest on farmlands in Tarim basin. The soil water contents of forestland of Populus euphratica and Populus pruinosa should be about 45%~50% and 60%~65% of the field capacity, respectively, key time of irrigation is July.