Ecological Characterization of Populus Euphratica’s Response to Non-deterministic Water Delivery
胡杨对非确定性输水响应的生态表征

Tarim River is a place which can best represent ecological contradiction and crisis of continental river basin in arid areas.Populus euphratica is the main constructive species in the lower reaches water delivery area of Tarim River as well as a kind of indicator plant that measures the recovery degree of vegetations in the water delivery area.With the methods of reference and comparison,fact finding and fixed point observation,this paper has analyzed the ecological characterizations of Populus euphratica’s increment,growth potential and flowering and seed setting under different groundwater conditions after long-term drought stress.The results show that:1)The growth of First Branch Annual Ring reduces with the increase of groundwater depth in a certain period of time after water delivery.Therefore,we can demarcate explicitly the response time,response range and response level of water delivery;2)With the water delivery,the growth of annual ring under different groundwater conditions gradually approaches the same;3)A good correlation is shown between the deadwood ratio of Populus euphratica’s bearing tree and groundwater depth,and the ratio can serve as a clear and easily measured indicator of the ecological restoration of Populus euphratica;4)Populus euphratica updates in a certain range after water delivery,but the groundwater condition required by updating range,modes and growth vigor of seedlings as well as flowering and seed setting and keeping the vigor of seeds is still limited by the mode,amount and time of water delivery.Whether there is mathematical correlation between the growth of Populus euphratica annual ring and groundwater depth in the lower reaches of Tarim River is an isssue that deserves research.But it should be clear that the response of Populus euphratica annual ring to water delivery is not only affected by groundwater depth,but also by the microtopography,origin,tree age,tree potential and other factors.Therefore,how to get the mathematical relationship between groundwater depth and the growth of Populus euphratica annual ring needs to be further studied.