胡杨树冠疏失度对塔里木河下游应急生态输水的响应

Response of Crown Loss of Populus euphratica to Ecological Water Transportation in the Lower Reaches of Tarim River

【目的】向塔里木河下游应急生态输水，恢复和自然更新胡杨为主体的荒漠河岸植被。【方法】以塔里木河下游阿拉干断面设立的长期监测样地内的胡杨为研究对象，采用野外调查实测与室内数据分析相结合的方法，研究胡杨树冠疏失度对应急生态输水的响应。【结果】应急生态输水后地下水位的抬升对胡杨树冠疏失度的降低产生一定的作用；总体上，胡杨的树冠疏失度随着离河道距离的增加逐步增大，而且离河道越远，疏失度增加的程度就越大；树冠疏失度小于10％的旺盛胡杨主要分布在离河道100m之内，其中多以疏失度少于50％的长势较好的胡杨为主。在离河道200～400m，树冠疏失度为50％．75％长势较差的过熟林、衰老林比例开始增多。距河道400m以外，胡杨密度开始急剧下降，树冠疏失度也明显增大。【结论】目前胡杨生长对生态输水的响应范围主要在距离河道400m之内。

[ Objective] Ecological water transportation into the lower reaches of Tarim River has a positive impact on the recovery and regeneration of desert riparian vegetation. [ Method ] In this paper, sample plat of the long - term monitoring section Argan in the lower reaches of Tarim River is taken as research object. According to the data obtained from field investigation and laboratory analysis, the response of crown loss of Populus euphratica to ecological water transportation is analyzed. [ Result] The results show that rising of groundwater levels after water transportation plays an important role in the decreasing in the crown loss of Populus euphratica, and the crown loss of Populus euphratica gradually increases with increasing distance from the river course. The trees crown loss was less than 10%, which mainly was distributed within 100 metres to each side from the river course. The proportion of crown loss of overmature and effete forests were 50% - 75% within 200 to 400 metres. At more than 400 metres, the density of Populus euphratica begins to drop dramatically. This shows that the crown loss of Populua euphratica is closely related to the groundwater availability. [Condusion] At present, the regime of ecological water transportation provides sufficient water for viable Populus euphratica stands within 400 metres from the river course.