Ecological Responses of Populus Euphratica to Water Supply in the Lower Reaches of Tarim River

Investigations of the breast-width,the root diameter,the height,the cover of crown,the ratio of dead stems and the ratio of preponderance,the maturing and extra-maturing Populus euphratica which have different distances to the downstream of Tarim River revealed that the ratio of the dead stems increases and that of the preponderance decreases with the increase of the distance to the river.The increasing and decreasing trends indicated by the breast-width,the height and the cover of the crown are unapparent.The increasing and decreasing trends are less and less evident with the increase of the distance to the river.And the three indicators,i.e.,the breast-width,the height and the cover of the crown of the renewed Populus euphratica after watering show the decline coincidently with the increase of the distance.In accordance with the investigations,we can classify the restoration class of the watered Populus euphratica with the distance to the river being 50-300m as best,300-500m asgood,500-1050m as medium and 1050-1500m aspoor.The restoration class of Populus euphratica shows a gradual decrease with the increase of the distance to the river,and eco-water transfer accelerates the restoration of the Populus euphratica.Water is one of the key factors controlling the growth and renewal of Populus euphratica.