Rational groundwater table indicated by the ecophysiological parameters of the vegetation： A case study of ecological restoration in the lower reaches of the Tarim River

The eco-physiological response and adaptation of Populus euphratica Oliv and Tamarix ramosissima Ldb during water release period were investigated. Nine typical ＇areas and forty-five transects were selected along the lower reaches of Tarim River. The groundwater table as well as plant performance and the contents of proline, soluble sugars, and plant endogenous hormone （ABA, CTK） in leaves were monitored and analyzed. The groundwater table was raised in different areas and transects by water release program. The physiological stress to P. euphratica and T. ramosissima had been reduced after water release. Our results suggested that the groundwater table in the studied region remained at -3.15 to -4.12 m, theproline content from 9.28 to 11.06 （mmol/L）, the soluble sugar content from 224.71 to 252.16 （mmol/L）, the ABA content from 3.59 to 5.01 （ng/g FW）, and the CK content from 4.01 to 4.56 （ng/g FW）, for the optimum growth and restoration of P. euphratica indicated by the plant performance parameters and the efficiency of water application was the highest. The groundwater table in the studied region remained at -2.16 to -3.38 m, the proline content from 12.15 to 14.17 （mmol/L）, the soluble sugar content from 154.71 to 183.16 （mmol/ L）, the ABA content from 2.78 to 4.86 （ng/g FW）, and the CK content from 3.78 to 4.22 （ng/g FW）, for the optimum growth and restoration of T. ramosissima indicated by the plant performance parameters and the efficiency of water application was the highest. The rational groundwater table for the restoration of vegetation in the studied region was at -3.15 to -3.38 m.