Effects of Replenishing Water into River on the Growth of Populus euphratica in Lower Reaches of Tarim River

Change of plant growth-ring width reflects the ecological information of plants responding to ecosystem.We investigated the branch diameter increment of P.euphratica in lower reaches of Tarim River and discussed the influence of river water replenishment on the individual growth of P.euphratica,and to further evaluate the effects appropriate river water replenishment on population restoration of the P.euphratica.At present,the recovery of population P.euphratica lies on groundwater supply,and there are differences in recovery degree due to refreshed water quantity and the water flowing distance.The research results showed that:(1) The branch diameter increment of the P.euphratica is evidently correlative to the groundwater level.The regression equation for the Yikanbujima section of Tarim river is y=0.0443x2-0.703x+3.5869,R=0.935,P=0.009.The higher water level,the higher the branch diameter increment of P.euphratica is.But when the water level ascends to four meters,the growth of P.euphratica becomes steadily.The order of branch growth of P.euphratica from larger to smaller follows that of plants in Kaerdayi to Yinsu to Alakan and to Yikanbujima section after eight times of water replenishments during 20022007.(3) The efficiency of water replenishment varies with time,being high efficient in growth seasons.