Study On Minimum Ecological Water Requirement Of Populus Euphratica Forest In Downstream Of Tarim River

Based on the previous research results and understanding,taking Tarim River downstream as the target region,with the help of the basic method of tree-ring hydrology,the main research object of populus euphratica in desert riparian forest is to quantitatively reveal the mechanism between radial growth and ecological water conveyance of populus euphratica in the downstream of Tarim River,The minimum ecological water requirement value for the growth of populus euphratica in each section is analyzed,and a reference is provided for the refinement of ecological restoration scheme and the efficient utilization of water resources in downstream of Tarim River.The main findings and conclusions are as follows:(1)The response of Populus euphratica growth to the two major environmental events,"long-term cut-off"and"ecological water conveyance",showed obvious effects on radial growth.In space,the response degree of Populus euphratica radial growth is different,and the response of Populus euphratica to radial growth is smaller.The same section is not the same as the distance from the river decreased,the"linear"ecological water transport Project on the Tarim River downstream vegetation recovery,the positive impact of the scope is limited.(2)The contribution value of the ecological water transfer to the radial growth of populus euphratica was analyzed by using the contribution value equation in the downstream of 1985 a Tarim River after the ecological water transfer was carried out by using a time boundary point.The ecological water transport has made a benign change in the radial growth of populus euphratica ring,and there is a certain time lag.The lag time of the Yinsu,Kaerdayi,Alagan,Yiganbujima is 1 years.(3)From the background of no ecological water conveyance project,according to the linear trend extrapolation model,the year of the growth of populus euphratica trees in 2022,2027,2018 a and the reasonable time period of complete decadence is 2018-2027 a;based on GM(1,1)The growth year of the model was 2025,2032,2015 a,and the reasonable time period was 2015-2032 a.comparing and analyzing the results of two models,the relative error of the time period for the growth of Populus euphratica trees is±1.5 a,±2.5 a,and the simulation results of the two models on long time series are significant and the simulation result is credible.excluding other external interference factors,the Tarim River downstream"green corridor"may be completely submerged by a sand dune between 2018-2027 a or 2015-2032 a.(4)The minimum ecological water requirement for the growth of populus euphratica in different sections of the lower reaches of Tarim River is different,the minimum ecological water requirement of the radial growth of Populus euphratica is to be maintained for many years:0.279 8×10~8 m~3(Yinsu),0.101 8×10~8 m~3(Kaerdayi),0.087 4×10~8 m~3(Alagan),0.066 7×10~8 m(Yiganbujima).In the recovery of Populus euphratica in different sections,It is necessaryto take different water supply measures to ensure that the minimum ecological water requirement of the radial growth of Populus euphratica in the downstream coast is the annual discharge 0.279 8×10~8 m~3.(5)In order to make the radial growth of Populus euphratica in the downstream of Tarim River reach the average level before the river stop,the minimum ecological water requirement is as follows:0.155 6×10~8m~3(Yinsu),0.102 4×10~8 m~3(Kaerdayi),0.088 5×10~8 m~3(Alagan),0.067 9×10~8 m~3(Yiganbujima).In order to ensure the minimum ecological water requirement of the radial growth of Populus euphratica to reach the average level before the river cut-off,the 0.155 6×10~8 m~3 should be discharged every year.