The Ring-width Of Populus Euphratica Respond On Ecological Water Conveyances In The Lower Reaches Of Tarim River

In view of the positive responses of the ground vegetation changes in lower reaches of the Tarim River in the process of ecological water conveyances, this paper takes the Populus euphratica built in the lower reaches of the Tarim River as a research object. The research works from the following aspects: analyzing the spatial and temporal variation characteristics of the growth ring index of different sections of the Populus euphratica; comparatively analyzing the change divergences of different sections of the amount of radial growth of Populus euphratica before and after ecological water conveyances; estimating the impact of ecological water conveyances on the growth volume and ratio of the radial growth amount of Populus euphratica. With the data collected by the complete groundwater monitoring system in the lower reaches of the Tarim River, using curve regression methods, we got the models between groundwater and radial growth amount of Populus euphratica.The main conclusions of this thesis are as follows:(1) Through the analysis of the analyzing the spatial and temporal variation characteristics of the growth ring index of different sections of the Populus euphratica, it shows that the implementation of ecological water conveyances project infects three sections of the radial growth amount of Populus euphratica. Then, during 1952-2008, the average annual growth value of Kaerdayi section is 0.996mm; during 1980-2008, the average annual growth value of Alagan section is 1.007mm, and during 1969-2008, the average annual growth value of Yiganbujima section is 0.952mm. As to the change of time, mesoscale change is not obvious, but in a small scale, it changes apparently.(2) For the significant change of the growth ring index of Populus euphratica, we choose the measured data of radial growth amount of Populus euphratica, comparatively analyzed the change divergences of different sections of the radial growth amount of Populus euphratica before and after ecological water conveyances. In these three sections, the Populus euphratica radial growth rate has a hysteresis on ecological water, before ecological water conveyance (1990-1999), the radial growth amount of Populus euphratica characteristics with significant fluctuation, and the radial grows in a low speed; after ecological water conveyance (2000-2008), the radial growth amount of Populus euphratica goes up and down, there is a significant difference, it indicating that to ensure normal growth of Populus euphratica, a continuous efforts to strengthen ecological water conveyance is needed for the growth of Populus euphratica.(3) On the basis of comparatively analyzing the amount of radial growth of Populus euphratica before and after ecological water, and estimating the impact of ecological water cconveyances on the amount of radial growth of Populus euphratica. The result shows that: the effect in the three sections of Kaerdayi section, Alagan section and Yiganbujima section is 1.010mm,0.457mm and 1.066mm respectively. The growth percentage are 1.219,0.418 and 0.997 correspondingly. So it has influence of ecological water conveyances on the radial growth amount of Populus euphratica.(4) With the relative groundwater data, and the curve regression method to analyze the relationship between the amount of radial growth of Populus euphratica diversifolia stem (y) and the groundwater level (x), the optimal function is as follows: Kaerdayi section is y = -0.0519x~4 + 1.4296x~3 - 14.389x~2 + 62.168x - 94.547; Alagan section is y = -0.0598x~4 + 1.8636x~3 - 21.488x~2 + 108.75x - 202.22; Yiganbujima section is y = -0.1212x~4 + 2.7992x~3 - 23.09x~2 + 78.935x - 88.785; the whole is y = 0.0061x~4 - 0.2218x~3 + 3.0262x~2 - 18.197x + 41.983.