Study On Ecological Respond Of Populus Euphratica And Tamarix To Water Transfusion In Lower Reaches Of Tarim River

This dissertation is a basic research work aiming at exploring the vegetation response mechanism to emergent water transfusion after the emergent water transfusion project has been implemented in the lower reaches of Tarim River. Taking Populus euphratica and Tamrix as control, which were growing in non flow-breaking channel of Ying Ba zha in middle reaches of Tarim River and on arable farming land sides in this region, the research analyzed ecological response mechanism of Populus euphratica and Tamrix in lower reaches to water transfusion under different distance from river on the basis of investigation data from four parts, that is, growing response, regeneration response, blossoming and bearing response and vigor of seed response. The results were shown as following:Growing response includes vigor response and increment response. When the distance from river was 50m～300m, vigor of Populus euphratica restored to some extent. In detail, ratio of first dead branches to all branches was 0.10; percentage of dominant Populus euphratica was 67%. When the distance from river was 1050m～1500m, the vigor of Populus euphratica badly restored. In detail, ratio of first dead branches to all branches was 0.74; percentage of dominant Populus euphratica was only 14%. After water transfusion, increment of Populus euphratica was obviously higher contrasted with that before water transfusion. Populus euphratica's increment response to the fourth water transfusion reached 1500m and increment decreased gradually with distance increasing as well as increment difference decreased gradually with water transfusion times increasing. Therefore, it concluded that growing restoration of Populus euphratica responded earlier after water transfusion and then healthy status restored gradually under continuous water transfusion. Within the distance of 550m, vigor of Tamrix restored to some extent. In detail, ratio of twigs to normal branches and ratio of increment of diameter to ground diameter were 65% and 85% respectively, up to those in middle reaches. Within the distance of 1050m, vigor of Tamrix badly restored. In detail, ratio of twigs to normal branches and ratio of increment of diameter to ground diameter were only 1% and 2% respectively, far below those in middle reaches. After water transfusion, increment of Tamrix reached 2.15mm within the distance of 300m far over that in middle reaches within the distance of 150m. Increment of Tamrix at the age of 1 to 2 years old increased slowly; which increased relatively faster at the age of 3 to 6 years old and increased slowly after 7 years old.Regeneration response: After 8 times of water transfusion, Populus euphratica had obtained regeneration ability by budding, but not possessed condition for seeding regeneration and within the distance of 750m in middle reaches, both seeding regeneration and budding regeneration of Populus euphratica were performing. However, regeneration of Tamrix in lower reaches occurred barely only in low marsh land of transfused riverside, where budding regeneration was the leading style, but within the distance of 750m in middle reaches, seeding regeneration occurred and became the leading style.When the distance from river was over 550m, Populus euphratica could not blossom. The buried groundwater level 6.5m was critical value for Populus euphratica to blossom. Different species of Tamarix requested different water condition. When the distance from river was 1050m, the single inflorescence length, the number of flowers of single inflorescence, the quantity of fruits of single inflorescence and the rate of bearing of single inflorescence of Tamarix hispida were evidently lower than those on arable farming land sides, but the rate of bearing maintained on an relative high level, which reached 90% and accordingly buried groundwater level was 7.39m. Within the distance of 750m from river, the single inflorescence length, the single inflorescence length, the number of flowers of single inflorescence, the quantity of fruits of single inflorescence and the rate of bearing of single inflorescence of Tamarix laxa decreased gradually with distance increasing. When the distance from river was 750m, the rate of bearing of single inflorescence decreased to 20% and buried groundwater level 7.39m was critical value. The distribution of Tamarix elongate was within the distance of 150m, which ability of blossoming and bearing was still inferior to that on arable farming land sides. Buried groundwater level 5.38m was critical value of blossoming and bearing of Tamarix elongate and distribution of this community.Critical value of buried groundwater level required by vigor of seed of Populus euphratica, Tamarix hispia, Tamarix laxa and Tamarix elongate was 6.05m, 7.39m, 6.05m and 5.38m respectively. Vigor of seed of the four species decreased when groundwater level was over critical value.