塔里木河下游植被空间分布特征及其用水策略

Spatial distribution of vegetation and its strategy in using water in the lower reaches of the Tarim River,western China

采用点位监测和取样测定的方法对塔里木河下游植被空间分布和影响因素进行了研究。定点监测选取了柽柳样地和胡杨样地各一个,取样测定选取了16个断面共计67个样点。结果表明:地下水位和植被盖度随着离河道距离增加分别呈显著性对数和指数下降关系。不同质地土壤的持水性有显著差异,粉壤土的田间持水量(0.32g/g)为沙土田间持水量(0.10 g/g)的3倍以上,前者的有效含水量约为后者的1.6倍。植被盖度受地下水位和土壤含水量的共同影响。胡杨和柽柳均具有适应极端干旱环境的能力,但二者的用水策略不同。胡杨根系可以直接吸收地下水和土壤水,且在生长季有明显的水力提升现象;柽柳根系主要吸收地下水和近地下水位饱和土壤水。

Spatial distribution of vegetation and their influencing factors in the lower reaches ot the Tarim River of western China were studied by the method of situ observations and sampling. 67 sampling points in 16 transects were selected, and two stands, the Tamarisk spp. stand and the Populus euphratica stand, were selected for situ observations. With the increase of the distance to the river channel, the groundwater level logarithmically declined, and vegetation cover exponentially decreased, respectively. Soil textures had significant impacts on soil water retention. The field capacity of silty loam （0.32 g/g） was more than 3 folds of that of sandy soil （0. 10 g/g） , and the effective water content of the former was 1.6 folds of the latter. The vegetation cover was controlled by the groundwater level and soil water content together. Populus euphratica and Tamarix spp. had the ability to adapt to hyper-dry environment, but the water use strategies of them were different. Roots of Populus euphratica directly took up groundwater and soil water, and had the obvious hydraulic lift during the growing season. However, Tamarisk spp. roots mainly absorbed groundwater and the saturated soil water in the layer near the groundwater level.