黑河流域下游绿洲-荒漠梯度上的植被数量特征

根据野外样方调查，以实际测量区域内各物种植株的多种指标为依据，分析黑河下游乌兰图格断面中植被的盖度、重要值（P_i）沿垂直于河道方向的梯度分布规律。结果表明：在垂直于河道方向上，乌兰图格断面植被总盖度呈现先增加后减小的趋势，并根据盖度值划分出1 200 m以内为河岸绿洲区、2 200~3 700 m为荒漠过渡区、4 300 m以外为荒漠区；从重要值（P_i）上观察乔、灌、草的分布规律，发现绿洲区近河道处胡杨占据生存优势，一定距离后草本占优势；荒漠过渡区和荒漠区灌木占据生存优势。同时分析乌兰图格断面植被盖度与土壤平均质量含水量的关系发现，在荒漠过渡区和荒漠区，两者具有一定的相关性。选取土壤水分、植被盖度分别为自变量和因变量，建构回归模型，利用SPSS软件进行分析，发现两者间的关系可用回归方程很好地反映出来。

Vegetation Quantity Characteristics at the Gradient of Oasis-desert in the Lower Reaches of Heihe River Basin

Based on the field investigation of sampling plots and the multiple indexes actual measured, the examination of vegetation coverage, P_i, and distribution law perpendicular to the watercourse in Ulan Tug section were presented. The result indicated that, the vegetation coverage turns from rising to decline perpendicular to the watercourse in Ulan Tug section. Based on the coverage value, we can divide that the oasis area is in the range of 1 200 meters. The range of oasis-desert transitional zone is from 2 200 to 3 700 meters. And, out of 4 300 meters are desert region. The investigation revealed the P_i values are different from vascular plants. Populus euphratica Oliv. flourishes near the river in the oasis area, and herbaceous plant flourishes after a certain distance.In the oasis-desert transitional zone and desert zone, shrub flourishes. Meanwhile, the vegetation coverage and soil moisture are relevant with the date base and knowledge we required in these zones. Select soil moisture as the independent variable, and vegetation coverage as the dependent variable, then build the regression model using the SPSS. We can found the relationship appropriately reflected with functional equation.