绿洲-荒漠交错带环境特征初步研究

以甘肃省石羊河下游的民勤绿洲为例，对其绿洲外围与荒漠交错地带的植被和植被关系密切的灌丛沙包特征进行了系统研究，结果表明，由于生态交错带边缘效应的存在，植被盖度的变化呈现绿洲附近与交错带外围靠近流沙的地方较低，而位于流沙和绿洲之间的部分相应较高，植被盖度较高的部位主要集中于自流动沙丘至绿洲外600m处，而非紧靠近绿洲、这与地下水自沙漠向绿洲方向运移有关，在绿洲外缘300～600m的范围内植被盖度出现下降，原因可能与绿洲荒漠交错带界外区的形成有关，说明研究区绿洲0～600m范围即是该区域绿洲界外区的存在区域，灌丛沙包上的裸沙率以绿洲界外区为最大，大量沙包裸露，可致沙子的活动性增强，因此该地带是对绿洲土地造成沙质荒漠化的最大流沙来源。

Preliminary research on environmental characteristics of oasis-desert ecotone

Taking Minqin Oasis in the downstream of Shiyanghe Rivers as example, the shrub characteristics of sand dune, which was closely related to the vegetation of the interface between the outside of oasis and desert, was studied in this paper. The change of vegetation coverage and dune density indicated that the vegetation coverage in the ecotone was obviously higher than that in the outside of oasis and in drift desert. There existed an area outside oasis that was obviously affected by human activies and 0-600 m away from the outside of oasis. Meanwhile, the appearing position of area outside oasis was different in different place. The naked area ratio of dune in the area outside oasis was the biggest, so that the area outside oasis was the main resource of drift sand resulting in desertification of oasis. Over extracting ground water in oasis district resulted in a forming of dropping funnel of ground water there, and resulted in a fluid of ground water from desert to oasis. Ultimately, human activites aggravated those processes to some extent.