中文摘要：

以民勤荒漠区5种主要植物群落10个样方12年的定位观测资料为基础,运用植被盖度和投影盖度2个指标对荒漠区植物群落的稳定性及其生态效应进行分析,以期阐释随着全球变暖荒漠植物群落的稳定性和生态效应的变化规律.观测结果表明,沙蒿（Artemisia arenaria）的植被盖度和麻黄（Ephedra przewalskii）的植被盖度以及沙蒿的投影盖度和梭梭（Haloxylon ammodendron）人工林的投影盖度显著下降,白刺（Nitraria tangutorum）的植被盖度亦下降.分析结果表明：（1）植被盖度相对较低的群落的稳定性较强,而植被盖度相对较高的群落的稳定性相对较差.（2）当年降水量是决定植被盖度及其投影盖度的关键因子.（3）单位面积的白刺的生态功能最大,其次是麻黄,再次是白刺＋梭梭,单位面积的沙蒿的生态功能最低.荒漠区植被稀疏,植株枝条分布极不规则,以冠幅计算所得的植被盖度不能反映植被实际覆盖地表的状况.

英文摘要：

Minqin County is one of the major areas of desertification in China. In this paper, the stability and ecological effects of 5 mainly plant communities were analyzed with 12 years of positioning observations in Minqin desert area. Observations show：Vegetation cover was significantly decreased of Artemisia arenaria and Ephedra przewalskii, and projective cover is significantly decreased of A. arenaria and Haloxylon am- modendron plantation. Vegetation cover of Nitraria tangutorum also decreased. The analysis showed that： （1） Plant community of cover relatively low stability is strong. The plant community of cover relatively high stability is weaker. （2）Year rain{all is the key {actor for determining the vegetation cover and the pro- jector cover. （3）Ecological functions of Nitraria tangutorum per unit area is the largest,followed by E. przewalskii, and the third is N. tangutorum＋ H. ammodendron. Ecological functions of A. arenaria per u- nit area is the lowest. Vegetation of desert area sparse and plant shoots distribution is extremely irregular. Vegetation cover is calculated with plants crown does not reflect the actual situation of surface covered by vegetation.