Alpine deserts are noteworthy habitats in temperate high mountain systems such as the Caucasus. Botanically this biome is well studied, yet little is known about its vegetation patterns in quantitative terms, whilst the role of soil pH in species distributions is particularly unexplored. Here we describe and quantitatively analyse vegetation patterns and soil pH in an alpine desert along elevation range (3000–4000 m a.s.l.) on two contrasting slope aspects (N versus S) of Mt. Kazbegi, the Central Greater Caucasus, Georgia. We sampled vegetation with standardized stratified-random design and collected soil samples for measuring pH; the collected data were analyzed using multivariate ordination methods. Overall, 63 species were recorded and, as expected, strong dependence of species distribution on elevation and between slopes was observed. However, we also found that soil pH increased monotonically and more steeply on N than on S slope, and many relatively abundant species changed their preference to slope aspect from N to S in parallel with the increasing difference in soil pH between N and S slopes. Our results suggest that the observed shift in slope preference from N to S, at least in part, can be explained by the differences in soil pH gradient between N and S slopes.

高山沙漠是温带高山系统（如高加索地区）中值得注意的栖息地。从植物学角度看，该生物群落已经得到了很好的研究，但从数量上来讲，人们对其植被格局知之甚少，而土壤pH在物种分布中的作用却尚未得到充分研究。在这里，我们描述并定量分析了两个不同坡度（N与坡向）之间海拔高度（3000-4000 m asl）的高山沙漠中的植被格局和土壤pH值S）的山 卡兹别吉，佐治亚州中部高加索地区。我们使用标准化的分层随机设计对植被进行采样，并收集土壤样品以测量pH值；使用多元排序方法分析收集的数据。总体上，记录了63种，并且正如预期的那样，观察到物种分布对海拔和斜坡之间的依赖性很大。然而，我们还发现，N上的土壤pH单调增加，而S上的陡峭，而N和S上土壤pH的差异越来越大，许多相对丰富的物种将其对坡度的偏好从N改为S。我们的结果表明，观察到的坡度偏爱从N到S的变化至少可以部分由N和S坡度之间的土壤pH梯度差异解释。