Data from: Snowbeds are more affected than other subalpine-alpine plant communities by climate change in the Swiss Alps

While the upward shift of plant species has been observed on many alpine and nival summits, the reaction of the subalpine and lower alpine plant communities to the current warming and lower snow precipitation has been little investigated so far. To this aim, 63 old, exhaustive plant inventories, distributed along a subalpine–alpine elevation gradient of the Swiss Alps and covering different plant community types (acidic and calcareous grasslands; windy ridges; snowbeds), were revisited after 25–50 years. Old and recent inventories were compared in terms of species diversity with Simpson diversity and Bray–Curtis dissimilarity indices, and in terms of community composition with principal component analysis. Changes in ecological conditions were inferred from the ecological indicator values. The alpha-diversity increased in every plant community, likely because of the arrival of new species. As observed on mountain summits, the new species led to a homogenization of community compositions. The grasslands were quite stable in terms of species composition, whatever the bedrock type. Indeed, the newly arrived species were part of the typical species pool of the colonized community. In contrast, snowbed communities showed pronounced vegetation changes and a clear shift toward dryer conditions and shorter snow cover, evidenced by their colonization by species from surrounding grasslands. Longer growing seasons allow alpine grassland species, which are taller and hence more competitive, to colonize the snowbeds. This study showed that subalpine–alpine plant communities reacted differently to the ongoing climate changes. Lower snow/rain ratio and longer growing seasons seem to have a higher impact than warming, at least on plant communities dependent on long snow cover. Consequently, they are the most vulnerable to climate change and their persistence in the near future is seriously threatened. Subalpine and alpine grasslands are more stable, and, until now, they do not seem to be affected by a warmer climate.

尽管在诸多高山与永久积雪（nival）峰顶均已观测到植物物种的上行迁移，但迄今为止，亚高山及低海拔高山植物群落对当前气候变暖与降雪量减少的响应仍鲜有探究。为此，研究团队对沿瑞士阿尔卑斯山亚高山-高山海拔梯度分布、涵盖多种植物群落类型（酸性与钙质草原、多风山脊群落、积雪床群落）的63份老旧且详尽的植物名录进行了时隔25至50年的回访复查。研究通过辛普森多样性指数（Simpson diversity）与布雷-柯蒂斯相异指数（Bray–Curtis dissimilarity）对比新旧名录的物种多样性差异，并借助主成分分析（Principal Component Analysis）解析群落组成变化；生态条件的变化则通过生态指示值（ecological indicator values）进行推断。所有植物群落的α多样性（alpha-diversity）均有所提升，这大概率与新物种的迁入有关。正如山地峰顶的观测结果一致，新物种的迁入导致了群落组成的均质化。无论基岩类型如何，草原群落的物种组成均较为稳定，这是因为新迁入的物种均属于被入侵群落的典型物种类群。与之形成鲜明对比的是，积雪床群落出现了显著的植被变化，且明显向更干燥的生境与更短积雪周期的方向转变——这一点可由周边草原物种的入侵得到佐证。更长的生长季使得更高大、竞争力更强的高山草原物种得以入侵积雪床群落。本研究表明，亚高山-高山植物群落对当前持续的气候变化呈现出差异化响应。至少对依赖长期积雪覆盖的植物群落而言，降雪/降雨比值下降与生长季延长的影响似乎比气候变暖更为显著。因此，这类群落是受气候变化影响最脆弱的类群，其在不久的将来的存续面临严重威胁。而亚高山与高山草原群落则更为稳定，截至目前似乎并未受到气候变暖的显著影响。