Mountain plant species are changing their ranges in response to global warming. However, these shifts vary tremendously in rate, extent and direction. The reasons for this variation are yet poorly understood. A process potentially important for mountain plant re-distribution is a competition between colonizing species and the resident vegetation. Here, we focus on the impact of this process using the recent elevational shift of the sedge Carex humilis in the northern Italian Alps as a model system. We repeated and extended historical sampling (conducted in 1976) of the species in the study region. We used the historical distribution data and historical climatic maps to parameterize a species distribution model (SDM) and projected the potential distribution of the species under current conditions. We compared the historical and the current re-survey for the species in terms of the cover of important potential competitor species as well as in terms of the productivity of the resident vegetation indicated by the Normalized Difference Vegetation Index (NDVI). We found that Carex humilis has shifted its leading range margin upward rapidly (51.2 m per decade) but left many sites that have become climatically suitable since 1976 according to the SDM uncolonized. These suitable but uncolonized sites show significantly higher coverage of all dwarf shrub species and higher NDVI than the sites occupied by the sedge. These results suggest that resistance of the resident vegetation against colonization of migrating species can indeed play an important role in controlling the re-distribution of mountain plants under climate change.

高山植物物种正在响应全球变暖而改变其范围。但是，这些变化在速率，程度和方向上都相差很大。造成这种变化的原因尚不清楚。对于山地植物的再分配而言，潜在的重要过程是殖民物种与常驻植被之间的竞争。在这里，我们专注于这个过程的使用最近的莎草高程转变的影响苔蒿草在意大利北部的阿尔卑斯山作为模型系统。我们对研究区域的该物种进行了重复和扩展的历史采样（于1976年进行）。我们使用历史分布数据和历史气候图来参数化物种分布模型（SDM），并预测当前条件下物种的潜在分布。我们根据重要潜在竞争物种的覆盖率以及归一化植被指数（NDVI）指示的常驻植被生产力，比较了该物种的历史和当前重新调查。我们发现Carex humilis根据SDM的未殖民化规定，其领先范围的利润迅速提高（每十年51.2 m），但留下了许多自1976年以来在气候上变得合适的站点。这些合适但非殖民化的地点比莎草占据的地点显示出所有矮灌木物种的覆盖率明显更高，NDVI也更高。这些结果表明，常驻植被对迁徙物种定居的抵抗力确实可以在控制气候变化下山地植物的重新分布中发挥重要作用。