Ever-increasing international trade and anthropogenic activity has led to the relocation of thousands of plant species worldwide. So far, the harsh climate of the European Alps historically has restricted the establishment of alien plants. However, new opportunities created by rising temperatures and increasing human activity might allow alien plants to spread further upwards. Here, the distribution of alien plants along an altitudinal gradient in two Austrian valleys is analyzed. Specifically, the distribution along two contrasting corridors (roads, rivers) and the spread of alien plants into adjacent habitats is examined. Following the MIREN sampling protocol, 20 transects composed of three plots along each river and main road, were established in each study region. Plant species cover and a range of site-specific factors were collected. In total, 641 plant species were recorded, of which 20 were alien. Alien species richness along roads was slightly higher compared to rivers, and the composition of the alien flora differed markedly between roads and rivers. Further, alien plant species richness decreases with distance to roads and rivers (indicating that adjacent habitats are less invaded), as well as with increasing elevation. Mowing along roadsides resulted in lower alien plant species cover, but higher alien plant species richness. Finally, compositional dissimilarity between sites showed that elevation, proximity of a plot to a river or road, and alien plant cover are important factors for higher dissimilarity. This study demonstrates that both natural (rivers) and man-made (roads) corridors play an essential role in the upward spread of different alien plants in mountains.

中文翻译：

---

一场艰苦的战斗？奥地利阿尔卑斯山沿河流和道路的外来植物物种的海拔分布

不断增长的国际贸易和人为活动导致全球数千种植物迁徙。迄今为止，欧洲阿尔卑斯山的恶劣气候历来限制了外来植物的建立。但是，气温升高和人类活动增加所带来的新机遇可能使外来植物进一步传播。在此，分析了两个奥地利山谷中外来植物沿高度梯度的分布。具体而言，研究了两个相对的走廊（道路，河流）的分布以及外来植物向相邻生境的扩散。遵循MIREN采样协议，在每个研究区域中建立了沿每条河流和主干道的三个样地组成的20个样带。植物种类覆盖并收集了一系列特定地点的因素。总共记录了641种植物，其中20种是外来物种。与河流相比，公路沿线的外来物种丰富度略高，公路与河流之间的外来植物区系组成明显不同。此外，外来植物物种的丰富度随着距道路和河流的距离而减少（表明邻近生境的入侵较少）以及海拔升高。沿路边割草可减少外来植物物种的覆盖率，但增加外来植物物种的丰富度。最后，地点之间的成分差异表明海拔，地块与河流或道路的距离以及外来植物的覆盖是造成差异较大的重要因素。这项研究表明，自然（河流）和人造（道路）走廊在山区不同外来植物的向上传播中都起着至关重要的作用。记录了641种植物，其中20种是外来物种。与河流相比，公路沿线的外来物种丰富度略高，公路与河流之间的外来植物区系组成明显不同。此外，外来植物物种的丰富度随着距道路和河流的距离而减少（表明邻近生境的入侵较少）以及海拔升高。沿路边割草可减少外来植物物种的覆盖率，但增加外来植物物种的丰富度。最后，地点之间的成分差异表明海拔，地块与河流或道路的距离以及外来植物的覆盖是造成差异较大的重要因素。这项研究表明，自然（河流）和人造（道路）走廊在山区不同外来植物的向上传播中都起着至关重要的作用。记录了641种植物，其中20种是外来物种。与河流相比，公路沿线的外来物种丰富度略高，公路与河流之间的外来植物区系组成明显不同。此外，外来植物物种的丰富度随着距道路和河流的距离而减少（表明邻近生境的入侵较少）以及海拔升高。沿路边割草可减少外来植物物种的覆盖率，但增加外来植物物种的丰富度。最后，地点之间的成分差异表明海拔，地块与河流或道路的距离以及外来植物的覆盖是造成差异较大的重要因素。这项研究表明，自然（河流）和人造（道路）走廊在山区不同外来植物的向上传播中都起着至关重要的作用。