MOUNTAIN ROADS AND THE HOMOGENIZATION OF PLANTS. A study on plant communities and their traits along the elevational gradient.

Abstract

Overexploitation, land use, and other anthropogenic disturbances have increased in recent years, and are expected to increase even further. A very common anthropogenic disturbance, that can be seen even as far as in mountain regions, is roads. Roads are known to fragment landscapes, modify environmental conditions, and help distribute plants (including non-native). Furthermore, they have been seen to have a homogenizing effect on plant species communities, making them more similar to each other. However, although there have been studies on how roads and elevational gradients in the mountains affect species composition, little is known about their effect on plant trait assemblage and functional diversity. Do roads and elevation homogenize the functional diversity of plant communities? By using plant trait data for three different traits, and abundance data covering different road proximities and elevations, this project aimed to answer this question. Analyses were done in R (v. 4.2.0) with the help of the vegan package, which made it possible to make dissimilarity plots, NMDS ordinations, and an ANOSIM analysis of the data. The results showed that the plant communities closest to the road were different from the communities in the natural vegetation, both in species and trait assembly, and that they had the least variation in trait and species composition. Moreover, the trait assemblage along the elevational gradient was not that different in the three road proximities, indicating little abiotic filtering of traits due to elevation. In conclusion, roads did have a homogenizing effect on both plant and trait communities, and this difference could be because of disturbances and different abiotic conditions. It would be a good idea to explore this relationship further, but at a more local level to include more abiotic factors than just the elevation, and by looking more into depth at the traits of non-native species