By Daria Corcos, Juri Nascimbene, Marta Campesan, Davide Donadello, Veronica Segat & Lorenzo Marini
Mountain areas are experiencing greater levels of exotic plant invasions due to global change. Increased temperatures and stronger propagule pressure (i.e. the number of individuals released into a new region) due to tourism and transport increase the probability of plant introductions. However, exotic plant establishment can only take place under favourable environmental conditions. In particular, soil disturbance could reduce native plant biomass and increase bare ground, thus facilitating plant invasions by providing colonization opportunities for exotics. For this reason, highly disturbed sites, such as roadsides, are often among the most invaded habitats.
How do soil disturbance and temperature interact in influencing the establishment dynamics of native and exotic species along disturbed roadsides? To answer this question, we designed a manipulative experiment along an elevational gradient in the Italian Alps. The study area is among the regions with the highest number of exotic species in Italy. In November 2017, we selected 83 sites across 12 roads, spanning an elevational gradient of c. 1200 m. At each site, we delimited two experimental plots of 1 m2. One of them was treated with mechanical disturbance (removal of vegetation and ploughing of topsoil at a depth of 20 cm) whereas the other was left undisturbed as a control.
After one year, plant communities showed reduced species richness of natives, total plant biomass and vegetation cover. Interestingly, the reported effects were stronger at higher compared to lower elevations, suggesting higher colonization opportunities for exotics at the upper part of the elevational gradient. Whereas species richness of exotic species did not increase with disturbance (probably due to low propagule pressure in the area), we observed strong species replacement between control and disturbed plots, indicating that novel plant communities established after disturbance.
Our results highlight that small-scale mechanical disturbance of topsoil promotes the establishment of novel plant communities and, if coupled with increased propagule pressure, may provide new potential opportunities for exotic invasions, especially at higher elevations.
This is a plain language summary for the paper of Corcos et al. published in the Applied Vegetation Science (https://doi.org/10.1111/avsc.12481). The post was prepared by Daria Corcos and Lorenzo Marini.