Establishment dynamics of native and exotic plants after disturbance along roadsides

Abstract

Questions How does small‐scale soil disturbance influence establishment dynamics of native and exotic species along roadsides? Does soil disturbance provide potential opportunities to exotic invasions along elevational gradients? Does the established plant community after disturbance reflect the surrounding vegetation? Location Prealps, Italy. Methods To disentangle the role of elevation and soil disturbance in promoting exotic invasions, we performed a manipulative experiment along 12 roads spanning an elevational gradient of ca. 1,200 m. Additionally, we sampled species richness of native and exotic plants in the surroundings of the experimental plots. Results Soil disturbance reduced species richness of native plants, total plant biomass and vegetation cover compared to the undisturbed plots. The decrease in species richness of natives and plant biomass was stronger at higher than lower elevations, suggesting higher colonization opportunities for exotics. However, exotic species richness did not increase with disturbance, probably due to a low propagule and colonization pressure. We observed strong species replacement between control and disturbed plots, indicating that plant communities established after disturbance were not a subset of species communities already occurring in the surrounding vegetation. Conclusions With increasing elevation, disturbance had a stronger negative effect on native than on exotic species. Higher elevations, hitherto considered to have low invasibility, may provide new potential colonization opportunities for exotics but only if disturbance is coupled with an increased propagule pressure. Disturbance along roadsides promoted the establishment of species that did not occur in the surrounding vegetation.

Investigating elevational gradients of species richness in a Mediterranean plant hotspot using a published flora

“…Alien species richness peaked at the lowest elevations, where human impact is stronger and human population density is higher. Currently, the greatest number of alien species in the world and the greatest knowledge about the extent of invasions are reported in economically developed countries (Pyšek et al 2008, McGeoch et al 2010, Early et al 2016, Corcos et al 2020. Due to an interplay between climate warming and direct human impact, an upward shift of the alien species is expected in the near future (Walther et al 2009, Alexander andEdwards 2010).…”

Contrasting response of native and non‐native plants to disturbance and herbivory in mountain environments

“…Besides the effect on species richness, soil disturbance has been identified as a key driver of plant community composition (Corcos et al, 2020; Haider et al, 2018). Beta‐diversity between disturbed and resident vegetation was high, indicating that a large proportion of established species did not occur in the surrounding vegetation but only in the seed‐bank (Figure 3).…”

“…In the last decades, soil disturbance related to the construction of roads, ski‐slopes and other infrastructures has become more frequent across temperate mountain ecosystems (Wipf et al, 2005). Disturbance (through the removal of existing vegetation) decreases competition for light and increases the chances of seed germination and establishment of ruderal plants and species present only in the seed‐bank (Corcos et al, 2020; Haeuser et al, 2017; Lembrechts et al, 2017; McDougall et al, 2018). Besides the direct effects on plants, disturbance also affects key soil properties such as nutrient and water content.…”

“…Given the likely emergence of complex interactions between biotic and abiotic drivers under global change, there has been a call to develop experimental approaches under realistic field conditions, to advance our understanding of plant invasion dynamics (Alexander, Diez, et al, 2016). However, most of the few previous experimental studies on non‐native establishment manipulated propagule pressures through seeding (Lembrechts et al, 2016), while studies evaluating natural succession are rare (but see Corcos et al, 2020).…”

Alien plant species on roadsides of the northwestern Patagonian steppe (Argentina)

“…A study of floristic composition in the north of Argentine Patagonia, carried out on a west-east precipitation gradient that included areas of forest, shrubland and steppe, revealed that the shrubland and steppe had the highest presence of exotic species, the most frequent being Bromus tectorum, Cerastium arvense and Rumex acetosella [36]. A large number of studies in the world have assessed the influence of roads on exotic plant dispersal and establishment in aboveground vegetation [9,11,13,37,38], but soil seed bank on roadsides have been less examined [27,39]. In particular these topics have been under-researched in Patagonian steppe roadsides [26,40].…”