Plant communities along Irish roads: the impact of humans and potential to improve biodiversity

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Thompson, Rosalyn
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University College Cork
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The vegetation, soil nutrients and soil seed banks of road verges (located along a national road scheme in the south of the Republic of Ireland) were examined along with their adjacent fields plus reference points in the non-road landscape. In addition, a controlled experiment was undertaken to assess the vulnerability of road verges (which followed different landscape treatments) to invasive non-native species. Regarding species richness, the road verge habitat was significantly greater than that found in the agricultural landscape except for field margins where there was no overall difference. However, the species richness of verges was significantly lower than that found in semi-natural grasslands. Road verges held greater resources for pollinators than the agricultural landscape, including field margins in many circumstances. Road verges contained the highest incidence of non-native species: few were recorded outside of the road landscape, thereby highlighting their capacity to act as corridors for non-native invasive species. Following an ecological landscape design could result in a verge significantly greater in both species richness and resources for pollinating insects than a traditional landscape treatment approach. The seed bank of the road verge contained more species than that of the adjacent field. A number of species were only found in the overall seed bank and were not recorded in any of the above-ground vegetation. There was a low co-efficient of similarity found between the above- and below-ground vegetation. Inclusion of a seed bank investigation can add significantly to a site’s overall species richness. Four invasive non-native species (Fallopia japonica, Rosa rugosa, Buddleja davidii and Petasites fragrans) were used to test the relative invasibility of four landscape treatments: two followed an ecological design, two a traditional approach. Undisturbed plant communities (following an ecological treatment or not) provided best resistance to invasion. Bare soil that had followed an ecological design (i.e. subsoil) resulted in plant that were significantly less robust than soil that had not (i.e. topsoil) due to the lower nutrient content.
Biodiversity , Road verges , Landscape treatments , Ecosystem services , Landscape connectivity , Soil seed bank , Non-native invasive species , Ecological landscape treatment , Species richness , Nutrient availability , Pollinating insects , Non-native species
Thompson, R. 2019. Plant communities along Irish roads: the impact of humans and potential to improve biodiversity. PhD Thesis, University College Cork.