Vegetation Change on Highway Verges in South-East Scotland

Abstract

At two time periods, exactly 10 and 20 years after the initial creation and seeding of the verges, vegetation surveys were carried out at seven sites along the highway verges of the A90 dual carriageway in West Lothian, Scotland. Although initially only five species were sown along the entire verges, eighty-four species were present 10 years later and sixty-eight species were identified after 20 years. During the 10-20 year period, the number of grass species increased from nine to thirteen and the number of bryophytes from none to nine. The total number of dicots dropped from seventy-two to forty-four. Hierarchical cluster analysis indicated four clear groups or vegetation associations in both 10 and 20 year data. The spatial locations of these groups were (i) intensively mown flat verges adjacent to the highway, (ii) cliff and rock outcrop, (iii) FaguslAcer understorey, and (iv) predominantly grassed embankments. The fourth group of embankment types could be further subdivided into two groups in the 10 year vegetation and three groups in the 20 year vegetation, according to the species dominants. In one group, FaguslAcer understorey, none of the original seeded species were present as either dominants or frequents at either 10 or 20 years. Cynosurus cristatus is not even an associate in any group after 20 years. Trifolium repens is not an embankment associate in any group after 20 years. Lolium perenne, the largest seed type input at 53.6%, is only a dominant in one group (mown verge). Festuca rubra is the main dominant in three out of five of the overall vegetation groups.