Floristic composition and environmental determinants of roadside vegetation in North England.

Abstract

The roadside vegetation in some counties of north England (north and west Yorkshire) was studied to determine the community structure according to the British National Vegetation Classification (NVC) and main environmental factors influencing its composition. The data from Phytosociological survey (699 quadrats) and from the physico-chemical analyses of 233 soil samples from 35 sites were obtained. Both the classification (TWINSPAN & MATCH) and ordination programs (Canonical Correspondence Analysis) were used. The roadside vegetation is mainly dominated by few grasses (Arrhenatherum elatius, Festuca rubra, Dactylis glomerata, Lolium perenne, Poa trivialis, Elymus repens, Holcus lanatus) and their associated herbs (Cirsium arvense, Heracleum sphondylium, Urtica dioica). Five NVC Mesotrophic grassland communities (Arrhenatheretum elatioris community MG1, Lolium perenne-Cynosurus cristatus grassland MG6, Lolium perenne leys MG7, Holcus lanatus- Deschampsia cespitosa grassland MG9, Festuca rubra-Agrostis stolonifera-Potentilla anserina grassland MG11) and one Upland Festuca ovina- Agrostis capillaris-Galium saxatile grassland, U4 were identified which in general, exhibited good fit with the typical NVC units. Altitude, pH, potassium, sodium and road age were found to be the main variables affecting the roadside vegetation. By relating the floristic composition with ecological characteristics of the roadside verges, three kinds of pattern of variation are observed. The first pattern is related to regional or geographical characteristics and the second pattern of variation exists across the width of the road verges showing a zonal pattern of plant distribution. The third scale of pattern is active at the local level including micro-environmental conditions, e.g., local edaphic variables.