Important environmental factors for plant species richness in road verges

ABSTRACT While the potential of road verges as habitats with conservation value is increasingly recognised, a better understanding of the drivers of differences in species diversity and richness is needed to devise appropriate management strategies. We quantified the effects of a set of key environmental variables on plant species richness along four roads in Sweden, all showing variation in vegetation along their stretches. We identified variables of particular importance but found that their effects differed depending on location, highlighting strong context dependence. We concluded that species richness was generally higher in road verges with low vegetation (e.g. low-productive habitats) and with less dense vegetation cover (e.g. habitats characterised by ground disturbance resulting in exposed or sparsely vegetated soil), and increased further with higher sun exposure. Our study contributes to the understanding of which environmental conditions and mechanisms should be considered when constructing and maintaining road verges and represents a step towards a unifying framework for road verge habitat ecology.