Phytosociological and floristic evaluation of a 15-year ecological management of roadside verges in the Netherlands.

This paper investigates and evaluates the effects of ecological management on the vegetation of roadside verges in the Netherlands, conducted by the Ministry of Transport (PublicWorks Department). A total of 545 relevés, made between 1986 and 1988, were re-examined in 2001. Data were analysed for changes in number of species, rarity of species, red list (endangered) species and syntaxonomical species groups. The total number of species almost did not change. Common species increased while rare species decreased. The red list species declined by 40%. Species from shrub and woodland, from fertile, wet soils and from nitrophilous fringes increased, while species characteristic of relatively open and nutrient-poor habitats and some pioneer communities decreased. Plant communities were valued, and phytosociological changes were evaluated, using the deductive method of Kopecký and Hejný and knowledge about vulnerability, rarity and replaceability. In 44.5% of the 465 evaluated relevés, the vegetation value remained unchanged, in 23.0% it decreased and in 32.5% it increased. The different trends tended to counterbalance one another, resulting in an unchanged mean vegetation value. The increase in vegetation value is mainly due to the increase in relevés containing species rich Arrhenatheretum-subassociations. The decrease is mainly due to a decrease in moist heath, dry sandy pioneer communities and grasslands on relatively poor soils, and the increase of species-poor nitrophilous tall herb communities and woody vegetation. In some of the verges studied, the vegetation value decreased as a result of inappropriate management and construction. Suggestions for improvement are given. Local successes indicate that appropriate management can considerably improve the botanical value of roadside verges, and consequently their value for other life forms.