Influence of management practices on plant assemblages of road–field boundaries in an agricultural landscape

Abstract

AbstractQuestionsPlant communities of road verges adjoining arable fields are often managed for conservation purposes. How do the diversity and composition of plant communities differ within and between berms, embankments and field margins? What is the influence of management practices on the diversity and composition of plant communities within and between these elements? Considering species frequently occurring in these three elements (hereafter generalist species), do road–field management practices influence their abundance in field margins?LocationCentral‐western France.MethodsThree adjacent elements located between district roads and winter cereal fields – i.e. berm, embankment and field margin – were sampled in 40 road–field boundaries situated in an agricultural area. Management practices on each element were characterized (i.e. mowing frequency and/or mowing period, inputs of herbicide and nitrogen fertilizers). We compared species diversity and taxonomic composition within and between elements. We tested the influence of management practices on (i) species richness and species evenness in each element, (ii) abundance‐based compositional dissimilarity between pairs of elements using a model averaging procedure, and (iii) abundance of generalist species in field margins using generalized Cochran‐Mantel‐Haenszel tests.ResultsCompositional dissimilarity between elements was mainly due to changes of dominant species. An early mowing of the berm increased berm species richness, while late mowing increased species richness of adjacent elements. An increase in embankment mowing frequency decreased species evenness in the embankment while input of herbicide on the embankment decreased the substitution rate between embankment and field margin. Finally, late mowing of the berm and one cut of the embankment both increased abundance of some generalist weeds in field margins.ConclusionsIn our agricultural landscape, mowing berms once in early summer is appropriate to promote plant species richness, while late mowing may potentially conflict with integrated weed management in adjacent arable fields. We suggest that programmes managing road verges should take into account the effects on plant assemblages within road verge elements and adjacent arable fields, as well as the potential increase in weed risk.