Quantifying the effect of organic farming, field boundary type and landscape structure on the vegetation of field boundaries

The general aim of the study was to determine the main factors of plant species richness and composition in field boundaries. We surveyed the vegetation of field boundaries in organic and non-organic farms, recorded the field boundary type and width. We characterized landscape structure around the vegetation plots (r = 250 m). We classified plant species into two ecological response groups: (1) common weeds and other species occurring frequently on agricultural land, i.e. ‘agrotolerant species’ (47 species), and (2) all other species intolerant to contemporary agricultural practices—so-called ‘nature-value species’ (190 species). We analysed the effect of organic farming, boundary type and landscape structure on the diversity of these two species groups. We found that field boundary type and landscape structure described most of the variation in species composition of these boundaries, while organic farming had little effect. However, the analysis of plant species diversity revealed that organic farming significantly supported the species richness of high nature-value species by increasing species richness on average by two species on 4 m2 plot, while the richness of agrotolerant species did not depend on farming type. Boundary type had a specific impact on species diversity—ditches enhanced the richness of nature-value species and suppressed agrotolerants; woody boundaries hosted only a few agrotolerant species and road verges increased the species richness of both species groups. The richness of nature-value species benefited from wider open boundaries, while narrow boundaries hosted more agrotolerant species.