Abstract
Question: How distinct is the flora of field boundaries'? How does the structure of field boundaries determine the composition of vegetation?
Location: Estonia, six 4 kin x 4 kin agricultural areas.
Methods: We studied the vegetation of fields and field boundaries using 2 m x 2 m sample plots. We estimated the frequency of species in both habitat types, applied an MRPP test to analyse the vegetation composition of field boundaries with various combinations of landscape features (ditches, roads, tree and bush layers) illustrating this by DCA ordination, and used indicator species analysis to determine the characteristic species of each boundary type.
Results: Ca. 45% of the flora of field boundaries comprised species found on agricultural land. Most typical species in fields - agrotolerants - were also the most common in field boundaries. The vegetation of road verges and grassy boundaries consisted mainly of disturbance-tolerant species. Woody boundaries were characterised by shade-tolerant and nitrophilous species. Ditch banks included species typical of moist habitats and semi-natural grasslands. Few threatened or protected species were observed.
Conclusions: The vegetation composition of field boundaries varied due to the complex effects of landscape structure around and in these boundaries. Plant species in agricultural landscapes can be classified into two broad emergent groups on the basis of their different responses to agricultural disturbances-agrotolerant species and nature-value species. Agrotolerant species are promoted by agriculture, nature-value species include rare weeds and habitat specialists. We suggest that high-nature-value species should prevail in monitoring the effects of land-use intensification on biodiversity rather than total species richness.