Patterns in species composition of arable field boundary vegetation

Vegetation composition in contrasting field boundary plots was analysed by means of transects perpendicular to the arable field 3 years after establishment. Plots were established on the outer meters of an arable field next to a pre-existing field boundary and sown with (1) a mixture of 30 forbs, (2) Lolium perenne * and (3) plots left regenerating naturally. Tall, competitive species concentrated biomass production in a zone within 1 m from the arable field, while small, stress tolerant species were predominantly found in a zone m from the field. The tall species were able to increase total vegetation biomass production significantly in the zone bordering the arable field, probably by means of capturing nutrients from the arable field. The two major arable weeds found in the boundary plots, Elymus repens and Cirsium arvense, colonized the plots with different strategies but both were seriously reduced in vigour when plots were sown with Lolium perenne or with forbs at the onset of the experiment. Species richness in the forbs-plots was relatively high but rather low in the grass- and regeneration-plots caused by a very limited colonization of potential field boundary species; only two species colonizing the boundary plots were new to the original field boundary, while 30% of the species from the original field boundary were not found in the boundary plots after 3 years. This limited colonization ability may seriously hamper efforts to restore field boundary diversity.