The distribution of dicotyledonous arable weeds in relation to distance from the field edge.
Three surveys were conducted in barley or other cereal crops in Hampshire, UK, during 1988 and 1989. In the first survey (of a spring barley crop), the number of dicotyledonous weed seedlings and seeds in the seed-bank were determined at 10 distances from the crop edge. In the second and third surveys, only the numbers of weed seedlings were counted. In the first survey, numbers of seedlings of 13 weedy species and numbers of seeds of 11 weedy species were found to decrease significantly as the distance from the crop edge increased. Viola arvensis was the only species for which numbers increased. The proportion of the seed-bank represented by the germinated seedlings of 21 species varied from 0.4% (Sonchus spp.) to 55% (Fumaria spp.). The half-life of the seed-bank was highly variable between species. In the second survey of spring barley, the number of seedlings from 17 weedy species was found to decrease significantly as distance from the crop edge increased. Polygonum aviculare was the only species whose numbers increased. In the survey of autumn-sown cereals, numbers of seedlings of 14 weedy species decreased significantly as distance from the crop edge increased. Viola arvensis was the only species whose numbers increased. It was concluded that these distributions have implications for the conservation of endangered weed species.