THE DISTRIBUTION OF DICOTYLEDONOUS ARABLE WEEDS IN RELATION TO DISTANCE FROM THE FIELD EDGE

1. Three surveys were carried out in cereal crops during 1988 and 1989. In the first, numbers of dicotyledonous weed seedlings and seeds in the seed-bank were determined at 10 distances from the crop edge. In the second and third, only the numbers of seedlings were counted. 2. In the first survey of spring cereals, numbers of seedlings of 13 species and numbers of seeds of 11 species decreased significantly as distance from the crop edge increased. Viola arvensis was the only species for which numbers increased. 3. The proportions 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. 4. In the second survey of spring cereals, numbers of seedlings of 17 species decreased significantly as distance from the crop edge increased. Polygonum aviculare was the only species whose numbers increased. 5. In the survey of autumn-sown cereals, numbers of seedlings of 14 species decreased significantly as distance from the crop edge increased. Viola arvensis was the only species whose numbers increased. 6. These distributions have implications for the conservation of endangered weed species.