DECLINE OF THE FLORA IN DANISH ARABLE FIELDS

1. Surveys of the weed flora in Danish arable fields were conducted in 1967-70 and 1987-89. Frequencies of 67 common weed species in spring barley, spring rape, winter rye, winter wheat and grass ley were compa red. 2. The comparison showed that the occurrence of common weed speci es has generally decreased during the last 20 years. 3. The frequency of some species such as Anagallis arvensis, Arenaria serpyllifolia, At riplex patula, Cerastium caespitosum, Galium aparine, Plantago major a nd Silene noctiflora has decreased remarkably, possibly because of int ensive chemical weed control. 4. The dominating weed species in the 19 87-89 survey were largely the same as in the 1967-70 survey, namely Ca psella bursa-pastoris, Chenopodium album, elymus repens, Myosotis arve nsis, Poa annua, Polygonum aviculare, P. convolvulus, P. persicaria, S tellaria media, Taraxacum, Veronica arvensis, V. persica and Viola arv ensis. 5. Some species occurred more frequently in 1987-89 than in 196 7-70, but only Stellaria media increased significantly and only in gra ss ley.