Comparing weed composition in natural and planted hedgerows and in herbaceous field margins adjacent to crop fields

Hedgerows and field margins are common features of the agricultural landsca pe in southern Quebec. In the last decade, hedgerow establishment has been encouraged primarily for the prevention of soil erosion, though many farmer s view them as reservoirs of invasive weeds and pests. In this study, we co mpared weed assemblages of several hedgerow types and herbaceous field marg ins. Ranking that takes into consideration weed abundance was clearly demon strated: planted hedgerows > herbaceous field margins > natural woody hedge rows. The latter harboured many perennial plant species of less weedy prope nsity than planted hedgerows, which accommodated a larger number of weedy s pecies. In planted hedgerows close to 50% of plants were weeds, even in the ir central position, although planted and natural hedgerows sheltered simil ar weed composition in their central parts. Likewise, most species inventor ied in adjacent fields were weeds. Weeds characterising the central positio n of hedgerows/field margins were often species of wet habitats (Lythrum sa licaria L., Equisetum arvense L., Cicuta maculata L.). Management practices of hedgerows and perhaps of crop fields adjacent to hedgerows may be mostl y responsible for the abundance of weeds in hedgerows and field margins.