The Modification of Ancient Woodland Ground Flora at Arable Edges

Abstract

The last five decades have witnessed an intensification of agriculture with a marked increase in the use of agrochemicals. This study investigated whether arable edges affect ancient woods and the extent of any modifications to the ground flora. Plant species were recorded from a total of 84 transects into the centre of the woods, of which 59 were taken from the arable–woodland interface and 25 were taken from non-arable land or woodland rides. Ellenberg indicator and CSR values were used to infer fertility and features of the environment. Results suggested that, after adjusting for light and moisture conditions, elevated nitrogen levels might occur in ancient woodlands to a distance of at least 100 m from arable farmland. Furthermore, the transects from the arable fields had a substantially altered herb-layer with respect to species composition, notably a greater percentage cover of ruderal and nitrophilous species, and a lower cover of stress tolerator species. Smaller woods contained a greater cover of competitor and nitrophilous species and a lower cover of stress tolerators and ancient woodland indicator species. We conclude that farming may be unwittingly modifying the ground flora of ancient woodlands adjacent to arable land and that small and irregularly shaped woods are most at risk. It is recommended that farmers apply agrochemicals in such a way that drift is minimised, and that large, valuable ancient woods be protected by a substantial buffer zone.