Botanical diversity of beetle banks. Effects of age and comparison with conventional arable field margins in southern UK

Beetle banks are simple, grass-sown raised strips providing habitat for the invertebrate predators of arable crop pests and other farmland wildlife. To date, research has mainly focussed on such predators. Establishment guidelines for these features, which are considered as inexpensive substitutes for the considerable amount of hedgerows that have been lost in the UK, are available, as is some funding, but long-term management guidance is lacking. The botanical composition and diversity of a range of beetle banks was examined in southern UK over two summers and a winter, and compared with that of typical, adjacent field margins including grassy strips and hedgebanks, with a view to indicating potential management requirements. Beetle banks had lower species ríchness and H' diversity than field margins, but these characteristics increased with age of the bank until those over a decade old had approximately equal diversity. Few individual plant species were found exclusively in either habitat. Beetle banks provided more grass cover, especially tussock, but less herbaceous cover and fewer nectar-providing plants compared with field margins. Weed cover was not significantly different between habitat types, and varied considerably. This may concern some farmers, particularly when economically threatening species are present, although crop encroachment may be mínimal and control is relatively straightforward. Overall, beetle banks appear to retain a dense vegetational structure, despite increasing botanical diversity, and are of value as refuge habitat for predatory invertebrates for over a decade. Increasing floral diversity may benefit beneficial invertebrates. As simple, inexpensive features, beetle banks provide a means of dividing fields and enhancing farmland biodiversity, while requiring minimal management. © 2002 Elsevíer Science B.V. All rights reserved.