Providing evidence to improve practice

Individual study: Assessing the value of beetle banks for enhancing farmland biodiversity

Published source details

Thomas S.R. (2001) Assessing the value of beetle banks for enhancing farmland biodiversity. PhD thesis. University of Southampton.


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Create beetle banks Farmland Conservation

A replicated, controlled study in 1998 in two sites with autumn-sown crops on an estate in Hampshire, UK (Thomas 2001) found that boundary-overwintering ground beetle (Carabidae) species (species that migrate into fields in spring) were clustered near two beetle banks and a hedgerow in the early part of the season (March), after which activity-densities were more evenly spread until they clustered again later in the summer (July). The distribution of field-inhabiting species (species resident in fields year-round) was fairly uniform or more associated with the centre of the fields through the early part of the season. The two sites differed in the latter part of the season with one displaying a gappy distribution near the beetle bank, and the other clustering near the hedgerow and the beetle bank. The distribution of overwintering ground beetles in January was irregular within the beetle banks and the hedgerow, but there was no apparent pattern in distribution of active beetles from February to July. Two sets of ten transects (connected, paired pitfall traps at 5, 25, 50, 75, 100 and 150 m into the crop) were set up at each site. At site A, transects extended at 10 m intervals into the winter barley crop at right angles from both sides of a beetle bank sown with cock’s foot Dactylis glomerata. At site B, transects extended into the crop from one side of a beetle bank sown with cock’s-foot and from a hedgerow at the opposite side of the field, parallel to the bank, leaving a 50 m gap between traps at the furthest distance. Transects of pairs of unconnected pitfall traps were established within the beetle banks and the hedgerow. Pairs of traps were set at 10 m intervals and opened concurrently with the within-field traps for 72 h-periods March-July (A) or February-June (B). Fifteen 20 x 20 x 20 cm turf samples were removed from the beetle banks and the hedgerow in early January. This study was part of the same experimental set-up as (Thomas et al. 2000, Thomas et al. 2001, Thomas 2002, Thomas et al. 2002).

 

Create beetle banks Natural Pest Control

A replicated study in 1998 at two arable sites in Hampshire, UK (Thomas 2001) found that numbers of ground beetles (Carabidae) known to overwinter in boundary habitats were highest near beetle banks and declined further into the crop field in March. Beetles were more evenly spread across the field in the following months until June, when they were again clustered near the beetle bank. Ground beetles known to overwinter in the field were patchily distributed and concentrated towards the centre of the field. Beetle banks were studied in barley Hordeum vulgare and wheat Triticum aestivum fields. The study used 10 transects from the beetle bank into the field, with pitfall traps at 5, 25, 50, 75, 100 and 150 m from the beetle bank edge. The first site had 20 transects in two fields either side of a single beetle bank and the second had 10 transects from a bank positioned along the edge of a single field. Ground beetles were categorised depending on whether they spend the winter in field boundaries or in the fields themselves. This study was part of the same experimental set-up as Thomas et al. 2000 and Thomas 2002.