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Providing evidence to improve practice

Individual study: The efficacy of agri-environment schemes to enhance bumble bee Bombus spp. abundance and diversity on arable field margins in central and eastern England

Published source details

Carvell C., Meek W.R., Pywell R.F., Goulson D. & Nowakowski M. (2007) Comparing the efficacy of agri-environment schemes to enhance bumble bee abundance and diversity on arable field margins. Journal of Applied Ecology, 44, 29-40


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Leave field margins unsprayed within the crop (conservation headlands) Bee Conservation

In a replicated controlled trial at six sites (two replicates/site) across central and eastern England, Carvell et al. (2007) found that unsprayed conservation headlands did not support more bumblebee individuals or species than conventional cropped field margins.

Sow uncropped arable field margins with an agricultural nectar and pollen mix Bee Conservation

In a replicated controlled trial at six sites across central and eastern England, Carvell et al. (2007) found that 6 m margins of cereal fields sown with a nectar flower mixture supported significantly more foraging bumblebees (species and individuals) than cropped, grassy or naturally regenerated unsown field margins. Visitors included the nationally rare long-tongued species Bombus ruderatus and B. muscorum.

The nectar flower seed mixture was based on four agricultural legumes (red clover, Alsike clover Trifolium hybridum, bird's-foot trefoil Lotus corniculatus and sainfoin Onobrychis viciifolia). Unlike a wild flower seed mixture in the same study, it supported more bumblebees than other treatments from the first year of the study. However, relative to a wild flower mixture, this mixture provided low numbers of flowers in May and June, when bumblebee queens of late-emerging species are foraging. It also showed a decline in flower numbers in year three, when it did not support significantly more bumblebees than the wild flower seed mixtures.

Leave arable field margins uncropped with natural regeneration Bee Conservation

In a replicated controlled trial at six sites across central and eastern England, Carvell et al. (2007) found that naturally regenerated field margins supported a greater number and diversity of foraging bumblebees than cropped margins (including conservation headlands), but only in the first year of the study. In subsequent second and third years, bumblebee numbers were not significantly different from cropped treatments, but this may be due to the presence of more attractive floral resources planted on the same field margins for the experiment.

Sow uncropped arable field margins with a native wild flower seed mix Bee Conservation

In a replicated controlled trial at six sites across central and eastern England (Carvell et al. 2007), 6 m margins of cereal fields sown with 21 annual and perennial wild flowers supported significantly more foraging bumblebees (species and individuals) than cropped field margins (including conservation headlands). In years two and three of the study, these seed mixtures also supported more foraging bumblebees (species and individuals) than grassy or naturally regenerated unsown field margins, and in the third year they supported as many bees as a nectar mix based on agricultural legumes. The wildflower mixture took a year to establish properly, but may provide forage for a longer period of the year than the nectar mix. It is also likely to persist for five to 10 years, not declining in flower numbers after three years like the nectar mix.

Create uncultivated margins around intensive arable or pasture fields Farmland Conservation

A replicated controlled trial in central and eastern England (Carvell et al. 2007) found that naturally regenerated field margins supported a greater number and diversity of foraging bumblebees Bombus spp. than cropped margins (including conservation headlands), but only in the first year of the study. In subsequent second and third years, bumblebee numbers were not significantly different from cropped treatments, but this may be due to the presence of more attractive floral resources planted on the same field margins for the experiment. Six sites were studied and two experimental plots (50 x 6 m) established in each cereal field along two margins. Six treatments were assigned to plots: conservation headland, natural regeneration, tussocky grass mixture, wildflower mixture, pollen and nectar mixture, crop (control treatment). Foraging bumblebees were counted from May to late August, on 6 m-wide transects between six and 11 times in each margin.

 

Leave headlands in fields unsprayed (conservation headlands) Farmland Conservation

A replicated controlled trial from 2001 to 2004 across central and eastern England (Carvell et al. 2007) found that unsprayed conservation headlands did not support more bumblebee Bombus spp. individuals or species than conventional cropped field margins. The number of flowers and flower species in conservation headlands was not significantly different from cropped field margins or margins sown with a tussocky grass mix. Six sites were studied and two experimental plots (50 m x 6 m) established in each cereal field along two margins. Six treatments were assigned to plots: wildflower mixture (21 native wildflower species and four fine grass species), pollen and nectar mixture (four agricultural legume species: red clover, Alsike clover T. hybridum, bird’s-foot trefoil and sainfoin Onobrychis viciifolia and four fine grass species), tussocky grass mixture, conservation headland, natural regeneration, crop (control treatment). Foraging bumblebees were counted from May to late August, on 6 m-wide transects between six and 11 times in each margin. Flower abundance was also estimated along the bumblebee transects in 2002, 2003 and 2004.

Plant nectar flower mixture/wildflower strips Farmland Conservation

A replicated controlled trial from 2001 to 2004 at six sites across central and eastern England (Carvell et al. 2007a) found 6 m-wide margins of cereal fields sown with pollen and nectar flower mixture supported significantly more foraging bumblebee Bombus spp. species and individuals than cropped, grassy or naturally regenerated field margins. Bumblebees included the long-tongued species B. ruderatus and B. muscorum. Wildflower mixture supported significantly more foraging bumblebee species and individuals than cropped field margins, including conservation headlands, in all three years of monitoring, and grassy or naturally regenerated unsown field margins in years two and three. In the third study year (2004), wildflower and pollen and nectar mixtures supported similar numbers of bumblebee species and individuals. Wildflower margins had more flowers in May-June than July-August (approximately 4,200 vs 2,000 forage flowers/plot). Pollen and nectar margins had few flowers in May and June when bumblebee queens of late-emerging species are foraging but a large number of flowers in July-August (2,000 vs 9,000 forage flowers/plot). The number of flowers declined in the nectar and pollen mix in year three. Flower numbers remained similar between years two and three in the wildflower mix. Native varieties of red clover Trifolium pratense and bird’s-foot trefoil Lotus corniculatus flowered earlier than agricultural varieties. Two experimental plots (6 x 50 m) were established in each field along two margins. There were six treatments: wildflower mixture (21 native wildflower, four fine grass species), pollen and nectar mixture (four agricultural legume, four fine grass species), tussocky grass mixture, conservation headland, natural regeneration, crop (control). Foraging bumblebees were counted May-late August, on 6 m-wide transects 6-11 times/margin. Flower abundance was estimated along bumblebee transects in 2002, 2003 and 2004.