Farming and ground beetles - effects of agronomic practice on populations and community structure

Published source details Carcamo H.A, Niemala J.K. & Spence J.R. (1995) Farming and ground beetles - effects of agronomic practice on populations and community structure. Canadian Entomologist, 127, 123-140.
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This study is summarised as evidence for the following.

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A randomised, replicated, controlled study in 1990-1991 in Alberta, Canada (Carcamo et al. 1995) found no difference in overall ground beetle (Carabidae) abundance between organic (averaging 194-200 beetles/plot) and conventionally farmed (145 beetles) plots. However, more ground beetles were found in organic (194-344 beetles/plot, across all species) compared to conventional (109-194 beetles) plots when a dominant non-native (and highly mobile) species was excluded from analysis. In 1991, four ground beetle species were more abundant in organic than conventional plots while two species showed the opposite trend. Species richness was also higher in organic (averaging 22.5-24 species) than conventional (16.5-21.5 species) plots in 1991. Organic and conventional regimes were examined in 10 x 25 m plots replicated eight times. Organic plots received mechanical and manual weed control and no synthetic fertilizers or herbicides. Conventional plots received synthetic fertilizer and/or herbicide. Each plot contained either barley Hordeum vulgare, faba bean Vicia faba or a barley-pea Pisum sativum intercrop. Beetles were sampled every two weeks from mid-June to mid-October 1990 and mid-April to mid-October 1991 using two pitfall traps in each plot.