Farming and Ground Beetles: Effects of Agronomic Practice on Populations and Community Structure

We studied the effects of agricultural practice on ground beetles, using pitfall traps in field plots and in an uncultivated meadow near Edmonton, Alberta. Ground beetle abundance and species richness were higher in plots operated under an organic farming regime than in those under a chemical regime, but neither crop type [barley (Hordeum vulgareL.), faba bean (Vicia fabaL.), barley-pea (Pisum sativumL.) intercrop] nor crop rotation had an effect. Reduced tillage did not significantly change overall carabid activity or species richness but species differed in their response to tillage treatments. The carabid assemblage from an uncultivated field differed conspicuously from assemblages in the crops and fescue. Carabid abundance was highest in the meadow and the fauna was dominated by the exotic speciesPterostichus melanariusIlliger. Effects of agronomic practice on carabid assemblages are complex, reflecting the interaction of biological traits of particular species and the combination of agronomic treatments applied.