FARMING AND GROUND BEETLES - EFFECTS OF AGRONOMIC PRACTICE ON POPULATIONS AND COMMUNITY STRUCTURE

We studied the effects of agricultural practice on ground beetles, usi ng pitfall traps in field plots and in an uncultivated meadow near Edm onton, Alberta. Ground beetle abundance and species richness were high er in plots operated under an organic farming regime than in those und er a chemical regime, but neither crop type [barley (Hordeum vulgare L .), faba bean (Vicia faba L.), barley-pea (Pisum sativum L.) intercrop ] nor crop rotation had an effect. Reduced tillage did not significant ly change overall carabid activity or species richness but species dif fered 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 species Pterostichus melanarius Illiger. Effects of agronomic practice on carabid assemblages are comp lex, reflecting the interaction of biological traits of particular spe cies and the combination of agronomic treatments applied.