Agricultural practices affect the biotic and abiotic conditions that
determine food and shelter for carabid beetles (Coleoptera: Carabidae). We
hypothesised that carabid communities would respond differently to 18 years
of contrasted cropping practices in cereal-based rotations. We measured the
effects of tillage (MP: moldboard plough; CP: chisel plough; NT: no-till)
and previous crop sequence (cereal monoculture versus
cereal–forage/cereal–oilseed rotation) on carabid beetle activity density,
diversity, and community structure in corn (Zea mays
Linnaeus, Poaceae) at La Pocatière, Québec, Canada. Carabid beetles were
sampled monthly from May to September 2006, using pitfall traps. Although 19
carabid species were observed, assemblages were dominated by
Harpalus rufipes (De Geer), particularly in the second
half of the season. Multivariate analyses indicated a strong affinity of
carabid species for the NT treatment throughout the season. Crop sequence
and tillage had no effect on diversity (Shannon's H′ ≤ 1.3)
and evenness of carabid assemblage, but species richness and activity
density were greater in NT than in tilled systems. Peak activity density of
dominant species occurred at different times during the season, generally in
accordance with preferred breeding season. Many species had greater activity
density in NT than in tilled treatments. Because of their granivorous
feeding habit, carabid populations such as that of H.
rufipes could be an important asset to NT, given the limited
weed management options available for this system.