HABITAT ASSOCIATIONS AND SEASONAL ACTIVITY OF GROUND-BEETLES (COLEOPTERA, CARABIDAE) IN CENTRAL ALBERTA

Carabid beetles were collected with grids of pitfall traps during two seasons in five habitats in the ecotone between aspen parkland and boreal mixedwood forest in central Alberta. The 23 abundant species (54 species in total) were divided into the following four distributional types: (1) Pterostichus adstrictus Eschz. was numerous in all five habitats (habitat generalist); (2) Platynus decentis Say, Calathus ingratus Dej., and Scaphinotus marginatus Fisch. were abundant in all four forest habitats (forest generalists); (3) another 10 species were common in one or two forest habitats (forest specialists); (4) nine species, representing mainly Agonum, Amara, and Bembidion, were restricted to a recently cleared timothy-clover grassland (meadow species). Soil moisture seemed to be important in determining habitat associations of the species among the forest types. Captures of most species were aggregated also within habitats, and the consistency of aggregation among particular traps suggests that it is mainly a response to subtle microhabitat differences. All abundant species, except S. marginatus, showed a peak of capture in May-June. Number of species, corrected for sample size by rarefaction, was highest in the meadow (27.5) and lowest in the dry upland aspen forest (11.9). Species diversity was highest in meadow and the lakeside forest habitats, but carabid assemblages of thc four forest habitats were more similar to each other than to the meadow assemblage.