SPECIES RESPONSES OF CARABID BEETLES (COLEOPTERA, CARABIDAE) DURING POSTFIRE REGENERATION OF BOREAL FOREST

Beginning 1 year after an intense forest fire in the Interlake region of Manitoba, carabid beetles were sampled by pitfall trapping in two burned sites and two unburned control sites. Before the fire, one burned site had been dominated by aspen, Populus tremuloides Michx., and the other by conifers (mostly Picea spp.). During the 11-year study, burned sites became dominated by aspen saplings. Three carabid species were caught significantly more frequently in burned sites than in control sites. Two of these, Harpalus laticeps LeConte and H. egregius Casey, invaded soon after the fire and were caught in the burned sites for several years after the fire. Seventeen species were caught significantly less often in burned than in control sites; catches of another 13 common species were not significantly affected by burning of the site. Burning influenced the seasonal patterns of catches of Carabus taedatus F. and Pterostichus adstrictus Eschscholtz; this was attributed to higher litter and soil temperatures in burned sites. Seasonal patterns of other common species were not markedly affected by burning. In burned sites, the incidence of brachypterous species and the size of beetles increased with time after the fire. In control sites, the incidence of brachyptery was independent of time, but the percentage of brachypterous species was significantly higher in the conifer site than in the aspen site. Trends of brachyptery and size are those expected if early colonizers are super-tramp r-strategists and later invaders are K-strategists. Patterns of species occurrence during forest regeneration can be explained in terms of dispersal and competitive abilities, preference for physical attributes of the habitat, and responses to prey availability.