THE IMPORTANCE OF HABITAT STRUCTURE AND FOOD SUPPLY FOR CARABID BEETLES (COLEOPTERA, CARABIDAE) IN PEAT BOGS

Abstract

AbstractDuring the period 1985–1989, the carabid assemblages of a raised peat bog in eastern central Sweden and of six peatlands in New York State and Maine were studied. The principal methods of investigation were pitfall trapping in summer, and quadrat sampling in winter. In addition to carabids, potential food organisms were evaluated from the pitfall catches.The bogs, although of different types and located on different continents, show similar physiognomic vegetation units. Eight of these units are considered relevant as carabid microhabitats. The carabid assemblages of open sunny, and wooded shaded habitats are clearly distinguished. Only a few species are adapted to the extreme environment of open Sphagnum L. habitats. Among them, stenotopic species are dominant. The seasonal distribution of two species on Swedish Ryggmossen [Agonum ericeti (Panzer), Pterostichus rhaeticus Heer] suggests that the carabids of open bog plateau habitats use damp Sphagnum lawns for their summer activities and migrate to drier hummocks for overwintering.On bog plateaus, larger populations of ground beetles were only found where a pronounced pattern of hummocks and hollows exists. In bogs with a prevailing uniform vegetation of Sphagnum mats, carabids were conspicuously scarce. Thus, the development of a bog indigenous carabid fauna is closely related to the presence of a hummock–hollow mosaic. The data indicate that in most bog habitats food is not a limited resource and does not play a key role as a population controlling factor.