THE SPATIAL DISTRIBUTION OF WOOD-NESTING ANTS IN THE CENTRAL COAST RANGE OF OREGON (HYMENOPTERA, FORMICIDAE, FOREST ECOLOGY)

Two coniferous forests in the central Coast Range of western Oregon were surveyed for nests of wood inhabiting ants. Nineteen species and 825 ant nests were found, corresponding to an average nest density of 0.079 nests/m('2) (maximum 0.38/m('2)) and a mean species density of 0.026 species/m('2) (maximum 0.08/m('2)). The spatial distribution of all species was random within the study areas. In contrast, the nest distribution patterns of the six most common species and all ants combined were found to be highly clumped (contagious) due to high nest densities on a few favorable sites. Most ants achieved greatest nest densities on high insolation, early successional plots such as clear-cuts. The nest abundances of 15 species were negatively correlated with tree canopy cover. However, Lasius pallitarsis and Leptothorax nevadensis had higher nest densities in woody debris on forested plots. Furthermore, the nest densities of all ants combined, and of nine individual species were greater in stumps than logs. Within stumps, the nests of all species combined, as well as Camponotus modoc, Tapinoma sessile, and Lasius pallitarsis were concentrated on the south sides of stumps. The bark, cambial zone, and wood of woody debris in all stages of decomposition were exploited by ants for nest sites. Leptothorax nevadensis, Tapinoma sessile, and Aphaenogaster subterranea occupied bark significantly more often than other tissues. Lasius pallitarsis and Camponotus modoc occupied wood significantly more often than other tissues although large nests extended through all tissues.