Terrestrial Riparian Arthropod Investigations in the Big Beaver Creek Research Natural Area, North Cascades National Park Service Complex, 1995-1996: Part III, Arachnida: Araneae

Glesne, Reed

Ground-dwelling spider communities of nine distinct habitat types were sampled within the riparian corridor of lower Big Beaver Creek, North Cascades National Park Service Complex during the snow-free seasons of 1996 and 1997. This study was part of a comprehensive project to begin development of protocols for the assessment of biological integrity in the Park Complex. Specific objectives were to document the species, relative abundance, and habitat associations of ground-dwelling spider communities. Spiders represent a diverse and functionally important group of arthropods. They are frequently the dominant predators in arthropod communities. The assessment of their status can provide much information useful in monitoring the integrity of biotic communities. Spiders were abundant in the study area. Pitfall captures of spiders were second to those of Coleoptera. A total of 8,922 spiders representing 10 families and 38 species are reported here. In addition, a few diverse families of small spiders, representing approximately 20% of all individuals collected, were not identified. Future efforts to identify these taxa and additional collections in the shrub and canopy layers should significantly increase the diversity of spiders found in the study area. In comparison, multi-layer sampling of spiders in the Western Cascades of Oregon at the H.J. Andrews Experimental Forest has resulted in the documentation of 30 families and 260 species (Parsons et al. 1991). Members of the family Lycosidae accounted for over 60% of all spiders collected. Agelenid spiders were second in abundance, representing greater than 20% of all individuals collected. The number of species collected varied little between the nine habitat types sampled. However, there were some major differences in individual species occurrence and abundance between habitat types. Both habitat generalists and habitat specialists were collected. Relative abundance of individuals collected exhibited greater variation among the habitat types than that observed for total species and habitat types. Capture rates were greater at habitats exhibiting low canopy closure and reflected the dominance of lycosid spiders in those samples. Agelenid spiders were the most abundant group of spiders collected at sites with closed canopies.

Terrestrial Riparian Arthropod Investigations in the Big Beaver Creek Research Natural Area, North Cascades National Park Service Complex, 1995-1996: Part III, Arachnida: Araneae

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