LITTER SPIDER SUCCESSION AFTER CLEAR-CUTTING IN A WESTERN CONIFEROUS FOREST

The litter spiders of a coniferous forest in western Oregon were trapped in pitfalls to study the effects of, and recovery after, clear-cutting. Traps were placed in old-growth sites (150 450 years) and in clearcuts of three different ages (4-7, 16-19, and 22-31 years); each age-class was represented by sites that differed along a gradient of moisture availability. A total of 8905 individuals were collected over the 2-year study period, comprising 93 species, 54 genera, and 15 families. Visual pursuit hunting spiders dominated clearcuts, while "sit and wait" microweb and trapdoor spiders dominated mature forests. Most of the common forest species were reestablished in the wettest sites by 30 years after clear-cutting; species composition in dry 30-year-old clearcuts more closely resembled the fauna of shrubby wet 16-year-old clearcuts. Microenvironmental conditions and the availability and species composition of prey are the most likely factors behind variation in spider species composition among sites. Prey and microenvironment are in tum largely influenced by canopy closure and litter depth. The use of litter spiders as bioindicators of litter habitat quality and forest recovery is discussed.