HABITAT TYPE AND SEASONAL EFFECTS ON THE DISTRIBUTION AND DENSITY OF PLECOPTERA IN OZARK STREAMS, ARKANSAS

Plecoptera nymphs were collected from coarse woody debris (CWD) and be nthic habitats from the White River, Illinois River, and Clear Creek o f Northwest Arkansas from February 1991 through February 1992. Two-way analysis of variance comparing habitat type and season showed signifi cant main effects. Densities were significantly greater in benthic hab itats than on CWD and greater during winter and spring than during sum mer and fall. Significant two-way interactions were found between habi tat type and season. Multiple regression analysis revealed a significa nt relationship among the seasonal density of winter stoneflies and fl ow rate, water temperature, and dissolved oxygen; densities increased as water temperature decreased and as dissolved oxygen concentration a nd flow rate increased. Densities of stonefly species with slow univol tine, semivoltine, or fast univoltine spring and summer life cycles sh owed no significant relationship with these factors. Two-way analysis of variance indicated that most species inhabiting coarse woody debris are found on wood with loose bark or wood that is well decayed and ha s many interstitial spaces. Prostoia completa (Walker) was the only sp ecies whose abundance was influenced by the volume of biofilm present on CWD and increased biofilm volume led to increased density. These re sults suggest that benthic habitats are preferred by most species of P lecoptera, but that CWD may also be an important habitat type for some species.