Ecological disrupting events can drastically alter biotic communities. Riparian assemblages are subject to significant amounts of such disturbance, resulting in succession. In a river system prone to annual and catastrophic disruptive events, we examined the ecological effects of the successional return of alder overstory on aquatic communities. To test for overstory effects, we measured aquatic invertebrate populations, fish populations, and river structure (speed and depth) between alder and control sites. Both mayflies (Ephemeroptera) and stoneflies (Plecoptera) were found in higher abundance in alder sites, while no difference in caddisflies (Trichoptera) were seen. Mayflies were found in higher abundance on both maple and alder leaf bags in control sites compared to alder grove sites while stoneflies were higher on alder leaf litter bags than on maple leaf litter bags, regardless of site type. River speed through the alder grove sites was faster than in the non-alder control sites, corresponding to fish abundance which decreased as river speed increased. Clear differences were found between the biological communities and physical characteristics of the two treatment types.

CEC Research Volume 2, Issue 1