Donna M. Drury and William E. Kelso. School of Forestry, Wildlife, and Fisheries, Louisiana State University, Baton Rouge, LA 70803

Removal of woody debris during stream alteration programs reduces habitat diversity, disrupts predator-prey relationships, and results in an overall loss of macroinvertebrate cover. Woody debris is a dominant macroinvertebrate substrate in southeastern coastal plain streams, and we investigated the rate at which invertebrates colonize newly introduced wood, differences in colonization rates between magnolia Magnolia grandiflora and water oak Quercus nigra debris, and the effects underlying substrate on colonization dynamics. Two units of twelve branches (0.91 m long, 1.3-2.5 cm diameter) of magnolia and water oak were introduced into the Bogue Falaya River at two sites over sand and gravel substrates. Branches were sampled weekly for four weeks, biweekly for two months, and monthly for four months. Data from weeks 1-4 indicate that the debris-associated macroinvertebrate assemblage is dominated by Trichoptera, and Ephemeroptera are the most diverse order colonizing (greatest number of genera) the branches. There does not appear to be substantial differences in colonization rates between tree species. Substrate type does appear to effect colonization number.