THE INFLUENCE OF LEPIDOSTOMA (TRICHOPTERA, LEPIDOSTOMATIDAE) ON RECOVERY OF LEAF-LITTER PROCESSING IN DISTURBED HEADWATER STREAMS

Two headwater streams draining catchments 53 and 54 (C53 and C54, respectively) at the Coweeta Hydrologic Laboratory in western North Carolina were treated with insecticide in 1980 (C53) and 1986-1988 (C54). During recovery periods in both streams, Lepidostoma spp. were abundant, early colonizers. Densities of Lepidostoma in litterbags and benthic samples collected from recovering streams were substantially higher than in untreated streams (pretreatment and reference streams). During treatment years, leaf-litter processing rates were severely reduced relative to pretreatment and reference streams. In contrast, litter processing rates in C53 and C54 during recovery were faster than those in untreated streams (pretreatment and reference). Rhododendron is one of the most refractory leaves commonly found in Coweeta streams; however, percent increase of rhododendron processing rates from treatment periods to recovery was greater than that of more labile red maple. Laboratory feeding experiments were performed in order to examine and quantify use of rhododendron and red maple litter by Lepidostoma larvae. In the laboratory, Lepidostoma consumed significantly more rhododendron (1.062 mg AFDM/mg AFDM body wt/day) than red maple (0.479 mg AFDM/mg AFDM body wt/day) (P = 0.001). Results suggest that changes in the taxonomic composition of stream macroinvertebrate communities due to disturbance may have significant effects on ecosystem processes for at least 2 yr after termination of disturbance. Lepidostoma colonize rapidly following disturbance, enhancing the restoration of vital ecosystem processes such as litter decomposition in Coweeta streams.