Background/Question/Methods Changes in the hydrologic gradients along the longitudinal course of stream channels can have multiple effects on biotic communities and ecosystem-level processes (e.g. leaf processing). This project assessed the differences in processing rates, macroinvertebrate colonization, and the fungal biomass of tulip poplar (Liriodendron tulipifera) leaves between ephemeral and perennial reaches of headwater streams in a Cumberland Plateau watershed in eastern Kentucky, U.S.A. The ephemeral channels are 0.5 – 1.0 m wide and typically are dry between May and November. In contrast, the perennial channels are > 1 m wide with surface flow even in the shallow sections through summer and autumn. Because L. tulipifera is a fast-processed leaf species, we hypothesized that despite the distinct hydrologic gradient there would be no impact on mass loss rates, macroinvertebrate colonization patterns and diversity, and fungal biomass. It is expected that most leaf material will have been processed prior to channel drying. Leaf pack samples were taken monthly from each stream. Packs were prepared as ash free dry mass to calculate processing coefficients (k). Macroinvertebrates were identified to the lowest practical level and placed into functional feeding groups. Fungal biomass on leaves was calculated by measuring ergosterol levels.
Results/Conclusions After one month of processing time, there were only minimal differences in mass remaining between the two channel types. The perennial reaches had an average of 75.3% mass remaining versus 72.2% from the ephemeral reaches. In addition, the one month macroinvertebrate colonization pattern was virtually identical between channel types. The functional feeding groups of macroinvertebrates were relatively the same for each type of channel also. These preliminary results suggest only minimal differences in processing dynamics between ephemeral and perennial channels, but mainly a function of a fast-processed leaf species.