The effects of riparian logging on terrestrial invertebrate inputs into forested headwater streams

Abstract

Terrestrial invertebrates (TIs) are an important food source for stream salmonids, especially in low-productivity headwater streams. Studies have shown that TIs can account for >50% of a salmonid’s summer diet, and the consumption of larger TIs is often the difference between feeding above or below maintenance ration. Riparian disturbance is assumed to affect the biomass and composition of TIs entering a stream, but consistent patterns have not emerged. In this study, pan traps were used to quantify the effects of riparian tree harvesting at 0, 50, and 90% basal area harvest (BAH) on TI inputs into 8 Appalachian headwater streams in West Virginia during the summers of 2007 and 2008. The biomass and composition of TI inputs were affected by both treatment and year. The 90% BAH treatments had significantly higher TI input biomass due to a shift in composition toward larger taxa. At greater harvest intensities, increases of grasshoppers (Acrididae) and katydids (Tettigoniidae), wood-associated Coleoptera, ants (Formicidae), and pollinating hymenopterans were observed. No significant changes were attributed to the 50% BAH treatments. These results indicate forestry practices can significantly affect TI inputs into Appalachian headwater streams and have the potential to alter fish production.