At 19 stream reaches distributed across three watersheds in northern Idaho, I have investigated the effects of both landscape and local, reach-level conditions on stream-riparian food web structure and energy flows (C and N). The effects of timber harvest and other land use changes, in conjunction with local factors were expected to compromise critical links between terrestrial and aquatic systems, leading to impaired energy exchanges and shifts in food web structure. Stable carbon and nitrogen isotope analysis were used to investigate energy flows and trophic complexity of stream-riparian food webs.
Results/Conclusions
Results indicate significant differences in trophic structure and complexity, as well as distinct patterns of energy flow as measured by C signatures across study reaches. Data suggest that timber harvest practices leading to even small reductions in forest cover and watershed road density interact with local stream condition to significantly affect energy flows and trophic structure in stream-riparian ecosystems. Taxa such as aerial insectivorous birds were particularly sensitive to these characteristics.
