This Doctoral Dissertation Research Improvement project is about historic stream channel disturbances and associated implications for ecosystem functioning. Previous research has demonstrated strong relationships between stream geomorphology and ecosystem processes such as stream metabolism, but little is known about how past stream channel disturbances influence these relationships or how streams recover from these historic disturbances. Understanding the link between geomorphic processes and ecosystem function as well as how these relationships are affected by disturbance has implications for the environmental management of streams, particularly the practice of stream restoration. Ecosystem metabolism refers to the balance between the processes of gross primary production (GPP) by algal and aquatic plant communities and ecosystem respiration (ER), which accounts for the total consumption of organic carbon by all aquatic communities in the system. Light, temperature, stream flow, and channel complexity all interact and influence rates of GPP and ER. This research will address the degree to which past stream channel disturbances and recent restoration efforts affect these controls. The project's research questions are 1) how do structural and functional geomorphic characteristics vary between disturbed, non-disturbed, and restored channel conditions?; and 2) how do GPP and ER respond to these changes? In the past mountain streams were impacted by a forest harvesting strategy known as 'tie-driving,' during which there was systematic clearing and channelizing of streams to aid in the transport of railroad ties. This practice was very common in Wyoming and Colorado and the legacy of this practice is still evident on the landscape today. We hypothesize that 1) GPP will be higher in tie-driven streams as compared to non-disturbed streams because of increased light availability as a result of thinner riparian cover and lower channel banks, 2) ER will be lowest in tie-driven streams compared to non-disturbed streams because of decreased organic matter standing stocks and decreased channel complexity, and 3) rates of ER will be greater than rates of GPP in all streams indicating that communities are reliant on energy subsidies originating from outside the channel. Results from this study will address knowledge gaps related to the interactions between stream geomorphology, riparian composition, and ecosystem metabolism and will develop an integrative foundation for understanding ecological outcomes of stream restoration projects.
Results of this project will help to inform future stream restoration and management efforts through the integrative investigation of stream geomorphology and ecosystem function within the context of a disturbance regime. Improving these disciplinary links will result in more efficient and effective stream restoration projects and more efficient use of federal and state restoration investments. Over the course of this project, results and associated data will be shared directly with local agencies such as the USDA Forest Service and the U.S. Fish and Wildlife Service, ensuring that research findings will be incorporated in agency management efforts quickly and efficiently. As a Doctoral Dissertation Research Improvement award, the project will provide support to enable a promising graduate student to establish an independent research career.
