A framework for process-based restoration: Riparian function and large woody debris dynamics in an Atlantic salmon river in Maine

Removal of the riparian forests along rivers in Maine began over 300 years ago during multiple land conversions, while channel alterations occurred directly from dams and log drives. These anthropogenic disturbances altered ecosystem processes, which impacted riverine ecosystem integrity and the ability to maintain biological diversity. Many ecosystem processes and species have been negatively affected by these disturbances, including the critically endangered sea-run Atlantic salmon (Salmo salar). Recovery of endangered species is complex and is guided by the Federal Endangered Species Act of 1973, which calls for the conservation of ecosystems as well as species. This study outlines a conceptual framework I developed for process-based restoration that focuses on ecosystem processes, because typical restoration approaches tend to ignore processes, whereas my framework presents a more holistic method. The framework consists of five steps: (1) articulate the problem, (2) treat and understand the symptoms of altered ecosystem processes, (3) treat and understand the causes of altered ecosystem processes, (4) identify and prioritize disrupted processes, and (5) research processes and develop restoration options. I use the example of the endangered Gulf of Maine Distinct Population Segment (DPS) of Atlantic salmon (Salmo salar) in the West Branch Sheepscot River and riparian function to illustrate the application of the framework. Recommendations for restoration of riparian function include managing the riparian forest for contributions of large woody debris (LWD) and placement of LWD in areas where the most benefit is likely to occur and where the pieces will be most stable. However, complete restoration of riparian function will take hundreds of years.