Incorporating science-based approaches into the rapid assessment of wetlands and streams : validation, restoration trajectory, and method development

Abstract

Human alterations within wetlands and streams have resulted in a decrease in ecological functions and associated benefits to society. The scientific literature highlights the functional benefits provided by ecosystems including flood protection, nutrient cycling, and habitat maintenance. Additionally, legislation and regulatory policy require mitigation and restoration as compensation for declines in ecological functions. As a result, the need for practical, repeatable, and technically sound ecosystem assessment methods remains essential to natural resource management. However, few studies determine the validity of rapid assessment approaches by applying quantitative parameters, especially with respect to biogeochemical functions. We assessed biogeochemical functions applied to restored wetlands in the Mississippi River Valley, USA. Significantly higher rapid assessment outcomes were associated with increased ecosystem functionality (r=0.64-0.86). Findings suggest that rapid assessment tools serve as reliable proxies for measurements of nutrient and biogeochemical cycling. Further, a framework for identifying restoration trajectory metrics was established, with four rapid assessment variables yielded positive restoration trajectories within <20 years>(r = 0.59-0.89). Rapid assessment components were classified as rapid response, response, and stable variables categories and restoration milestones should focus on rapid response variables. In order to evaluate rapid ecological assessment in different environments, we examined proxy measures of biogeochemical function in headwater stream systems. Biogeochemical cycling proxies of C and N input and processing significantly, positively correlated with the results of a rapid assessment approach (r = 0.64-0.81). Also, stream loading equations demonstrate that N and P transport, sediment, conductivity, and temperature significantly, negatively correlated with rapid assessment scores (r = -0.56-0.81). Significant differences in nutrient processing, stream loading, water quality, and rapid xii assessment results were also observed between headwater streams located in recently altered (e.g., mined) and older second growth forested catchments (U = 0.01-0.24). Findings indicate that rapid assessment scores respond to a combination of alteration type and recovery time. An analysis examining the time and economic requirements of biogeochemical proxy measurements highlights the benefits of rapid assessment methods in evaluating biogeochemical functions. Based on these findings, a technical standard for rapid ecological assessment was developed. The technical standard establishes nine testable components that promote validity and defensibility in the development and application of rapid ecological assessment approaches.