Date of Award

Fall 2021

Project Type

Thesis

Program or Major

Biological Sciences

Degree Name

Master of Science

First Advisor

Gregg E Moore

Second Advisor

Thomas P Ballestero

Third Advisor

David M Burdick

Abstract

The restoration of tidal and freshwater wetlands either through compensatory mitigationor voluntary efforts have become a major strategy to conserve remaining wetland resources after historic losses and in the face of current unprecedented threats. Prior efforts of wetland restoration have often fallen short of expectations due to the reliance of a compliance success framework, which requires short monitoring timeframes, misapplies successional theories, and defines success of projects into a yes or no dichotomy. Decades of advancement in restoration ecology theory and its application to wetland ecology and botany have led to the development of a functional success framework to improve outcomes in wetland restoration. Functional success is a framework of thinking in restoration ecology that includes concepts of resiliency and alternative stable-state theory, long-term monitoring requirements, adaptive management, and a view of success as a progression. Elements of functional success were applied to two unique wetland creation studies to improve the understanding of restoration trajectories and baseline expectations for possible outcomes and adaptive management needs. New Hampshire has adopted a policy for erosion control that establishes living shorelines as the preferred shoreline stabilization method over the past five years. Despite widespread use ii on the mid-Atlantic and Southeastern coast in the United States, living shoreline performance has not been well-documented in New England, where shorter growing seasons and ice rafting pose unique challenges that increase with latitude. The vegetation, nekton, and biogeochemical processes were monitored for two years at three living shoreline projects and compared to both references and no-action shorelines to gauge recovery. The recovery of the system was assessed with the Restoration Performance Index and restoration trajectories of the Restoration Performance Index scores and individual metrics were assessed over project age. Living shorelines recovered over 50% of ecosystem structure, function, and services within four years post-constructions. The restoration trajectory followed a logistic regression indicating two phases of recovery: an initial rapid phase driven by nekton and vegetation and a slower, more incremental phase driven by biogeochemical processes. Adaptive management of living shorelines were documented and included wrack removal, measures to prevent herbivory, and replanting of vegetation. Wetland ecology and restoration historically developed successional models of the vegetation community by studying wetlands of various ages simultaneously. The experimental approach has been cheap, quick, and effective at understanding broad floristic trends, allowing for practitioners to set expectations including the widely held notion that the vegetation community reaches a dynamic equilibrium after 15 years. A created freshwater wetland in Portsmouth, New Hampshire was floristically reevaluated in 2020 to add to a thirty-five-year data set of the species composition and community distribution of the vegetation community. The wetland followed similar documented patterns of being dominated by hydrophytes, perennials, and natives over time. Species turnover, the rate of succession, declined by half between the 7 – 18 and 18 – 35 years post-construction. Conversely, the distribution of wetland communities experienced drastic change after 18 years post-construction with double the number of wetland communities, major cattail expansion into graminoid meadows and aquatic beds, proliferation of woody vegetation, and development of unique vegetation communities like sedge meadow marshes and red maple swamps.

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