Date of Award

Spring 5-4-2024

Degree Type

Thesis

Degree Name

Master of Science in Ecological Restoration

Committee Chair

Robert Pal

First Advisor

Joe Griffin

Second Advisor

Dan Autenrieth

Abstract

Floodplain restoration is an intricate process aimed at promoting water quality, biodiversity, and maintaining ecological balance. However, mapping vegetation patterns on a restored floodplain can be challenging due to different geomorphic locations across a river sections, including flooding regimes, sediment characteristics, elevation, and ground water availability. This study investigates the drivers of vegetation succession in floodplains post-restoration along the Upper Clark Fork River, encompassing Phases 1, 2, 3, and 5. We analyzed key factors influencing vegetation response, including total canopy cover and woody vegetation health, in comparison to soil compaction, geomorphic location, distance from streambank, time post-restoration, and metal levels to determine which factor statistically had the most benefit at influencing vegetation expansion. Time post-restoration showed the most significant factor in vegetation height and ground cover completing the requirements set by the Record of Decision for the Clark Fork River Operable Unit. The presence of bare ground facilitated woody seedling establishment and promoted woody vegetation growth. Soil compaction was not significant in vegetation expansion into the floodplain. Sandbar willows were found to be the most effective woody species in developing habitat for wildlife and higher shrub layer percentages. To prevent contamination into restored phases, restoration design should clean up phases in upstream to downstream sequential order. Understanding the drivers of vegetation succession enables river restoration practitioners to improve current restoration approaches and to formulate optimized restoration designs, thereby fostering superior ecological outcomes.

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