Year of Award

2017

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Committee Chair

H. Maurice Valett

Commitee Members

Diana Six, Winsor Lowe

Keywords

Stream Restoration, Macroinvertebrates, Organic Matter, Riparian, Habitat

Publisher

University of Montana

Subject Categories

Terrestrial and Aquatic Ecology

Abstract

Channel reconfiguration projects command a large portion of stream restoration resources, while long-term monitoring and research is severely underfunded and rarely implemented. This has led to a limited knowledge base about ecological response and efficacy. Although channel reconfiguration projects are being implemented to restore biological function to lotic systems, the document responses are highly variable and little evidence has shown these projects are reaching their target goals. I predicted the inconsistent response to these projects is the result of disturbance-induced successional processes and catchment-scale water quality impairment. To address how these endogenous and exogenous factors influence stream response to channel reconfiguration, I developed the phased recovery framework and tested it by assessing nine channel reconfiguration sites in western Montana. Each site was composed of a restored reach ranging in age from 1 to 18 years and reference reach representing a minimally disturbed target condition. Five sites were located in unimpaired forested watersheds, while four sites were located in a human-developed watershed experiencing nutrient enrichment, increased fine sediment loads, and elevated stream temperatures. At each site, I assessed macroinvertebrates and associated habitat metrics (physical habitat, canopy cover, stream temperature, dissolved oxygen, and organic matter) and evaluated their response to endogenous and exogenous controls. While physical habitat appears to reach restoration targets immediately following channel reconfiguration, other metrics do not. Channel reconfiguration projects appear to undergo a reorganization phase where organic matter standings stocks and macroinvertebrate densities are significantly reduced for one to two years. Following the reorganization phase, watershed condition drives the recovery trajectory of restored reaches. In unimpaired watersheds, endogenous control, particularly the successional sere of the riparian zone drives ecosystem recovery. Over time, organic matter standing stocks, based on benthic chlorophyll a, become more similar to reference condition (r2 = 0.46, p = 0.05). This corresponds with shredder abundance increasing as projects get older (r2 = 0.78, p = 0.05). Additionally, macroinvertebrate communities become more similar with project age based on Bray-Curtis Dissimilarity (r2 = 0.59, p = 0.13). At impaired sites, oldest restoration reaches were closest to point-source nutrient enrichment and this exogenous control dictated ecosystem recovery. Specifically, benthic chlorophyll a (r2 = 0.98 , p = 0.01) and collector-gatherer abundance (r2 = 0.84 , p = 0.09) increased as sites got older, the opposite trend of unimpaired sites. These results suggest that free of watershed-scale impairment, restoration reaches likely take upwards of two decades to recover to reference condition. If impairment is present, it can exert a strong endogenous control on recovery that overwhelms the influence of channel reconfiguration restoration.

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© Copyright 2017 Jacob M. Dyste