Date of Award

Spring 5-8-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Hamish Greig

Second Committee Member

Amanda Klemmer

Third Committee Member

Stephen Coghlin

Abstract

Riparian buffers are used as a management tool for sustaining freshwaters during forest harvest, but the log-term (decadal) outcomes of riparian management practices are not well understood. To address the impact that variable riparian timber harvest has on stream invertebrates, fish, terrestrial invertebrates and forest composition, environmental data were collected from streams that experienced a range of harvests; clear-cuts with 0m, 11m, or 23m buffers, selection harvest or no harvest at all. Riparian zones were initially harvested during the winter of 2000-2001. Results within this thesis are from data collected during the summers of 2018 and 2019. Aquatic invertebrates were collected via Surber samples and leaf bags. Aerial invertebrates within the terrestrial landscape, including emerged adult aquatic invertebrates, were collected using sticky traps placed within the stream corridor. Fish were collected using quantitative electrofishing. Lastly, forest composition was calculated using forest inventory plots with diameter at breast height (DBH) and species was recorded for every stem over 1.37 meters tall. Results show a shift in forest community composition towards smaller stems and more deciduous trees with more disturbance to the riparian zone. Aerial invertebrates show a shift in community composition both seasonally and with respect to treatment type. This was noted as a change in proportion of adult aquatic to terrestrial invertebrate as well as composition of adult aquatic invertebrate. Aquatic invertebrates experienced a shift in community composition as well with an increase towards shredders, scrapers and more diverse Diptera taxa in streams with more disturbed riparian habitat. Abundance and condition of brook trout also increased with greater disturbance. Importantly, we observed stronger effects of riparian forest harvest on community composition for each our response variables than total abundance and diversity of taxa. This suggests that the scale to which data was analyzed is important in detecting ecosystem responses to riparian management, and also that aggregate measures like diversity and total abundance may be more robust to environmental change than specific taxa. In this case, current management guidelines could prove ineffective to maintaining stream and riparian zone community composition.

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