Semester

Summer

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Forestry and Natural Resources

Committee Chair

Brent Murry

Committee Member

Carol Arantes

Committee Member

Dustin Smith

Committee Member

Stuart Welsh

Abstract

Freshwater lotic communities are complex, dynamic, and quick to respond to changes to their environment. However, some of the specific mechanisms driving those changes are yet to be fully understood. Here, I will use the community size spectrum (CSS) approach to assess how the CSS slope, elevation, and food chain length of the fish and macroinvertebrate assemblages as well as the combined CSS of 15 mid-sized (2nd-4th order) streams in north-central West Virginia respond across gradients of watershed factors (drainage area, mean drainage slope, mean drainage elevation, drainage % forest, and stream specific conductance). Field sampling was carried out in summer of 2022, and laboratory analysis was completed in spring of 2023. Log2 size bins vs. log2 densities were used to build CSS for each stream community. Results from the CSS were then used in an analytical procedure combining principal component analysis and univariate correlation which produced a set of significant correlations between certain watershed factors and CSS parameters that either followed established ecological knowledge or revealed caveats unique to the study design. Results provide evidence for including external watershed factors such as drainage elevation, slope, and land cover when assessing stream community structure as they could play a role in explaining variation between communities that cannot be accounted for by analyzing only biotic factors such as functional groups or diversity. Through this research, the community size spectrum approach to aquatic community assessment was shown as a valuable tool for stream ecologists due to its close link with changes to watersheds. It would be beneficial to add CSS to the repertoire of stream community assessment tools when seeking to better understand these diverse, dynamic, and vulnerable systems. Future research should focus on streams from a single major watershed to remove geographic location as a driver of variation so the importance of the other watershed factors on CSS parameters could be more effectively teased out, and then integrate these results into an analysis with well-studied biotic factors so that the level of explanatory power for each can be better understood. An ideal future goal for using CSS in stream community management would then be to develop a predictive model that can output estimated future CSS parameters (slope, elevation, and FCL) once biotic factors, geomorphology, and proposed land cover/water quality remediation effects are put into the model. This would give managers the capability to set targets for holistically improving community structure before breaking ground on any restoration/management projects along with thresholds for how much development can be done to a watershed before the stream community structure is significantly harmed.

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