Author ORCID Identifier

https://orcid.org/0000-0001-7105-3917

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Arts and Sciences

Department

Geography

First Advisor

Dr. Jonathan D. Phillips

Abstract

The dynamic interactions between fluvial processes and vegetation vary in different environments and are uncertain in bedrock settings. Bedrock streams are much less studied than alluvial in all aspects, and in many respects act in qualitatively different ways. This research seeks to fill this lacuna by studying bedrock streams from a biogeomorphic perspective. The first part of this research aims to identify the impacts of woody vegetation that may be common to fluvial systems and rocky hillslopes in general, or that may be unique to bedrock channels. A review of the existing literature on biogeomorphology — mostly fluvial and rocky hillslope environments — was carried out, and field examples of biogeomorphic impacts (BGIs) associated with fluvial systems of six various bedrock environments were then examined to complement the review. This research shows that bedrock streams exhibit both shared and highly concentrated BGIs in relation to alluvial streams and bedrock hillslope environments. It shows that while no BGIs associated with bedrock streams are unique to the environment, the bioprotective function related to root-banks (when the root itself creates the stream bank) and the processes related to bioweathering and erosion are rarely addressed in alluvial fluvial literature, despite their importance in bedrock fluvial environments. The second part of the dissertation is largely grounded upon the important BGIs associated with bedrock fluvial environments identified in the first part. Drawing from ecological lexicon, this part introduces some biogeomorphic concepts, most importantly biogeomorphic keystone species and equivalents, with respect to different biotic impacts on surface processes and forms. Later, it explores these concepts by examining the general vs. species-specific BGIs of trees on a limestone bedrock-controlled stream, Shawnee Run, in central Kentucky. Results suggest that Platanus occidentalis plays a keystone role by promoting development of biogeomorphic pools in the study area. Further, some species play equivalent roles with respect to surface processes and landforms by promoting development of avulsion-associated islands and can be recognized as biogeomorphic equivalents. Finally, this dissertation also examines the relative importance of systematic up-to downstream vs. local scale variation explaining channel morphology and biogeomorphological phenomena in Shawnee Run. Results show that local scale variation − primarily attributable to the local scale structural controls, incision status and edaphic variation − largely explains channel morphology and vegetation patterns. These patterns may therefore be common in bedrock rivers strongly influenced by geological controls.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.289

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