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Comparing hypotheses proposed by two conceptual models for stream ecology

Collins, Sean E
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396532770

Abstract Details

2014, PhD, University of Cincinnati, Arts and Sciences: Biological Sciences.
The broad goal of stream ecology is to understand and predict complex interactions between environmental factors and processes that occur within streams and rivers, such as biological community composition and their interactions, system metabolism (productivity and respiration), and nutrient sources and concentration. Multiple factors are thought to play important roles in these processes including regional environmental conditions (i.e., hydrology, geology, stream form/morphology) and longitudinal position within a stream network (defined by Strahler stream order). In the past, several theoretical concepts have been proposed to attempt to describe and explain how streams behave, and each concept uses various factors weighted differently to characterize streams and gain a better understanding of ecological processes and overall system functions. Here, two differing theories of stream ecology are compared – the River Continuum Concept (RCC) and the Riverine Ecosystem Synthesis (RES). Each of these theories has unique predictions based on either Strahler stream order (SSO; used by the RCC) or Functional Process Zone (FPZ; used by the RES) defined by hydrogeomorphic characteristics. Predictions from both theories were tested across sites representing multiple SSOs and FPZs within the Kanawha River Basin. Measures of environmental heterogeneity (an important concept for differentiating between FPZs) were also assessed. This project has shown that some predictions from both the RCC and the RES are valid. The physical character of the basin is variable; sampling of riverbed substratum at each site revealed that similarities within each FPZ in riverbed composition exist and that each FPZ is distinct. Hydrogeomorphic factors including underlying geology and valley floor width strongly influence the character of the riverbed substratum. The ratio of primary productivity to ecosystem respiration (i.e., a measure of metabolism) aligned with predictions from the RES where potential light availability and environmental heterogeneity were major drivers of this ratio. On the other hand, a “sliding scale” (i.e., one that changes with environmental variables) may be more appropriate for predictions from the RCC as the apparent trend toward higher rates of primary productivity was shifted from mid-order to larger streams. Neither the RCC nor the RES provide clear hypotheses for fluctuations in nutrient concentrations, and changes in these concentrations were not accurately explained by either SSO or FPZ. Finally, results from stable isotope analysis of carbon and nitrogen revealed that consumers in the Kanawha River Basin utilize a combination of aquatic and terrestrial organic carbon. While food web metrics and the proportional dependence upon in-stream and terrestrially derived carbon follow predictions of the RCC more closely, the mechanisms underlying these predictions are not always met. That is, there was no relationship between high measured rates of aquatic primary productivity and low dependence on terrestrial carbon sources. The RES also explains well the shift in organic carbon use from various sources by consumers. Perhaps the best model for understanding these processes is a combination of both concepts. Understanding the reasons for changes in processes and functions within streams and rivers is critical for developing a useful and successful model. It is through this process of model conceptualization, testing, and refining that true advancements in knowledge can take place.
Stephen Matter, Ph.D. (Committee Chair)
Joseph E. Flotemersch, Ph.D. (Committee Member)
Ishi Buffam, Ph.D. (Committee Member)
Eric Maurer, Ph.D. (Committee Member)
Amy Townsend-Small, Ph.D. (Committee Member)
181 p.
Ecology
River Continuum Concept; Riverine Ecosystem Synthesis; system metabolism; macronutrient concentrations; food web structure; organic carbon source

Recommended Citations

Citations

  • Collins, S. E. (2014). Comparing hypotheses proposed by two conceptual models for stream ecology [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396532770

    APA Style (7th edition)

  • Collins, Sean. Comparing hypotheses proposed by two conceptual models for stream ecology. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396532770.

    MLA Style (8th edition)

  • Collins, Sean. "Comparing hypotheses proposed by two conceptual models for stream ecology." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396532770

    Chicago Manual of Style (17th edition)

ucin1396532770
694
© 2014, some rights reserved.Creative Commons License Comparing hypotheses proposed by two conceptual models for stream ecology by Sean E Collins is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.