Multiple Stressors and Multiple Invaders in Linked Stream-Riparian Ecosystems: Combined Research and Pedagogy Contributions

• Main Author: Heinrich, Kaleb K
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2015
• Subjects: Biology; Ecology
• ISBN: 9798380082327

Streams and riparian areas are closely linked and essentially operate as one ecosystem with reciprocal fluxes of energy, materials and organisms. The linked stream-riparian ecosystem is inherently complex, dynamic and affected by factors that interact across multiple spatial and temporal scales. Multiple stressors can alter these stream-riparian ecosystems with effects that propagate in both directions between land and water. Additionally, multiple invasive species are involved in a variety of complex interactions that can lead to profound consequences for native communities and ecosystem processes. I studied the effects of multiple stressors and multiple invasive species on southeastern Idaho stream-riparian ecosystems. My work had three components. First, I investigated the effects of both riparian vegetation loss and invasion by New Zealand mudsnail (Potamopyrgus antipodarum) on in-stream macroinvertebrates, emergence of adult aquatic insects, and the abundance of terrestrial insectivores along the Portnuef River. I found that riparian habitat loss did reduce web-weaving spider abundance. Unexpectedly, sites with high mudsnails were more productive in that they had greater flux of insect emergence. Abundances of spiders and birds were positively related to emergence flux. Second, in Deep Creek, a representative cold desert stream and site of long term studies, I investigated the interaction between two non-native species widespread in the western USA: common carp (Cyprinus carpio) and Russian olive (Elaeagnus angustifolia), an invasive riparian tree associated with di-nitrogen fixation. I found that the carp population increased ~4X subsequent Russian olive invasion. Russian olive made up nearly 40% of carp diets and sustained ~1/3 of carp production. In turn, subsidized carp were associated with 2-3-fold reductions in chlorophyll-a, benthic organic matter, and aquatic macrophytes, and carp that consumed Russian olive recycled up to 2X more nitrogen than those that did not. This scenario is characteristic of an “invasional meltdown” that extends across the land-water boundary. Third, I developed a guide for an inquiry-based outreach activity and collaboration between stream ecologists and students whose aim is to stimulate student understanding of ecosystem connectivity. Traditionally, exploration of ecosystems has been restricted to connections within conventionally defined ecosystem boundaries (i.e., within a stream, within a forest). Further, investigations that have treated linked ecosystems highlight unidirectional inputs. I employed a constructivist approach to explore connections across ecological boundaries and how these linkages couple habitats and organisms in their vulnerability to agents of environmental change.