Doctor of Philosophy, The Ohio State University, 2014, Environment and Natural Resources

In recent years, a holistic ecosystem conceptualization has emerged that structurally and functionally links the river, and its riparian and floodplain zones into an integrated ecological unit - the riverine landscape. The riverine landscape often exhibit lotic water-driven disturbance biophysical complexity (e.g., patchiness) over both fine and broad spatio-temporal scales. However, despite the well-documented importance of river corridors (e.g., as biological refuges in human-modified landscapes), the role of riverine landscape pattern and composition on ecosystem structure and function is largely unknown. This study investigated the influence of internal (river size, lateral flow connectivity) and external (catchment land use and land cover) factors on site-specific riverine landscape patterns. It then used riparian spiders of the family Tetragnathidae and ants as model organisms to explore the associations between internal riverine landscape patchiness and the distribution, diversity, and trophic dynamics [e.g., trophic position (TP), and dependency on aquatically derived carbon (CA)]. Riverine landscape patchiness was measured using a combination of field (vegetation surveys, canopy photography, shoreline habitat measurements) and remote-sensing approaches [e.g., using a GIS, aerial photos, and Light Detection and Ranging (LiDAR) data]. Ants and spiders were surveyed on each side of the river at each study reach. A suite of analytical methods were used including Analysis of Variance (ANOVA), linear regression, Principal Component Analysis (PCA), Maximum Entropy (MaxEnt) modeling, a model-selection approach using Akaike Information Criterion (AIC) and Non-Metric Multidimensional Scaling (NMDS). Results indicate that both external and internal factors were associated with riverine landscape pattern (patch area and shape and size) including drainage area (a proxy for ecosystem size), proximity to impoundment (a proxy for lateral flow connectivity), and catchm (open full item for complete abstract)

Committee: Mazeika Sullivan Dr. (Advisor); Charles Goebel Dr. (Committee Member); Desheng Liu Dr. (Committee Member) Subjects: Ecology; Environmental Management

Master of Science, The Ohio State University, 2012, Environment and Natural Resources

I investigated aquatic-to-terrestrial contaminant fluxes at 11 study reaches in the Olentangy and Scioto Rivers (OH, USA), representing urban, agricultural, and mixed land uses. At nine study reaches, I collected benthic sediment, aquatic emergent insects, ants (Formica subsericea), spiders of the family Tetragnathidae, riparian vegetation, and periphyton. At eight of these reaches, as well as additional four reaches where I erected nest-boxes, I sampled riparian swallows including: bank (Riparia riparia), northern rough-winged (Stelgidopteryx serripennis), tree (Tachycineta bicolor), and cliff (Petrochelidon pyrrhonota) swallows. All biological samples were analyzed for δ13C and δ15N and tested for toxic elements including arsenic (As), selenium (Se), lead (Pb), and mercury (Hg). Mixing models indicated that Tetragnathidae were highly reliant on aquatic insects (mean = 76.9%, SD = 8.9%), whereas ant dependence was less but with greater variability (mean = 27.8%, SD = 25.1%). Characteristics of shoreline habitat explained much of the variation in the contribution of aquatic prey to F. subsericea and Tetragnathidae. Spider density was positively related to land-cover characteristics associated with urbanization and nearshore habitat. Shoreline habitat also was strongly related to the overall flux of Se (R2 = 0.58) and As (R2 = 0.51) to the tetragnathid spider assemblage, and Pb flux to spiders was higher in urban and agricultural reaches than in mixed reaches (F = 6.10, P = 0.025). F. subsericea density exhibited a positive relationship with urbanization (R2 = 0.83). As and Se flux to F. subsericea assemblages was positively related to urbanization (R2 = 0.70) as well as shoreline habitat, and Pb flux was higher in urban reaches than other land use types (F = 8.68, P = 0.017). For swallows, Hg concentrations were significantly higher at rural reaches than at urban reaches (t = -2.96, P = 0.003, df = 24), and Hg concentrations in swallows were positively related to (open full item for complete abstract)

Committee: Mazeika Sullivan PhD (Advisor); Stanley Gehrt PhD (Committee Member); Amanda Rodewald PhD (Committee Member) Subjects: Ecology; Environmental Science