Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 208-223). Also available on the World Wide Web.

This study compared the avian communities of treatment wetlands in South Florida called Stormwater Treatment Wetlands (STAs) to those in natural marshes and crop lands, and examined factors that influenced the size and structure of the avian communities within the STAs. The STAs contained a more abundant, rich and distinct avian community compared to reference land types. The STAs were dominated by wintering waterfowl, and therefore community patterns fluctuated more seasonally other land types. Within the STAs, density and richness in the fall and winter were much greater in the submerged aquatic vegetation than in the mixed emergent vegetation when waterfowl were present. The STAs maintain two vegetation treatments which enhanced their biodiversity value by supporting distinct avian communities with different migratory strategies This suggests the increase in treatment wetlands could partially offset the loss of natural wetlands, but avian communities in treatment wetlands are not surrogates for natural wetlands. / by Tyler J. Beck. / Thesis (M.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

No description available.

Depressions in the prairie pothole region (PPR) are commonly referred to as sloughs and were formed during the most recent glacial retreat, ~10-17 kyrs ago. They are hydrologically isolated, as they are not permanently connected by surface inflow or outflow channels. Extreme thunderstorms are common across the prairies and the hydrologic response of isolated wetlands to intense rainfall events is poorly understood. The purpose of this study was to compare the response of different landscape/ecological elements of a prairie wetland to snowmelt and extreme rainstorms. Comparisons were completed by investigating the spring snowmelts of 2005 and 2006 and the rainstorm event of June 17 - 18, 2005, in which 103 mm fell at the St. Denis National Wildlife Area (NWA) Saskatchewan, Canada (106°06'W, 52°02'N). The wetland was separated into five landscape positions, the pond center (PC), grassed edge (GE), tree ring (TR), convex upland (CXU), and concave upland (CVU). Comparison of the rainfall of June 17 18, 2005 with the spring snowmelts of 2005 and 2006 indicates that the hydrologic consequences of these different events are similar. Overland flow, substantial ponding in lowlands, and recharge of the groundwater occur in both cases. Analysis of this intense rainfall has provided evidence that common, intense rainstorms are hydrologically equivalent to the annual spring snowmelt, the major source of water for closed catchments in the PPR.

Depressions in the prairie pothole region (PPR) are commonly referred to as sloughs and were formed during the most recent glacial retreat, ~10-17 kyrs ago. They are hydrologically isolated, as they are not permanently connected by surface inflow or outflow channels. Extreme thunderstorms are common across the prairies and the hydrologic response of isolated wetlands to intense rainfall events is poorly understood. The purpose of this study was to compare the response of different landscape/ecological elements of a prairie wetland to snowmelt and extreme rainstorms. Comparisons were completed by investigating the spring snowmelts of 2005 and 2006 and the rainstorm event of June 17 - 18, 2005, in which 103 mm fell at the St. Denis National Wildlife Area (NWA) Saskatchewan, Canada (106°06'W, 52°02'N). The wetland was separated into five landscape positions, the pond center (PC), grassed edge (GE), tree ring (TR), convex upland (CXU), and concave upland (CVU). Comparison of the rainfall of June 17 18, 2005 with the spring snowmelts of 2005 and 2006 indicates that the hydrologic consequences of these different events are similar. Overland flow, substantial ponding in lowlands, and recharge of the groundwater occur in both cases. Analysis of this intense rainfall has provided evidence that common, intense rainstorms are hydrologically equivalent to the annual spring snowmelt, the major source of water for closed catchments in the PPR.

There is a growing interest to restore Bay of Fundy salt marshes diked for agriculture. Marshes recovering for several decades from storm-breached dikes can serve as analogues for restored marshes. In this study I examine factors driving sub-surface hydrology and vegetation at recovering and reference Bay of Fundy salt marshes. In Fundy marshes, groundwater at channel edges is insensitive to tidal flooding (<10 cm change in depth) and deep draw-downs (40-100 cm) occur. Sub-surface hydrology here differs from organogenic, microtidal marshes due to low saturated hydraulic conductivity, infrequent flooding of marsh interiors, and larger hydraulic gradients imposed at channel edges. By calculating marsh elevation at dike-breach and considering Spartina alterniflora's vertical range, it is apparent that salt marsh vegetation could establish when dikes breached. Multivariate analysis indicates that reference and restored/recovering sites should have similar sizes and tidal ranges. These criteria introduce problems as Fundy dikelands are more extensive than marshes not targeted for agriculture and tidal range increases exponentially up-Bay.

No description available.

The design of wetlands to replace those lost to development requires quantitative understanding of the wetland water budget in order to estimate the amount of water available to the wetland over time. Many methods exist to estimate each component of the wetland water budget. In this study, monthly values of the water budget components namely, precipitation, runoff, evapotranspiration, and groundwater seepage were calculated using a water budget model and compared to on-site field measurements for a wetland in Manassas, Prince William County, VA. The monthly precipitation estimated from a weather station 32.18 km from the site differed from the on-site values by as much as 2.9 times. Runoff estimates calculated by the Soil Conservation Service (SCS) method using antecedent moisture condition (AMC) II underpredicted runoff for every month by as high as 100 percent compared to the on-site measured runoff. The choice of AMC greatly affected the SCS runoff estimates. Runoff was the dominant water budget component at the Manassas wetland. The evapotranspiration (ET) estimates using the Thornthwaite method either over or underestimated ET when compared to ET calculated from diurnal cycles of the water table in the wetland. Groundwater seepage losses were calculated using Darcy's equation with an assumed hydraulic gradient of one, and with gradients measured with nested piezometers. Seepage losses at the Manassas wetland were negligible. Overall, the water budget model provided conservative estimates of the available water in the wetland during the 10-month period of observation. / Master of Science

The Great Dismal Swamp (GDS) is a forested peatland located in the Atlantic Coastal Plain. Once a mosaic of wetland communities, disturbances (e.g., timber harvesting and ditching) have resulted in altered hydrologic regime, homogenized forest communities, and increased peat subsidence. In response, hydrologic restoration and forest management aim to enhance community composition and function. To help inform these efforts, we investigated variability and drivers of forest communities by surveying vegetation composition and structure, hydrologic indicators, and soil properties at 79 monitoring plots across GDS. Data were augmented with modeled water levels and peat depths. Our results demonstrate red maple (Acer rubrum) dominance across GDS, which decreases tree density, richness, and diversity. However, hierarchical cluster analysis identified four community types: Gum (G), Maple-Gum (M-G), Sweetgum-Maple (SG-M), and Maple (M). These communities differed in tree composition and structure; differences in other growth forms (shrubs, herbaceous, and regeneration) were limited. Modeled water levels failed to explain vegetation differences, but community associations with soil properties suggest that communities exist along a hydrologic gradient. Specifically, the G community likely exists on wetter sites whereas SG-M communities occur at drier locations. Maple-dominated communities (M and M-G; 78% of plots) likely occur across broader hydrologic gradients, explaining their dominance. However, more characterization of hydrology (i.e., time-varying water levels and soil moisture) and other drivers (e.g., site history and soil hydraulics) is needed to further explain community variation. As such, we propose future strategies for long-term monitoring to inform ongoing hydrologic restoration and forest management efforts. / Master of Science

The feasibility of predicting porewater salinity based on calibrated surface electromagnetic methods is discussed in a coastal wetland on the southern banks of Tampa Bay in West-Central Florida. This study utilizes a new method to float commercial land based electromagnetic (EM) instruments in shallow marine waters of less than 1.5 meters. The floating EM-31 (Geonics, Ltd.) effectively sensed the magnitude and lateral extent of high and low salinity porewaters within mangrove lined ditches and ponds. Resistivity and EM geophysical methods are merged with direct sampling data to calibrate layers in electromagnetic models to infer shallow (<30m) groundwater salinity patterns. Initial marine resistivity surveys are necessary to discriminate between equivalent EM model solutions for seafloor conductivities beneath shallow (0.1-1.5m) marine (~30 ppt) waters. Using formation factors computed from nearby resistivity surveys, porewater conductivity predictions based on surface EM-31 and EM-34 measurements are successful at distinguishing overall porewater salinity trends. At the Tampa Bay study site, the most distinctive terrain conductivity anomalies are associated with mangroves bordering marine waters. Highly elevated porewater conductivities are found within 5m of the mangrove trunks, falling sharply off within 10m, presumably due to saltwater exclusion by mangrove roots. Modeling indicates the shallow water EM-31 measurements probably lack the resolution necessary to image more subtle porewater conductivity variations, such as those expected in association with diffuse submarine groundwater discharge. However, the technique has potential application for locating high contrast zones of freshwater discharge and other salinity anomalies in shallow and nearshore areas not accessible to conventional marine resistivity or land-based arrays, and hence may be useful for interdisciplinary studies of coastal wetland ecosystems.