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<p>Aquatic vegetation in the pristine coastal marshes of eastern Georgian Bay (GB) provides critical spawning and foraging habitat for fish species, with complex habitat supporting the greatest diversity. These wetlands are threatened by a changing water level regime and forecasted lower water levels. To monitor and conserve these wetlands, we must understand how they function and respond to this stressor. The overall goals of this thesis are to determine the impact of declining water levels on both wetland fish habitat and the fish community as well as identify the spatial scale of habitat utilization by fishes.</p> <p>We first delineate all coastal wetlands in eastern GB, identifying 3771 wetlands that provide habitat for Great Lakes fishes. Using satellite imagery, we develop an object-based classification method to classify four types of wetland vegetation. Since submerged aquatic vegetation (SAV) is not visible from satellite imagery in GB, we develop a model to predict potential area of this important habitat. The model suggests that the response of SAV to declining water levels depends on wetland geomorphology, but generally, the area of SAV decreases. To assess the response of fish habitat coverage and structure to sustained low-water levels, we classify vegetation in images collected in 2002 and 2008. The result is increasingly homogeneous habitat, a net loss of fish habitat and a decrease in fish species richness. Finally, mark-recapture and radio-tracking are used to evaluate fish movement among closely situated wetlands. Results suggest that the current distance used to group and protect small wetlands provincially (750 m), likely protects most resident fish species, but does not cover movement patterns of a top predator. This research will advance our scientific understanding of freshwater coastal ecosystems and aid in the creation of conservation strategies to mitigate future threats from declining water levels.</p> / Doctor of Philosophy (PhD)

Wet site timber harvesting often results in rutted and/or compacted soils. These impacts damage inherent site and soil properties and can reduce subsequent pine seedling survival and growth. Site preparation treatments such as bedding, disking, and fertilization are often employed on harvested sites to mitigate these impacts; however, their effectiveness has not been fully documented. Moreover, a distinction between rutting and compaction has not been made in previous research. This study’s objectives were to quantify the effects of rutting and compaction on site and soil properties and pine seedling growth and survival, and to quantify the effectiveness of bedding, disking, and fertilization in mitigating these impacts. Six wet pine flats were salvage logged following Hurricane Hugo in the fall of 1989. High soil moisture conditions during the salvage operations resulted in compaction and rutting damage. Two studies were established to quantify the effects of trafficking on the functions and productivity of wetland sites. One study addressed soil compaction while the other addressed soil rutting. Each study consisted of three sites, each containing four trafficked and four untrafficked plots. Four site preparation treatments, one on each disturbance plot, were installed in the fall of 1991. The four treatments were 1) no treatment, 2) bedding, 3) disking, .and 4) disking and bedding. The treatment plots were further split with half of each plot receiving 227 kilograms per hectare of 10-10-10 fertilizer. Genetically improved seedlings were hand-planted on the treatment plots in February, 1992. The site preparation treatments did not completely ameliorate compaction or rutting effects on pine seedling growth and survival. Rutting reduced pine seedling second-year height growth, total volume, and survival by 43, 90, and 9 percent, respectively. Compaction reduced second-year height growth by 31 percent and seedling survival by 14.5 percent. Bedding resulted in 35 and 106 percent greater second-year height growths and 117 and 421 percent greater seedling volumes than disking on the rutted and compacted sites, respectively. Phosphorous fertilization had an additive effect to the site preparation treatments and increased pine seedling height growth by 54 and 65 percent and seedling volume by 125 and 155 percent on the rutted and compacted sites, respectively. The factors that affected pine seedling growth and survival were water supply and movement and phosphorous supply. Management implications for wetland sites suggested by this study are as follows: 1) avoid rutting and compaction when possible, 2) schedule wet-site harvesting during the driest periods of the year, 3) use specialized wet-site harvesting equipment when needed, and 4) use bedding and fertilization for site preparation. / Master of Science

Due to the paucity of long-term harvest impact data, the primary goals of this study were to quantify the long-term effects of different harvest disturbances twenty-four years after harvest on two major wetland functions: stand productivity and C storage. This study evaluated the effects of three harvest types that were originally applied in 1986 to a tupelo (Nyssa aquatic)-cypress (Taxodium distichum) forested wetland in the Mobile-Tensaw River Delta of southwestern Alabama. Treatments were: 1. Helicopter harvest (HELI), 2. Skidder simulation where 50% of the site was rutted to a depth of 30 cm (SKID), and 3. Helicopter harvest followed by glyphosate herbicide removal of all sprouts and seedbank regeneration for two years following harvest (GLYPH). An adjacent mature stand (94 years old) within the same original composition represented mature forest or pre-harvest reference conditions (REF). Above- and belowground plant biomass, belowground woody debris, soil C, and soil CO2 efflux were measured. Twenty-four years after treatments were applied, forest C levels were higher in SKID treatments (206.1 Mg C ha-1) than in HELI treatments (168.7 Mg C ha-1). GLYPH treatments are holding less (144.2 Mg C ha-1) while REF areas hold 332.6 Mg C ha-1. SKID treatments are also holding the most biomass of all treatments with 243.2 Mg ha-1 of overstory biomass. Ecosystem C and biomass patterns indicate HELI and SKID are becoming similar to the original site conditions represented by the REF areas. The resiliency of these highly disturbed stands are explained by the frequent inputs of non-compacted sediments, presence of species well adapted to very poorly drained and aerated conditions, high rates of coppice regeneration, shrink-swell ameliorative properties of the soil and creation of more complex microtopography within SKID treatments. / Master of Science

Floating treatment wetlands (FTWs) are an innovative best management practice that can enhance the performance of traditional retention ponds by increasing removal of the nutrients nitrogen (N) and phosphorous (P). FTWs consist of floating rafts on which wetland plants are planted, allowing the roots to be submerged below the water surface while the shoots remain above. A growing body of research has documented FTW performance with regard to urban runoff treatment, however evaluation of FTW effectiveness for treatment of agricultural runoff has received less attention. Due to high fertilization and irrigation rates, commercial nursery runoff contains much higher concentrations of N and P than runoff from urban areas. We conducted this study over two growing seasons (2015 and 2016) to assess the effectiveness of FTWs for use in commercial nursery retention ponds. In the first study we used two different nutrient concentrations, one to simulate nursery runoff (17.1 mg∙L-1 TN and 2.61 mg∙L-1 TP) and one to simulate concentrations that fall between urban and nursery runoff (5.22 mg∙L-1 TN and 0.52 mg∙L-1 TP). Four treatments were used: 1) Pontederia cordata planted in cups supported by a Beemat, 2) Juncus effusus planted in cups supported by a Beemat, 3) a Beemat with no plants, and 4) no treatment (open-water). Performance was evaluated based on a 7-day hydraulic retention time (HRT). Pontederia cordata removed between 90.3% and 92.4% of total phosphorus (TP) and 84.3% and 88.9% total nitrogen (TN), depending on initial loads. These reductions were significantly more than other treatments at both high and low nutrient loading rates. Juncus effusus performed better than the control treatments for TP removal at low nutrient concentrations, but did not perform any better than the control at higher nutrient loads. In the second study, conducted in 2016, we evaluated different plant species over two 8-week trials using simulated nursery runoff. We used five monoculture FTWs with the following species: Agrostis alba, Canna ×generalis, Carex stricta, Iris ensata, and Panicum virgatum. Additionally, two treatments were created from mixed species plantings and the final treatment consisted of an open water control mesocosm. Nutrient removal performance was evaluated over a 7-day HRT. P removal (phosphate-P) by FTW treatments ranged from 26.1% to 64.7% for trial 1 and 26.8% to 63.2% for trial 2. Trial 1 N removal (sum of ammonium-N, nitrate-N, and nitrite-N) efficiencies ranged from 38.9% to 82.4%, and trial 2 ranged from 12.9% to 59.6%. Panicum virgatum removed significantly more N and P than the control and any other FTW treatment in the second study. Both studies indicated, depending upon plant species, that FTWs can effectively remove nitrogen and phosphorous from urban and commercial nursery retention ponds. / Master of Science / Floating treatment wetlands (FTWs) are used to enhance the nutrient removal performance of stormwater retention ponds. FTWs consist of a buoyant raft on which wetland plants are planted, allowing the shoots to extend above the water surface while the roots stay submerged. The purpose of this research was to evaluate FTW nutrient removal performance in a commercial nursery environment where runoff has much higher concentrations of nitrogen and phosphorous than urban stormwater. The study spanned across two growing seasons (2015 and 2016), during which, different plant species and nutrient concentrations where evaluated. The first study evaluated Pontederia cordata and Juncus effuses as well as two control treatments at a high nutrient concentration and a low nutrient concentration. The Pontederia cordata performed better than the other treatments at both the high and low initial nutrient concentrations. In the second study, the following species were evaluated using a combination of mixed and monoculture plantings: Agrostis alba, Canna ×generalis, Carex stricta, Iris ensata, and Panicum virgatum. Panicum virgatum removed significantly more nitrogen and phosphorous than any other FTW treatment in the second study. Both studies indicated that FTWs can be effective technologies for nutrient removal from urban and commercial nursery retention ponds.

Harvesting of forested wetlands in the Atlantic and Gulf lower coastal plains has the potential to cause intense site disturbance. Often, as a result of poor pre-harvest planning, silvicultural activities are performed on wetland soils highly susceptible to rutting and puddling. Potential decreases in pine productivity have been connected with increased soil strength and decreased aeration that are commonly remnants of site disturbances associated with wet-weather harvesting. A simple and economical rating system is needed to identify soils susceptible to disturbance by various types of equipment. The use of such a system could lower the impact on wetland soils and lower the cost of extensive site preparation methods. Logging efficiency and operational productivity could also be increased by identifying equipment types compatible with site conditions. The purpose of this study was to characterize and model soil strength as a function of soil physical properties and site characteristics. The soil strength model was subsequently used to develop a trafficability hazard index. Forested wetland sites in the South Carolina coastal plain were characterized to develop the trafficability hazard index. The study site consisted of three blocks located on poorly drained loblolly pine plantations. Five sequences of measurements were taken consisting of soil moisture, water table depth, and soil strength. The five sequences of measurements were taken over a wide range of soil moisture contents and water table depths to characterize the effects on soil strength. Bulk density, porosity, texture, organic matter, and hydraulic conductivity were also determined to characterize the blocks and identify effects on soil strength. Evaluating the effects of these properties on soil strength identified two relatively easily determined soil properties that could be used for the trafficability index. Volumetric moisture content and penetration resistance of the A horizon were used due to their relationships with trafficability and ease of determination. Estimates of pressure applied to the soil by harvesting equipment were used to find the limits of the sandy loam A horizon to support various types of equipment. Equipment pressures were compared to soil penetration resistance pressures estimated by soil moisture. The trafficability hazard index presented used general ground pressures for various harvesting equipment, but use of specific equipment pressures would provide the best results. Using the trafficability hazard index, sites with less than optimal conditions for traffic can be avoided or special harvesting equipment can be identified to limit site disturbance. / Master of Science

Many soils are marginally suited for installation of on-site wastewater disposal systems. With soil limitations, additional wastewater treatment prior to soil application may allow for a reduction in soil depth. Undisturbed 20-cm-diameter soil columns (fine loamy, mixed, mesic Typic Hapludult), in a factorial arrangement between depth of soil (15, 30, and 45 cm) and type of effluent (septic tank, constructed wetlands, and recirculating sand filter), were used in this study. Effluent (670 cm³/d) was applied 6 times daily. Additional treatment of septic tank effluent by a constructed wetland and a recirculating sand filter resulted in 30 and 70% higher average soil infiltration rates, 92 and 96% reduction in fecal coliforms, 34 and 44% reduction in total nitrogen, and a 60 and 94% reduction in BOD₅, respectively. Fecal coliforms were present only in soil leachate from the 15 and 30 cm soil depths receiving septic tank effluent and the 15 cm depth that received constructed wetland effluent. Average soil leachate NO₃⁻-N concentrations were 19, 10 and 14 mg/L from soil columns receiving septic tank, constructed wetland, and recirculating sand filter effluents, respectively. Soil leachate contained <5 mg/L TKN and 1.8 mg/L NH4⁺-N. Total nitrogen losses were 55, 73, and 66 for the septic tank, constructed wetland, and recirculating sand filter treatments, respectively. BOD₅ averaged less than 4 mg/L in the soil column leachate, despite a 10 fold difference among influent types. In comparing the 1993 and 1994 growing seasons, average plant tissue dry weight, percent nitrogen, and percent phosphorus were greater during the 1994 growing season. The results from this study indicate that additional treatment of septic tank effluent can be substituted for soil depth. / Master of Science