1. Large rivers in the central United States experience a variety of ecological interactions. Both short- and long-term temporal changes affect both fish and zooplankton communities in rivers. Variation in diel patterns of predation could affect differences of behavior in prey. Long term temporal changes across seasons can lead to different areas of rivers providing growth or costing energy. Spatial changes also affect habitat quality and behaviors of the aquatic organisms within large rivers. Spatial variation can be dynamic and occur between longitudinally connected habitats or vary through different sections of the reach and can also change seasonally. 2. Invasive species have major economic and ecological impacts. In aquatic ecosystems, plankton are the base of the food web and a planktivore invader can cause major ecological disruptions. The Wabash River is a large free flowing river with a variable hydrology, which causes dramatic changes in habitat availability through time. Therefore, habitat usage, quality, and availability may differ for native and invasive species through time. The objectives of this study were to assess how habitat quality changes in a large, flashy, free-flowing river over time, and to compare the quantity and overlap of quality macrohabitat for invasive and native fish. Growth rate potential (GRP) was used to quantify habitat quality for Silver Carp (Hypophthalmichthys molitrix; invasive) and Gizzard Shad (Dorosoma cepedianum; native). To calculate GRP, bioenergetic models were used with monthly observations of food abundance (zooplankton, phytoplankton, and detritus), water temperature, dissolved oxygen, and water velocity of various habitat types from the Wabash River’s confluence with the Ohio River upstream to Terre Haute, Indiana, approximately 215 river miles. Negative GRP for both Silver Carp and Gizzard Shad occurred during spring and most of summer. However, in the fall, the majority of the river had a positive GRP for both species. Reduced flows and increases in food abundance were the cause for the switch from negative to positive GRP. There was a high degree of spatial overlap in positive GRP areas between Silver Carp and Gizzard Shad, suggesting that there is a high degree of competition. Acoustically tagged Silver Carp selected for areas predicted to have a positive GRP from the model presented in the study. This model showed that regulation of flows in hydrologically altered systems could potentially lower the impact of Silver Carp in those systems. With Silver Carp selecting for predicted habitats, a bioenergetics model can be used to inform commercial fishers where to focus effort to maximize catch.3. Temporal changes in rivers tend to be quantified at broad seasonal scales. However, river conditions including water flow, water temperature, dissolved oxygen, and availability of zooplankton prey may change daily. In large rivers, these conditions may change in a diel fashion between backwater and main channel habitats. To assess diel changes in the Illinois River, zooplankton, paired with mobile hydroacoustic surveys for fish were sampled from three main channel and three off-channel sites in the LaGrange reach every four hours in a twenty-four-hour period at different depths between October 22 and 26, 2018. Water depth, water temperature, water velocity, and fish (planktivore and nonplanktivore) densities were quantified during each sampling time. Water temperature and water velocity differed between the two habitat types. Water temperature was higher and water velocity was lower in the off-channel. Water temperature was colder in the morning in both the main channel and off-channel. Water velocity did not change throughout the day. The majority of the zooplankton community was comprised of rotifers which were less mobile than larger taxa and did not migrate. When evaluating the more mobile, large body zooplankton, time and depth affected copepod density in off-channel environments, where the deeper depth had a higher copepod density than the shallower depth. In contrast, only time of day affected off-channel cladoceran density, where densities increased at night. Fish did not exhibit diel patterns and the off-channel habitat had a higher density. The most likely mechanism behind the diel movements of the large bodied zooplankton was predation by planktivorous fish. The present study suggests that connections to the off-channel habitats in large rivers will promote quality habitat for both zooplankton and fish.

My research findings have implications for applied ecology and restoration policy in Ontario. I my discussions, and final chapter, I offer suggestions for the practitioner. / Restoration practitioners are tasked with recreating ecosystems using appropriate plant material that will provide ecological goods and services. However, best-practices for this type of intervention are not well developed for the southern Ontario landscape. Therefore, we evaluated approaches from four different aspects of seed-based restoration. First, we quantified the impact of seeding rate and application method on the success of grassland recreation. We also measured the impact of this restoration on the local bee community. Next, we compared a suite of native and nearly native wetland plants for their potential to prevent the establishment of invasive Phragmites australis. We measured the effect of competition on Phragmites across soil moisture and salinity gradients. Finally, we sought evidence for local specialization in a grassland forb, Monarda fistulosa, that would warrant policies to prevent the transfer of grassland seed for revegetation. In re-creating grasslands from seed, we found an interaction between seeding rate and application method. At a high rate, both methods had the same outcome, but at a low rate, a two-phase application method produced better results than a single-phase method. However, we also found that a single-phase method produced target plant cover with a higher floristic quality index after three years. In one study region, restored sites supported a greater bee abundance than un-restored sites, but bee abundance did not change after restoration in all regions. Of all the native species tested, Phragmites was supressed most by Bidens frondosa, a fast growing annual. We also found evidence that Phragmites may be less competitive at low soil moisture, and more competitive at high soil salinity. Finally, we found no evidence of local adaptation in M. fistulosa at the watershed scale; instead, we see independent effects of site and seed origin. This implies that current site conditions may not be favorable to the offspring of relic populations, and that local genotypes may not always be the best choice for restoration. / Dissertation / Doctor of Philosophy (PhD) / I tested four approaches to seed-based restoration. First I found that a two-phase hydroseeding method can be more efficient at a low seeding rate. Second, I found that the response of the bee community to local restoration may depend on broader landscape factors. Next, I found that Monarda fistulosa is not locally adapted at a watershed scale. Finally, I found that native annuals may be best at resisting invasion from Phragmites, and that some native species actually can facilitate invasion.

The coastal plain of the southeastern United States is historically wet pine savannahs, prairie, and hardwoods. However, many exotic species have invaded this area and become a serious threat to native forest ecosystems. Among those exotic species, Chinese tallow (Triadica sebifera) has become one of the most pervasive tree species in the southern coastal states, including Alabama, Mississippi, Louisiana, and Texas. Therefore, to understand the distribution and spread mechanisms has become important in the management and control of Chinese tallow in the southeastern United States. In this research, distribution and spread mechanisms of Chinese tallow were studied at multiple spatial scales, including regional, landscape, and stand. Effects of predisposing (community and landscape features) and inciting (natural disturbance and human activities) factors on Chinese tallow invasion had been evaluated by using a comprehensive data set (field data and Forest Inventory and Analysis data) and spatial statistical models. Results indicated that propagule pressure of Chinese tallow is the main force driving tallow dispersal at different spatial scales. Predisposing and inciting factors such as natural disturbances, anthropogenic disturbances, forest types, forestland ownerships, and landscape features are significantly related to the spread of Chinese tallow at different spatial scales. Regionally, Chinese tallow initially started to spread from southern Texas and Louisiana to the northeastern portion of the Gulf Coastal area. At landscape and stand scales, Chinese tallow has commonly invaded from edges of forests and habitats such as roads and firebreaks. Inciting factors, including hurricanes/storms and prescribed fires, could accelerate the spread of Chinese tallow at different spatial scales, especially in habitats that have previously been invaded. Compared to pine forests, it is easier for Chinese tallow to invade bottomland hardwood forests at the regional scale. The efficient dispersal distance of tallow seeds is 250-300 m, and its distribution is affected by the microtopography in forest stands. Management of Chinese tallow invasion should be focused at selected scales, such as landscape and stand levels, because of variations of site conditions.

Aquatic vegetation plays an important role in the ecological interactions and processes within a water body. However, the presence of the invasive exotic aquatic plant species, waterhyacinth [Eichhornia crassipes (Mart.) Solms], negatively affects those interactions as well as interfering with water use for recreation and navigation. An implemented management plan for waterhyacinth control relies on the use of herbicides. Efficacy is commonly assessed using visual injury and control ratings as well as estimating biomass. The problem is that those approaches are labor intensive only assessing single points throughout the entire water body. Therefore, technology like remote sensing, which is the focus of this research, is recommended as an additional tool to assess implemented management plans. Studies were conducted in a mesocosm research facility to evaluate the relationship between simulated spectral bands 3, 4, 5, and 7 Landsat 5 TM and waterhyacinth treated with the herbicides imazapyr and glyphosate. Results indicate that injury is better detected and predicted with band 4 and that relationship is negative when either herbicide was used. However, prediction is better when plants have developed sufficient injury to influence the spectral response of band 4. In the second study, the biomass of waterhyacinth was estimated using the Normalized Difference Vegetation Index (NDVI) using simulated data from Landsat 5 TM. This study was conducted over natural populations of waterhyacinth in Lakes Columbus and Aberdeen, MS over two growing seasons. Results indicate that the use of NDVI alone is a weak predictor of biomass; however, its combination with morphometric parameters like leaf area index enhanced predictive capabilities.In order to assess field herbicide treatments for waterhyacinth control and its consequent impact on native aquatic vegetation, lake-wide surveys were performed in Lake Columbus, MS using a point-intercept method. The herbicide assessed was 2,4-D which was applied aerially and by boats. Point-intercept surveys in a 400 by 400 grid of points aided with global positioning system (GPS) were performed before and after herbicide treatments. Obtained results indicate that the frequency of occurrence of waterhyacinth significantly decreased after herbicide treatments which consequently led to the reestablishment of native aquatic vegetation on the system.

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