Headwater catchments play a large role in the storage and release of water and chemical constituents, thereby influencing downstream flows and water quality. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variation by using high temporal resolution, in situ sensors. However, despite these new technologies, there have been limited studies on installation approaches and their effects on sensor measurements. Accurate in situ monitoring is particularly important to capture catchment disturbance effects that may be highly dynamic over time (e.g., following storms) or limited in duration. For example, prescribed fire is a commonly applied forest management tool, but there remain questions regarding how this disturbance affects catchment soils and resultant stream water chemistry. Effective assessment of prescribed fire thus requires coupled monitoring of both soil properties and water chemistry. In this thesis, I addressed two linked objectives: i) assess the effects of commonly used protective housings on in situ sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I compared four different housing types (mesh, screen, holes, and open) using in situ specific conductance measurements over time and from salt tracer injections for discharge estimates. This study demonstrated substantial effects from some of the housing types evaluated, where flow resistance reduced water exchange between stream water and water in contact with the sensor. From these findings, I suggest that in situ water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I assessed prescribed fire effects on soil properties (particle size, aggregate stability, and chemistry), stream discharge, and fine-scale water chemistry dynamics. Findings demonstrated some significant differences following fire in soil properties (e.g., overall decrease in aggregate stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of DOC, turbidity, and nitrate) and discharge (increases in stage and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether the minor level of disturbance observed in this study results in any negative environmental impacts. / Master of Science / Headwater catchments (where precipitation first becomes streamflow) provide important aquatic habitat and regulate downstream water flows and chemistry. Recent advances in water quality monitoring technologies have created an opportunity to better assess water chemistry variability by using high frequency, submerged water quality sensors. However, these new technologies present new, unique challenges, such as measurement errors that may be induced by different installation methodologies. Accurate measurements are particularly important to evaluate how changes in catchment conditions (e.g., soils, vegetation) impact local and downstream water quality. For example, prescribed fire is a commonly used forest management tool, but questions remain about how it affects catchment soils and headwater stream chemistry. Consequently, understanding the effects of this and other catchment disturbances requires coupled monitoring of both soil properties and water quality. In this thesis, I addressed two objectives: i) assess the effects of commonly used protective housings on water quality sensor measurements (Chapter 2) and ii) evaluate prescribed burn effects in a southwestern Virginia, USA headwater catchment (Chapter 3). In Chapter 2, I demonstrated substantial effects from some of the housings evaluated and suggest that water quality sensors should be deployed in housing types with large openings perpendicular to flow. In Chapter 3, I demonstrated some significant effects of prescribed fire on soil properties (e.g. overall decrease in soil stability, general decreases in total carbon and nitrogen of mineral soils), water quality (e.g., increased levels of dissolved organic matter, turbidity, and nitrate) and flow (increases in stream water levels and flow). While these changes were statistically significant, differences in parameters before and after fire were generally small. Future work should examine if these effects persist through time, and whether this minor level of disturbance causes any negative environmental impacts.

Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape. / Master of Science

Fire occurrence was widespread in the central Appalachians pre-European settlement due to Native American ignition and occasional lightning strikes, and continued through European settlement. During this time, low to mixed severity burns supported a suite of ecological communities that were fire adapted. In the mid-20th century, the frequency and intensity of fire decreased regionally, resulting in profound forest composition shifts. Land managers now are prioritizing prescribed fire as a restoration tool in current and transitioning fire dependent communities. However, it is unclear how the re-introduction of fire will affect bat community assemblages, particularly after the severe White-nose Syndrome related population declines of many cave-hibernating bat species. To address this concern we used acoustic detectors to sample bat activity levels in burned and unburned environments to examine habitat and temporal effects of fire on bat species in a repeatedly burned landscape. We found evidence for weak positive fire effects on the northern long-eared bat, Indiana bat, little brown bat, big brown bat/silver-haired bat group, high frequency phonic group, and total bat activity. Temporal effects of fire were only apparent for the big brown bat, where we observed a negative relationship between activity and time since fire. Additionally, historic wildfires may offer a suitable surrogate to assess long-term burn impacts on bats, which in turn can be used to better inform bat and prescribed fire relationships. To examine effects of historic fire on bats, we assessed bat presence using acoustic detections at 16 paired burned and unburned forest stands in Shenandoah National Park. Overall, we found few or mostly equivocal relationships of bat occupancy across species relative to burn condition or time since fire at SNP, indicating there is little evidence to support the concept that fire has a significant ecological effect on bats in this portion of the central Appalachians. Riparian areas are particularly important for bats, and serve as foraging and drinking areas, roost sites, and travel corridors. Because fire impacts dry upland and mesic riparian areas differently, is possible that fire will impact bats differently in burned and riparian habitats. To examine fire effects on bats in riparian and upland habitats, we used paired sampling to monitor bat activity in burned, unburned, riparian, and non-riparian areas. Burn and riparian variables had empirical support to explain activity of all bat species. However, coefficients for these species were small and confidence intervals overlapped zero indicating that differences between habitat configurations were marginal. Our results suggest bats have somewhat species-specific responses to fire that differ between upland and riparian habitats, but that large landscape level prescribed fire has a slightly positive to neutral impact on all bats species identified in at our study site post-fire suppression. / Master of Science

Rosebay rhododendron (Rhododendron maximum L.) is an ericaceous shrub commonly found in riparian areas of the Appalachian Mountains. After more than a century of fire exclusion in the U.S., the distribution of R. maximum and its dominance of forest understories have increased. Rhododendron expansion has caused a decline in overstory regeneration and the potential for dangerous fuel conditions around suburban structures near the wildland-urban interface. The purpose of this study was to determine the effects of seven silvicultural treatments on both the fuel loading within an R. maximum thicket and the control of R. maximum as a forest weed. The final objective of the project was to determine the cost effectiveness of each implemented treatment. Due primarily to moisture conditions, a single prescribed burn was relatively ineffective in reducing fuel loading and causing R. maximum mortality. Mechanical cutting caused a drastic shift in the size-class distribution of R. maximum but resulted in heavy sprouting and increased fuel loading. Herbicide application did not reduce or increase fuel loading and was important in R. maximum control only when combined with other treatments. The prescribed burning treatment was the least expensive individual treatment while mechanical cutting was the most expensive. Combination treatments showed increased effectiveness in controlling R. maximum but were more expensive than the individual treatments. The results of the treatments from this study will be used over the long term to demonstrate to land managers the effects of vegetation control on rhododendron. / Master of Science

Fire may alter both aquatic and terrestrial habitat used by all amphibian life stages, yet, our knowledge of its effects on amphibians is primarily limited to adult responses. I present an integrated approach to test the response of Cope’s Gray Treefrog (Hyla chrysoscelis) to fire by examining responses in tadpole performance and survivorship, adult abundance, and oviposition. Tadpoles raised with burned leaf litter had similar survival, but total mass and total length were 440% and 170% greater, respectively, for tadpoles raised in unburned litter. I assessed terrestrial and aquatic oviposition cues by embedding burned and unburned litter treatments within burned and unburned terrestrial plots. Oviposition was an order of magnitude higher in unburned plots, regardless of the litter treatment. This difference was not statistically significant or driven by adult abundance. My results indicate the need to explore the dynamic effects forest management practices can have on amphibians across life stages.

This study quantifies the changes in vegetation composition and structure of a fire-excluded Pinus palustris (longleaf pine) wetland savanna restoration site in southeastern in comparison to a proximate contemporary reference site. The restoration site was invaded by hardwood species and off-site pines, and never underwent extensive soil disturbance. The restoration treatments involved logging across portions of the site and the reintroduction of fire across the entire site. All species present in 10m2 quadrats were recorded prior to treatment and throughout the 17 year study at reference and treatment sites. The community composition of both logged and unlogged sites converged over time, and became more similar to the reference site. We conclude that logging of off-site pine coupled with the reintroduction of frequent fires can be effective in restoring ground cover in remnant longleaf pine savannas withdisturbance.

The successful completion of this work is dedicated first to my grandparents for having always shown their unwavering love and encouragement in my journeys (most of which they kindly and politely only pretended to understand) and for having also served as life-long role models who upheld an unparalleled work ethic. To many whom I consider to be my chosen family, especially Ann Williams and Brittany Sears, who kept me laughing, but more importantly, kept my crazy train from derailing during these tumultuous years. To Wayne Price and Tom Jackman, who fostered the success of my career and are the epitome of patience and kindness. To DeAngelis, for the many hours of laughter, conversations, and adventuresome treks that further kindled my knowledge, love, and respect for Florida’s ecology. To family in Alabama who have either helped shape my brazen character or made this education possible. To Taego, the one to whom I am bound through so many of the stories that begin with, “Remember when…?” and who is often so kind and thoughtful though he still holds tightly to the stereotype of the selfish youngest sibling. Finally, to Fen for being my smiling, bright blue-eyed, spunky kid who has been on this journey with me from the get-go; for keeping me from getting too big for my britches; for your intrinsic fire that burns for equality, fairness, and friendship; and for inspiring me to be the best example of a mother that I can possibly be.

In the southern Great Plains, the encroachment of grassland ecosystems by mesquite (Prosopis glandulosa), is widespread, and prescribed fire is commonly used in its control. Despite this, substantial quantitative information concerning their influences on the community composition, functional dynamics, and soil organic carbon (SOC) storage potential of grassland ecosystems is lacking. The objectives of this study were to: a) quantify the effects of seasonal prescribed fire treatments and mesquite encroachment on aboveground net primary productivity (ANPP) and herbaceous community composition; b) characterize SOC pool sizes, turnover, and storage potential relative to vegetation type and fire treatment; c) evaluate the structure and diversity of soil microbial communities relative to vegetation type; and d) characterize the functional diversity of these same microbes using the GeoChip functional gene microarray. Repeated winter and summer fires led to increased ANPP rates (average, 434 and 313 g m-2 y-1, respectively), relative to unburned controls (average, 238 g m-2 y-1), altered herbaceous community composition, and increased the storage of resistant forms of SOC, but did not affect overall SOC storage. Herbaceous ANPP rates did not differ significantly as a result of mesquite encroachment, but herbaceous community composition and SOC storage did. Mesquite soils contained significantly more total, slow-turnover, and resistant forms of SOC than those that occurred beneath C3 or C4 grasses. Similarity among the soil bacterial and fungal communities associated with the major vegetation types in this system was low to moderate. Significant differences were detected among soil fungi, with the mesquite-associated fungi harboring significant differences in community structure relative to the fungal communities associated with each of the other vegetation types examined. Despite this result, few significant differences were detected with respect to the functional diversity of these communities, suggesting either a high degree of functional redundancy, or that the functional differences harbored by these communities are beyond the scope of the GeoChip. The results of this study demonstrate that both fire and mesquite encroachment have the potential to alter ecosystem components and processes significantly, providing new insight regarding the effects of these widespread land use and land cover changes on ecosystem structure and function.

Exotic species are a great concern because of the possibility of negative effects once they become established. The exotic cactus moth, Cactoblastis cactorum has a reputation for being detrimental to Opuntia populations throughout Florida and the southeastern United States. Multiple projects are currently underway to attempt to contain and eradicate this species before it can migrate to the Opuntia-rich desert southwest and the agricultural Opuntia fields in the Mexican highlands. These projects have been undertaken without previous studies to determine what negative effects, if any, the moth is having on the common native Opuntia species. This is understandable; since it was earlier suggested that C. cactorum was doing great harm to rare and endangered species in the Florida Keys (Stiling et al. 2004). This study looks at the effects of the native moth borer, Melitara prodenialis and the exotic invader, Cactoblastis cactorum on two common Opuntia spp. within central Flo rida. Throughout the duration of this study, the coastal plants were subjected to damage solely by C. cactorum and the inland plants by M. prodenialis. The amount of moth damage was compared between three inland and three coastal sites, as well as between plants subjected to prescribed fire and those that were not within these sites. Plant mortality was determined for both the sites and burn treatments. The number of eggsticks was also compared between inland and coastal sites and burned and unburned treatments. The results of this study show that although there is a significant difference in plant mortality between inland and coastal sites (higher mortality was shown at inland locations), there is no difference in moth damage at these sites. This suggests that the exotic moth is doing similar or less damage to the cactus than is the native moth. The number of eggsticks was also greater at coastal sites. This indicates that although the exotic moth is more prolific than the native, it is still unable to cause higher cactus mortality rates. None of the data was significant between burned and unburned treatments, indicating that prescribed fire does not have any effect, negative or positive on the Opuntia.

No description available.