Prescribed fire has become a management tool utilized to restore or maintain the ecology of the mixed hardwoods ecosystem in the Ozark hills of southwestern Illinois. One effect of prescribed burning is consumption of fuel beds, including the litter layer that protects soil from erosion. Amount of sediment loss after prescribed burning in the steep topography of the Ozark hills is unknown. Erosion after prescribed burning could lead to increased soil loss and possibly stream sedimentation (Bladon etal., 2014). The objective of this research was to quantify the amount of sediment transport occurring on a watershed scale. Sediment yields were measured from five paired watersheds located in Trail of Tears State Forest in Union County, IL, USA from April 2009 into 2010. This location was selected because of the highly erodible loess soils and steeps slopes which present the highest probability of sediment transport following a prescribed burn treatment. One of the paired watersheds was randomly assigned as the control and the other assigned as the treatment. The treatment was a prescribed burn applied at standard burn prescription levels. Sediment loads were determined by collecting samples from a known volume of overland flow held in storage tanks below each watershed after rain events which produced runoff. The prescribed burn treatment significantly reduced the litter depth with 12.6%–31.5% litter remaining in the prescribed burn treatment watersheds. When data were combined across all watersheds, no significant differences were obtained between burn treatment and control watershed for total suspended solids and sediment concentrations or loads. The annual sediment losses varied between 1.41 to 90.54 kg·ha-1·year-1 in the four prescribed burn watersheds and 0.81 to 2.54 kg·ha-1·year-1 in the four control watersheds. Prescribed burn watershed 7 showed an average depth of soil loss of 4.2 mm, whereas control watershed 8 showed an average accumulation of sediments (9.9 mm), possibly due to steeper slopes. Prescribed burning did not cause a significant increase in soil erosion and sediment loss and can be considered acceptable in managing mixed hardwood forests of Ozark uplands and the Shawnee Hills physiographic regions of southern Illinois.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Charles J. Barden / Recurrent, landscape-level fires played an integral part in the development and persistence of eastern oak (Quercus spp.) forests of the United States. These periodic surface fires helped secure a competitive position for oaks in the regeneration pool by maintaining a desirable species composition and forest structure. This historical fire regime was altered with the European settlement of North America, and fire suppression within forestlands became a standard practice since 1930s. With decades of fire suppression, mature oak-dominated woodlands have widely converted to shade-tolerant tree species. Prescribed fire has successfully been used to enhance oak regeneration in eastern forests. However, oak woodland restoration within the forest-prairie ecotone of the Central plains has not been systematically studied. Fuel beds under shade-tolerant species are often less conducive to fire. Therefore, monitoring fuel loading (FL) and its changes are essential to inform management decisions in an oak regeneration project. Rapid expansion of eastern redcedar (Juniperus virginiana/ERC) is another ecological issue faced by land managers throughout North America’s midcontinent forest-prairie ecotone. Hence, it is worthy to monitor ERC expansion and effects on deciduous forests, to inform oak ecosystem restoration interventions within this region. Therefore, the main objectives of this dissertation were three-fold: (1) understand the effects of prescribed burning and mechanical thinning to encourage oak regeneration; (2) investigate the initial effects of an oak regeneration effort with prescribed fire and mechanical thinning on FL; and (3) monitor the spatio-temporal dynamics of ERC expansion in the forest-prairie ecotone of Kansas, and understand its effects on deciduous forests. The first two studies were conducted on a 90-acre oak dominated woodland, north of Manhattan, Kansas. The experimental design was a 2 (burn) x 2 (thin) factorial in a repeated measures design. The design structure allowed four treatment combinations: burn only (B), thin only (T), burn and thin combined (BT), and a control (C). Burning and thinning treatments were administered in spring 2015. Changes in the FL estimates after the burn treatment revealed that the BT treatment combination consumed more fuel and burned more intensely compared to the B treatment. This observation was reflected in vegetation responses. The thinning reduced the canopy cover significantly, but under enhanced light environments, both oaks and competitive species thrived when no burn was incorporated. In contrast, burn treatments controlled the competitive vegetation. Hence, the most promising results were obtained when both fire and thinning were utilized. The remote sensing study documented the expansion of ERC in three areas of eastern Kansas over 30 years. The use of multi-seasonal layer-stacks with a Support Vector Machines (SVM) supervised classification was found to be the most effective approach to map ERC distribution. Total ERC cover increased by more than 6000 acres in all three study areas investigated in this study between 1986 and 2017. Much of the ERC expansion was into deciduous woodlands. Therefore, ERC control measures should be incorporated into oak woodland restoration efforts within the forest-prairie ecotone of Kansas.

Imported fire ants are invasive and cause injury to people, crops, livestock and wildlife. Disturbance may increase abundance and activity of fire ants. However, native grass field buffers established for grassland birds require periodic disturbance. I experimentally tested if fire ant mound density and foraging activity changed after burning and disking in native grass buffers and examined relationships among fire ants, vegetation, and grassland bird and butterfly metrics in undisturbed buffers. In 2008, disking increased mound density and foraging activity, but burning did not. In 2009, disking had no effect, but effects of disking the previous season persisted. Fire ant metrics were not related generally to bird or butterfly metrics. Mound density and foraging activity were related negatively to grass cover and related positively to forbs. Burning had less influence on abundance and activity of fire ants, and may better conserve grassland habitats in areas with fire ants.

Prescribed fire in the southern Appalachians is a frequently used and controversial forest management practice. Research is limited on the effects of prescribed fire in the mesic southern Appalachians, where many of Tennessee's rare and regionally endemic plant species occur. This study examined the effects of prescribed fire on the herbaceous layer. Field work was conducted on six previously burned sites within the Cherokee National Forest in northeast Tennessee. Complimentary non-burned sites were selected based on similarity of physical characteristics and forest structure. The numbers of herbaceous species and individuals and the total numbers of species and individuals were determined and used to compare burned and unburned forest. Following prescribed fires there were significant reductions in the number of herbaceous species and individuals. Species with myrmecochorous (ant-dispersed) seeds were markedly reduced on burned sites. Despite considerable variation among sites, the negative impact of fire on forest herbs was clearly evident.

The Florida mouse (Podomys floridanus), a species restricted to the Lake Wales Ridge and the Atlantic Coastal Ridge, is recognized by the Florida Fish and Wildlife Conservation Commission as a species of special concern, highlighting its status as a species that is threatened by habitat loss statewide. Publicly owned lands offer protection for the species, but management is generally focused on protecting biodiversity in general and not a particular species. The response of the Florida mouse to land management practices such as mechanical treatment and prescribed fires is poorly documented. This research examined the population responses of Florida mice on three public lands in central Florida, namely, Bullfrog Creek Mitigation Park in Hillsborough County, Split Oak Mitigation Park in Orange County, and Chuluota Wilderness in Seminole County. Florida mice numbers increased or recovered to pre-burn levels within six months following prescribed burns in 2003 and 2004 on the Bullfrog Creek site. Florida mice dropped in numbers following a fire on the Split Oak site, but were increasing when the study ended. The steady decrease in numbers of mice at the Chuluota Wilderness site remained unaffected by habitat modification. Management of public lands that support Florida mice should continue to utilize prescribed fire to maintain upland habitats. When possible, prescribed fires should be limited to the spring and early summer months and applied to only a portion of the total available area in any year.

Society requires better insights into how disturbances will alter the global carbon cycle. Ecosystem models help us understand the carbon cycle and make predictions about how the terrestrial land sink will change under future climate regimes. Disturbances drive ecosystem cycling, but modeling disturbances has unique challenges, particularly in incorporating heterogeneity and parameter uncertainty. In this dissertation, I explore two questions. 1) How can we capture disturbance ecology in models?, which I explore in my first and second chapters, and 2) How can we use those models to make projections for the Southeastern US?, which I explore in my third and fourth chapters. Both my first and second chapters point to the practical trade-offs in model structure and realism. In my first chapter, I found that representing spatially implicit contagious disturbances in terms of shape and frequency accurately captured structural changes over time and separated the disturbance regimes of different regions. Representing spatially implicit disturbances in terms of shape and frequency sacrificed the specificity of a space-based approach but may be more computationally efficient. In my second chapter, I developed a framework for calibrating models based on an iterative cycle between uncertainty analysis and literature synthesis, targeted field campaigns, and statistical constraint. I found that targeted field work and statistical constraint reduced parameter uncertainty until structural uncertainty began to dominate. Models that capture disturbance dynamics can help us anticipate effects of global change factors like climate change and invasive species. In my third chapter, I found that elevated temperatures reduce cogongrass biomass, and that cogongrass facilitates pine dominance over oaks in a mixed pine-oak stand. This suggests that cogongrass mediates inter-species competition at an ecosystem scale. Prescribed burns are a management technique used to suppress cogongrass and has an add-on benefit of reducing tick populations. However, climate change may threaten how frequently prescribed fires can be safely deployed. In my fourth chapter, I found that tick populations are most sensitive to leaf litter and humidity, which allows for management strategies as an alternative to prescribed burns.

Across the central and eastern United States, upland oaks are experiencing regeneration complications. This thesis comprises two studies evaluating challenges in regenerating upland oaks. One study evaluates upland Quercus spp., Carya spp., and Acer rubrum L. response to prescribed fire and impacts on seedling growth and mortality. This study found prescribed fire promoted oak growth when canopy cover was < 77%. Oaks displayed lower percent mortality and higher resprout capacity after fire compared to red maple. The second study investigates impacts of Microstegium vimineum presence on Quercus alba L., Liriodendron tulipifera L., and Acer rubrum L. seedlings under different light and moisture environments. Microstegium vimineum presence decreased growth of both sweetgum and red maple; white oak was less impacted, likely because of its conservative growth strategy and high-water use efficiency. Oaks’ conservative growth strategy may offer more resiliency compared to its competitors in response to prescribed fire and Microstegium vimineum.

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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