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The factors affecting tree establishment in boreal forests after fire will help determine the community composition of the regenerating forest. These may have large consequences on the community dynamics for years after the fire disturbance. Factors such as burn severity and soil moisture among others have been shown to play a key role in influencing several facets of establishment. However, tree establishment after megafire in boreal forest in Europe has not yet been fully understood. Here I capitalise on a megafire in Sweden in 2014 to investigate the relative impact of different abiotic factors and preconditions on tree establishment six years after the fire. This study used a systematic survey of tree saplings (height >30cm) at 625 locations inside the nature reserve set up within the burnt area. Tested factors were: The number of dead trees lying down, slope and slope aspect, elevation, soil wetness, pre-fire standing volume, distance to fire perimeter, forest stand age, stand productivity index, previous stand dominant tree species, humus thickness after fire and depth of burn. Generalized Linear Mixed Models (GLMMs) were used to estimate the effect of these factors on specific tree species abundance. Strong influences from previous wood volume, soil wetness, elevation, and dead wood lying down had an effective influence on sapling abundance but were typically species-specific. Only elevation and wood volume had a consistent effect on all species’ abundances. Habitat context was important on a landscape scale. These results support the pattern of increasing boreal deciduousness caused by high burn severity and shorter disturbance intervals, in turn, caused by hotter, drier weather, which will have implications on the composition of boreal forests of tomorrow.

Prescribed fire use in Virginia and West Virginia has increased over the past ten years as forest managers on public lands have increasingly used prescribed fire to meet management goals. These goals include hazardous fuel reduction, wildlife habitat restoration and management, and control of less desired vegetation. Research is needed to better understand the effects of wildland fire on forest ecosystems. In this study, we addressed wildland fire's effects on water, vegetation, and soil resources in the central Appalachian Region. Moreover, the long-term efficacy of various types of timber harvests on forest fuel reduction was analyzed. Over fifty peer-reviewed articles were evaluated to characterize the effects of prescribed fire on physical, chemical, and biological water quality parameters throughout the eastern United States. It was determined that fires of low to moderate intensity and severity may cause short-term sediment and nutrient increases in nearby waterbodies, but these effects often dissipate within 2-3 years. Effects on biological organisms are more transient, frequently lasting from a few weeks to a few months. Regeneration following wildfires at three sites in Virginia and West Virginia varied due to fire behavior and time since fire. Preferred and undesired species responded differently at each site. Follow-up treatments and continued monitoring are needed to obtain desired vegetative compositions post-fire. Two dormant season prescribed fires on the Fishburn Forest near Blacksburg, Virginia were studied for mineral soil chemistry effects. Both treatment and time affected macronutrient levels, but no differences were present 6 and 14 months post-fire between burned and unburned locations. Forest fuels were quantified approximately 20 years following different silvicultural harvests on the George Washington-Jefferson National Forest. Fuels of different size classes responded differently to different harvests as fine fuels were reduced by the high-leave shelterwood treatment, and coarse woody fuels were reduced by the clearcut and low-leave shelterwood treatments. Overall, low intensity and low severity fires induce minimal, potentially negative changes in water and soil quality. In contrast, wildfires of high intensity and severity may potentially contribute to changes in species composition and forest floor properties. Furthermore, varying levels of overstory removal may reduce extreme wildfire risk for decades. The findings of this study reinforce the need for continued research and monitoring of both wildfire effects and prescribed fire use in the central Appalachian Region. / Doctor of Philosophy / It is well-documented that fire has occurred in forested ecosystems for millennia. In addition to natural ignitions, indigenous peoples used fire for various reasons, such as understory reduction, hunting, and crop cultivation. As European settlers arrived and advanced across North America, they continued to use fire as a tool to shape the landscape to fit their societal needs. The use of fire by humans in North America all but ceased in the early 20th century. Large fire events in the western United States motivated the newly created United States Forest Service to restrict fire from the landscape. The fire exclusion policy of the early 20th century had unintended consequences, such as increased fire risk due to fuel accumulation and a shift from fire-tolerant species, such as oaks and pines, to fire-intolerant species. More recently, the perception of wildland fire has been re-examined due to ecological and societal issues. Although federal and state agencies are burning more acres, the public's wariness towards wildland fire is prevalent. As attitudes about wildland fire have changed, so have the research needs. Information regarding the effects of both wild and prescribed fires on forest ecosystems is needed throughout the United States, including the eastern United States, and more specifically, within the central and southern Appalachian Mountains. This dissertation discusses the effects of both wild and prescribed fires on various forests processes within these regions. In this dissertation, 1) the impacts of prescribed fire on water quality, 2) the responses of forest vegetation to wildfire, and 3) and the effects of prescribed fire on soil nutrients were investigated. Additionally, different timber harvests were studied to determine their long-term effects on potentially hazardous fuel loads. The results indicated that water quality is generally not impacted by low intensity and severity prescribed fires in the eastern United States. It was determined that vegetation often responds vigorously to wildfires, and subsequent species composition varies based on factors such as fire severity, site conditions, time since fire, and overstory species composition. When examining soil nutrients for 14 months following prescribed fires, nutrient changes occurred in both unburned and burned locations. When fuel loads were compared between timber harvests of varying intensities, woody fuels were reduced in the long-term. This reduction may minimize potential wildfire behavior and effects. While both wild and prescribed fires impact forest processes, they generally do so in different ways. This is mainly due to differences in fire behavior between these fire types. Effects of wildfires on water quality, soil chemistry, and vegetation tend to last longer than prescribed fire. Additionally, prescribed fire, when used in conjunction with other forest management activities, may reduce potentially negative wildfire impacts. Monitoring post-fire effects is critical to understanding the best way to use prescribed fire as a forest management tool.