Browsing by Author "Dey, Daniel C."

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    Effects of an intermediate-scale wind disturbance on mixed pinus-hardwood stands
    (University of Alabama Libraries, 2016) Trammell, Benjamin Walker; Hart, Justin L.; University of Alabama Tuscaloosa
    All forest ecosystems are subject to natural disturbances that influence development and succession. Forest disturbances are typically classified based on severity and spatial extent with events ranging from small, single-tree gaps to large, stand replacing disturbances. Intermediate-scale disturbances occur along the gradient between the two endpoints. On 20 April 2011 in Lawrence County, AL, an EF1 tornado tracked 5 km, leaving a patchwork mosaic of disturbed areas that included multiple mixed Pinus-hardwood stands. The objectives of this thesis were to describe the effects of intermediate-scale wind disturbance on forest composition, structure, succession, and development, and to compare and contrast the effects of silvicultural entries to those of natural disturbance. The storm disproportionately removed large Pinus stems, and effectively accelerated succession and promoted hardwood dominance. The ISD created understory light levels in the disturbed neighborhoods that were significantly higher than pre-disturbance conditions after five growing seasons. Similar to the naturally disturbed stands, the intermediate treatments also accelerated succession by preferentially removing Pinus canopy stems and promoting Quercus dominance. This study addresses the gap in our understanding of the effects of intermediate-scale wind disturbance on composition, structure, succession, development, biodiversity, and sub-canopy light regimes in mixed Pinus-hardwood systems. This study will serve as a reference point for natural disturbance-based management in this forest type.
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    Effects of an intermediate-scale wind event on forest composition, structure, and structural complexity
    (University of Alabama Libraries, 2016) Cox, Lauren Elizabeth; Hart, Justin L.; University of Alabama Tuscaloosa
    Forest disturbances alter environmental conditions, influence species composition and stand structure, and affect successional and developmental pathways. Natural disturbances differ in magnitude, severity, and return interval and range from frequent, gap-scale disturbances, to infrequent stand-replacing events. Disturbances at the gap and intermediate scale increase structural complexity and intra-stand heterogeneity. On 20 April 2011 in Lawrence County, AL, an EF1 tornado tracked 5 km, leaving a patchwork mosaic of disturbed areas. To analyze the intra-stand spatial patterns of tree morality and biological legacies after an intermediate-scale wind disturbance, I established a 100 × 200 m (2 ha) rectangular plot perpendicular to the path of the storm within an affected Quercus alba stand. Based on the basal area removed by the wind event, I divided the plot into disturbance classes (minimal, light, and moderate) to compare compositional and structural attributes across areas of increasing disturbance severity. I analyzed species- and size-specific mortality trends within each disturbance class. In addition, I quantified the structural complexity of each disturbance class and described the effect of the intermediate-scale disturbance on stand development. Composition was not substantially affected by the disturbance, but large stems were disproportionately removed by the storm. Structural complexity increased as a result of the wind event. However, the spatial distribution of stems was more uniform after the disturbance. The intermediate-scale wind event altered the stand size class from a mature stand to a mature–sapling mosaic stand. This size class characterizes a stand in the mixed stage of development. Results from this thesis contribute to the understanding of the compositional and structural attributes of upland Quercus stands after an intermediate-scale wind event. Quantitative descriptions of this stand may be used as references to inform silvicultural systems intended to enhance structural complexity and minimize the disparity between natural and managed stands.
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    Effects of thinning and burning on ground flora in mixed pinus-hardwood stands
    (University of Alabama Libraries, 2018) Barefoot, Carson Reid; Hart, Justin L.; University of Alabama Tuscaloosa
    Commercial thinning and prescribed fire are tools used to accomplish forest management objectives such as increased timber revenue, fuel reductions, and increased biodiversity. Silvicultural treatments can alter forest structure and nutrient flow to increase resiliency by promoting regeneration of native species, especially in the ground layer, where the majority of plant diversity is stored. Management regimes that optimize ground layer attributes in mixed Pinus-hardwood stands following timber monoculture are less understood. I examined the effects of thinning without fire and thinning with different fire frequencies to identify changes in community structure and species composition with a focus on taxonomic richness, evenness, diversity, and percent cover of ground flora in Pinus-hardwood stands on the Cumberland Plateau in northern Alabama. Overstory (live woody individuals ≥ 5 cm dbh; diameter at breast height, 1.37 m above the root collar) basal area and density decreased with increased management intensity. Sapling (live woody individuals < 5 cm dbh and > 1 m in height) density substantially increased with increased management intensity in the second growing season post-fire. Sapling density did not negatively affect light reaching the ground layer, as light availability increased with management intensity. Ground flora richness, diversity, evenness and cover were greatest in stands that were thinned, and then burned every three years, negatively correlated with litter depth and positively correlated with exposed mineral soil based on a non-metric multidimensional scaling (NMS) solution. Ground flora diversity was greater in thinned stands with fire compared to stands that were thinned and never burned, emphasizing the need of the combination of thinning and burning in these systems for native biodiversity conservation. Forest managers who wish to promote biodiversity may consider frequent burning to promote ground flora richness, diversity, and cover.
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    FIRE IN EASTERN NORTH AMERICAN OAK ECOSYSTEMS: FILLING THE GAPS
    (Springer, 2016) Varner, J. Morgan; Arthur, Mary A.; Clark, Stacy L.; Dey, Daniel C.; Hart, Justin L.; Schweitzer, Callie J.; Virginia Polytechnic Institute & State University; University of Kentucky; United States Department of Agriculture (USDA); United States Forest Service; University of Alabama Tuscaloosa
    This special issue of Fire Ecology is focused on the fire ecology of eastern USA oak (Quercus L.) forests, woodlands, and savannas. The papers were presented as part of the Fifth Fire in Eastern Oak Forests Conference in Tuscaloosa, Alabama, USA, in 2015. The topic of fire in Eastern oak ecosystems is one that has received insufficient interest from the broader fire ecology community. Specific papers in this issue address the historical role of fire in the region, the response and adaptations of plant and animal species to fire and fuels treatments, and the future of these important ecosystems under a future of global change. We hope that this issue provokes future research on the past, present, and future of fire in eastern North American oak ecosystems.
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    Patterns of competition and insolation along a canopy disturbance severity gradient: implications for the Quercus bottleneck
    (University of Alabama Libraries, 2015) Keasberry, Amanda Marie; Hart, Justin L.; University of Alabama Tuscaloosa
    Regeneration failure of Quercus has been widely reported throughout the Central Hardwood Forest of the eastern United States across all but the most xeric site types. Quercus seedlings are often abundant in upland hardwood stands, but typically fail to recruit to larger size classes (i.e. the Quercus bottleneck). The goal of my study was to investigate the competition with small-sized Quercus stems to elucidate what variables may cause resistance or facilitation of Quercus recruitment. I established a 2 ha plot in the Sipsey Wilderness, AL that was subdivided into 5 x 5 m quadrats to encompass the entire extent of damage caused by an EF1 tornado in 2011. The study area encompassed a range of damage (light, moderate, severe), starting from the center of the tornado tract and ending in an undamaged area (control). The canopy disturbance provided a range of light conditions in the understory (0.5–91.0% full sunlight). In each quadrat, the height of all small-sized Quercus stems (≥ 0.5 m in height to >5 cm DBH) were measured and recorded. The nearest neighbor was identified by species and measured for height and distance from the focal Quercus stem. Photosynthetically active radiation was quantified at 1.4 m above the forest floor. Quercus’ competition was largely interspecific and the majority of competitors were shade-tolerant species such as Acer saccharum and Ostrya virginiana. Competitive indices of Quercus’ primary competitors were significantly different (p < 0.01) revealing the relative competitive ability amongst species within the plot. Disturbance neighborhoods had no significant (p > 0.01) effect on the competitive ability of species. Spatial patterns of Quercus stems, their nearest neighbor, and percent full sunlight were analyzed at 5 x 5 m, 10 x 10 m, and 20 x 20 m. Analysis at a fine-scale resolution revealed spatial patterns which would otherwise not be apparent at coarser scales. Creative and flexible silvicultural techniques may need to be implemented at finer scales to optimize the recruitment of Quercus spp.
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    A review and case study of multiple interacting disturbances in forest ecosystems
    (University of Alabama Libraries, 2021) Kleinman, Jonathan Samuel; Hart, Justin L.; University of Alabama Tuscaloosa
    Strategies to enhance ecosystem resilience are increasingly needed in forest management plans. Natural and managed disturbances that alter ecosystem resilience to other perturbations are called compound disturbances. This dissertation first synthesized the literature on compound disturbances in forest ecosystems. I used a systematic review to catalogue case studies of compound forest disturbances and identify trends in the types, timing, environmental settings, and ecological consequences of each disturbance combination. The review emphasized that the detection of positive, negative, and neutral disturbance impacts on ecosystem resilience were often contingent on which response variables were used to monitor forest recovery. To illustrate and investigate this and other key concepts described in the review, I then examined a combination of wind disturbance, salvage logging, and prescribed fire in the Alabama Fall Line Hills. A range of woody plant, ground flora, and ground surface material metrics were collected before and after prescribed fire in Pinus palustris Mill. woodlands differentially impacted by an EF3 tornado and salvage logging. In support of the review, salvage logging and prescribed fire had different effects on post-wind disturbance recovery depending on which response variables were assessed. Pinus palustris saplings exhibited the greatest densities in salvage-logged sites and were more resistant to prescribed fire than most other sapling species. This indicated that recovery toward P. palustris canopy dominance was not negatively affected by salvage logging and was enhanced by prescribed fire. Ground flora diversity and community dissimilarity, however, were reduced in salvage-logged sites before and after prescribed fire. Nonetheless, prescribed fire did impose some consistent selective pressures on understory plants with common life-history strategies. Overall, this dissertation supported the use of prescribed fire to promote P. palustris woodland recovery. Leaving some wind-disturbed zones unlogged was also recommended to support ground flora resilience. Moving forward, a diversity of response variables should be measured to achieve comprehensive assessments of disturbance effects on ecosystem resilience.
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    Temporal dynamics affecting ground flora recovery after fire in thinned pinus-quercus stands
    (University of Alabama Libraries, 2018) Willson, Kevin; Hart, Justin L.; University of Alabama Tuscaloosa
    The ground flora stratum affects stand structure, resource acquisition, nutrient cycling, and taxonomic richness in forest ecosystems. Disturbances, such as thinning and prescribed fire, alter understory growing conditions that generally increase ground flora cover and richness in stands across the U.S. However, few studies have quantified annual changes in ground flora after a prescribed fire in thinned stands to provide finer temporal resolution of ground flora recovery. I performed a space-for-time study that quantified changes in ground flora assemblages over three growing seasons post-fire in thinned and frequently burned Pinus-Quercus stands. My results corroborated trends from other forest types and regions that indicated greater ground flora richness and cover after thinning and burning compared to thin-only treatments. I also found that the stratum experienced relatively rapid succession between growing seasons. Forbs had annual reductions in cover and richness with increasingly difficult growing conditions after the first growing season, while woody plants and shrubs increased in richness over time. The transition from herbaceous to woody dominance in three years was indicative of changing competition dynamics that favored quick growth in the first growing season and long-term investment in vertical growth in the third growing season. Although beneficial for increased ground flora cover, forb taxonomic richness, and reduced fuel levels, the three-year fire return interval did not produce comparable Pinus and Quercus regeneration to overstory composition. Management of eastern U.S. Pinus-Quercus stands may need to account for potential mesophytic dominance in seedling and sapling size classes that occur in thinned and burned stands over time. If mesophytic dominance becomes an issue, managers could include growing season fires and a secondary thin to foster desired regeneration to recruit into the overstory, although general weather conditions during the growing season could make fires hard to routinely implement.