Theses and Dissertations - Department of Geography

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Biogenic modification of sediments by unionid mussels and their implications for sediment transport in the Sipsey River of Alabama
(University of Alabama Libraries, 2018) Koerner, Matthew Ryan; Davis, Lisa; University of Alabama Tuscaloosa
Few studies have tested the influence of freshwater mussels on sediment properties and their potential influence on geomorphic processes outside of lab-based flume studies. Freshwater mussels have historically constituted a great proportion of the benthic biomass in many rivers in the southeastern United States and may maintain or transform the physical stability of river bed sediment indirectly by their biogenic structure or directly through processes including biodeposition and bioturbation. We tested the effects of freshwater mussels on sediment properties (D50 median grain size and sorting), sediment scour and reach scale bedload transport by deploying 36 mussel enclosures in the Sipsey River, Alabama, for a 9-week period. We employed a randomized design consisting of 4 replicates of the following treatments: 3 diversity treatments (Cyclonaias asperata; Fusconaia flava; Cyclonaias asperata and Fusconaia flava), 2 abundance treatments (24 indiv/m2, 48 indiv/m2), a sediment only control, and 2 sham mussel controls (24 indiv/m2, 48 indiv/m2). Sliding-bead monitors were installed in the center of each mussel enclosure to measure the amount of scour over the 9-week period, and biomodifications to surface layer D50 particle sizes and Folk and Ward sorting coefficients were measured using ImageJ photo analysis software. Hypothetical differences of bedload transport rates between reaches containing mussels (24 indiv/m2; 48 indiv/m2) and no mussels were computed using BAGS (Bedload Assessment in Gravel-bed Streams, Version 2008.11) bedload transport model. The results of this experiment suggest freshwater mussels contribute to bed scour, and increase surface layer D50 particle sizes and the degree of surface layer sorting. BAGS predicted that bedload transports rates in a reach with high abundances of freshwater mussels were lower than a reach containing no mussels (88.6% lower under baseflow conditions and 55.3% lower under bankfull flow conditions), based on biomodifications to surface layer D50 particle sizes and sorting by freshwater mussels. These results suggest that alterations to sediment properties by freshwater mussels are quantifiable in non-flume based settings, and that freshwater mussels may play a significant role as ecogeomorphic agents in the Sipsey River, AL, and other rivers that contain dense, long-lived communities of freshwater mussels.
Edge influence on composition and structure of a Pinus palustris woodland following catastrophic wind disturbance
(University of Alabama Libraries, 2019) Goode, Jonathan Davis; Hart, Justin L.; University of Alabama Tuscaloosa
Forest edges are an important legacy of natural and anthropogenic disturbances. Edges of forest fragments are influenced by adjacent non-forested ecosystems, resulting in compositional and structural differences at the edge. Edge influence is the altered biotic and abiotic interactions that occur along the edge-to-interior gradient in disturbed forests. Few studies have analyzed natural disturbance created edges, particularly in woodland forest structures, which contain fewer trees ha-1 than forests and are typically less light limited. The goal of our study was to examine edge influence of a tornado created edge in a longleaf pine (Pinus palustris Mill.) woodland. In 2011, an EF-3 tornado impacted a restored longleaf pine woodland, resulting in a distinct woodland edge. To quantify distance of edge influence into the stand, nine transects were installed perpendicular to the tornado swath, with 11 plots on each transect at variable distances from the edge. Biotic and abiotic response variables were measured at the appropriate spatial scales. To determine the distance of edge influence, the magnitude of edge influence was calculated at each distance, and compared to the reference forest using a non-parametric randomization test. Edge influence on forest structure was negative, with a maximum distance of 70 m. Ground flora richness and diversity experienced a positive edge influence, with higher richness and diversity in the tornado swath and edge, however, ground flora communities at the edge were not compositionally distinct from the tornado swath or the interior. Results of this study add to our understanding of edge influence on woodland forest structure and naturally created edges.
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.
Evaluation of Florida bay seagrass after Hurricane Irma
(University of Alabama Libraries, 2019) Loria, Aubrey; Steinberg, Michael K.; University of Alabama Tuscaloosa
When Hurricane Irma made US landfall on the Florida Keys on September 10, 2017, the category 4 storm became the first major hurricane to hit the state since 2005. This study investigated the impacts that Irma had on seagrasses in Florida Bay – an estuary at the southern outlet of the Florida Everglades that is crucial to the environment and economy of South Florida but that is threatened by anthropogenic impacts on water quality. A massive seagrass die-off in 2015 left the bay with hypersaline water and sulfide-saturated sediment that was held in place by the bay’s network of carbonate mud banks. The promise of rainfall and storm surge from a major hurricane offered a chance to refresh the bay and begin the process of recovering from the die-off. By comparing seagrass density and community composition from after the 2015 die-off to after Irma, I found that seagrass cover has become more uniform and that species richness has increased throughout the study area. Seagrass density was lost in some shallow sections of the study area, but pioneer species Halodule wrightii had begun colonizing the disturbed areas, indicating that water quality had changed enough to support the less salt-tolerant species. The positive changes in seagrass density, distribution, and diversity after Hurricane Irma indicate that the storm may have flushed out the hypersaline water left after the 2015 die-off that had been limiting seagrass recovery for two years.
Habitat use, activity patterns, and human interactions with jaguars in southern Belize
(University of Alabama Libraries, 2015) Dobbins, Michael; Steinberg, Michael; University of Alabama Tuscaloosa
We examined the presence of jaguar (Panthera onca) and analyzed its habitat use, activity patterns, and human interactions in a community-dominated tropical landscape in the Maya region of southern Belize. Jaguar presence was detected from camera traps, and informal interviews with 48 residents were conducted to assess the perception of jaguars in the study village of Blue Creek. Seven individual jaguars were identified from 28 independent photographic events over 1,200 camera trap nights, indicating a relative abundance index (RAI) of 2.8 photographs per 100 trap days. Jaguars tended to prefer lowland broad-leaf tropical forest, between the hours of 13:00-18:00. They were rarely observed at night, with only 11% of records occurring after dark. The perception of jaguars in this community was largely positive, with 88% of respondents not fearing jaguars living around the village, and 81% of respondents understanding the positive effect that jaguars have on the ecosystem. There was no significant correlation between respondents' religious affiliation or education level and their perception of jaguars. Although 92% of respondents had reported seeing a jaguar within the last two years, jaguar attacks on livestock in the village are rare, with only two occurrences in the past three years. In recent years, ecotourism has rapidly grown in Belize. Blue Creek is home to several natural tourist attractions, as well as an eco-lodge that brings in tourists, school groups, and researchers to the village. Ecotourism has provided an economic incentive for the village to be invested in conservation, as 94% of respondents thought that the preservation of wildlife, including jaguars, and the forests would be beneficial to their well-being.
Habitat-level mapping of mangrove cover trends in Ciénaga de Zapata, Cuba, using landsat imagery and local knowledge
(University of Alabama Libraries, 2017) Cissell, Jordan Robert; Steinberg, Michael K.; University of Alabama Tuscaloosa
The mangrove forests of Ciénaga de Zapata, Cuba, are of critical importance from both biodiversity and ecosystem service perspectives. The peninsula is home to more than 1,000 invertebrate species, more than 80 percent of the island’s total bird species, and numerous fish, mammals, and reptiles, including the Cuban crocodile (Crocodylus rhombifer) and Cuban gar (Atractosteus tristoechus), two species found only in Cuba. Zapata’s mangroves also support populations of sport and commercial fish such as bonefish (Albula vulpes), tarpon (Megalops atlanticus), permit (Trachinotus falcatus), and snook (Centropomus undecimalis). Despite the ecological importance of Zapata’s mangroves, no published work has documented any changes in the forests’ extent or distribution throughout the past two decades. This project combined unsupervised classification and visual interpretation of Landsat imagery with local knowledge to quantify and map area changes in Zapata’s mangrove forests from 1994 to 2014. Habitat zones mapped by local stakeholders were used to measure and compare mangrove change at the scale of individual species’ preference areas. Study results demonstrated a negligible (1.20 percent) decrease in total mangrove area during the study period. However, changing socio-political and economic dynamics between the United States and Cuba could precipitate rapid development along nearby coastal locations in the near future, and these results provide necessary baseline information against which to measure future pressures on Zapata’s mangroves at the cusp of a period of potentially substantial future change.
Hydro-geomorphological influences on plant patch density and distribution in bedrock shoal habitats of the Cahaba River, AL
(University of Alabama Libraries, 2014) Vaughn, Ryan Scott; Davis, Lisa; University of Alabama Tuscaloosa
Abstract There is a growing body of research that examines bedrock channels. Despite this, biotic-abiotic interactions remain a topic mostly addressed in alluvial systems. This research seeks to identify patch-scale hydro-geomorphic factors operating at the patch-scale in bedrock shoals of the Cahaba River (AL) that help determine the distribution of the emergent aquatic macrophyte, Justicia americana. Macrophyte patch density (number of stems/m2) and percent bedrock void surface area (rock surface area/m2 occupied by joints, fractures, and potholes) were measured (n = 24) using stem counts and underwater photography, respectively. One-dimensional hydrologic modeling (HEC-RAS 4.1.0) was completed for one cross-section within a shoal to examine whether velocity and channel depth are controlling variables for macrophyte patch density. A Pearson's Correlation test between bedrock surface void area and stem density demonstrated a statistically significant positive correlation (r=.665, p=0.01). Results of an independent t-test between the velocity and depth model outputs for within and outside plant patches showed a significant difference in average velocity (p =0.011) and depth (p = 0.001) between the two types of locations across discharges, ranging from 7 m3/sec to 226 m3/sec. These results suggest that the amount of void space present in bedrock surfaces and localized depth and velocity help control the macrophyte patch density, and by extension, the distribution of macrophytes in bedrock shoal complexes. The utility of geomorphology in explaining patch-scale habitat heterogeneity in this study demonstrates potential to use geomorphology to explain macrophyte habitat heterogeneity at reach and system-scales and highlights the need for more research that helps understand biotic-abiotic interactions in bedrock fluvial systems.
The impact of storm surge from successive hurricanes on the Alabama beach mouse population
(University of Alabama Libraries, 2011) Yuro, Alexandra Marie; Steinberg, Michael; University of Alabama Tuscaloosa
Global environmental change affects plants and animals by changing their distributions and phenology, and altering ecosystem functions. Already endangered plants and animals subject to these changes may be more vulnerable to extinction. It is important to understand how species are likely to respond to environment change so that proper steps can be taken to protect them in the future. This thesis observes the case of the Alabama beach mouse (Peromyscus polionotus ammobates), a population endangered initially because of habitat loss and fragmentation. The Alabama beach mouse population likely will be negatively affected by environmental change through increased hurricane frequency and intensity. Using Alabama beach mouse trapping data provided by the U.S. Fish and Wildlife Service, I examined the storm surge effects of Hurricanes Ivan and Katrina on mouse populations before, during, and after these hurricanes. Analysis of the data was performed through contingency tables and Wilcoxon signed-rank tests. The results of the analysis show that the Alabama beach mouse has the ability to survive hurricanes in the future, if they are not successive. The Alabama beach mouse possesses certain traits that make it more vulnerable to extinction in the near future by environmental change, such as greater than normal disturbances both from humans (i.e. habitat loss and fragmentation) and the natural environment (i.e. hurricanes and climate change.) I postulate that the Alabama beach mouse population will be completely extirpated from Gulf Shores in the event of successive major hurricanes in the future. The intended result of this study is not only to find out how the Alabama beach mouse may be affected by global environmental change, but to contribute to the literature concerning the species to be used in effective management strategies.
Influence of coarse woody debris on seedlings and saplings in a Pinus palustris woodland
(University of Alabama Libraries, 2020) Logan, Alexandra; Hart, Justin L.; University of Alabama Tuscaloosa
Coarse woody debris (CWD) has beneficial effects on plant growth and establishment. Longleaf pine (Pinus palustris Mill.) stands support relatively low amounts of CWD — 2 to 30 m3 ha-1. In April 2011, an EF3 tornado passed through the Oakmulgee Ranger District of the Talladega National Forest in the Fall Line Hills of Alabama. This disturbance resulted in the large addition of CWD to a longleaf pine woodland, and a rare opportunity to analyze how CWD can influence a managed, pine woodland. The goal of this study was to examine the effect of CWD on woody plant richness, density, and growth rate (quantified by height) in a longleaf pine woodland that experienced a catastrophic wind disturbance. A total of three 1 m2 quadrats were established against either side of a piece of CWD (> 3 m in length and ≥ 10 cm in diameter). Another quadrat was established at least 3 m away from the focal CWD piece. For each plot, the presence and height of every woody plant (< 5 cm dbh) were recorded. Sapling density, oak and hickory density, and organic matter were all found to be significantly higher in quadrats adjacent to CWD than away (all p < 0.05). There was also a significant relationship between CWD decay class and average plant height, richness, density, and organic matter (all p < 0.05). Results from this study help to inform managers about the ecological functions of CWD in longleaf pine systems and other pine woodlands.
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.
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.

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