Thesis (M.S.)--University of North Carolina Wilmington, 2007. / Includes bibliographical references (Leaves: 51-57)

archives@tulane.edu / The influence of environment on microbial community structure is of increasing interest, especially in coastal habitats where climate change is rapidly altering the landscape. In this dissertation, I characterize the microbial communities associated with a key wetland species, the baldcypress tree (Taxodium distichum), and examine the relationship between environment, geographic distance, and microbial community composition. In a culture-based study of T. distichum leaf and root endophytes, I found that both salinity and flooding contributed to bacterial and fungal endophytic community composition. Additionally, I report that diversity and endophyte isolation frequency were higher in roots than in leaves, with leaf bacteria being almost negligible. Using 16S Illumina profiling, I found that geographic distance correlated with rhizosphere but not root endosphere bacterial communities and that mean water level, mean salinity, and the volume of woody debris were correlated with both endosphere and rhizosphere bacterial communities of T. distichum. Finally, using salt challenge assays, I isolated five strains of extreme halotolerant endophytes and eleven strains of moderately halotolerant endophytes— a necessary first step towards using endophytes for restoration, or towards understanding the functions of some of these organisms in situ. This dissertation demonstrates a connection between environmental variables, plant symbionts, and a key restoration species and may help in predicting future outcomes of sea level rise for endophytes communities in baldcypress and other wetland plants. / 1 / Elizabeth Kimbrough

Taxodium distichum (L.) Rich. is a widely adaptable, long-lived tree species for landscape use. It is tolerant of substantial soil salt levels, but tends to defoliate in periods of extended or severe drought, when leaves come into contact with salty irrigation water, and tends to develop chlorosis on high pH soils. The purpose of this research was to identify provenances which may yield genotypes tolerant of these stresses. The appropriate name for baldcypress is Taxodium distichum (L.) Rich. var. distichum, for pondcypress is T. distichum var. imbricarium (Nutt.) Croom, and for Montezuma cypress is T. distichum var. mexicanum Gordon. A germination study of T. distichum var. mexicanum revealed that if immediate germination of ripe seed is desired, then the best treatments are a citric acid soak and hot water baths, however, if seeds can be stratified, then no pre-germination seed treatment is needed. Citric acid scarification and hot water baths produced the best germination. Stratification hastened germination rates and cumulative mean germination percentages. Stratification for 45 d appears to be sufficient, although for the best pre-germination treatments stratification requirements were less pronounced. Greenhouse screening studies of open-pollinated families for drought tolerance show genotypes from eastern localities were less tolerant than western genotypes. Taxodium distichum likely relies on both drought avoidance and drought tolerance strategies to deal with drought stress. A field screening for alkalinity tolerance showed a strong geographic component to the variation in tolerance of alkaline soils. When selecting plant material for an alkaline site, genotypes from Mexico and south Texas should be preferred, followed by central Texas genotypes. Greenhouse salinity screening showed that most genotypes tolerate moderate levels of soil salts, but at high soil salinities the tolerance appears to be highly genotype-dependent, rather than having a strong geographic pattern. Field evaluations demonstrated that T. distichum var. mexicana grew more rapidly on three Texas sites than the other varieties. These evaluations also suggest that when selecting plant material for an alkaline or xeric site, Mexican and south Texas genotypes should be preferred, followed by central Texas genotypes. Cold tolerance was not determined north of USDA hardiness zone 8.

Thesis (Ph. D.)--Washington University, 1899. / Cover title. "Printed in advance from the eleventh Annual report of the Missouri Botanical Garden."

Thesis (M.S.)--University of New Orleans, 2004. / Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Biological Sciences."--Thesis t.p. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Washington University, 1899. / Cover title. "Printed in advance from the eleventh Annual report of the Missouri Botanical Garden."

Urbanization is accelerating in the United States and is contributing to fragmentation of natural habitats, causing changes in species composition and declines in native species. Human population growth in Orlando is typical of growth in the southeastern United States and throughout the range of cypress (Taxodium distichum). Orlando has numerous isolated cypress wetlands, called cypress domes, and many remain among the current urbanized area. This makes Orlando ideal to study the effects of urbanization on cypress domes. Specifically, I tested how urbanization and its effects on fragmentation, hydrology, and fire regime) affected (a) the numbers and spatial pattern of cypress domes in central Florida and (b) the recruitment of cypress within cypress domes. Analysis of historical loss found over 3,000 cypress domes identified in images from1984, of which 26% were lost or degraded (i.e., no longer cypressdominated) by 2004. Due to changed land use, many remaining cypress domes, formerly surrounded by natural lands, have become surrounded by urban lands causing spatial clustering and homogenization. Surprisingly, I found that both natural and urban cypress domes showed lower recruitment than agricultural cypress domes, where the natural fire regime has not been altered. The probability of cypress recruitment in cypress domes urbanized for more than 20 years is very low. Previous to that, cypress tends to recruit on the edge of cypress domes where there is less competition and hydrological conditions are more favorable. I estimate that only ~50% of the current cypress domes are recruiting and the existence of those wetlands are tied to the lifespan of the current adults. By 2104, I estimate that ~89% of the cypress domes currently recruiting will fail to recruit. I believe that reducing urban sprawl and restoring the natural fire iii regime to natural cypress domes will mitigate the current fate of cypress domes. Without this, cypress in isolated wetlands in central Florida, and providing Orlando urbanization is typical, throughout urbanized areas of the range, could be at risk. Cypress in urban areas will be then relegated to riparian zones and with unknown consequences for the species that utilize the former cypress dome habitat

Thesis (Ph.D.)--Mississippi State University. College of Agriculture and Life Sciences. / Title from title screen. Includes bibliographical references.

The Atchafalaya River Basin (ARB) in Louisiana is the principal distributary of the Mississippi River, and it contains the largest contiguous area of baldcypress-water tupelo swamp forests in North America. After designation of the ARB as a federal floodway following the destructive 1927 Mississippi River (MR) flood, it was extensively modified to accommodate a substantial portion of the MR flow (~30%) to mitigate flooding in southern Louisiana. The resulting reach to system scale modifications for regional flood mitigation, navigation, and hydrocarbon extraction have substantially altered the lateral connectivity between the AR and its floodplain wetlands, threatening the ecological integrity of this globally-important ecosystem. Multiple stakeholder groups agree that restoring flow connectivity is essential to maintaining the basin’s water quality and forest health, and several flow-connectivity enhancement projects (hereafter, project elements) have been proposed by the Atchafalaya Basin Program’s Technical Advisory Group within the Flat Lake Water Management Unit (FLWMU) study area to increase lateral hydrologic connectivity within the management unit and beyond. Additionally, a new flow prescription to improve floodplain habitat has recently been suggested for the ARB. Flow into the ARB is now regulated through the Old River Control Structure (ORCS; operational in 1963), and represents the opportunity for large-scale flow experiments to enhance a multitude of ecosystem services that have been degraded due to anthropogenic alteration. For this study, I compiled existing datasets and constructed a 1D2D hydraulic model to evaluate: 1) if the suggested flow prescription would have the desired inundation impacts; 2) whether the proposed project elements would improve lateral connectivity in the FLWMU; and 3) whether recommended project elements would increase the area suitable for baldcypress recruitment in the study area. To examine the first two research questions above, I examined two scenarios – a baseline scenario to examine current conditions (no restoration projects), and a full-implementation scenario, where all proposed project elements that could be examined at the model resolution were implemented. Comparison of the modeling results for the baseline scenario to the suggested flow prescription goals suggests the overbank discharge and the extreme low-flow targets would have the desired impacts of inundating and drying out of the majority of the FLWMU, respectively. Proxy indicators of enhanced flow connectivity suggest that proposed projects will improve water quality, especially at intermediate to high flow conditions, when ~90% of the FLWMU experiences improved drainage as indicated by higher rates of water surface elevation decrease and lower overall system water volume. The stated objectives of the project elements recommended by the Technical Advisory Group are to improve connectivity and water quality, but another important and related restoration goal for stakeholders includes baldcypress restoration. To examine the third objective, I used a model-derived proxy indicator of habitat improvement (depth reduction) at two key discharges, along with other ecological suitability factors, to determine areas most likely to support baldcypress recruitment. Here, I compared baseline conditions to two alternative restoration scenarios – 1) a targeted implementation scenario where 22 project elements were implemented, and 2) the full-implementation scenario, where all projects that could be examined at the model resolution were implemented. Suitable habitat area for both natural and artificial baldcypress recruitment increased under intermediate flow conditions but remained unchanged for higher discharge conditions. For the intermediate discharge scenario, the full-implementation scenario results in a 2 km2 increase in the class considered most suitable for natural baldcypress regeneration within the calculated recruitment band, and a decrease of ~16 km2 in the areas considered least suitable for the entire FLWMU study area. Coupled with the connectivity results, which indicate that nutrient-rich river water will be exchanged between main channels and the backswamp at a greater range of flows, it appears that project implementation alone will benefit baldcypress recruitment, especially artificial regeneration efforts. However, full project implementation coupled with large-scale flow modifications at ORCS would likely provide maximum benefit for baldcypress restoration efforts that seek to increase the area supportive of natural baldcypress regeneration.

No description available.