Louisianas small streams provide critical habitat for diverse ecologically and economically important fish species. However, the relationship between these fish assemblages and habitat variables remains poorly understood. The role of anthropogenic alteration of dendritic stream connectivity is of specific interest and has been shown to significantly influence stream ecology. This study explored the interaction among watershed characteristics, stream connectivity, stream physico-chemistry, and fish assemblages in little-studied Red River basin of central Louisiana as well as how reservoir littoral zones compared to streams, both in terms of fish assemblage and habitat. Fish and habitat were sampled in 21 headwater streams, half of which flowed directly into a reservoir, and in four reservoir littoral zone sites. Multivariate analyses indicated that level of dendritic connectivity did not explain a significant amount variation in stream fish assemblages. Fish assemblage composition and its relationship to common environmental gradients were similar in in all streams regardless of connectivity. Additionally, the assemblage and habitat of the reservoir littoral zone was comparable to that found in streams indicating that reservoirs were not serving as deleterious barriers to stream fish assemblages. However, individual species modeling revealed greater abundance of three species in streams with unaltered connectivity. These results do not parallel trends observed in other examinations of altered dendritic connectivity, however, they are concurrent with studies of coastal plain fishes response to other disturbances. Understanding the magnitude and structure of response to disturbance is critical for preserving aquatic ecosystems and focusing conservation efforts. Even systems such as the Red River Basin, which evidence strong resilience to human disturbance, warrant closer inspection before heedless system alteration continues.

The future of Louisianas coastal cypress-tupelo forests is threatened by prolonged or permanent flooding during the growing season. Permanent inundation prevents baldcypress seedlings from becoming established. The upper limit of submergence with respect to adequate planted baldcypress seedling performance has not been effectively tested under actual field conditions. Similarly, an effective method for determining a sites regeneration potential based on present vegetation attributes has not been developed. To test first-year performance of planted baldcypress seedlings under varying levels of submergence, I planted 900 of both 1-0 and 2-0 age-class bare-root seedlings across 12 different sites covering a range of hydrologic conditions and monitored their performance over the 2014 growing season. Water levels were continuously monitored for each individual seedling, and survival and height growth were documented. Due to their taller starting heights, 2-0 seedlings were submerged, on average, less often (1.4 days) than 1-0 seedlings (34.8 days). Survival was high across sites for both age classes (79% for 1-0 and 89% for 2-0). Survival of 1-0 seedlings decreased to only 9% following more than 90 cumulative days of submergence. Height growth across sites was greater for 1-0 seedlings (0.29 m) than 2-0 seedlings (0.13 m). Height growth of 1-0 seedlings decreased significantly following more than 30 cumulative days of submergence. To relate present vegetation attributes to baldcypress regeneration potential, I sampled the vegetation on all 12 sites in addition to using vegetation and hydrology data from five sites monitored by the Coastwide Reference Monitoring System (CRMS). Sites were separated into three categories based on how their hydrologic regime related to baldcypress regeneration potential. Sites with potential for natural regeneration were indicated by a species-diverse overstory and a high midstory stem density. Sites with only artificial regeneration potential were indicated by an overstory layer consisting almost exclusively of cypress-tupelo and a dense midstory layer with a high percentage of stems rooted on elevated structures. Sites with neither natural nor artificial regeneration potential were indicated by an overstory layer consisting almost exclusively of cypress-tupelo and a sparse midstory layer with a high percentage of stems rooted on elevated structures.

Multiple wetland restoration and enhancement techniques are used in Louisiana to combat land loss and provide habitat for waterbirds. We investigated the avian response to three wetland restoration techniques in the Lower Mississippi Birds Foot Delta to determine if the different habitat types resulted in differences in the value of edge habitat. Species richness, guild richness, total bird density, bird density by foraging guild, and bird abundance relative to distance from the marsh edge was compared among (i) crevasse splays, a type of sediment diversion which allow the river to build new wetlands, (ii), beneficial use of dredged material marshes, where heavy equipment to create new wetlands from sediments dredged from navigation channels, (iii) marsh terraces, where lighter equipment is used to create strips of edge habitat from sediments dredged from the restoration site, (iv) old edge marshes, representing pre-restoration conditions at degrading marshes, and (v) open water sites. Seasonal bird counts and vegetation surveys were conducted from March 2013 to October 2014 at plots within the Pass a Loutre State Wildlife Management Area and Delta National Wildlife Refuge in Plaquemines Parish, Louisiana, USA. We found bird abundance and diversity differs among the five habitat types during some times of the year, with habitat type and season often having a significant affect on the composition of the avian community. There was a significant relationship between habitat types and environmental factors (p=0.002), and a significant relationship between foraging guilds and environmental factors (p=0.002). Habitat type functions as a useful predictor of guild richness, but alone is not a perfect substitute for environmental variables when identifying the source of all variation in avian community composition. All habitat types studied provided habitat for birds, but were not utilized by all species or foraging guilds equally. We found that old edge marshes supported similar species richness as restored marshes during summer and winter (p<0.05) and open water supported the highest bird density in winter and spring (p<0.05). Any marsh habitat type, however, can be expected to support greater guild and species richness than open water areas during all seasons, but not greater bird density.

Managing for the long-term survival of a species requires an understanding of its population genetics. The desert tortoise, Gopherus agassizii, inhabits the Mojave and Sonoran deserts of North America. Desert tortoises face many threats to their continued survival, including habitat loss and fragmentation. I used mitochondrial and microsatellite DNA markers to examine genetic structure within and among populations of desert tortoises. I found that both the Mojave and Sonoran populations of desert tortoise exhibit similar patterns of population genetic structure. Gene flow among localities within each region is part of the evolutionary history of the desert tortoise and dispersal events probably play an important role in the long-term maintenance of populations. Movement barriers caused by anthropogenic landscape changes have the potential to effect desert tortoise population viability. Understanding the historical connectivity between and within the Mojave and Sonoran populations of desert tortoises will help facilitate the conservation of this species.

Gulf killifish, Fundulus grandis, shows promise for commercial development as a marine baitfish species. Significant markets for F. grandis already exist throughout the Gulf Coast, with the vast majority of supply coming from wild-harvests, which can be hampered by seasonal availability and inconsistent fish health and size. The genus Fundulus also represents an important group of model vertebrates for biological study. A recent review paper described this genus as the premier teleost model for environmental biology. New information generated as a result of the work contained in this dissertation may be more broadly applicable to sister species of F. grandis, enhancing the primary goal of improving reproductive output and fitness in cultured individuals of this species. Results of this dissertation include optimization of culture salinity, female broodfish body size, and dietary lipid composition. Optimal salinity for culture of juvenile F. grandis was 12.0, with growth incrementally increasing between 0.5, 5.0, 8.0, and 12.0. Survival was negatively affected at 0.5. Optimal body size for female broodfish was 12-13 g. Minimum size recommended for broodfish was 7 g and per-unit-mass fecundity begins to level off in females greater than 13 g. Fecundity of F. grandis was less sensitive to manipulations of dietary lipid content than many other fishes. No difference in fecundity was found among fish fed isonitrogenous diets ranging in lipid content from 4.0 to 13.8%. Excess lipid was mostly stored in the intraperitoneal cavity, rather than being partitioned for reproduction. Dietary lipid composition produced very little effect on overall fecundity in F. grandis, despite experimental diets with very different fatty acid (FA) composition. Differences did occur in subsequent larvae at extreme physiological conditions, but these variations were unlikely to have any effect on survival in culture or natural settings. Examinations of FA dynamics across time revealed that F. grandis likely utilizes a combination of mobilization from somatic reserves and de novo biosynthesis of long chain polyunsaturated FAs to compensate for dietary FA deficiency. Overall, the characteristic physiological plasticity of F. grandis also applied to lipid dynamics.

Regenerated cellulose nanoparticles (RCNs) including both elongated fiber and spherical structures were prepared from microcrystalline cellulose (MCC) and cotton using 1-butyl-3-methylimidazolium chloride followed by high-pressure homogenization. The RCN has a two-step pyrolysis, different from raw MCC and cotton that had a one-step process. The crystalline structure of RCNs was cellulose II in contrast to the cellulose I form of the starting materials. Also, the RCNs have decreased crystallinity and crystallite size. The elongated RCNs produced from cotton and MCC had average lengths of 123 ± 34 and 112 ± 42 nm, and mean widths of 12 ± 5 and 12 ± 3 nm, respectively. The average diameter of spherical RCNs from MCC was 118 ± 32 nm. Cellulose nanocrystals and cellulose nanofibers with I and II crystalline allomorphs (designated as CNC I, CNC II, CNF I, and CNF II) were isolated from bleached wood fibers by alkaline pretreatment and acid hydrolysis. The effects of concentration, particle size, surface charge, and crystal structure on the lyophilization-induced self-assembly of cellulose particles in aqueous suspensions were studied. Within the concentration range of 0.5 to 1.0 wt %, cellulose particles self-organized into lamellar structured foam composed of aligned membrane layers with widths between 0.5 and 3 ì m. At 0.05 wt %, CNC I, CNF I, CNC II, and CNF II self-assembled into oriented ultrafine fibers with mean diameters of 0.57, 1.02, 1.50, and 1.00 ì m, respectively. Cellulose nanoparticle (CNP) reinforced Polyvinyl alcohol-borax (PB) hydrogels were prepared through a facile approach in an aqueous medium. The obtained stiff, high-water-capacity (~96%), low-density (~1.1g/cm3), translucence hydrogels exhibited birefringence textures. These free-standing, high elasticity and mouldable hydrogels also exhibited self-recovery under continuous step strain and thermo-reversibility under temperature sweep. The rheological tests and compression measurements confirmed the incorporation of well-dispersed CNPs to PB system significantly enhanced the compressive strength, viscoelasticity and stiffness of the hydrogels. Highly-crystalline CNPs not only tangled with PVA chains though numerous hydrogen bonds, but formed chemically crosslinked complexes with borax ions as well, thus acting as multifunctional crosslinking agents and nanofillers to physically and chemically bridge the 3D network hydrogels.

I sought to understand how forest fragmentation and secondary growth affect avian movement at the Biological Dynamics of Forest Fragments Project (BDFFP) near Manaus, Brazil. When deforested areas are abandoned, secondary forests regenerate, allowing rainforest animals to gradually recovery their ability to use formerly inhospitable habitat. My colleagues and I captured 2773 understory birds of ten foraging guilds along the edges of primary forest fragments and variable secondary forest. Age of secondary forest along edges was the most important variable driving capture rates on primary/secondary edges. Mean recovery to pre-isolation capture rates was 26 years after abandonment, but terrestrial insectivores took far longer to recover than other guilds, ¡Ý 54 years. I radio-tracked 73 understory insectivores of three species in variable landscapes to uncover patterns in avian movement in secondary growth¡ªspecifically evaluating space use (home range, movement rate, etc.), edge responses and habitat transition probabilities. Space use varied widely as secondary growth recovered, with species showing vastly different spatiotemporal strategies in returning to forest. Woodcreepers Glyphorynchus spirurus and Xiphorhynchus pardalotus recovered to primary-forest-level edge responses and transition probabilities after 11¨C15 and 15¨C20 years, respectively. En route to recovery, both woodcreepers increased home range sizes and movement rates in young secondary forests. Formicarius colma, a common terrestrial insectivore, had a far more rigid strategy, avoiding young secondary forest, then using space in older secondary forest similarly to the way it used space in primary forest. With bird ages pooled, F. colma showed a return to no edge response about 28¨C30 years after land abandonment, with some evidence for an edge response by young birds even 27¨C31 years post-abandonment. Further, through habitat transition probabilities, I showed that F. colma preferred primary forest over 27¨C31 year-old secondary forest (the oldest at the BDFFP), indicating that even after 27¨C31 years, secondary forest had not recovered for movements of this terrestrial insectivore. By quantifying how land-use patterns affect avian movement, connectivity, and community dynamics, we will be generating the understanding necessary to manage heterogeneous landscapes for biodiversity conservation in the 21st century and beyond.

Predictive models were developed for stiffness and bending strength of southern pine 2x6, eight ft. lumber using nondestructive measurements of stresswave velocity, density and visual characteristics such as knots, slope of grain and rate of growth. To account for local areas of weakened material due to knots and slope of grain, a grid system was developed to quantify general knot size and location. Multiple regression models were created using these physical and visual measurements. Two sets of models were developed: one that removed influential samples with abnormal wavespeeds (greater than 18,000 ft./s) indicative of poor wood quality; and, models that included all samples. Static modulus of elasticity (MOEs) model performance was significantly better for those that removed influential samples compared to the all-sample models, with an R2 of 0.892 and 0.720, respectively. Modulus of rupture (MOR) model performance was slightly better with influential samples removed R2 of 0.714 and 0.690, respectively. The location of knots within a board significantly altered the mechanical properties, especially bending strength. The results indicate potential for greater specification of allowable stresses for different orientations during bending. A simulated grading study was conducted to assess the feasibility of the developed models. Thousands of samples were generated according to estimated variable distributions and graded according to the American Lumber Standards Committee Machine Graded Policy. Results suggest that these models may be feasible in an actual lumber grading scenario.

Understanding gene flow and population structure in wildlife populations helps managers to protect distinct genetic lineages and genetic variation in small, isolated populations at high risk of extinction. I assessed genetic diversity in Bachmans Sparrows (Peucaea aestivalis) to evaluate the role of natural barriers in shaping evolutionarily significant units as well as the effect of anthropogenically-caused habitat loss and fragmentation on population differentiation and diversity. Genetic diversity was assessed across the geographic range of Bachmans Sparrow by genotyping 226 individuals at 18 microsatellite loci and sequencing 48 individuals at nuclear and mitochondrial DNA genes. Multiple analyses consistently demonstrated high levels of gene flow, which appear to have maintained high levels of genetic variation and panmixia in populations throughout the species range. Based on these genetic data, separate management units/subspecies designations or artificial gene flow among populations in habitat fragments do not seem necessary. High vagility in Bachmans Sparrow may be an adaptation to colonize ephemeral, fire-mediated longleaf pine habitat, but in recent times, it also appears to have reduced inbreeding and loss of genetic diversity in habitat fragments.

Floodplain lakes in floodplains of large rivers undergoing intensive alterations are subject to hydrologic alteration. One example is in the Lower Mississippi Alluvial Valley (LMAV) and pivotal habitat for wildlife. Catahoula Lake has experienced hydrologic regime alterations over the past ~150 years that may be contribute to changes in the habitat with expansion of woody plants. A Diversion Channel was constructed in 1972 to provide the natural, annual de-watering of the lake to maintain its ecological integrity, but ecologic changes are still occurring. Our general goal is to understand the hydrologic regime of the lake, particularly the historical hydrologic regime of Catahoula Lake and to identify the contribution of the adjacent rivers Little, Atchafalaya, Red, Black, Ouachita, Tensas, and Mississippi rivers to the variability of Catahoula Lake prior to and after extensive hydrologic modifications in the LMAV. Historical lake level and neighboring rivers stage time series were used to estimate the hydrologic links between the lake and its surrounding rivers. Our analyses were done for three time periods: (1) immediately prior to the Diversion Channel construction, (2) post-Diversion Channel period, and (3) estimated condition in the late 1800s prior to incision of the Atchafalaya River. Results indicate that water levels on the lake are complexly related to the influxes of the Little River or the stage of the Black River stage at Jonesville, and the most consistent relationship is with the Atchafalaya River, which controls the lake level via a backwater effect at stage 7.3 m or higher. This backwater effect has been reduced from 207 to 120 days per year between 1880 and 2010. Compared to its condition prior to hydrologic alterations, results indicate modifications in the LMAV and the construction of the Diversion Channel have altered the lake regime. Our best estimates is that current lake levels are lower in the high-water spring, less variable in the dry period, and lack the extreme high water events of 100+ years ago.