This dissertation research aimed to quantify current soil organic carbon (SOC) stocks across Louisianas landscape, examine the spatial relationships between SOC and terrain factors at the watershed and river basin scales, and predict SOC changes in surface soils during future climate change. Using Louisiana as an example, a spatially-explicit modeling framework was developed that is conducive to watershed-scale prediction of soil carbon stock and change. SOC densities at the watershed scale were estimated using the USDA NRCS Soil Geographic Database (STATSGO). Louisiana watersheds and National Land Cover Database (NLCD) were used to aggregate total soil carbon and estimate average soil carbon density. Watershed drainage densities and slopes were quantified with 1:24 K Digital Elevation Models (DEM) data and the Louisiana hydrographic water features. Potential changes in SOC under 0.5° x 0.5° high-resolution climate change projections in Louisiana were simulated using a RothC model at a watershed scale under three greenhouse gas emissions scenarios (A1FI, A2, B2) based on the HadCM3 climate model. LIDAR and DEM datasets were used to assess the spatial distribution of potential inundated coastal areas; estimate the current wetland areas, SOC storage, and nitrogen contents at risk in Louisiana, classified by the National Wetlands Inventory (NWI) and DEM datasets. The research found that SOC density ranged from 22 to 108 tons/ha in the upper 30-cm soil at the watershed scale, with the highest density in emergent herbaceous wetlands. Among Louisianas 12 river basins, the Barataria, Terrebonne, and Lake Pontchartrain Basins in southeast Louisiana showed the highest SOC density. SOC density was positively correlated with watershed drainage density (r2=0.43), but negatively correlated with watershed slope gradient (r2=0.52) and elevation (r2=0.50). The modeling study on climate change effects showed that SOC storage in the top 30-cm soil layer of Louisiana forests, croplands, and grasslands would significantly decrease under all climate change scenarios. Coastal areas in southeastern Louisiana have some freshwater and estuarine wetland ecosystems that store a large quantity of organic carbon. Much of these areas have elevations less than 100 centimeters and are, therefore, prone to inundation of sea level rises during future climate change.

Recovery of heavy metals from chromated copper arsenate (CCA) treated southern pine wood samples with three different dimension was investigated by recovery with acetic acid, oxalic acid and phosphoric acid in microwave reactor. Diluted phosphoric acid mixed with acetic acid was found to be very effective to remove copper, chromium, and arsenic from spent CCA-treated southern pine sawdust at a high temperature and in a short time. No single acid can totally recover all these three metals in one step in this method. Oxalic acid was effective in removing chromium and arsenic, and acetic acid was effective in removing copper and arsenic; However, CCA cannot be recovered with the mixture of acetic acid and oxalic acid because of a possible conflict effect. The effects of mixed acid concentration, reaction time, and temperature in microwave on recovery of CCA-treated wood samples were determined. The minimal reaction condition for maximum extracting CCA elements was 2.75% phosphoric acid mixed with 0.5% acetic acid, for 10min. at 130°C. The total recovery rate of CCA can reach 100% arsenic, 93.5% chromium, and 98.5% copper in one step. Statistical analysis showed the concentration of phosphoric acid and temperatures were two important factors. Three sizes of wood chips were also extracted in the microwave reactor. For the particle size of 0.5×0.5×0.5cm, 93.5% arsenic, 64.5% chromium, and 95.89% copper was extracted by 3.5% phosphoric acid mixed with 0.5% oxalic acid after 50 min at 130°C. Although it needs a longer time to achieve the total CCA extraction, the microwave reactor assisted acid extraction method was more effective than previous approaches.

Water chemistry, habitat quality, and channel stability interact to influence a streams biological integrity. The goal of this project was to assess how channel stability, together with other physicochemical stream measurements, are associated with the structure and abundance of resident macroinvertebrate communities. I recorded multiple physicochemical parameters and calculated a Pfankuch habitat stability index monthly for a year at potential reference streams in southeastern Louisiana. I assessed the relationships of channels stability with measured physicochemical parameters with multiple regression and principle components analysis. Mixed model multivariate analysis of variance was used to determine associations of habitat characteristics with resident macroinvertebrate genera and communities. In the September woody debris sample, macroinvertebrate abundance was generally determined by habitat factors that describe stream metabolism and woody debris habitat, in the May woody debris sample, abundances of xylophilic macroinvertebrates appeared to be more associated with geomorphologic components of a stream rather than stream productivity. The PSI was associated with multiple habitat variables, and variability in channel stability between streams was found to affect macroinvertebrate genera and community abundances in both seasons regardless of stream size or stream productivity. Because of the high correlations between the PSI, other habitat variables, and macroinvertebrate abundance, I believe the PSI should be used in future studies that focus on developing a biotic index in low gradient Louisiana streams. Integrating biological monitoring, more precise habitat measurements, and current physicochemical monitoring protocols will result in managers having more tools to evaluate stream degradation and protect Louisianas waterways.

In riverine wetlands, the rate and magnitude of water exchanged between river channels and adjacent wetlands have a major influence on hydrologic function and associated aquatic habitat and water quality. River channels are generally separated from backswamps by natural levees; however, preferential flow may allow potentially substantial water and solute exchange between them. Determining the influence of preferential flow on water and solute transport in natural levees requires an innovative approach that allows measurement of transport rates at a scale large enough to capture field-scale variability. To test the hypothesis that preferential flow is important to subsurface water movement through natural levees, we measured hydraulic gradients and solute tracers in a 10 x 9 m grid of 19 shallow (2m) monitoring wells within a large volume (300 m3) of natural levee in the Atchafalaya Basin, Louisiana. In addition to measuring transient responses to natural events, we constructed a small reservoir on the backswamp side of the levee to create a hydraulic gradient from the swamp to the adjacent river channel. We used a simple linear system approach to model residence time distributions of water and solute within the natural levee. Overall, hydraulic response to forcing events, whether from rain or reservoir filling, was rapid in all wells (mean pressure wave velocity 2.5 E-2 m/s) and relatively uniform; in comparison, tracer transport was much slower (mean 3.2 E-4 m/s) and more variable. Spatially, mean subsurface tracer velocities varied over several orders of magnitude: between 1.6 E-7 and 6.8 E-5 m/s under a 12-cm hydraulic gradient and between 2.1 E-7 and 2.2 E-3 m/s under a 70-cm hydraulic gradient. Comparatively greater variability of chemical verses hydraulic behavior indicates multiple functioning transport mechanisms in natural levee sediments and suggests preferential flow; thus, methods that estimate transport rates based on standard point measurements likely greatly underestimate exchange at the field scale. Results suggest that preferential, subsurface flow through natural levees may provide hydrologic connectivity that is meaningful to basin-scale biogeochemical processes.

North American grassland birds have been declining at an alarming rate. Winter habitat for grassland species in the southeastern U.S. generally occurs within forests subject to management. I studied wintering grassland bird communities in De Soto National Forest in southern Mississippi. My objectives were to: 1) Assess bird communities and vegetation structure in upland forest stands that were salvage-logged following Hurricane Katrina, in stands managed for Red-cockaded Woodpeckers (Picoides borealis, RCW), and in stands containing bogs; and 2) Determine the extent of the association between vegetation and occurrence of the common wintering grassland birds. I conducted bird and vegetation surveys in 27 stands over two winters. The wintering grassland bird community included Bachmans Sparrow (Aimophila aestivalis), Henslows Sparrow (Ammodramus henslowii), and Sedge Wren (Cistothorus platensis). Forest-stand associations varied among species. Bachmans Sparrows occurred only in upland and RCW-managed stands, Henslows Sparrows occurred only in bogs and RCW-managed stands, and Sedge Wren occurred in all stand types. None of these species densities was statistically different between salvaged and unsalvaged stands. There were no statistically significant differences in total grassland bird density or species richness among stand types. Henslows Sparrow use of RCW stands was mostly ephemeral, but our data were consistent with previous studies suggesting that RCW management benefits grassland birds. Spatially uniform, dense herbaceous cover, and cover of Scleria muhlenbergii, a preferred food item, best predicted Henslows Sparrow stand occupancy. Increased woody understorey vegetation and decreased tree density best predicted Sedge Wren occupancy. I recommend management practices focusing on small-scale herbaceous ground-layer restoration in bogs, an increase in the number of RCW clusters, and the thinning of trees in dense stands.

As a multi-million dollar industry, production of the eastern oyster <i>Crassostrea virginica</i> is significant to the economy of the nations coastal regions. The cost of commercial oyster aquaculture has higher inputs than the oyster fishery, but larger, better quality oysters can be produced for culture by the stable availability of triploid individuals.<br><br> The goal of this project was to determine if the use of an estrogen, estradiol-17&beta; or estradiol-3-benzoate, at a consistent environmental temperature would increase the percentage of females in a population, as well as ovarian development of eastern oysters. Ultimately, this could be applied to triploids to increase the number of viable oocytes produced for use in tetraploid induction. Tetraploids are used in direct triploid production to produce 100% triploid offspring when crossed with diploids.<br><br> When estradiol-17&beta; was administered to oysters obtained late in the spawning season (August), there was no significant change in sex distribution. The gonad-to-body ratios on day 10 were significantly greater than on day 14 (<i>P</i> < 0.0001) and the stages of ovarian development in oysters treated with 150 ng differed from the other treatments (<i>P</i> = 0.002); significant differences were also seen between days 10 and 14 in this treatment (150 ng; <i>P</i> = 0.004).<br><br> When estradiol-3-benzoate was administered to out-of-season oysters obtained in February prior to the spawning season, there was a significant difference in sex distribution from days 10 to 14 between the non-injected control (<i>P</i> = 0.030) and 37.5 ng treatment (<i>P</i> = 0.010). There was not enough gonadal tissue to calculate the gonad-to-body ratio, but there were no significant differences in the stages of ovarian development.<br><br> Overall, the decrease in ovarian size over time is indicative of exogenous factors negatively affecting gonadal development. By increased management of factors such as high nutrient availability and decreased stress during transport and hormone administration could improve the response to estrogen treatment. Due to the short half-life of estrogens <i>in vivo</i>, a sustained-release system could also increase the treatment efficacy. Under the present conditions, there was not a clear, predictable effect of either estrogen on increasing gonadal development, maturity, or sex.

Rice is the most common wetland crop in the world, and important for waterbirds and shorebirds worldwide, including the United States. In Louisiana, shorebirds use rice fields during spring migration, and are an important for foraging and refueling during migration. However, competing land uses and restoration projects may reduce the availability of rice fields, and impact the landscape that shorebirds use during migration. To determine how shorebirds use the landscape, I evaluated local and landscape factors affecting shorebird use of rice fields during spring migration in southwestern Louisiana. Using five habitat suitability zones (HSZs) based on rice density and canopy cover, I performed stratified random surveys at rice fields within each of the 5 HSZs. I surveyed 94 fields in 2008 and 85 fields in 2009. I quantified all habitat types within 3 km of each field, recorded habitat conditions during each visit, and recorded all shorebirds observed. Mixed modeling analyses indicated that shorebird density was primarily influenced by local field conditions: flooding extent (p<00001), the percent of the field perimeter bordered by trees (p=0.0075), surveyed rice field area (p<0.0001), and rice height (p<0.0001). Shorebirds responded positively to flooding extent, and negatively to tree border, field area, and rice height. Overall shorebird density was not influenced by any landscape variables at any scale (1, 1.5, 2, 2.5, or 3 km). The percent of non-rice crop (p=0.0437) and fallow land (p=0.0400) immediately adjacent to surveyed fields was a positive influence on density of the seven most common species, and HSZ was a positive influence on shorebird habitat use for 3 of the most common species or species groupings: Dowitchers (2 spp), Peeps (3 spp), and Yellowlegs (2 spp). These species comprised > 50 % of all birds observed, indicating the importance of HSZ for individual species. Rice density was significantly higher in HSZ4 and HSZ5, and the percent of forest (an alternate measurement of canopy cover) was significantly lower in HSZs 4 and 5. These results support the validity of the habitat suitability model. By maintaining rice production in the higher HSZs, suitable local habitat conditions would be provided for shorebirds.

Population growth for mallards (Anas platyrhynchos), and presumably other upland nesting ducks, in the Prairie Pothole Region is most sensitive to nest success, and nest success is most strongly influenced by predation. I evaluated the efficacy of reducing predator populations to improve nest success and increase local breeding populations of upland nesting ducks on township-sized (93.2 km2) management units in eastern North Dakota, USA, during 2005−2008. I also examined potential territorial limitations on local population growth for mallards. Trappers annually removed an average of 245 predators per trapped site. I monitored 7,489 nests on 7 trapped and 5 nontrapped sites, and I found nest success to be 1.4−1.9 times greater on trapped sites, depending on year. I surveyed an average of 621 wetlands twice annually and observed 3,674 blue-winged teal (A. discors), 3,227 mallard, 2,287 gadwall (A. strepera), 1,539 shoveler (A. clypeata), and 679 pintail (A. acuta) breeding pairs. I found little evidence that local breeding populations of upland nesting ducks increased following predator reduction. Defense of territories, which may limit local population growth, was most frequent during settling and declined as greater portions of local mallard populations commenced nesting. Territorial defense was strongly correlated to the ratio of breeding pairs to available wetland habitat, such that sites with higher pair densities had greater frequencies of territorial behavior. Hence, defense of territories may function to limit local breeding populations. Though predator reduction provides managers with an effective tool to improve nest success at large spatial scales, they should not rely on the practice to increase local breeding populations.

Mallards Anas platyrhnchos are arguably the most researched waterfowl species in North America. They exhibit great flexibility in certain breeding metrics such as timing of nest initiation and clutch size. A study on captive female Mallards (Batt and Prince 1979) fed ad libitum, held in identical breeding compartments, and paired with the same mate in each year of the study exhibited substantial variation in the timing of nest initiation within a given year, yet some individual females demonstrated consistency in initiation date among years. My objective was to examine breeding metrics such as timing of nest initiation and clutch size and to evaluate age-related productivity in conjunction with those metrics. More specifically, I wanted to know if individual females were consistent in first initiated nests among years. Secondly, I wanted to know if age affected both the timing of nest initiation and clutch size. From 2006-2009 nest searching crews found 2274 Mallard nests and captured 944 females using various trapping techniques. I found strong evidence for variation among birds within year. I failed to find a significant influence of individual variation among birds between years. Age was not significant in impacting when an individual nests. The effects of nest year were also tested but were not significant. For my clutch size analysis, all 944 females captured were used and categorized to an age group based on wing feather characteristics. Age, year, and julian date all had significant impacts on clutch size. After second year (ASY) females had 0.32 more eggs than second year (SY) females. Clutch size varied by year and declined seasonally, such that for every day of delay clutch size was reduced by 0.05 eggs. Mallards exhibit great flexibility in the timing of nest initiation for which they breed. However, approximately 36% of the females show consistency in their individual nesting dates which were prior to the mean annual initiation date. Some individuals consistently nested later than the mean annual initiation date. Nevertheless, there appears to be strong directional selection for early nesting.

The Louisiana Gulf Coast is an important wintering area for North American gadwall (Anas strepera). Conservation of winter habitat is a top priority of the Gulf Coast Joint Venture. Quantitative estimates of habitat use by wintering gadwall would help improve energetic demand models and subsequent estimates of habitat requirements. I used satellite telemetry (PTTs) to estimate winter habitat and refuge uses, spring migration chronology and corridors, as well as inter- and intra-regional winter movements of females. I used a split-plot MANOVA to evaluate the effects of individual females, female age, winter, hunt periods within winter, time of day, and all possible interactions among these explanatory variables on habitat use. I used a mixed model ANOVA to evaluate the effects of individual females, female age, winter, hunt periods within winter, time of day, and all possible interactions of these explanatory variables on refuge use. I used mixed models to evaluate the effects of hunt periods within winter, refuge use, winter, individual female, female age, and body condition at time of capture on intra-regional movements. Finally, I used a MANOVA to evaluate the effects of female age, spring of tracking, and body condition at time of capture on several spring migration parameters. I found that habitat use in winter 2007-08 was dominated by intermediate marsh, whereas habitat use during winter 2008-09 showed an increased dependence on freshwater marsh (P = 0.0001). Use of non-hunted refuges by adult females was greater when hunting season was open than when closed (P = 0.0061). I found no significant relationships among the explanatory variables and intra-regional movements (all Ps > 0.09). Peak migratory departure from the Louisiana Gulf Coast Chenier Plain occurred during late-March to early-April. HY females traveled a greater total migratory distance, spent more days migrating, used more stopovers, and arrived at inferred breeding locations later than did AHY females (all Ps ≤ 0.061). My results suggest that intermediate marsh is important for wintering gadwall; however, freshwater marsh may become important after tidal surge events. Finally, my migration data provides habitat managers with quantitative information to consider when implementing conservation programs and management practices.