While there is growing evidence that shade/flood tolerance tradeoffs may be important in distributions of bottomland hardwood trees and indications that they should apply to herbs, no studies have definitively explored this possibility. Four years of field data following historic flooding were supplemented with a greenhouse experiment designed to identify interactions congruent with tradeoffs. Fifteen bottomland species were grown in two levels of water availability and three levels of shade over 10 weeks. Results indicate responses of Fimbristylis vahlii and Ammannia robusta are consistent with tradeoffs. Modification of classical allometric responses to shade by substrate saturation indicates a potential mechanism for the tradeoff in A. robusta. Responses indicating potential for increased susceptibility to physical flooding disturbance are also discussed.

Red oak (Quercus spp.) acorns provide food for wildlife and are propagules for regeneration of these trees. Annual yield of acorns varies temporally and site-specifically. I examined acorn yield in relation to hydrology and soils of hardwood bottomlands at five sites in the Mississippi Alluvial Valley and a site in the Mississippi Interior Flatwoods Region during fall-winter 2012-2013. Acorn yield varied among sites (mean = 44.9 acorns/m2; SE = 6.7; CV = 14.9%). Duration of flooding during the growing season differed among sites which influenced soil characteristics. Acorn yield varied inversely with number of days sites were inundated during the growing season (R2 = 0.6725; P = 0.0456; n = 6) during 2012-2013. Managers should consider alleviating growing season flooding of red oaks, which may increase acorn yield and sustain red oaks and other bottomland hardwoods.

Bottomland hardwood forests provide forage and other important resources for wintering and breeding waterfowl in the Southeastern United States. My objective was to conduct an initial investigation of possible influences of habitat features, flood events, and human disturbance on relative abundances of wintering ducks in Delta National Forest (DNF), Mississippi. I surveyed 65 wetlands in DNF 17 times from November 2012 to March 2013 and analyzed abundance data from wood ducks (Aix sponsa), mallards (Anas platyrhynchos), gadwalls (Anas strepera), and hooded mergansers (Lophodytes cucullatus). Waterfowl abundance varied by species but generally increased during major flood events and on wetlands having an approximately equal interspersion of scrub-shrub and open water consistent with the “hemi-marsh” concept. I recommend partial removal of scrub-shrub from selected wetlands to promote emergent plant communities and increased duck use and experimental evaluation of waterfowl responses to management of wetlands and human activities during winter in DNF.

Many bottomland hardwood stands in southern Mississippi lacked management prior to Hurricane Katrina. Following removal of overstory oaks, no seed source was available to naturally regenerate these stands. Artificial regeneration became the most viable option, but information was lacking on how to successfully reestablish thousands of acres of bottomland forests quickly and successfully. Bareroot and conventional containerized seedlings of Nuttall oak (Quercus texana) and swamp chestnut oak (Quercus michauxii) were planted on two sites in southern Mississippi. After two growing season’s Nuttall oak exhibited similar survival to (93.4%), better groundline diameter growth (13.0 mm) than, and better height growth (68.8 cm) than swamp chestnut oak (92.5%, 6.6 mm, 43.9 cm, respectively). Bareroot seedlings had the highest survival (94.5%), best groundline diameter growth (10.3 mm), and best height growth (66.6 cm), though conventional containerized seedling survival (91.4%), groundline diameter growth (9.3 mm), and height growth (46.0 cm) were all acceptable. Considering seedling cost and overall performance, bareroot seedlings provide the most effective option for artificial regeneration on high quality bottomland hardwood sites.

The objective of this study was to examine some mechanisms of bottomland hardwood afforestation and their impacts on above- and belowground carbon sequestration. Six combinations of bottomland hardwood species and two levels each of fertilizer and herbicide were applied in a completely randomized design on two sites in the LMAV. Survival, ground line diameter and total height were monitored for two growing seasons. Soil carbon and nitrogen to a depth of one meter, herbaceous biomass, and tree biomass were sampled in the first and second years of establishment. Species mixes, fertilizer, and herbicide application significantly affected survival, growth, above- and belowground tree biomass carbon after two years of establishment. Survival was generally average, while growth for most species mixes was below expectation. Species mixes E (green ash/oak mix) and F (NRCS species mix) had the highest tree vegetation carbon both above- and belowground. Soil carbon and nitrogen were not significantly affected by any treatments.

Riparian forests are integral components of the landscape. The inherent biogeochemical processes that occur in such forests provide numerous benefits to wildlife and society. Maintaining good water quality is a major benefit from riparian forests and therefore, the maintenance, creation, or restoration of riparian forests is indispensable. This study was designed to broaden current knowledge of the complex, interrelated biogeochemical processes and determine indices for riparian forest restoration based on the various carbon pools/fluxes that may represent restoration success. This study was implemented on the Savannah River Site, an Environmental Research Park, where several riparian forests are recovering from thermal disturbances. The streams in these forests were subjected to thermal discharges that increased flows and resulted in removal of soil and a decline in the amount of woody vegetation. Two of these riparian forests are at different ages post-disturbance and represent different stages of recovery, which provides an exceptional opportunity to study successional processes in riparian forests and enhance restoration efforts. Linear transects perpendicular to the main stream channels were established in 2 recovering riparian forests of different ages (two areas in Pen Branch ~ 8 years post-disturbance; Fourmile Branch ~ 12 years post disturbance) and an undisturbed (thermally) more mature riparian forest (Meyer's Branch ~ 60 years). Along these transects quantitative data were obtained on above and belowground carbon pools and fluxes. Carbon pools exhibited a close correlation with riparian forest development. Biomass and carbon pools increased with increasing riparian forest stand age. The importance of the herbaceous carbon pool declined relative to the total above ground biomass, and the root carbon pool increased with forest age/succession. In general, net primary production (NPP) in young riparian forests (~8-10 years) rapidly approached and even exceeded NPP of more mature riparian forests. Once the herbaceous stage of succession was surpassed, the litterfall component of NPP plays a greater role riparian forests. As a woody overstory became established (after ~ 8-10 years), annual litterfall rates as a function of NPP were independent of forest age. Establishment of woody species occurred ~8 to 10 years after thermal disturbance and litterfall amount in young riparian forests rapidly became comparable to mature riparian forests. Lateral litter movement from the riparian forest toward the stream was less than the amount of litter (carbon pool) deposited from upstream into the riparian forest during a flood event. Overall lateral litter movement supplied less energy to the stream system than vertical inputs. A decline in riparian forest floor biomass was observed with increasing riparian forest development. However, a difference in foliar forest floor percent carbon lended itself to a minimal increase in the forest floor carbon pool with increasing riparian forest age. Woody debris in riparian forests comprised a relatively small carbon pool compared to tree and soil carbon pools. The species composition of litter appeared to be more of an overriding factor influencing decomposition rates than forest age. The influence of litter quality was evident in the decomposition rates of the different litter composites used in this study. In all 4 sites the litter composite from the mature riparian forest decomposed significantly more than the litter composites from the younger riparian forests. The fairly rapid decomposition of red maple (Acer rubrum L.), which was one of the main components in the mature riparian forest litter composite, influenced the greater decomposition rate. The litter composites from the younger riparian forests were similar and both included more decomposition resistant litter types, specifically waxmyrtle (Myrica cerifera L.) and alder (Alnus serrulata (Ait.) Willd.). Decomposition rates did not differ between the individual successional stages. Riparian forests are intimately associated with their hydroperiod. During flood events the riparian forest receives inputs of organic matter and sediment, and the amount of deposition may decrease along a distance gradient from the main stream channel. The differential amount of inputs could affect forest productivity. However, in these riparian forests, a distance gradient effect was not observed. Trends in herbaceous biomass were evident along a microtopographic moisture gradient. The ridge and swale microtopography prevalent in the younger riparian forests counteracted a distance from the stream channel gradient effect across the riparian forest. This study provided knowledge of how carbon pools and fluxes change with riparian forest recovery from disturbance as well as through different seral stages. Implementing the findings of this study will enhance restoration evaluation efforts to ensure that these areas continue to provide the numerous benefits gleamed from them. / Ph. D.

Reforestation of bottomland hardwood (BLH) forests has occurred within the Lower Mississippi Alluvial Valley (LMAV), USA, to support a wide range of ecosystem services, but especially wildlife habitat enhancement. As ecosystem restoration efforts proceed in BLH ecosystems, managers and policymakers are seeking criteria to evaluate wildlife habitat enhancement goals. Specialist wildlife that evolved within forest ecosystems can be sensitive to the composition, structure, and function of an ecosystem in relation to the system's natural or historical range of variation and thereby serve as indicators of habitat quality. The swamp rabbit (Sylvilagus aquaticus) is a specialist of BLH forests throughout the LMAV and therefore may be an appropriate indicator species for this ecosystem. In Chapter 1, I reviewed peer-reviewed literature to evaluate the utility of swamp rabbits as an indicator species according to three commonly-used criteria: habitat factors defining swamp rabbit relationships to BLH forests, the importance of swamp rabbit habitat to other wildlife, and the efficiency of swamp rabbit monitoring. I concluded that the swamp rabbit is a suitable indicator of wildlife habitat quality in BLH ecosystems in the LMAV because they evolved and remain endemic to the ecosystem, use habitat that integrates desirable characteristics that positively influence wildlife biodiversity, and are easy to monitor routinely.

Bottomland hardwood forests are highly productive ecosystems which perform many important ecological services. Unfortunately, many bottomland hardwood forests have been degraded or lost. Accurate land cover mapping is crucial for management decisions affecting these disappearing systems. SPOT-5 imagery from 2005 was combined with Light Detection and Ranging (LiDAR) data from 2006 and several ancillary datasets to map a portion of the bottomland hardwood system found in the Sulphur River Basin of Northeast Texas. Pixel-based classification techniques, rulebased classification techniques, and object-based classification techniques were used to distinguish nine land cover types in the area. The rule-based classification (84.41% overall accuracy) outperformed the other classification methods because it more effectively incorporated the LiDAR and ancillary datasets when needed. This output was compared to previous classifications from 1974, 1984, 1991, and 1997 to determine abundance trends in the area’s bottomland hardwood forests. The classifications from 1974-1991 were conducted using identical class definitions and input imagery (Landsat MSS 60m), and the direct comparison demonstrates an overall declining trend in bottomland hardwood abundance. The trend levels off in 1997 when medium resolution imagery was first utilized (Landsat TM 30m) and the 2005 classification also shows an increase in bottomland hardwood from 1997 to 2005, when SPOT-5 10m imagery was used. However, when the classifications are re-sampled to the same resolution (60m), the percent area of bottomland hardwood consistently decreases from 1974-2005. Additional investigation of object-oriented classification proved useful. A major shortcoming of object-based classification is limited justification regarding the selection of segmentation parameters. Often, segmentation parameters are arbitrarily defined using general guidelines or are determined through a large number of parameter combinations. This research justifies the selection of segmentation parameters through a process that utilizes landscape metrics and statistical techniques to determine ideal segmentation parameters. The classification resulting from these parameters outperforms the classification resulting from arbitrary parameters by approximately three to six percent in terms of overall accuracy, demonstrating that landscape metrics can be successfully linked to segmentation parameters in order to create image objects that more closely resemble real-world objects and result in a more accurate final classification.

Bottomland hardwood forests present a unique opportunity to examine the ecological response to hydrologically altered river and floodplain systems. These ecosystems, under natural conditions, are floodplain forests directly linked to the river. However, with major alterations to the river-floodplain system, bottomland hardwood forests can now provide insight into the loss of river connectivity and history of the flood pulse. This study reviewed the age distribution and growth of Quercus lyrata Walt. and the anatomical response of Quercus spp. to high magnitude floods in the 19th and 20th century in an old-growth Mississippi River floodplain forest in southeastern Missouri. Tree-ring samples collected from 43 trees at Big Oak Tree State Park contain physiological signatures (`flood rings') associated with growing season floods in the 20th century, and similar signatures are present in years corresponding to historical floods of the 19th century. The duration of 20th century Mississippi River growing season floods were examined to compare the occurrence of flood rings and the duration and intensity of floods on the Mississippi River at New Madrid, Missouri. Patterns in the occurrence of flood rings are developed as a response to alterations to the Mississippi River, river floodplain, and park hydrologic system.

Exotic plant species pose a great risk to restoration success in post-agricultural bottomlands, but little information exists on their dynamics during early succession of actively restored sites. Compositional trends of exotic plants may be similar to those published for natives in other systems, with an early peak in herbaceous richness followed by a decline as woody species establish. I established 16 sites in an 18-year chronosequence (1991-2008) of restored forests, with an additional four mature sites for comparison, within the Cypress Creek NWR, Illinois. Within each site, I identified all vascular plant species and quantified soil texture, total soil C, total soil N, and canopy openness at three strata (1.5m, 1.25m, & 0.75m). Trends in exotic assemblages were significantly correlated with canopy openness at all strata (all p < 0.0001). Richness of exotic herbaceous species and native herbaceous species were related to stand age consistent with a non-linear Weibull regression model (R2 = 0.543, p = 0.005; R2 = 0.483, p = 0.013, respectively). Average percent herbaceous species cover also showed a similar reduction in overall abundance for both native and exotic plants but followed an exponential decay model (R2 = 0.3777, p = 0.0039; R2 = 0.3003, p = 0.0124, respectively). Woody native richness over time conformed to a logistic model (R2 = 0.404, p = 0.012). Woody exotic plants exhibited no discernible relationship with stand age, although they were in sites of all ages. My results indicate that herbaceous exotic species exhibit successional trends similar to natives and therefore may not pose a lasting threat to restoration projects in these floodplain forests. In contrast, woody exotic species can establish earlier or later in succession, persist under closed canopy conditions, and may pose a lasting threat. Thus, bottomland restorations and mature forests are quite vulnerable to exotic plants even after canopy closure.