Short term studies have suggested that ground based timber harvesting on wet sites can alter soil properties and inhibit early survival and growth of seedlings. Persistence of such negative effects may translate to losses in forest productivity over a rotation. During the fall and winter of 1989, numerous salvage logging operations were conducted during high soil moisture conditions on wet pine flats in the lower coastal plain of South Carolina following Hurricane Hugo. A long-term experiment (split-plot within an unbalanced randomized complete block design) allowed assessment of long term effects of rutted and compacted primary skid trails and subsequent site preparation on soil properties and loblolly pine (Pinus taeda L.) productivity. The experiment had 12 blocks, four levels of site preparation as the whole plot factor (bedding, disking with bedding, disking, and no site preparation), and two levels of traffic as the subplot factor (primary skid trail, no obvious traffic). After 23 years, bedding and disking with bedding treatments effectively enhanced soil physical properties and stand productivity via promoting greater survival and stocking, but had little effect on the size of individual trees relative to disking and no site preparation treatments. Primary skid trails significantly reduced the size of individual trees, but had no appreciable long term effects on soil properties or stand productivity after 23 years. The study suggests that bedding is the most efficient practice to enhance soil properties, seedling survival, and stand productivity on wet sites. However, site preparation is not necessary for these soils and sites, if strictly intended to restore soil properties and stand productivity in primary skid trails. Reduction in individual tree sizes on primary skid trails emphasizes benefits in minimizing the spatial extent of disturbance. / Master of Science

Research documenting the functional changes of wetlands in response to harvest disturbance has often been limited to initial-response time frames of one or two years. A cypress (Taxodium distichum L. Rich.)-water tupelo ~ aQuatica L.) swamp located in the Mobile-T ensaw River Delta of Southwestern Alabama was harvested in the fall of 1986. Harvest treatments included: c1earcutting the entire study area with helicopter log removal, or with an added simulated rubber-tired skidder transport, or with herbicide control of all regenerating vegetation. An adjacent nondisturbed stand served as a reference area. Remeasurement of the area was initiated seven years after harvest. The helicopter logged and skidder simulation treatments have produced stands of comparable diameter, height, density, and basal area. ~ aqyatica was dominant in the skidder simulation treatment~ ~ tica, ~ nigra, and Fraxinus caroliniana dominated the helicopter treatment. Overstory biomass was less in the helicopter logged areas (20,981 kg/ha) than in the skidder simulation treatment (30,533 kglha). Lowerstory trees in both treatments were of comparable diameter and height, however, the helicopter treatment contained a greater density, basal area, and biomass ofFraxinus caroliniana. The rutting and mounding associated with the skidder simulation treatment favored a greater diversity of both diversity of both lowerstory and herbaceous species. Groundflora biomass was greatest in the herbicide controlled treatment (13,127 kg/ha), comparable in both the helicopter logged and skidder simulation treatments (5128 kg/ha; 5648 kglha, respectively), and least in the reference area (1495 kglha). Sediment accumulation reflected these differences in groundflora biomass; 104 mm in the herbicide controlled treatment, 79 mm and 63 mm in the helicopter logged and skidder simulation treatments, respectively, and 37 mm in the reference area. Three gradients were identified in the study areas via the tests of Latin squares, rows, and columns which actually corresponded to gradients of hydrology and! or sediment deposition. Square two was wetter than squares one or three because square two had fewer residual pullboat runs, which facilitate greater water movement. The rows are indicative of the distance from the main river channel; rows nearer the river are slightly higher in elevation, less inundated, and favor the less flood tolerant species. The columns reflect the sediment trapping patterns of the vegetation and the subsequent effects of site hydrology and nutritional status. / Master of Science

Disturbances impact abiotic and biotic components within forested ecosystems. This dissertation identifies the impacts of recreational crossing disturbances on water quality, uses dendrochronological techniques to estimate sediment deposition and identify impacts hydrology and climate on radial growth in riparian forested wetlands, and quantifies influences of biotic and abiotic factors on the occurrence of frost-induced cambial damage. In southwestern Virginia, modeled soil erosion rates for multiple-use (hiking, mountain biking, and horseback riding) recreational trail approaches to stream crossings were found to be 13 times greater than rates for undisturbed forests. Downstream changes in macroinvertebrate-based indices indicated water quality was negatively affected downstream from culvert and ford crossings. These findings illustrate recreational stream crossings have the potential to deliver sediment into adjacent streams, particularly where best management practices are not being rigorously implemented, and as a result can negatively impact water quality below stream crossings. Impacts of hydrologic regime were apparent on sediment deposition and on green ash (Fraxinus pennsylvanica Marsh.) and water tupelo (Nyssa aquatica L.) radial growth along the Tensaw River in southwest Alabama. Annual dendrogeomorphic sediment accretion rates were significantly greater for a recent time period (25 years) when compared to longer term rates (131 years) along a natural levee and backswamp. Radial growth in green ash along the natural levee and backswamp was found to be significantly correlated with days flooded and average daily stage level during April while water tupelo further in the backswamp appeared resistant to hydrologic and climatic fluctuations. Results illustrate the importance of riparian wetlands in trapping sediment from adjacent waterways and highlight the role hydrologic regime plays in bottomland succession and productivity. Across northern lower Michigan, late spring frost-induced cambial damage in jack pine (Pinus banksiana Lamb.) occurred more frequently in younger trees and in trees with smaller diameters. Biotic and abiotic factors were found to influence the occurrence of earlywood frost rings. Frequent occurrences of frost-rings can be used to identify frost-prone environments and geographical boundaries for plant species. This dissertation bridged gaps in knowledge of recreational, hydrogeomorphic, and climatic disturbances in forested ecosystems which can be used to develop management strategies. / Ph. D.

The Great Dismal Swamp (GDS) is a forested peatland located in the Atlantic Coastal Plain. Once a mosaic of wetland communities, disturbances (e.g., timber harvesting and ditching) have resulted in altered hydrologic regime, homogenized forest communities, and increased peat subsidence. In response, hydrologic restoration and forest management aim to enhance community composition and function. To help inform these efforts, we investigated variability and drivers of forest communities by surveying vegetation composition and structure, hydrologic indicators, and soil properties at 79 monitoring plots across GDS. Data were augmented with modeled water levels and peat depths. Our results demonstrate red maple (Acer rubrum) dominance across GDS, which decreases tree density, richness, and diversity. However, hierarchical cluster analysis identified four community types: Gum (G), Maple-Gum (M-G), Sweetgum-Maple (SG-M), and Maple (M). These communities differed in tree composition and structure; differences in other growth forms (shrubs, herbaceous, and regeneration) were limited. Modeled water levels failed to explain vegetation differences, but community associations with soil properties suggest that communities exist along a hydrologic gradient. Specifically, the G community likely exists on wetter sites whereas SG-M communities occur at drier locations. Maple-dominated communities (M and M-G; 78% of plots) likely occur across broader hydrologic gradients, explaining their dominance. However, more characterization of hydrology (i.e., time-varying water levels and soil moisture) and other drivers (e.g., site history and soil hydraulics) is needed to further explain community variation. As such, we propose future strategies for long-term monitoring to inform ongoing hydrologic restoration and forest management efforts. / Master of Science

Due to the paucity of long-term harvest impact data, the primary goals of this study were to quantify the long-term effects of different harvest disturbances twenty-four years after harvest on two major wetland functions: stand productivity and C storage. This study evaluated the effects of three harvest types that were originally applied in 1986 to a tupelo (Nyssa aquatic)-cypress (Taxodium distichum) forested wetland in the Mobile-Tensaw River Delta of southwestern Alabama. Treatments were: 1. Helicopter harvest (HELI), 2. Skidder simulation where 50% of the site was rutted to a depth of 30 cm (SKID), and 3. Helicopter harvest followed by glyphosate herbicide removal of all sprouts and seedbank regeneration for two years following harvest (GLYPH). An adjacent mature stand (94 years old) within the same original composition represented mature forest or pre-harvest reference conditions (REF). Above- and belowground plant biomass, belowground woody debris, soil C, and soil CO2 efflux were measured. Twenty-four years after treatments were applied, forest C levels were higher in SKID treatments (206.1 Mg C ha-1) than in HELI treatments (168.7 Mg C ha-1). GLYPH treatments are holding less (144.2 Mg C ha-1) while REF areas hold 332.6 Mg C ha-1. SKID treatments are also holding the most biomass of all treatments with 243.2 Mg ha-1 of overstory biomass. Ecosystem C and biomass patterns indicate HELI and SKID are becoming similar to the original site conditions represented by the REF areas. The resiliency of these highly disturbed stands are explained by the frequent inputs of non-compacted sediments, presence of species well adapted to very poorly drained and aerated conditions, high rates of coppice regeneration, shrink-swell ameliorative properties of the soil and creation of more complex microtopography within SKID treatments. / Master of Science

Sediment accumulation and loss were measured in a water tupelo (Nyssa aquatica)- baldcypress (Taxodium distichum) forested wetlandin years 2, 7, 10 and 12 following harvesting disturbance. A 3 X 3 Latin Square design was replicated three times and compared to a psuedo-replicate reference stand (REF). Disturbance treatments were chainsaw fellind of trees with (1) helicopter removal of logs (HELI), (2) helicopter removal of logs followed by a simulated skidder removal (SKID), and helicopter removal of logs follwed by glyphosphate application (GLYPH). Measurements of sediment accretion show little difference between treatments and reference in the first two years following harvest. After two years the harvest treatments accumulate more sediment than the REF. Of the harvest treatments, the GLYPH plots accumulate the greatest quantities of sediment. The difference in sediment accretion between the harvest treatments begins to fade in the 12th year of recovery. Results show that skidder and helicopter removal of logs differ very little in the amount of sediment trapped, while glyphosphate application increased the wetland's ability to trap sediment beginning in the second year. In addition, sediment trappin is associated with herbaceous cover that slows flood waters and allows soil particles to precipitate from flood water. / Master of Science

Wet pine flats are some of the most productive and intensively-managed wetland forests in the eastern United States. Wet-weather logging of these sites causes extensive rutting and churning of the soil surface and may alter the subsurface flow of soil water. An operational-scale experiment was established in 20-year-old loblolly pine (Pinus taeda) plantations to determine the hydrologic response of wet pine flats to wet- and dry-weather harvesting operations. Three 19-ha treatment blocks were established in the coastal plain near Charleston, South Carolina. Site hydrology was monitored monthly with a 20 x 20 m grid of water table wells for 18 months prior to treatment installation. Three treatments were applied to each block: wet-weather harvesting, dry-weather harvesting, and a control (nonharvested). Prior to harvesting, the water table depths followed a uniform pattern throughout the sites with seasonal fluctuations between 5 and 75 cm below the soil surface. The uniform pattern and poor inherent drainage of the site prior to harvest was due to lack of surface topography and impedance of internal vertical drainage by a restricting Btg soil horizon. After harvesting, the hydrologic pattern changed by the degree of soil disturbance as defined by soil physical properties and microtopographic changes. Such hydrologic changes could influence long-term site productivity and interfere with management of this wetland ecosystem. / Master of Science

Dissolved organic matter (DOM) is present in all forested catchments and can be important in binding metals, absorbing UV, and the transport of nutrients (C, N, S, P). DOM is extremely heterogeneous in time and space, making it difficult to characterize. New techniques have been developed to determine δ34S and δ18O in DOM. These techniques have been applied to samples from Harp and Plastic Lake catchments (45??23'N, 79?? 08'W, 45??11'N, 78?? 50'W) in order to obtain information about sources and sinks of DOM within forested catchments on the Canadian Shield. In conjunction with sulphate and DOC concentrations, this new data provides valuable insight into sulphur cycling and DOM alteration within these catchments. Data generated for δ34S-DOM and δ18O-DOM appears to be the first data reported in the literature for DOM. The inorganic (δ34S-SO42-) and organic S (δ34S-DOM) differs by environment in both catchments. The range of δ34S-SO42- is between 3. 3‰ and 10. 3‰, and the range of δ34S-DOM is from 3. 4‰ to 8. 7‰. Sulphate in the Harp Lake catchment in most samples is subject to some sort of cycling within the watershed, since δ34S-SO42- differs from precipitation. In the Harp Lake catchment, upland δ34S-SO42- is influenced by historical precipitation. The δ34S-DOM is derived from leaching and microbial activity of DOM from organic horizons in the soil. The δ34S-SO42- and δ34S-DOM of wetland streams is extremely variable, controlled by hydrology. The δ34S-SO42- provides information on oxidation-reduction dynamics in the wetland, and δ34S-DOM provides information about sources of DOS in the wetland. The δ34S-SO42- and δ34S-DOM are possibly related in Harp Lake. Mineralization of DOS as evidenced by δ34S-DOM and DOS concentrations could be a small input of SO42- into Harp Lake. It is possible δ18O-DOM could be an indicator of DOM alteration. The range of δ18O-DOM is between 8. 2‰ and 14. 4‰. The δ18O-DOM in the Harp Lake catchment is highly correlated with relative molecular weight, which has been shown to decrease with increasing alteration. Wetland streams show the largest range in δ18O-DOM, while uplands, groundwater, and Harp Lake are the least varied. The highest δ18O-DOM values are from sources of DOM such as leaf leachates (representative of forest floor litter) and wetlands. The most depleted samples are from groundwater and Harp Lake which typically contain highly altered DOM. The δ34S-DOM and δ18O-DOM can provide valuable information on sources of DOM and DOM alteration within the catchment. The δ18O-DOM could also allow the separation of autochthonous and allochthonous DOM in lakes.

Ecological restoration of a converted wetland was characterized within a recently drained impoundment along the James River in Charles City County, Virginia. Colonizing vegetation was assessed over three growing seasons in both tidal and non-tidal environments. Study objectives were to (1) examine geospatial relations of recruitment patterns among colonizing species over three growing seasons, (2) quantify species composition and potential differences between extant species cover and soil seed banks across restored and natural wetland habitats and (3) assess geospatial patterns to develop a GIS model of bald cypress (Taxodium distichum L.) recruitment. The two most common native colonizing species during 2009, 2010 and 2011 growing seasons were narrow-leaf cattail (Typha angustifolia L.) and rice cutgrass (Leersia oryzoides L.). Vegetative communities dominated by these two species covered 72% of the basin in each growing season. Differences were observed between extant species cover in the field and seed bank species across habitats. Two hundred and eighty T. distichum individuals have been located in wetland habitats at the VCU Rice Center. Using a GIS weighted suitability model we identified potential areas within the restored wetland for natural and facilitated bald cypress recruitment. At the VCU Rice Center ~9.7 ha have potential for natural regeneration and ~48.5 ha have potential for facilitated restoration of T. distichum.

Com o objetivo de compreender quais fatores abióticos determinam a ocorrência das diferentes formações florestais na região de Batatais, entre as coordenadas 20038S e 20058S e 47037W e 47028W, foram escolhidas três propriedades agrícolas (Fazenda Monte Belo, em Restinga, SP e Fazenda Magnólia e Sítio Pratinha, em Batatais, SP), que apresentavam remanescentes florestais representativos da região (floresta ribeirinha paludícula, floresta estacional semidecídua ribeirinha e cerradão). Para descrever a composição florística e a estrutura da comunidade arbórea foram amostradas 05 parcelas de 10 x 10 m ao redor de cada estação tensiométrica. Para o estudo dos fatores abióticos foram determinados os parâmetros físicos e químicos dos solos e as curvas de retenção de água nos solos e piezometria. A discriminação das variáveis abióticas e de vegetação foi feita através da análise de componentes principais (PCA) e, na correlação entre a abundância de espécies e fatores abióticos, foram feitas análises diretas de gradiente por meio de Análise de Correlação Canônica (CCA). A textura dos solos (teores de argila, silte e areia) e a posição no terreno (cota), foram as variáveis ambientais mais importantes na distribuição das espécies e nas variações das fisionomias florestais, com influência na retenção hídrica e nos índices de fertilidade dos solos. Essas diferenças nos teores de argila em profundidade ao longo do declive, com influência direta na retenção de umidade dos solos ou mesmo na formação de ambientes paludículos, determinaram grupos distintos de espécies e fisionomias florestais: (i) um grupo de espécies de ocorrência típica nas fisionomias de Cerrado e fortemente associado às cotas mais elevadas (solos menos férteis, bem drenados e porcentagens mais baixas de argila e silte nas camadas mais profundas), entre as quais: Matayba juglandifolia, Trichilia pallida, Lithraea molleoides, Anadenanthera falcata, Myrcia tomentosa, Copaifera langsdorffii, Erytrhoxylum pelleteranum, Platipodium elegans, Chrysophyllum marginatum, Luehea divaricata, entre outras e (ii) um grupo com espécies indicadoras de Florestas Paludículas ou de ocorrência comum nestas fisionomias, associado aos solos das cotas mais baixas (Gleissolos), com porcentagens altas de argila e silte nas camadas superficiais, mais férteis e maior retenção hídrica: Cecropia pachystachya, Citronella gongonha, Rapanea guianensis, Talauma ovata e Tapirira guianensis. Pode-se considerar um terceiro grupo de transição entre Floresta Estacional Semidecídua e Cerradão, nas cotas intermediárias e menos úmidas (espécies amostradas em parcelas localizadas nas bordas das Florestas Paludículas), onde ocorreram espécies tanto de ambiente de Cerradão, como de Floresta Estacional Semidecídua, e algumas poucas de ambiente paludículo. As porcentagens mais elevadas de Areia nos solos do Sítio Pratinha, com influência na menor retenção hídrica e também nos índices de fertilidade (solos álicos, com maior acidez e os menos férteis), podem explicar algumas diferenças na composição e abundância das espécies entre fisionomias florestais iguais. O Cerradão da Fazenda Monte Belo, mostrou-se diferente floristicamente do Cerradão do Sítio Pratinha. Esta mesma diferença ocorreu em relação às Florestas Paludículas da Fazenda Magnólia e a do Sítio Pratinha. As poucasespécies de ocorrência comum tiveram populações diferentes. A CCA evidenciou também correlações de algumas espécies com determinadas variáveis de solo. / In order to understand what abiotic factors determine the occurrence of different forest formations in the region of Batatais, coordinated between 20038\'S and 20058\'S and 47037\'W and 47028\'W, three agricultural properties were chosen (Monte Belo, in the city of Restinga, SP and Magnolia and Pratinha in Batatais, SP, Brazil), which had forests representative of the region (swamp forest, semi-deciduous riverine forest and forested savanna). To describe the floristic composition and structure of the arboreal community, 05 plots of 10 x 10 meters around each tensiometric station were sampled. For the study of abiotic factors, the physico-chemical characteristics of the soils, the soil-water-retention curves and the groundwater fluctuation were determined. The discrimination of the environmental variables and arboreal species were made through the Principal Components Analysis (PCA), and in the correlation between the abundance of species and abiotic factors, direct analyses of gradient through Canonical Correspondence Analysis (CCA) were made. The texture of the soil (levels of clay, silt and sand) and the position on the ground (altitude) were the most important environmental variables in the distribution of species and variations of forest physiognomies, with influence in the retention rates of water and soil fertility. These differences in levels of clay in depth along the slope, with direct influence on the retention of soil moisture and even in the development of swampy environment, determined distinct groups of species and forest physiognomies: (i) a group of species of typical occurrence in physiognomies of Forested Savanna and strongly associated with higher altitude (less fertile, well-drained soil and lower percentages of clay and silt in the deeper layers), including: Matayba juglandifolia, Trichilia pallida, Lithraea molleoides, Anadenanthera falcata, Myrcia tomentosa, Copaifera langsdorffii, Erytrhoxylum pelleteranum, Platipodium elegans, Chrysophyllum marginatum, Luehea divaricata, among others, and (ii) a group with indicator species of Swamp Forests or common occurrence in these physiognomies, associated with lower altitude (Gleisoil), with high percentages of clay and silt in the upper and more fertile layers, and greater water retention: Cecropia pachystachya, Citronella gongonha, Rapanea guianensis, Talauma ovata and Tapirira guianensis. A third group of transition between Semi-deciduous Forest and Forested Savanna, in intermediate altitude and soils less humid (species sampled in plots located at the edges of Swamp Forests), occurred both in the Forested Savanna and in Semi-deciduous Forest and a few in swampy environment. The highest percentages of sand in the soil of Pratinha, with less influence on water retention and also on the rates of fertility (alic soils, with greater acidity and less fertile), may explain some differences in the composition and abundance of species of forest physiognomies equal. The forested Savanna of Monte Belo, has proved floristically different from the Forested Savanna of Pratinha. This same difference occurred in swamp forests of Magnolia and Pratinha. The few species of common occurrence had differentpopulations. The CCA also revealed correlations of some species with certain variables of soil.