Mammalian herbivory of bottomland hardwood seedlings has been listed as one of the primary causal factors of failed afforestation efforts in the Lower Mississippi Alluvial Valley (LMAV). This study examined the biological and economic effects of mammalian herbivory on recently afforested carbon sequestration sites in the LMAV. Selected seedlings of six planting mixes were observed through the first year following planting to monitor seedling survival, growth, and mammalian herbivory. It was determined that greater than 10% of selected seedlings were browsed by various mammalian herbivore species, and some species mixes were browsed in excess of 50%. Financial analyses compared alternative afforestation strategies and determined to what extent herbivore-induced seedling mortality could reduce investment returns of landowners engaged in afforestation activities. In the presence of extreme mammalian herbivory, landowner returns can be reduced by hundreds of dollars per acre and could prevent further afforestation activities in the LMAV.

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A large number of concepts related to carbon offset trading policy are currently being discussed such as baseline, leakage, permanence, monitoring, verification, enforcement, financial feasibility, and third party verification. Cutting across these concepts are a variety of risks and uncertainties. These risks play a major role in developing effective market designs that achieve aggregate emission caps while encouraging market participation and investment in carbon reduction activities. What are the risks associated with carbon offset policy and how do such risks affect incentives for investing in carbon offsets? A literature review of carbon trading risks is developed. Risks associated with carbon offsets policy can be classified into three major categories: institutional/policy, project level and measurement risks. Institutional/policy risks are related to uncertainties surrounding the future policy decisions and the institutional arrangements established to define baselines, stipulate monitoring/enforcement requirements, and define and estimate leakage. Baseline estimates are necessary to calculate the net carbon reduction of a program or project. Monitoring/enforcement risk is associated with the regulators' ability to detect whether the promised carbon sequestration activities are undertaken. Leakage occurs when carbon sequestration at one site encourages increase in carbon emissions on some other site. Project risk refers to non-performance of a carbon sequestration project in terms of not achieving the requisite target of carbon sequestration. Project risk includes physical risk and financial risk. Physical risks are associated with unexpected carbon emissions due to natural hazards or events such as fire, or hurricanes or changes in the rate of sequestration, which depend on weather and pests. Landowners will not participate in carbon sequestration programs if they expect to incur financial losses by participating. Measurement risk arises because it is difficult to measure actual rates of carbon sequestered due to spatial and temporal heterogeneity of carbon present in agricultural and forest production. Forests are a principal carbon "sink" for sequestering carbon from the atmosphere. The provision of trading emission rights under the Kyoto Protocol will provide forest landowners the opportunity to reap financial gains from sequestering carbon and trading rights to emit carbon in carbon permit markets. However, landowners may be liable for repaying all or some of the proceeds received for sequestering carbon if stored carbon is released during the contract period. Hurricane damage to forests may cause extensive mortality and subsequent emission of carbon dioxide from decomposing biomass. Such liabilities may reduce landowners' incentives to sequester carbon. This research evaluates incentives of an individual forest landowner for sequestering and trading carbon, given the risk of carbon loss from hurricanes. Results of our simulation model reveal that the effect of hurricane risk on landowners' behavior depends on the variability of returns from carbon and timber and the ability of landowners to mitigate risk by diversifying forest holdings across regions with different sequestration rates and different hurricane strike probabilities. Some risk mitigation strategy might be required to create the necessary incentives for landowner participation especially in hurricane prone regions. We evaluate incentives of forest landowners for sequestering and trading carbon, given the risk of carbon loss from hurricanes, and an opportunity to insure their losses. Results of simulation model reveal that the effect of hurricane risk depends on the variability of returns from carbon and timber and landowners' ability to mitigate risk by diversifying forest holdings across regions or transferring risk by purchasing insurance. Although, landowner can spread the risk of carbon loss by diversifying into different regions, insurance has a role to play over and above diversification by reducing landowners' risk (variance) from forestry investments for sequestration and timber purposes, even when timber losses are not insured. / Ph. D.

To protect the integrity of the United State's waters, the Federal Water Pollution Control Act of 1972 promoted the establishment of Best Management Practices (BMPs) for forestry. A commonly used BMP is the reservation of Streamside Management Zones (SMZs). In this study the effectiveness of three different SMZ widths, 30.5 m (100 ft), 15.3 m (50 ft), and 7.6 m (25 ft), as well as thinning in 15.3 m SMZs were studied. The objectives of the study were to determine the effects these SMZ treatments had on carbon pools, carbon fluxes and environmental conditions in the SMZ. The benthic macroinvertebrate populations present within the stream were also examined because of their relationship to ecosystem carbon dynamics. Carbon storage in plant communities, litter layer, soil (upper 10 cm), and total organic carbon present (TOC) within streams were measured and quantified. Total CO₂ efflux and the major environmental drivers of soil CO₂ efflux, soil moisture and soil temperature, were monitored along a single transect within each SMZ. This study showed that carbon dynamics and stream biota (benthic macroinvertebrates) were not adversely effected by more narrow SMZ width and thinning within the SMZ. SMZ width did affect soil temperature, one of the environmental drivers affecting soil respiration. Based on these short-term results a 15.3 m SMZ with thinning or without thinning appears adequate to prevent changes in ecosystem function and water quality for forest applications. / Master of Science

Analysis of synthetic data was performed to determine the most cost-effective tomographic monitoring system for a geologic carbon sequestration injection site. Artificial velocity models were created that accounted for the expected velocity decrease due to the existence of a CO₂ plume after underground injection into a depleted petroleum reservoir. Seismic events were created to represent induced seismicity from injection, and five different geophone arrays were created to monitor this artificial seismicity. Double-difference tomographic inversion was performed on 125 synthetic data sets: five stages of CO₂ plume growth, five seismic event regions, and five geophone arrays. Each resulting velocity model from tomoDD—the double-difference tomography program used for inversion—was compared quantitatively to its respective synthetic velocity model to determine an accuracy value. The quantitative results were examined in an attempt to determine a relationship between cost and accuracy in monitoring, verification, and accounting applications using double-difference tomography. While all scenarios resulted in little error, no such relationship could be found. The lack of a relationship between cost and error is most likely due to error inherent to the travel time calculation algorithm used. / Master of Science

Soils are a major component of the global carbon budget and may serve an important role in mitigating increasing atmospheric CO2 through their capacity to store carbon. In this regard, it is important to evaluate the implications of forest management on changes in carbon cycling and sequestration and to determine the magnitude by which the efflux of CO2 from the soil surface can vary in time and space. For this study, soil CO2 efflux was measured in 5 replicate blocks of naturally regenerated and planted loblolly pine (Pinus taeda), shortleaf pine (Pinus echinata), and eastern white pine (Pinus strobus) in a 50-acre clear-cut on the Virginia Piedmont. Rates of CO2 efflux were measured every 2 weeks immediately adjacent and away (1m) from newly planted seedlings and cut stumps using a dynamic, closed-chamber infrared gas analyzer system. For each measurement date, volumetric water content was taken in the top 17cm, using time domain reflectometry (TDR) and soil-surface temperature was recorded in the top 7cm, using a temperature probe. For the October measurement a 12cm depth soil core (7cm diameter) was collected for each location. Carbon, nitrogen, coarse fragments, roots, surface litter and coarse woody debris were measured separately for each core. Position (near and away from seedling) had a strong effect on soil CO2 efflux rates. For the first measurement date, rates were higher near the newly planted seedlings (3.09μmol/m2/s) than those taken away from the seedlings (2.29 μmol/m2/s).. The same trend was maintained for the CO2 efflux rates measured near a cut stumps (3.51μmol/m2/s) and those taken away from the stump base (2.56μmol/m2/s). Species proved to have no significant effect on respiration rates for any date and no interaction between species and position was observed. Regression analysis was used to model the influence of soil and plant factors on efflux rates. Temperature (29.2%), position (near and away from the seedlings and stumps base)* temperature, (7.7%), soil carbon (4.1%), organic matter (1.6%), and soil moisture (0.7%) proved to be the major drivers for soil respiration (R2 = 0.4329). When only data near seedlings or stumps were modeled, species had a significant effect on soil CO2 efflux rates. The largest seedlings, loblolly pine (100 cm3 seedling value), had on average the highest rates followed by shortleaf pine (30 cm3 seedling value) and eastern white pine, which were the smallest (9 cm3 seedling value). Stumps had the highest efflux rates. The mean soil respiration rate measured over a seven month sampling period was 2.58 μmol/m2/s,, while the calculated carbon loss from the soil over the same period added up to 575 g C/ m2. The annual carbon loss was estimated to be 675 g C/ m2. / Master of Science

Forests have the ability to alleviate the impact of global warming through carbon sequestration. Six forest management scenarios for a 27,000 acre study area are modeled to determine the impact of forest management on carbon sequestration. Forest management determines annual harvested volume and end-use disposition category of wood products, and inventory volume. Shorter rotations tend to produce short-lived wood products, while longer rotations produce long-lived wood products. Thinning removes pulpwood, which increases the average diameter of the stand and increases the proportion of sawtimber products. Changing forest management complicates accounting for changes in future C storage. Understanding the distinction between pre- and post-regulation harvest volume and C storage is essential to understand the effects of forest regulation. Plotting harvested volume and C storage volume over time shows distinctive pre- and post-regulation characteristics. The pre-regulation curves exhibit irregularities and varying thinned volume due to the uneven area in the existing age classes. Post-regulation curves are level because a constant area is annually thinned and clearcut. Carbon storage is the amount of C that is sequestered into a C pool, which for the purposes of this study is either inventory volume or residual wood product volume. Converting volume flows to C storage involves tracking the accumulation of wood products and standing volume over time then converting volume to a measure of C. Once the forest is regulated, C stored in the inventory pool remains constant from year to year, while the C stored in wood products continually increases. Longer rotations store more carbon than shorter rotations because they have larger inventory pools. Wood products are a substantial carbon pool: at the end of 50 years; the ratio of incremental C in the wood products carbon pool to incremental C in the inventory pool ranges from 6 to 122 for the modeled scenarios. Three accounting periods are evaluated to examine the importance of C sequestration timing to determine if a market for C can influence forest management. Long rotations meet the objectives of maximizing C sequestration and NPV for the modeled regimes regardless of the accounting period considered, or if the forest is regulated or un-regulated. Model sensitivity to decomposition rate, discount rate and timber prices is assessed to determine the effects of uncertainty (measurement error and future trends) on the results of the model. Short rotations are most sensitive to decomposition assumptions and stumpage prices because they produce a large amount of fast-decaying wood products. Long rotations are most affected by discount rate. Carbon storage of all scenarios increases substantially when the pulpwood decomposition rate equals the sawtimber decomposition rate to reflect a potential future increase in composite lumber production. / Master of Science

Forests of the southeastern U.S. play an important role in meeting the increasing demand for forest products, and represent an important carbon (C) sink that can be managed as a potential tool for mitigating atmospheric CO2 concentrations and global climate change. However, realizing this potential depends on full accounting of the ecosystem carbon (C) budget. The separate evaluation of root-derived, autotrophic (RA) and microbially-derived heterotrophic (RH) soil respiration in response to management and climate change is important, as environmental and ecological factors often differentially affect these components, and RH can be weighed against net primary productivity (NPP) to estimate the C sink or source status of forest ecosystems. The objective of this research was to improve the quantitative and mechanistic understanding of soil respiratory fluxes in managed loblolly pine (Pinus taeda L.) plantations of the southeastern U.S. To achieve this overall objective, three studies were implemented to: 1) estimate the proportion and seasonality of RH:RS in four stand age classes, and identify relationships between RH:RS and stand characteristics 2) evaluate the effects of forest nutrient management and throughfall reduction on factors that influence RH and decomposition dynamics, including litter quality, microbial biomass, and enzyme activity and 3) evaluate the sensitivity of sources of RH (mineral soil-derived heterotrophic respiration; RHM, and leaf litter-derived heterotrophic respiration; RHL) to varying soil and litter water content over the course of a dry down event, and assess whether fertilization influences RH. Stand age and measurement season each had a significant effect on RH:RS (P < 0.001), but there were no interactive effects (P = 0.202). Mean RH:RS during the 12-month study declined with stand age, and were 0.82, 0.73, 0.59, and 0.50 for 3-year-old, 9-year-old, 18- year-old, and 25-year-old stands, respectively. Across all age classes, the winter season had the highest mean RH:RS of 0.85 while summer had the lowest of 0.55. Additionally, there were highly significant (P < 0.001) and strong (r > 0.5) correlations between RH:RS and peak LAI, stem volume, and understory biomass. Fertilization improved litter quality by significantly decreasing lignin:N and lignin:P ratios, caused a shift in extracellular enzyme activity from mineral soil N- and P-acquiring enzyme activity to litter C-acquiring enzyme activity, and increased microbial biomass pools. Throughfall reduction decreased litter quality by increasing lignin:N and lignin:P, but also increased C-acquiring enzyme activity. RHL was more sensitive to water content than RHM, and increased linearly with increasing litter water content (R2 = 0.89). The contribution of RHL to RH was greatest immediately following the wetting event, and decreased rapidly to near-zero between three – 10 days. RHM also had a strong relationship with soil water content (R2 = 0.62), but took between 200 – 233 days to attain near-zero RHM rates. Fertilization had no effect on RHM (P = 0.657), but significantly suppressed RHL rates after the wetting event (P < 0.009). This research provides estimates of RH:RS in managed loblolly pine systems that can be used to improve regional ecosystem C modeling efforts, and demonstrates the need to consider the impact of stand age and seasonal patterns to identify the point at which plantations switch from functioning as C sources to C sinks. Additionally, it demonstrates that the controls over RH are dynamic and influenced in the short-term by fertilization and changed precipitation regimes, with the greatest impact on properties affecting litter RH compared to mineral soil. Future research should work to improve the mechanistic understanding of the seasonal and spatial variability of RH and related controlling biotic and abiotic parameters to remedy the variability in existing RS and ecosystem C models. Understanding how management and climate change may impact factors that control RH will ultimately improve our understanding of what drives changes in forest C fluxes. / Ph. D.