Browsing by Subject "carbon"
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Item Application of Remote Sensing Technology and Ecological Modeling of Forest Carbon Stocks in Mt. Apo Natural Park, Philippines(2015-01-23) Leal, Ligaya RubasThis dissertation work explored the application of remote sensing technology for the assessment of forest carbon storage in Mt. Apo Natural Park. Biomass estimation is traditionally conducted using destructive sampling with high levels of uncertainty. A more accurate and non-destructive method for assessment of biomass level is imperative to characterize remaining forest cover. This research study aimed to: 1) examine the vegetation profile and estimate species-specific biomass of Mt. Apo Natural Park, 2) develop an algorithm to assess biomass in plot-level using a terrestrial lidar system (TLS), and 3) generate landscape-level biomass estimates using interferometric synthetic aperture radar (IFSAR). This research endeavors to provide answers to these questions: 1) how the 3 tropical allometries compare in estimating field collected species-level biomass and carbon stocks in three management zones?, 2) what are the significant terrestrial laser scanning-derived metrics to assess plot-level biomass?, and 3) to what degree of uncertainty can IFSAR estimate biomass at the landscape level? Field data was gathered from 1382 trees, covering 52 local species during fieldwork in July and August 2013. Twenty-six plots (30 m x 30 m) were sampled on three management zones: multiple use, strict protection and restoration. Local insurgency problems restricted the research team from sampling additional plots. Destructive sampling was not permitted inside the protected area, thus requiring biomass to be estimated via the use of referenced biomass from 3 allometric equations by relating tree height, diameter-at-breast height, and wood specificity volume. A vegetation profile across the park was generated using a canopy height map (CHM). Results showed that resampled IFSAR products can be used to characterize biomass and carbon storage at the landscape level. This research has demonstrated the adoption of IPCC?s Tier 2, a combination of field and remote sensing data in the assessment of available biomass levels in a tropical forest. The maps created can assist in providing information for biomass and carbon level in MANP for monitoring, reporting and verification in compliance with REDD requirements. Furthermore, this study can provide helpful information regarding policy implications for reforestation and afforestation activities. Results showed that resampled IFSAR products can be used to characterize biomass and carbon storage at the landscape level. This research has demonstrated the adoption of IPCC?s Tier 2, a combination of field and remote sensing data in the assessment of available biomass levels in a tropical forest. The maps created can assist in providing information for biomass and carbon level in MANP for monitoring, reporting and verification in compliance with REDD requirements. Furthermore, this study can provide helpful information regarding policy implications for reforestation and afforestation activities.Item Diagenesis in seagrass vegetated sediments: biogeochemical processes on diurnal time scales(Texas A&M University, 2005-11-01) Hebert, Andrew BrianSeagrass productivity is largely limited by nutrient and light availability. However, increasing evidence suggests that sedimentary geochemical processes may play an essential role in seagrass productivity/health. Much of this work has been largely phenomenalistic and has not clearly identified the spatio-temporal behavior of the major geochemical parameters involved in diagenesis of seagrass sediments. In this study, a much broader range of both dissolved and solid phase chemical parameters in eelgrass vegetated sediments was investigated. Parallel measurements were made on adjacent unvegetated sediments (<10 m) to more clearly refine the specific influences of seagrass (Zostera marina) on chemical gradients in associated sediments. Previous studies have pointed strongly toward diurnal ??ventilation?? of sediments vegetated with seagrass by the exudation of photosynthetically produced oxygen. However, strong lateral variability of sediment geochemical parameters among and between seagrass vegetated and unvegetated sediments made the observation of diurnal effects sufficiently difficult. Changes resulting from temporal variability were difficult to discern within the spatial variability. A critical question that is often not dealt with in the study of the early diagenesis of sediments is what spatial and temporal sampling intervals are required to account for the dominant source of variability. The auto-covariance function (ACF) was used to determine the optimum scaling length for sample intervals (?x) of ?H2S and Fe2+. Characteristic scale lengths obtained for sediments from seagrass environments are not significantly different from those observed for unvegetated sediments and averaged 13.7?? 2.2 mm. Lateral variations in our scales analyses showed that scale length approximated our sampling interval and that lateral sampling intervals were smaller than the vertical sampling intervals. Our results indicate that macrofauna dwelling in the sediment, the seagrass root/rhizomes, and aggregations of bacteria, microalgae, and meiofauna may be responsible for the vertical and lateral variability. Model calibrations and sensitivity analyses from a sediment-seagrass diagenetic model revealed that changes in physical parameters of the sediments (irrigation, advection, and porosity, for example) had the greatest effect on organic carbon and total dissolved sulfides. This study revealed that sedimentary geochemical parameters that are both vertically and laterally heterogeneous may also affect seagrass productivity.Item Grassland carbon and nitrogen dynamics: effects of seasonal fire and clipping in a mixed-grass prairie of the southern great plains(Texas A&M University, 2006-08-16) Harris, Wylie NealPlant production and soil microbial biomass (SMB) in grassland ecosystems are linked by flows of carbon (C) and nitrogen (N) between the two groups of organisms. In native mixed grasslands of the southern Great Plains, these cycles are strongly influenced by climate. They may also be modulated by the timing and intensity of disturbances such as fire and clipping. We assessed the relative influence of climate and disturbance on plant community and soil C and N dynamics. Combined effects of fire and clipping were assessed in a 2x3 factorial design including spring fire and light clipping or continuous clipping. Seasonal fire effects were evaluated in a one-way analysis incorporating spring and fall fire in unclipped plots. Plant cover and biomass (by functional type), litter mass, SMB C and N, soil density fraction concentration and composition, soil organic C, total N, and inorganic N, soil temperature and moisture, soil respiration, and net N mineralization were measured at monthly intervals. C4 grasses were unaffected by fire or clipping, probably as a result of summer drought in both studyyears. Clipping reduced cover of C3 annual grasses but increased that of C3 perennials, resulting in no net change in C3 grass biomass. Fire did not affect C3 grass cover or biomass. Both fire and clipping reduced litter mass. This was reflected in seasonal declines in SMB C in fire treatments, suggesting that the primary input of microbial C in this ecosystem occurs by decomposition of current-season plant litter. Litter removal offers a single mechanism by which fire-induced increases in soil temperature and reductions in light soil density fraction concentration, soil moisture, and net N mineralization rates may be explained. Lack of treatment effects on soil respiration rates suggest that plant roots represent an important component of the plant-soil C cycle, not quantified in this research. Overall, treatment effects were relatively minor compared to seasonal climate-related changes in response variables, particularly in light of repeated summer drought.Item Soil and Plant Responses to Lipid-Extracted Algae(2014-08-25) Lewis, KatieAlthough algae is much more productive per area of cultivation compared to first-generation biofuel feedstocks, algae production may not be economically sustainable without high value coproducts. One of many possible coproducts may be algae residue following lipid extraction that might be used as a soil amendment for agricultural production. The overall objective of this series of experiments was to determine the feasibility and management strategies required to best utilize lipid-extracted algae (LEA) as an organic fertilizer and soil conditioner. Effects of LEA on nutrient availability, soil C storage, aggregate stability, soil acidity and salinity, greenhouse gas (GHG) loss, changes in soil microbial activity and community composition, and forage growth were assessed. Soil organic C (SOC) measured 392-d after amending soil with 1.5 and 3.0% LEA for a microcosm incubation was increased by approximately 0.2 and 0.3% OC, respectively, compared to the control. Approximately 10% of added LEA-C was mineralized and lost as CO2 compared with 15% of added wheat straw-C. Lipid-extracted algae enhanced aggregate formation and soil SOC storage in microaggregates at 0-15 cm depth over a 12-month field incubation with greater mean weight diameter by 12 months and approximately 42 and 66% of total SOC from 1.5 and 3.0% LEA treatments, respectively. With glass house and field studies, nutrient availability was enhanced with LEA amendments; however, LEA applied at a 30% rate decreased seedling emergence of foxtail millet (Setariaitalica) and salt-tolerant ryegrass (Lolium multiflorum), and thus, herbage mass (HM) and nutrient uptake were also decreased. Soil amended with 1.5% a LEA, however, increased HM of peal millet (Pennisetum glaucum), salt-tolerant ryegrass, and a sorghum-sudangrass hydrid [(Sorghum bicolor (L.) Moench ? Sorghum Sudanese (P.)]. Soil LEA-application should be a significant source of organic nutrients for microbial transformation and usage and plant uptake, and thus, may reduce inputs of inorganic fertilizer. The potential for LEA amendments enhancing aggregate formation, and consequently soil C storage, was indicated by mean weight diameter and SOC within macro- and microaggregates increasing over time. Lipid-extracted algae application may be a means of mitigating SOC losses due to agricultural production, and also, maintaining or improving soil structure and quality. However, problems with excess soil salinity, sodicity, and nutrients may occur at high LEA addition rates.Item Study of Adsorption of Methanol in an Activated Carbon and Carbon Nanotube Matrix for Use in a Solar Based Refrigeration Cycle(2012-07-16) Sambath, SrivathsThis thesis seeks to investigate the adsorption capabilities of activated carbon and carbon nanotubes. The adsorption of methanol on both of these substances was tested for their application in a solar based refrigeration cycle. Research on carbon nanotubes and their growth has been carried out for applications in the semiconductor industry. Enough focus has not been given to the use of nanotubes for refrigeration purposes. Adsorption refrigerators have been designed with the energy source being solar energy. Various adsorbent/adsorbate pairs have been tested in literature. The present work focuses on carbon nanotubes because theoretically, nanotubes should be able to adsorb better than activated carbon due to their high surface to volume ratios and hence a higher number of adsorption sites available for methanol to adsorb. The amount of adsorption of methanol on nanotubes depends on whether the end caps of the nanotubes are open or closed and also on the hydrophilic nature of the nanotubes. Nanotubes with ends closed are supposed to adsorb less than the nanotubes with their ends opened. The ends of carbon nanotubes can be blocked because of iron and other impurities. In this project, nanotubes are annealed under high vacuum to open the end caps. The hydrophobic nature of the nanotubes is corrected by treating them with concentrated nitric acid. The hydrophobic nature of the nanotubes is corrected by treating them with concentrated nitric acid. The acid treated nanotubes are used to obtain adsorption data at different temperatures. The adsorption of methanol on activated carbon, pristine and treated carbon nanotubes is measured at different temperatures. Electron microscopy is used to validate that annealing the nanotubes at high temperature under vacuum opens the end caps of the nanotubes. Finally, a matrix of nanotubes and carbon powder is prepared with different concentrations. The mixture is tested for adsorption of methanol. It is observed that the carbon nanotubes, pristine or treated, do not perform better than activated carbon. However, performance seems to increase when mixtures of activated carbon and carbon nanotubes are used as adsorbent. Also, it is found that mixtures containing annealed nanotubes perform better than mixtures with pristine nanotubes. Kinetics of the adsorption process is calculated for the different adsorbents used, which is used to explain the increase in the amount of methanol adsorbed for the activated carbon-carbon nanotube mixture.Item Sustainable Management of Biogeochemical Cycles in Soils Amended with Bio-Resources from Livestock, Bioenergy, and Urban Systems(2011-10-21) Schnell, Ronnie WayneBioresources are generated in a variety of environments and each presents unique risks and benefits associated with land application. Bioresources from livestock, urban and bioenergy systems were selected and evaluated through field, greenhouse and laboratory studies of potential risk and benefits of recycling to agricultural and urban landscapes. The waste stream, including feedstock sources and treatment processes, affects composition and properties of bioresources and effects on biogeochemical cycles of amended soils. Variation of decomposition and nutrient mineralization rates among bioresources used to amend soil for turfgrass and forage reflected variation among contrasting feedstock sources and treatments prior to application. During turfgrass establishment, plant available nitrogen and nitrogen mineralized from a bioresource from livestock waste streams, (Geotube! residual solids, supplied N in excess of crop uptake potential and contributed to leaching loss of N. In contrast, N mineralization rates from bioresources generated during methane production from dairy manure (manure solids) were not sufficient to maximize crop production, necessitating N fertilizer application. In addition to variation of composition, bioresource effects on crop productivity and environmental quality vary among management practices and between forage and turfgrass cropping systems. Large application rates of bioresources increase soil nutrient concentration and potential crop productivity, but contribute to increased nutrient loss in drainage and surface runoff. Yet, incorporation or Alum treatment of bioresources will reduce runoff loss of dissolved P and protect water quality without sacrificing crop productivity. Alum treatment of bioresources prior to land application effectively reduced runoff loss of dissolved P to levels observed for control soil. For situations in which large, volume-based bioresource rates are top-dressed or incorporated, export of applied nutrients environmental impacts were compared between forage and turfgrass systems. Starting during the initial year of production, annual export of applied N and P in Tifway bermudagrass sod was greater than export through forage harvests of Tifton 85. Low forage yield limited N and P export from Tifton 85 during the year of establishment, but increased forage yield during the second year increased export of manure N and P to levels more comparable to sod. As variation between compost sources, turfgrass and forage production systems, and application methods indicated, effective management of bioresources is necessary to balance benefits and risk in cropping systems. Integrated assessment of bioresource composition and crop-specific management of application method and rate will enable sustainable bioresource cycling and crop productivity.Item The Carbon Footprint of Bioenergy Sorghum Production in Central Texas: Production Implications on Greenhouse Gas Emissions, Carbon Cycling, and Life Cycle Analysis(2013-06-13) Storlien, Joseph OrgeanEnhanced interest in biofuel production has renewed interest in bioenergy crop production within the United States. Agriculture?s role in biofuel production is critical because it has the potential to supply renewable energy while minimizing greenhouse gas (GHG) emissions. However, agronomic management practices influence direct and indirect GHG emissions, and both can have a significant impact on biofuel production efficiency. Our overall objective was to determine the carbon (C) footprint of bioenergy sorghum (Sorghum bicolor L.) production in central Texas. Specifically, we determined the impacts of crop rotation, nitrogen (N) fertilization, and residue return on direct and indirect GHG emissions, theoretical biofuel yield, C pools, and life cycle GHG emissions from bioenergy sorghum production in 2010 and 2011. An experiment established in 2008 near College Station, TX to quantify the impacts of crop management practices on bioenergy sorghum yield and soil properties was utilized, and included two crop rotations (sorghum-sorghum or corn-sorghum), two fertilization levels (0 or 280 kg N ha^(-1) annually), and two residue return rates (0 or 50% biomass residue returned) to assess management impacts on sorghum production, C cycling, and life cycle GHGs. Corn production was poor under moderate drought conditions, while bioenergy sorghum produced relatively large yields under both moderate and severe drought conditions. Nitrogen addition increased crop yields, and rotated sorghum had higher yield than monoculture sorghum. Fluxes of CO_(2) and N_(2)O were higher than those reported in literature and highest soil fluxes were frequently observed following precipitation events during the growing season. Residue return increased cumulative CO_(2) emissions and N fertilization increased N_(2)O emissions. Residue return also increased soil microbial biomass-C, an important indicator of soil quality. Continuous sorghum significantly increased soil organic C (SOC) concentrations near the soil surface and at two depths below 30 cm. Analysis of change in SOC across time to estimate net CO_(2) emissions to the atmosphere revealed bioenergy sorghum production accrued high amounts of SOC annually. Most treatments accrued more than 4 Mg C ha^(-1) yr^(-1) from 2008 to 2012, which indicated great potential for C sequestration and offsetting GHG emissions. Life cycle GHG emissions (as g CO_(2)-eq MJ^(-1)) were all negative due to high SOC increases each year and indicated all bioenergy sorghum production treatments sequestered atmospheric CO_(2) per unit of theoretical energy provided. Despite its relatively low production efficiency, rotated sorghum with N addition and residue return was selected as the ideal bioenergy sorghum production scenario due to a number of sustainability factors. Bioenergy sorghum may offer great benefit as a high-yielding biofuel feedstock with minimal impacts to net GHG emissions.Item The role of grain sorghum in conservation of predatory arthropods of Texas cotton(Texas A&M University, 2004-09-30) Prasifka, Jarrad ReedFour separate but complimentary studies investigated the role of grain sorghum as a predator source for Southern Rolling Plains cotton in 2001 and 2002. Objectives were to: (1) determine the timing and magnitude of predator movement between crops, (2) test putative causes of movement by manipulating prey levels at different stages of crop phenology, (3) explore the feeding and reproductive behavior of a common predator colonizing cotton, and (4) examine the effects of grain sorghum and uncultivated areas on cotton predator abundance at an area-wide scale. Rubidium mark-recapture experiments indicated grain sorghum fields produced a net predator gain for adjacent cotton. Analysis suggested two coccinellids, Hippodamia convergens Gu?rin-M?neville and Scymnus loewii Mulsant, were responsible for the overall pattern of predator movement. Predator movement into cotton did not appear to be concentrated at specific stages of sorghum phenology. Manipulations of aphid levels in field cages were used to determine if prey abundance or phenology influenced the movement of H. convergens into cotton. In both years, more lady beetle adults were collected on cotton during the latest stages of sorghum phenology. In the second year, relatively low aphid densities (15 per plant) appeared to influence the movement of beetles onto caged cotton. Carbon isotope ratios of H. convergens were used to assess adult feeding behavior after colonizing cotton and to determine if prey consumed in sorghum contributed to egg production in cotton. Though aphids were absent 2001, H. convergens adults stayed in cotton, did not produce eggs and apparently consumed few prey. Cotton aphids were present in 2002 and H. convergens isotope ratios changed from prey consumed in cotton. The isotope ratios of egg masses collected in 2002 indicated prey consumed in grain sorghum contributed very little to egg production in cotton. An area-wide pattern analysis suggested the abundance of grain sorghum and uncultivated areas both positively influenced cotton predator levels. While these landscape effects were less important overall than prey levels and cotton planting dates, in some sampling periods landscape composition appeared to be the most important factor in determining cotton predator levels.