Dissertations / Theses: 'Greenhouse gas inventories and fluxes'

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Welch, Bertie. "Trace greenhouse gas fluxes in upland forests." Thesis, Open University, 2018. http://oro.open.ac.uk/55812/.

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Tree stems can act as a conduit for trace greenhouse gases (GHG) produced in the soil. However, the majority of studies describing tree stem fluxes of methane (CH₄) and nitrous oxide (N₂O) have focused on wetland ecosystems. Tree stem fluxes of GHGs on free-draining soils are understudied, but they are assumed to be a source of CH₄ and a weak source of N₂O. The work presented in this thesis aimed to determine how climatic variables, soil abiotic conditions, and tree species influence CH₄ and N₂O fluxes in forests on free-draining soil. Soil and stem CH₄ and N₂O fluxes were measured in lowland tropical rainforest in Panama, Central America and temperate woodland in the UK, using chambers installed on the forest floor or strapped to individual stems of two common tree species. Air samples were collected every two to four weeks during 5 months in 2014 and during November 2015 at the tropical site, and between February 2015 and January 2016 at the temperate site. Tree stem CH₄ fluxes differed significantly between species at both sites and stem N₂O fluxes also differed between species at the tropical site. However, there was little variation in soil CH₄ or N₂O fluxes. At both sites, tree-mediated CH₄ fluxes declined from positive values (emission) at the stem base to negative values (uptake) higher up. Stem CH₄ fluxes generally increased significantly with solar radiation, suggesting a link to photosynthetic activity mediated by tree water transport. Collectively, these results show that trees on free-draining soils could act as net sinks for CH₄ and N₂O. These findings will improve GHG budgets because tree stem uptake is currently unaccounted for. In particular, if uptake of CH₄ by tree stems on free-draining soils is widespread, the global terrestrial CH₄ sink could be much larger than currently estimated.

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Dinsmore, Kerry J. "Atmosphere-soil-stream greenhouse gas fluxes from peatlands." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4040.

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Peatlands cover approximately 2-3% of the world’s land area yet represent approximately a third of the worlds estimated total soil carbon pool. They therefore play an important role in regulating global atmospheric CO2 and CH4 concentrations, and even minor changes in their ability to store carbon could potentially have significant effects on global climate change. Much previous research has focussed primarily on land-atmosphere fluxes. Where aquatic fluxes have been considered, they are often in isolation from the rest of the catchment and usually focus on downstream losses, ignoring evasion (degassing) from the water surface. However, as peatland streams have been repeatedly shown to be highly supersaturated in both CO2 and CH4 with respect to the atmosphere, they potentially represent an important pathway for catchment GHG losses. This study aimed to a) create a complete GHG and carbon budget for Auchencorth Moss catchment, Scotland, linking both terrestrial and aquatic fluxes, and b) understand what controls and drives individual fluxes within this budget. This understanding was further developed by a short study of C exchange at the peat-aquatic interface at Mer Bleue peatland, Canada. Significant variability in soil-atmosphere fluxes of both CH4 and N2O emissions was evident at Auchencorth Moss; coefficients of variation across 21 field chambers were 300% and 410% for CH4 and N2O, respectively. Both in situ chamber measurements and a separate mesocosm study illustrated the importance of vegetation in controlling CH4 emissions. In contrast to many previous studies, CH4 emissions were lower and uptake greater where aerenchymous vegetation was present. Water table depth was also an important driver of variability in CH4 emissions, although the effect was only evident during either periods of extreme drawdown or when the water table was consistently near or above the peat surface. Significant pulses in both CH4 and N2O emissions were observed in response to fluctuations in water table depth. Despite the variability in CH4 and N2O emissions and the uncertainty in up-scaled estimates, their contribution to the total GHG and carbon budgets was minor. Concentrations of dissolved CO2 in peatland drainage waters ranged from a mean of 2.88 ± 0.09 mg C L-1 in the Black Burn, Scotland, to a mean of 7.64 ± 0.80 mg C L-1 in water draining Mer Bleue, Canada. Using non-dispersive infra-red (NDIR) CO2 sensors with a 10-minute measurement frequency, significant temporal variability was observed in aquatic CO2 concentrations at the 2 contrasting field sites. However, the drivers of this variability differed significantly. At Mer Bleue, Canada, biological activity in the water column led to clear diurnal cycles, whereas in the Black Burn draining Auchencorth Moss, dilution due to discharge was the primary driver. The NDIR sensor data also showed differences in soil-stream connectivity both between the sites (connectivity was weak at Mer Bleue) and across the range of conditions measured at Auchencorth Moss i.e. connectivity increased during periods of stormflow. Compiling the results from both the terrestrial and aquatic systems at Auchencorth Moss indicated that the catchment was functioning as a net sink for GHGs (382 kg CO2-eq ha-1 yr-1) and a net source of carbon (143 kg C ha-1 yr-1). The greatest flux of GHGs was via net ecosystem exchange (NEE). Terrestrial emissions of CH4 and N2O combined returned only ~5% of CO2-equivalents captured by NEE to the atmosphere, whereas evasion of CO2, CH4 and N2O from the stream surface returned ~40%. The budgets clearly show the importance of aquatic fluxes at Auchencorth Moss and highlight the potential for significant error in source/sink strength calculations if they are omitted. Furthermore, the process based understanding of soil-stream connectivity suggests the aquatic flux pathway may play an increasingly important role in the source-sink function of peatlands under future management and climate change scenarios.

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Skoglund, Björn. "Diffusive gas fluxes in neotropical rainforest streams." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-105692.

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Rainforests are of great importance to global carbon cycling, but the importance of deforestation and change in land use is poorly understood due to a lack of studies quantifying the difference in carbon fluxes between original rainforest and agricultural land. Furthermore, the aquatic outgassing of neotropical systems have been proven to have greater impact on global carbon cycling than previously anticipated (Richey et al 2002).In this study we investigated the aquatic concentration and daily diffusive gas flux of CO2 and CH4 from 4 pristine sites and 4 impacted sites, respectively, in 4 streams running along a gradient of anthropological impaction in the Atlantic Rainforest, Brazil. Statistically significant differences between pristine and impacted sites were found in all streams for both CO2 and CH4. On average, the impacted sites were found to be emitting almost three times as much C into the atmosphere as the pristine sites, mainly owing to CO2 emissions (14172±5226 mg C m-2 d-1). Exploring an area of the neotropical carbon cycle that is not yet fully understood, the study draws attention to the significant difference in aquatic outgassing from rivers observed at different impaction levels and highlights the need for further field studies.

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Nkongolo, Nsalambi Vakanda. "Quantification of greenhouse gas fluxes from soil in agricultural fields." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1474.

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Field studies were conducted at Lincoln University of Missouri (USA) and Hokkaido University (Japan) to: (i) study the relationships between greenhouse gases emissions and soil properties, (ii) assess the influence of agricultural practices on greenhouse gas fluxes and soil properties and (iii) improve the quantification of greenhouse gases from soil in agricultural fields using geospatial technologies. Results showed that besides soil temperature (T), soil thermal properties such as thermal conductivity (K), resistivity (R) and diffusivity (D) and soil pore spaces indices such as the pore tortuosity factor and the relative gas diffusion coefficient (Ds/Do) are controlling factors for greenhouse gases emissions. Soil thermal properties correlated with greenhouse gases emissions when soil temperature could not. The study has found that predicted Ds/Do and correlate with greenhouse gas fluxes even when the air-filled porosity and the total porosity from which they are predicted did not. We have also showed that Ds/Do and can be predicted quickly from routine measurements of soil water and air and existing diffusivity models found in the literature. Agricultural practices do seriously impact greenhouse gases emissions as showed by the effect of mechanized tillage operations on soil physical properties and greenhouse gas fluxes in a corn and soybean fields. In fact, our results showed that tractor compaction increased soil resistance to penetration, water, bulk density and pore tortuosity while reducing air-filled porosity, total pore space and the soil gas diffusion coefficient. Changes in soil properties resulted in increased CO2, NO and N2O emissions. Finally, our results also confirmed that greenhouse gas fluxes vary tremendously in space and time. As estimates of greenhouse gas emissions are influenced by the data processing approach, differences between the different calculation approaches leads to uncertainty. Thus, techniques for developing better estimates are needed. We have showed that Geographic Information Systems (GIS), Global Positioning System (GPS), computer mapping and geo-statistics are technologies that can be used to better understand systems containing large amounts of spatial and temporal variability. Our GIS-based approach for quantifying CO2, CH4 and N2O fluxes from soil in agricultural fields showed that estimating (extrapolating) total greenhouse gas fluxes using the “standard” approach – multiplying the average flux value by the total field area – results in biased predictions of field total greenhouse gases emissions. In contrast, the GIS-based approach we developed produces an interpolated map portraying the spatial distribution of gas fluxes across the field from point measurements and later process the interpolated map produced to determine flux zones. Furthermore, processing, classification and modeling enables the computation of field total fluxes as the sum of fluxes in different zones, therefore taking into account the spatial variability of greenhouse gas fluxes.

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Storer, Kate Elizabeth. "Interactions between arbuscular mycorrhizal fungi and soil greenhouse gas fluxes." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/5022/.

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Arbuscular mycorrhizal fungi (AMF) can form a mutualistic symbiosis with over two-thirds of all land plants, providing phosphorus and/or nitrogen in exchange for carbon. They can have a significant effect on the surrounding soil, altering pH, water content, structure, and drainage. Important greenhouse gases (GHG) including carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) can be influenced by these factors, yet to date the interactions between AMF and soil GHG fluxes are surprisingly understudied. A microcosm system was developed to study GHG fluxes in the presence and absence of AMF hyphae. A central compartment contained an AMF host plant (Zea mays L.), with two outer compartments, that either allowed (AMA) or prevented (NAMA) AMF hyphal access. Organic matter patches of dried, milled, Z. mays leaves mixed with soil were added to the outer compartments to encourage proliferation of AMF hyphae and GHG production. Soil-atmosphere fluxes of N2O, CO2 and CH4 from the outer compartments were quantified, and gas probes were developed to measure N2O concentrations within the organic matter patches. Data from a series of microcosm experiments provide evidence for AMF interactions with soil fluxes of N2O and CO2, but not CH4. Soil CO2 fluxes were found to be a useful non-invasive method for determining the presence of AMF in hyphal compartments. The N2O concentrations in organic patches decreased in AMA treatments, and a subsequent experiment demonstrated that N2O production by nitrifiers may be limited in the presence of AMF hyphae. In contrast, following harvesting, N2O fluxes from organic matter patches were higher in the AMA treatment; possibly because carbon release from severed AMF hyphae fuelled denitrification. These interactions have important implications for N cycling and sustainable agriculture. The evidence presented in this thesis suggests that AMF may play a previously unappreciated role in reducing soil-atmosphere losses of N2O.

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Hermans, Renee Elisabeth Maria. "Impact of forest-to-bog restoration on greenhouse gas fluxes." Thesis, University of Stirling, 2018. http://hdl.handle.net/1893/27319.

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Large areas of northern peatlands have been drained and afforested in the second half of the 20th century with significant impacts on important ecosystem services, including loss of biodiversity and potential changes in C storage. A considerable effort is currently invested into restoring original peatland function and ecosystem services, with an increasing area of newly restored peatland areas over recent years. However, the effect of restoration on the greenhouse gas (GHG) budget is unknown. This study is the first quantification of CO2, CH4 and N2O fluxes from forest-to-bog restoration sites spanning 0 to 17 years in age. Further, the impact of afforestation on peat decomposition is measured in situ, and the impact of afforestation on the biochemical composition of the peat in relation to CO2 and CH4 fluxes is investigated. Results show that forest-to-bog restoration is successful from a GHG perspective, since all three major GHG fluxes of the restoration sites are changing along the chronosequence towards the fluxes from near pristine bog sites. The peat decomposition rate under the forest plantations is a big part of the total soil respiration at 126.8 ± 14.7 g C m-2 y-1 (44% of total soil CO2 efflux) and our results indicate a slowing down of peat decomposition towards the near pristine bog. CH4 fluxes increase with restoration age, whilst all sites remain a small sink for N2O. I observed changes in peat quality and nutrient availability in the pore water under forests. Different CO2 fluxes between vegetation-free peat cores from different sites for the same temperature and water level show that these differences in peat quality and nutrient availability shape the biogeochemical processes in the peatlands. However only small differences in CH4 fluxes between sites were evident, suggesting that on its own (and in absence of biotic interactions under field conditions), forestry effects on CH4 flux are limited.

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Pitt, Joseph. "Novel methods to constrain regional greenhouse gas fluxes using aircraft data." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/novel-methods-to-constrain-regional-greenhouse-gas-fluxes-using-aircraft-data(e9aea30c-dd81-43c6-917b-27e22b32352f).html.

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Anthropogenically induced changes to the Earth's climate system are widely accepted to be one of the greatest threats to the sustainable future of humanity. Greenhouse gas emissions constitute the largest driving factor behind these changes, and with annual emissions still increasing further perturbation is projected. Accurate quantification of these emissions, broken down both spatially and sectorally, is vitally important in guiding effective policy for emission reduction at both national and international levels. This thesis focusses on methods to improve top-down estimates for greenhouse gas emissions within the UK, using data sampled on board the UK atmospheric research aircraft. Novel instrumentation and analytical techniques are presented and evaluated, based on measurements made as part of the GAUGE (Greenhouse gAs UK and Global Emissions) and MAMM (Methane and other greenhouse gases in the Arctic: Measurements, process studies and Modelling) projects. A new quantum cascade laser absorption spectrometer (QCLAS) for measuring CH4 and N2O on board the aircraft has been characterised. Its performance was evaluated over 17 flights during summer 2016, and a sensitivity to changes in aircraft cabin pressure was observed. A new calibration procedure was derived to minimise the effect of this sensitivity on the data, and the impact of this new procedure was quantified through analysis of in-flight target cylinder measurements and comparison against simultaneous CH4 measurements made using a previously characterised analyser. The impact of water vapour on the retrievals was also investigated, with superior results derived by directly including line broadening due to water vapour in the mole fraction retrieval algorithm. Applying the new calibration procedure to the data, total 1-sigma uncertainties of 2.47 ppb for CH4 and 0.54 ppb for N2O have been calculated for 1 Hz measurement. The British Isles CH4 flux has been derived for a case study on 12 May 2015, using aircraft and ground-based sampling and a combination of local dispersion modelling, global chemical transport modelling and a composite inventory comprised of anthropogenic and natural sources. A new multiple variable regression technique was used to compare measured and modelled CH4 mole fractions, and to derive scale factors used to estimate posterior fluxes based on prior inventory values. A maximal range for the total British Isles CH4 flux has been calculated to be 67 kg/s -- 121 kg/s, with a central estimate of 103 kg/s based on an assessment of the most likely apportionnment of model uncertainty. A further case study measuring CO2, CH4 and CO fluxes from London and surrounding urban areas using a mass balance technique has also been performed. Fluxes have been found to be a factor of ~0.7 lower for CH4, ~0.8 lower for CO, and ~1.3 higher for CO2, relative to a similar study in 2012. Likely sources of difference between the derived fluxes, as well as the overall utility of this technique, have been assessed.

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Adams, Christopher Alan. "Carbon Burial and Greenhouse Gas Fluxes of New Intertidal and Saltmarsh Sediments." Thesis, University of East Anglia, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.514279.

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Carbon (C) and nitrogen (N) burial within new intertidal and saltmarsh sediments from the Blackwater estuary, Essex were investigated. These sediments were created as part of a 'managed realignment' of coastal sea defences in the East of England to address issues such as loss of intertidal habitat, the effects of relative sea level rise and the unfeasibility of maintaining aging sea defences. The fluxes of greenhouse gases (CH4 & N20) from the sediments were quantified using non-steady state chambers and their ability to offset a portion of the C burial to give net carbon sequestration was investigated. C and N contents in natural intertidal sediments were higher than in managed realignment (MR) sediments and comparable to saltmarsh sediments from around the East coast of England. Mature MR sites possessed C and N burial rates at least as great as natural marshes and if increased sedimentation in these predominantly low lying intertidal areas is accounted for, the mature MR sites far outstrip natural marsh C burial rates. Less mature, MR midmarsh areas had lower C and N burial rates more inline with those found in intertidal mudflats. Both natural and MR intertidal areas were small sources of the powerful greenhouse gases CH4 (0.10-0.40 g m'2 y(l) and N20 (0.03-0.37 g M-2 y('). These gas fluxes reduced net C sequestration within the MR marshes by as much as 49%, but by only 2% from natural saltmarshes. The current C sequestration of Blackwater estuary managed realignment sites is -690 tonnes of CO2eq yr' (carbon dioxide equivalents). If the total area identified as potentially suitable for MR to take place is reverted back to intertidal area this will sequester -10200 tonnes of CO2eq yr' and -440 tonnes of N per year. Another -480 tonnes N will be removed through denitrification and -80-320 tonnes P yr"' will be buried within the new intertidal areas.

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Girkin, Nicholas T. "Tropical forest greenhouse gas emissions : root regulation of soil processes and fluxes." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52949/.

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Tropical forested peatlands are a major carbon store and are a significant source of global carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions. While the role of environmental variables, including temperature and water table depth have been relatively well studied, uncertainty remains in the extent to which plant roots regulate greenhouse gas (GHG) fluxes and peat biogeochemistry. This study examined the role of roots, and root inputs of carbon and oxygen in regulating fluxes from peat under two dominant plant species, Campnosperma panamensis and Raphia taedigera, a broadleaved evergreen tree and canopy palm, in San San Pond Sak wetland, in Bocas del Toro Province, Panama. A combination of in situ and ex situ experiments were performed between February 2015 and August 2017. Small scale variation in GHG fluxes and peat biogeochemistry was measured at two distances within the rooting zones of C. panamensis and R. taedigera. Peat organic matter properties were assessed using Rock-Eval 6 pyrolysis. Results indicated significant variation in CH4 but not CO2 fluxes at different distances within the rooting zone, with CH4 fluxes subsequently linked to measures of the overall size of the available organic carbon pool (S2). Rock-Eval pyrolysis data was used to construct a three-pool model of organic matter thermostability which indicated significant differences in organic matter composition between peats derived from different botanical origins, in addition to a high level of heterogeneity within the rooting zone. Changes in GHG production and peat biogeochemical properties in response to the addition of root exudate analogues were assessed in an ex situ anoxic incubation experiment. A combination of organic acids and sugars, identified as common forest plant root exudate components, were added over a two week period to peats derived from C. panamensis and R. taedigera. GHG fluxes varied significantly between treatments but not by peat botanical origin, and were associated with significant changes in soil properties including, pH and redox potential, thereby demonstrating a link between plant root carbon inputs, peat properties and GHG fluxes. In situ mesocosms were used to assess the effects of root exclusion on peat biogeochemistry and GHG fluxes. Partial and full root exclusion significantly reduced dissolved oxygen concentrations and was associated with greater root necromass. Full root exclusion increased CH4 fluxes five-six fold compared to partial root exclusion, equivalent to an 86 - 90% reduction in CH4 oxidation, demonstrating the important role of root inputs of oxygen in mitigating CH4 efflux from tropical peat. A 13CO2 pulse labelling experiment was conducted using both R. taedigera, C. panamensis, and Symphonia globulifera, a second broadleaved evergreen tree species, to demonstrate a direct link between plant photosynthesis and CH4 fluxes, and identify aspects of the bacterial and fungal community associated with the turnover of labile carbon. The extent of 13C enrichment of CH4 differed significantly between plant types (palms vs broadleaved evergreen trees), as did the extent of net CH4 efflux. Phospholipid fatty acid (PLFA) biomarker analysis indicated both peat types were dominated by Gram negative bacteria. There was strong 13C enrichment of Gram negative bacteria, supporting their previously proposed role as important decomposers of labile carbon. Collectively, these results demonstrate that root inputs of carbon and oxygen can strongly regulate tropical peatland GHG fluxes, and that the extent of regulation can vary significantly between tropical wetland plant species from contrasting dominant plant types. This is particularly important in understanding regulatory processes in a globally significant carbon store and understanding possible consequences of land use change in the tropics.

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Vardag, Sanam Noreen [Verfasser], and Ingeborg [Akademischer Betreuer] Levin. "Greenhouse gas measurements with the Fourier Transform Infrared analyser – Our tool to study greenhouse gas fluxes / Sanam Noreen Vardag ; Betreuer: Ingeborg Levin." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/118061478X/34.

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Ishtiaq, Khandker S. "Robust Modeling and Predictions of Greenhouse Gas Fluxes from Forest and Wetland Ecosystems." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2287.

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The land-atmospheric exchanges of carbon dioxide (CO2) and methane (CH4) are major drivers of global warming and climatic changes. The greenhouse gas (GHG) fluxes indicate the dynamics and potential storage of carbon in terrestrial and wetland ecosystems. Appropriate modeling and prediction tools can provide a quantitative understanding and valuable insights into the ecosystem carbon dynamics, while aiding the development of engineering and management strategies to limit emissions of GHGs and enhance carbon sequestration. This dissertation focuses on the development of data-analytics tools and engineering models by employing a range of empirical and semi-mechanistic approaches to robustly predict ecosystem GHG fluxes at variable scales. Scaling-based empirical models were developed by using an extended stochastic harmonic analysis algorithm to achieve spatiotemporally robust predictions of the diurnal cycles of net ecosystem exchange (NEE). A single set of model parameters representing different days/sites successfully estimated the diurnal NEE cycles for various ecosystems. A systematic data-analytics framework was then developed to determine the mechanistic, relative linkages of various climatic and environmental drivers with the GHG fluxes. The analytics, involving big data for diverse ecosystems of the AmeriFLUX network, revealed robust latent patterns: a strong control of radiation-energy variables, a moderate control of temperature-hydrology variables, and a relatively weak control of aerodynamic variables on the terrestrial CO2 fluxes. The data-analytics framework was then employed to determine the relative controls of different climatic, biogeochemical and ecological drivers on CO2 and CH4 fluxes from coastal wetlands. The knowledge was leveraged to develop nonlinear, predictive models of GHG fluxes using a small set of environmental variables. The models were presented in an Excel spreadsheet as an ecological engineering tool to estimate and predict the net ecosystem carbon balance of the wetland ecosystems. The research also investigated the emergent biogeochemical-ecological similitude and scaling laws of wetland GHG fluxes by employing dimensional analysis from fluid mechanics. Two environmental regimes were found to govern the wetland GHG fluxes. The discovered similitude and scaling laws can guide the development of data-based mechanistic models to robustly predict wetland GHG fluxes under a changing climate and environment.

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Johansson, Elisabeth. "Constructed wetlands and deconstructed discourses : greenhouse gas fluxes and discourses on purifying capacities /." Linköping : Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/arts253s.pdf.

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Brill, Katie Ellen. "Impacts of inundation and season on greenhouse gas fluxes from a low-order floodplain." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/19213.

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The global climate is changing and much of this is attributed to the greenhouse effect, which has been exacerbated by increased anthropogenic releases of greenhouse gases (GHGs). However, important GHGs, carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), are produced naturally in the soil during the metabolism of many soil microbial and plant communities. The generation rate of GHGs depends on many factors, including soil community composition, nutrient availability, temperature, and soil moisture. Predicted climate variability is expected to alter temperature and rainfall patterns, which can impact the factors regulating natural generation of GHGs. With changing fluxes of GHGs, the natural feedback loops between GHG generation and climate may change. Increased emissions from natural sources would exacerbate climate change, whereas decreased emissions may mitigate its impacts. Floodplains may be particularly susceptible to climate change, as their biogeochemical processing is driven by hydrology. For this study, ten mesocosms were installed on the floodplain of Stroubles Creek in southwest Virginia. A flood event was simulated in half of these mesocosms in both early spring and mid-summer, which represent extremes in soil moisture and primary productivity on the floodplain. Headspace gases were monitored for CO, N2O, and CH4. Efflux of CO2 and N2O was higher in summer than spring, and also increased following wetting events. Methane production was greater in the spring, with no detectable change with wetting. Increases in summer rainfall events could increase the release of important GHGs to the atmosphere, potentially at levels significant to climate change.
Master of Science

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Ventura, Robert E. "Wetlands and Greenhouse Gas Fluxes: Causes and Effects of Climate Change – A Meta-Analysis." Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/pomona_theses/107.

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Climate change is one of the largest problems facing this generation. Anthropogenically caused increases of greenhouse gas emissions is a significant culprit to this problem. Although the obvious problems such as cars, industry, and urbanism garnish a significant amount of the criticism, natural sources such as wetlands are also beginning to contribute to this issue. This is becoming increasingly significant as wetlands shift from being sinks of greenhouse gases to becoming sources as various anthropogenic impacts, including global warming itself, begin to affect the health of the wetlands. The aim of this project is to look at four common types of wetlands, being tropical mangroves, temperate coastal marshes, inland meadows, and subarctic peatlands, all located in different climactic areas of the world, and by doing a meta-analysis of available data of greenhouse gas production for each wetland type, observe how differences in their greenhouse gas production may contribute or be affected by climate change and global warming. Results of the meta-analysis revealed that the most significant production of the potent greenhouse gas nitrous oxide occurs in coastal wetlands such as tropical mangroves and coastal marshes, while the greenhouse gas methane is seen to be produced most in subarctic peatlands. These contributions of wetlands to global greenhouse gas production are not as significant as other anthropogenic contributions. However, subarctic wetlands contribute to more than half of the global methane emissions, and the most important aspect of wetland greenhouse gas production is that they are producing more greenhouse gases than they would normally be sequestering, contributing more than the basic greenhouse gas production data can display. Global climate changes such as temperature increase and sea level rise could also make these levels of greenhouse gas production become worse, although measures to decrease the effects of this such as regulations on anthropogenic nitrogen input, macrophyte presence, and prevention of peat burning.

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Mustamo, P. (Pirkko). "Greenhouse gas fluxes from drained peat soils:a comparison of different land use types and hydrological site characteristics." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526214610.

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Abstract Peat starts to decompose more rapidly after drainage, due to exposure to oxygen. While methane (CH4) emissions tend to decrease after drainage, carbon dioxide (CO2) and nitrous oxide (N2O) emissions from drained peatlands are considerable, especially the if the area is used for cultivation. Drainage and subsequent land management change the physical characteristics and thus hydrology and thermal conductivity of the soil, which affects greenhouse gas production. This thesis examined CH4 and N2O emissions and respiration from a peatland complex in Northern Finland, including a cultivated peatland, a forested peatland, a peat extraction site and a pristine mire. Chambers were used during the snow-free period and the snow gradient method during winter. Peat physical properties at the sites were also measured. The DRAINMOD model was used to assess measured peat hydraulic conductivity compared with the values needed to fit observed groundwater depth fluctuations. Effects of mineral soil content, drainage conditions and temperature on thermal conductivity of peat were examined and well-known equations for thermal conductivity of organic soils were tested. Respiration was highest in the cultivated study site, and this site and the peat extraction site were major sources of N2O. The pristine site was a large source of CH4 during the growing season. During winter, the peat extraction site and the cultivated site emitted CH4. The results suggested that raising mean groundwater level from 60 cm to 40 cm could potentially mitigate the greenhouse gas emissions at the cultivated site. Soil hydraulic conductivity at the drained sites was found to be better predicted by land use type than by soil physical parameters. Hydraulic conductivity values needed for DRAINMOD were at least one order of magnitude higher than those observed in field measurements. This demonstrates the potential role of land use and macropore flow in controlling hydrological processes in peat soils. The samples with the highest mineral soil content and bulk density had the highest thermal conductivity, especially at above-zero temperatures. The best equation for predicting thermal conductivity for unfrozen and frozen mineral soil-enriched peat soils was the Brovka-Rovdan equation, but the deVries equation performed fairly well for unfrozen soils. Soil water content and vegetation cover strongly influenced soil thermal regime
Tiivistelmä Turve alkaa hajota nopeammin ojituksen jälkeen happipitoisuuden lisääntyessä maassa. Metaanin (CH4) päästöt ovat yleensä vähäisiä ojituksen jälkeen, kun taas hiilidioksidin (CO2) ja typpioksiduulin (N2O) päästöt erityisesti viljellyiltä turvemailta voivat olla merkittäviä. Ojitus ja sen jälkeinen maankäyttö vaikuttavat maan fysikaalisiin ominaisuuksiin ja siten alueen hydrologiaan ja maan lämmönjohtavuuteen, mikä vaikuttaa kasvihuonekaasujen muodostumiseen. Tässä tutkimuksessa mittasimme CH4- ja N2O-päästöjä ja respiraatiota (talvella lumigradientti-menetelmällä ja kasvukauden aikana kammiomenetelmällä) turvemaa-alueella Pohjois-Suomessa. Koealue sisälsi turvepellon, turvemetsän, turvetuotantoalueen ja luonnontilaisen suon. Mittasimme alueilla myös maan fysikaalisia ominaisuuksia. DRAINMOD-mallia käytettiin saatujen hydraulisen johtavuuden mittausarvojen mallinnukseen sopivuuden tarkasteluun. Maan mineraaliaineksen osuuden, ojituksen ja lämpötilan vaikutusta turpeen lämmönjohtavuuteen tutkittiin ja testattiin eräiden tunnettujen lämmönjohtavuusmallien toimivuutta. Respiraatio oli suurinta turvepellolla ja turvetuotantoalue ja pelto olivat merkittäviä N2O-lähteitä. Suo oli sulan maan aikana merkittävä CH4-lähde. Talvella turvetuotantoalue ja pelto olivat CH4-lähteitä. Tutkimus viittasi siihen, että pohjavedenpinnan nostaminen turvepellolla 60 cm tasosta 40 cm tasoon voisi vähentää kasvihuonekaasupäästöjä. Maankäyttö ennusti hydraulista johtavuutta paremmin kuin fysikaaliset parametrit. DRAINMOD-malliin tarvittiin vähintään kertaluokkaa suurempia arvoja kuin kentällä mitatut. Tutkimus viittasi maankäytön ja macrohuokosten mahdollisesti merkittävään vaikutukseen turvemaa-alueiden hydrologiassa. Lämmönjohtavuus oli korkein näytteissä, joissa mineraalimaan osuus ja kiintotiheys olivat korkeita, erityisesti sulissa näytteissä. Brovka & Rovdan- malli oli paras näiden näytteiden kuvaamiseen mutta myös de Vries-malli toimi kohtalaisen hyvin sulille näytteille. Lämmönjohtavuus oli vähemmän merkittävä maan lämpötilojen kannalta kuin maan vesipitoisuus ja kasvillisuuspeite

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16

Hawthorne, Iain. "Impacts of biochar application to a Douglas-fir forest soil on greenhouse gas fluxes and water quality." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61373.

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Forest management for carbon sequestration is a valuable tool to combat rising greenhouse gas (GHG) concentrations in the Earth’s atmosphere. This thesis examined the use of biochar, a product of the thermal decomposition of waste organic matter in a reduced oxygen environment (i.e. pyrolysis) that is applied to soil, as an option for increasing carbon sequestration in a Coastal Douglas-fir forest soil in British Columbia when applied with and without urea fertilizer at 200 kg N ha-¹. Biochar produced from Douglas-fir forestry slash materials was used in this study to address this from a systems-based perspective. A soil incubation study showed that biochar application at high rates (10% oven dry soil basis) significantly increased CO₂ and N₂O emissions when applied without fertilizer and at both low (1%) and high rates (10%) decreased CH₄ consumption without fertilization. In terms of carbon dioxide equivalent emissions (CO₂e), it was shown that CO₂ accounted for >98% from all treatments. In a field study, GHG fluxes were measured after application of 5 t ha-¹ of biochar to a Douglas-fir forest soil in the first year followed by urea-N fertilization in the second year. The results showed that 5 t ha-¹ of biochar had little effect on GHG fluxes and their total CO₂e fluxes. Applying biochar prior to fertilizer application following industry-standard practices did not significantly change treatment CO₂e fluxes. It was concluded that low rates of biochar application to this forest soil would improve soil C sequestration with or without fertilization. In the field and laboratory experiments, soil pore water was extracted and analyzed for C and N concentrations and dissolved organic carbon using spectral indices. The results showed that low biochar application rates could be beneficial for both increasing C-sequestration and N-retention. Changes in spectral indices measured in the laboratory suggested that alterations in the dissolved organic matter pool could lead to changes in GHG emissions due to changing substrate supply for microbes as application rates increased. There is a recognized need for further studies prior to large-scale industrial applications; however, as result of this work it is possible to provide recommendations for large-scale pilot studies.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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17

Shrestha, Paliza. "Greenhouse gas fluxes and root productivity in a switchgrass and loblolly pine intercropping system for bioenergy production." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23769.

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This study is part of a larger collaborative effort to determine the overall environmental sustainability of intercropping pine (Pinus taeda L.) and switchgrass (Panicum virgatum L.), both of which are promising feedstock for bioenergy production in the Lower Coastal Plain in North Carolina. We measured soil CO₂ efflux (RS) every six weeks from January 2012 to March 2013 in four-year-old monoculture and intercropped stands of loblolly pine and switchgrass. RS is primarily the result of root respiration (RA) and microbial decomposition of organic matter (RH) releasing CO₂ as a by-product and is an important and large part of the global carbon (C) cycle. Accurate estimates of the two components of total soil respiration (RS) are required as they are functionally different processes and vary greatly spatially and temporally with species composition, temperature, moisture, productivity, and management activities. We quantified RA and RH components of RS by using a root exclusion core technique based on root carbohydrate depletion, which eliminates RA within the cores over time. We determined the relationship between RS, RA and RH measurements and roots collected from the cores. We took fresh soil cores in July 2012 to compare root productivity of loblolly pine and switchgrass in monoculture versus the co-culture. Additionally, CH₄ and N₂O fluxes were monitored quarterly using vented static chambers. Pure switchgrass had significantly higher RS rates (July, August, September), root biomass and root length in the top 0-35 cm relative to switchgrass in the co-culture, while loblolly pine with and without switchgrass had no significant changes in RS and roots. Correlations between RA and roots showed significantly positive correlation of RA to grass root biomass (r = 0.37, p ≤ 0.001), fine (r = 0.26, p ≤ 0.05) and medium root surface area (r = 0.20, p ≤ 0.1). The estimated portions of RS attributed to RA in the intercrop stand were 31% and 22% in the summer and fall, respectively. No significant treatment differences were observed in either CH₄ or N₂O flux. Our study indicates a decrease in switchgrass root productivity in the intercropped stand versus the monoculture stand which could account for differences in the observed RS.
Master of Science

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18

Menichino, Nina Marie. "The effects of restoration on biodiversity, water quality and greenhouse gas fluxes in a rich fen peatland." Thesis, Bangor University, 2015. https://research.bangor.ac.uk/portal/en/theses/the-effects-of-restoration-on-biodiversity-water-quality-and-greenhouse-gas-fluxes-in-a-rich-fen-peatland(de08dda4-6ffe-4932-9559-0a72c3c69480).html.

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Rich fens are globally significant wetlands due to their high biodiversity and provision of multiple ecosystem services, such as water purification and climate mitigation. However, many U.K. rich fens have become botanically degraded. This is principally due to abandonment, following the cessation of management (mowing/grazing) and has led to a decline in plant species richness. Although the response to mowing on plant species richness has been well documented across Europe, there is no prior knowledge of this research being undertaken at U.K rich fens. Additionally, the effects of mowing on water quality are largely unquantified. Furthermore, the spatial heterogeneity of greenhouse gases across and within botanically rich and botanically poor sites is also unknown. Two rich fen plant communities: Cladio-Molinietum (n=9) and Scheonus nigricans - Juncus subnodulosus (n=8) were examined across three sites; chosen for their conservation value and current degraded condition. A 50 % success rate was achieved following mowing to increase species richness, which meant assumptions were not met for both plant communities. Nitrate, phosphate and dissolved organic carbon concentrations did not reduce following mowing, however there was a beneficial increase in concentration of base cations at both sites. The greenhouse gas investigation revealed that the net gaseous carbon flux between both sites was comparable, which did not meet expectations that the botanically impoverished site would have higher carbon emissions, however, expected differences between plant communities were observed at both sites. Therefore, this study shows the complexity of the botanical, hydro-chemical and greenhouse gas spatial heterogeneity at rich fens. Careful examination prior to restoration is needed to determine whether environmental/ecological barriers have been removed, so that restoration is not in any way inhibited. In addition, this study has demonstrated that objectives for biodiversity may be in conflict with objectives to manage for other ecosystem services, in these multi-functional wetlands.

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Harley, James Fraser. "From source to sea : spatial and temporal fluxes of the greenhouse gases N2O, CO2 and CH4 in the river Tay catchment." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7527.

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River networks act as a link between components of the terrestrial landscape, such as soils and groundwater, with the atmosphere and oceans, and are now believed to contribute significantly to global budgets of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). The idea of rivers being an inert conduit for carbon and nitrogen to reach the coast has been challenged recently, with considerable processing of carbon and nitrogen occurring in both the water column and bed sediments in the various aquatic components that make up a river network, including lakes, streams, rivers and estuaries. Although understanding of the cycling of carbon and nitrogen has improved markedly in the last 20 years, there is still much uncertainty regarding the production and emission of greenhouse gases (GHGs) linked to this processing across river catchments and few studies have quantified GHG fluxes from source to sea. Therefore this study aimed to a) understand the spatial and temporal saturations and fluxes of GHGs from both the freshwater River Tay catchment (Scotland) and the River Tay estuary, and b) understand what controls the production of GHGs within both a freshwater lake and across multiple sites in the freshwater river using laboratory incubations of sediment. Hotspots of in-stream production and emission were evident both in the freshwater catchment and the estuary, with significant temporal and spatial variability in saturation and emission (density) for CH4, CO2 and N2O. CH4 emission densities, across the freshwater river sites, ranged from 1720 to 15500 μg C m-2 d-1 with a freshwater catchment wide mean of 4640 μg C m-2 d-1, and in general decreased from upland to lowland sites along the main river stem, with notable peaks of emission in a lowland tributary and at the outflow of a lowland loch. This corresponds well with the main drivers of spatial variability which include allochthonous inputs from gas rich soil waters and in-situ production in fine grained organic rich sediments. CH4 production was observed to be higher in the lowland tributaries (R. Isla 4500 μg C m-2 d- 1) compared to main-stem river sites both in the lowland river (129 μg C m-2 d-1) and upland river which displayed an uptake of CH4 (-1210 μg C m-2 d-1). The main driver of spatial variability in CH4 production rates was the quality of the sediment, as production was higher in fine grained sediments rich in carbon compared to sand and gravels with a low carbon content. CH4 production also varied seasonally, with temperature and seasonal variation in sediment quality as the predominant driving factors. CO2 emission densities across the freshwater catchment ranged from 517 to 2550 mg C m-2 d-1 with a catchment mean flux density of 1500 mg C m-2 d-1. Flux densities on the whole increased along the main river stem from upland sites to lowland sites, with higher fluxes in lowland tributaries. Seasonally, CO2 flux density was highest in late summer and autumn and lowest in winter at most sites, highlighting the importance in seasonal environmental controls such as temperature, light, and substrate availability. Production rates in the sediment increased from upland to lowland sites with highest production rates evident in the lowland tributaries, and in autumn sediment samples. N2O emission density also showed considerable spatial and seasonal variation across the catchment with flux densities ranging from 176 to 1850 μg N m-2 d-1 with a mean flux of 780 μg N m-2 d-1. Mean fluxes were highest in the lowland tributaries and lowest in the upland river with sediment experiments finding similar spatial variation in N2O production. On the whole, in-stream N2O production and emission across the freshwater catchment was driven by increases in nutrient concentration (NO3 -, NH4 +) which in turn was related to the proportion of agricultural landuse. The saturation and emission of GHGs also varied substantially both spatially and temporally in the River Tay estuary, with a mean emission density of 2790 μg CH4-C m-2 d-1, 990 mg CO2-C m-2 d-1 and 162 μg N2O-N m-2 d-1. The spatial variability of GHG concentrations and emission densities in the estuary were predominantly controlled by the balance between lateral inputs (from tidal flushing of surrounding intertidal areas), in-situ microbial production/consumption (both in the water column and bed sediments) and physical mixing/loss processes. Although emission densities of CH4, CO2 and N2O appear low compared to the freshwater river, this is because the estuary is emitting large quantities of gas in the middle and outer estuary, for example net annual emission of N2O increased from 84.7 kg N2O-N yr-1 in the upper freshwater section of the estuary to 888 kg N2O-N yr-1 in the middle estuary section, then decreased to 309 kg N2O-N yr-1 in the saltwater lower estuary. Overall, this study has shown that both dissolved and aerial fluxes of GHGs vary markedly both spatially and temporal from source to sea in a temperate river catchment, with hotspots of in-stream production and emission across the river catchment. The catchment (river, lake and estuary) was a smaller source of CO2, CH4 and N2O emission (total emission and by area) compared to other highly polluted aquatic systems both in the UK and globally.

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Beijer, Martin, and Madeleine Skoglund. "Summer CO2 fluxes : A field study from three large lakes in Sweden." Thesis, Linköpings universitet, Tema Miljöförändring, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-157304.

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Increasing levels of CO2 in the atmosphere is a contributing cause to climate change. To give a better understanding, natural sources of CO2 is as important as anthropogenic sources, such as burning fossil fuels. The current role of large boreal lakes as emitters of CO2 are poorly understood and there is a clear lack of data from different types of systems. The aim of this thesis was to examine CO2 fluxes from Roxen, Glan and Vättern, three large lakes in Sweden. The purpose of the study was also to compare different approaches to get empirical CO2 flux data, and to investigate if there was difference between the lakes and study periods. Floating chambers were used as method with both direct measured fluxes and calculated fluxes. The direct fluxes were measured with sensors equipped inside the chambers. The calculated fluxes were obtained with gas samples from the chambers, water samples and wind speed in k-wind models. The results showed both temporal and spatial variability between the periods and the lakes. The results also showed a difference between the methods, where CO2 fluxes from sensors (direct measurements) ranged from -36 to 152 mmol m-2 d-1 and the calculated fluxes from the CC-model (Cole & Caraco 1998) ranged from –29 to 58 mmol m-2 d-1.
Ökande halter av CO2 i atmosfären är en bidragande faktor till klimatförändringar. För att få en bättre förståelse för de så behövs kunskap om naturliga flöden, inte enbart antropogena källor, som t.ex. förbränning av fossila bränslen som störst fokus kretsar kring. Den nuvarande kunskapsnivån om större nordiska sjöars CO2 utsläpp är begränsad, och det finns en tydlig brist i data från dessa typer av system. Målet med denna uppsats var att utforska CO2 flöden från Roxen, Glan och Vättern, tre stora sjöar i Sverige. Syftet med studien var också att jämföra olika sätt att samla in empiriskt material samt undersöka om det fanns skillnader mellan sjöarna samt de olika studerade perioderna. Flytande kammare användes för att samla in prover som mättes direkt genom en sensor, men de användes också för att ta manuella gasprover som sedan beräknade flödet av CO2 med hjälp av modeller i efterhand. Resultatet visade både på skillnader i tid och rum mellan perioderna och sjöarna. Resultatet visade även att det fanns en skillnad mellan de olika metoderna vi använde oss av, där sensor (direkta mätningar) var mellan -36 to 152 mmol m-2 d-1 och flödesberäkningarna från CC-modellen (Cole & Caraco 1998) var –29 to 58 mmol m-2 d-1.

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21

Ensor, Breanne Leigh. "Spatial and Temporal Trends in Greenhouse Gas Fluxes from a Temperate Floodplain along a Stream-Riparian-Upland Gradient." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71424.

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Increased floodplain and wetland restoration activity has raised concerns about potential impacts on the release of greenhouse gases (GHGs) to the atmosphere due to restored connectivity between aquatic and terrestrial ecosystems. Research has shown GHG fluxes from hydrologically active landscapes such as floodplains and wetlands vary spatially and temporally in response to primary controls including soil moisture, soil temperature, and available nutrients. In this study, we performed a semimonthly sampling campaign measuring GHG (CO2, CH4, and N2O) fluxes from six locations within a third-order stream floodplain. Site locations were based on dominant landscape positions and hydrologic activity along a topographic gradient including a constructed inset floodplain at the stream margin, the natural levee, an active slough, the general vegetated floodplain, a convergence zone fed by groundwater, and the upland area. Flux measurements were compared to abiotic controls on GHG production to determine the most significant factors affecting GHG flux from the floodplain. We found correlations between CO2 flux and soil temperature, organic matter content, and soil moisture, CH4 flux and pH, bulk density, inundation period length, soil temperature, and organic matter content. But minimal correlations between N2O flux and the measured variables. Spatially, our results demonstrate that constructed inset floodplains have higher global warming potential in the form of CH4 than any other site and for all other GHGs, potentially offsetting the positive benefits incurred by enhanced connectivity. However, at the reach scale, total CO2 flux from the soil remains the greater influence on climate since the area covered by these inset floodplains is comparatively much smaller than the rest of the floodplain.
Master of Science

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22

Levy-Booth, David. "Microbial functional groups involved in greenhouse gas fluxes following site preparation and fertilization of wet low-productivity forest ecosystems." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51781.

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Forest site preparation and fertilization can improve stand productivity, but can alter the efflux rates of greenhouse gases (GHGs), CO2, CH4 and N2O, from wet soils. This study investigated the effects of these management practices on GHG fluxes (using static closed chambers), soil physico-chemical parameters, microbial community structure (using terminal-restriction fragment length polymorphism (TRFLP) of bacterial 16S and fungal ITS targets) and microbial functional group abundance (methanogens, methanotrophs, nitrifiers, denitrifiers, sulphate-reducing bacteria, using quantitative PCR) in both forest floor and mineral soils. The research took place in British Columbia (BC), Canada, at the Aleza Lake Research Forest (ALRF), near Prince George, in a hybrid spruce stand subject to mounding and at the Suquash Drainage Trial (SDT) site near Port McNeill, Vancouver Island, in a western redcedar‒western hemlock‒yellow cedar stand subject to drainage. Mounding reduced CO2 fluxes and carbon (C) concentrations, but created anaerobic hot-spots of CH4 and N2O fluxes. Ditch drainage increased soil C about 20% after 15 years and did not affect respiration rates, though CH4 fluxes were reduced. Fertilization transiently increased N2O fluxes up to a maximum of 209 µg m-2 h-1, two months following fertilization. Bacterial and fungal T-RFLP profiles showed distinct patterns based on soil layer, and were altered by mounding, drainage and fertilization. Up to 84.4% of variation in CO2 emissions could be explained, with almost 50% of explained variation allocated to soil temperature. CH4 flux variation was explained by soil water content, soil temperature, methanogen (mcrA) and methanotroph (pmoA) functional gene abundance. Variation in N2O fluxes were significantly explained by soil water content, soil pH, NH4-N concentration, AOB amoA, nitrate reductase (narG) gene and nirSK gene abundance. In addition to denitrification genes, these data highlight AOB as important determinants of denitrification either by mediating nitrification or by direct nitrifier denitrification. This study elucidates the influence of different microbial functional groups on GHG flux rates in forest ecosystems.
Forestry, Faculty of
Graduate

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23

Kostinek, Julian Alexander Daniel [Verfasser], and André [Akademischer Betreuer] Butz. "Quantification of greenhouse gas fluxes by a new airborne laser absorption spectrometer / Julian Alexander Daniel Kostinek ; Betreuer: André Butz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1203067550/34.

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Arias-Navarro, Cristina [Verfasser], Klaus [Akademischer Betreuer] Butterbach-Bahl, and Heinz [Akademischer Betreuer] Rennenberg. "Spatial variability of greenhouse gas (GHG) fluxes in tropical systems of East Africa: Effects of land use and topography." Freiburg : Universität, 2017. http://d-nb.info/1154385752/34.

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25

Rodjom, Abbey M. "Greenhouse Gas Fluxes of Soil in a Miscanthus x giganteus Crop Grown for Cellulosic Bioenergy on Abandoned Agricultural Land." Ohio University Honors Tutorial College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1524837572902621.

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Hallgren, Erik, and Olle Åman. "Methane fluxes in lakes at different spatiotemporal scales." Thesis, Linköpings universitet, Institutionen för tema, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-159818.

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Freshwater bodies such as lakes release the greenhouse gas methane (CH4) into the atmosphere. Global emissions from lakes are estimated to emit more CH4 than oceans, despite that lakes occupies a much smaller global land area. Lakes are therefore significant components for global budgets of CH4. Accurate global estimations of lakes are troublesome, partly because of the spatial and temporal variability of CH4 fluxes, making regional and global assessments filled with uncertainties. Yet, few studies consider the spatial and temporal variability of CH4 fluxes. Therefore, this study investigates the spatial and temporal variability of CH4 fluxes in lakes at different scales. Measurements were made during two field campaigns in lake Venasjön and Parsen, located in the municipality of Söderköping, Sweden. We used the commonly used floating chamber (FC) method for CH4 flux measurements. In order to investigate the small-scale flux variability, we redeveloped the FC-method by constructing two grids consisting of seven FCs distributed approximately 1m apart from each other. One grid was placed at the shallow zone at the inflow of each lake and the other at the lakes deepest zone. By sampling the grid several times every field campaign, spatial and temporal variability of fluxes at different scales could be measured. Overall, we found a significant difference of CH4 fluxes in both lakes depending on field campaign and grid location. Our results also indicate that there is a small-scale variability of CH4 fluxes in lakes. Our hope is that these findings can illustrate the importance of investigating lake fluxes at small spatial and temporal scales.
Sjöar släpper ut växthusgasen metan (CH4) i atmosfären. Globala utsläpp från sjöar beräknas avge mer CH4 än havet, trots att sjöar har en mycket mindre global areal. Sjöar är därför viktiga komponenter för globala budgetar av CH4. Dessvärre är noggranna globala uppskattningar av sjöar svårt att göra, delvis på grund av den spatial och temporala variationen av CH4, vilket gör regionala och globala bedömningar fyllda med osäkerheter. Trots detta undersöker få studier metanflödets spatiala och temporala variabilitet. Denna studie undersöker den spatiala och temporala variabiliteten av CH4-flöden från sjöar i olika skalor. Mätningar genomfördes under två fältkampanjer i sjöarna Venasjön och Parsen som ligger i Söderköpings kommun, Sverige. För att undersöka variabiliteten i en liten skala utvecklade vi den redan använda floating chamber (FC) metoden för flödesmätningar genom att bygga två grids med sju FCs, ungefär 1m mellan varje kammare. En grid placerades vid den grunda delen vid inflödet av varje sjö och den andra vid respektive sjös djupaste del. Genom att mäta griden flera gånger varje fältkampanj kunde den spatiala och temporala variationen av flöden i olika skalor undersökas. Sammantaget fann vi signifikanta skillnader i båda sjöarnas CH4-flöden mellan fältkampanjer och grids. Våra resultat tyder också på småskaliga variationer av CH4-flöden i sjöar. Vårt hopp är att dessa resultat kan ytterligare bekräfta betydelsen av att undersöka sjöflödena i små spatiala och temporära skalor

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Adjuik, Toby A. "Effects of Hydrochar, Digestate, Synthetic Fertilizer on Soil Greenhouse Gas Fluxes in Miscanthus x giganteus Grown as Advanced Biofuel Feedstock." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1557220009015982.

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Jimmy, Sjögren, and Enhäll Elin. "Methods of measuring GHG fluxes at a full-scale Swedish WWTP: : A focus on nitrous oxide, methane and carbon dioxide in the SHARON treatment." Thesis, Linköpings universitet, Tema Miljöförändring, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138803.

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The Stable high rate ammonia removal over nitrite (SHARON) at Nykvarnsverket in Linköping is a relatively new kind of biological treatment. Fluxes of nitrous oxide (N2O) has not been fully mapped at Nykvarnsverket and additional efforts are needed for increased knowledge about possible emissions. The primary goals of the study were to measure and compare fluxes of N2O in the SHARON and to do a general greenhouse gas (GHG) flux comparison to those of the Biological treatment, the Chemical treatment and the Second denitrification at Nykvarnsverket. Secondary goals were to evaluate the use of two gas sensors, a SiC-FET sensor for N2O emissions, a CO2 Engine ELG sensor for carbon dioxide (CO2) emissions and their applicability in a WWTP environment. The measurements of GHG fluxes were performed by measuring the temporal change of GHG concentrations in the headspace of floating flux chambers placed in treatment tanks. The two gas sensors were tested either via tests in lab or via field measurements. The flux chamber method made it possible to estimate the fluxes at three out of four targeted tanks. The total daily GHG flux estimations (mmol m-2 d-1 ) in the SHARON were 6900 CO2, 320 methane (CH4) and 35 N2O. The estimations (mmol m-2 d-1) in the Biological treatment were 22 000 CO2, 120 CH4 and 23 N2O for 75% of the time. The estimations (mmol m-2 d-1) in the Chemical treatment were 110 CO2, 0.073 CH4 and 0.60 N2O. The largest N2O emissions were found to occur during nitrification processes in the SHARON. The fluxes in the SHARON were also the largest compared to those in the Biological treatment and the Chemical treatment, except for the CO2 flux that was larger in the Biological treatment. The CO2 sensor could be used during measurements over shorter time periods were CO2 levels did not exceed 10 000 ppm. Further tests on the SiC-FET sensor are needed to evaluate the sensor for measurements of N2O.

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Thieme, Christoph-Josef [Verfasser], Eckart [Akademischer Betreuer] Priesack, Eckart [Gutachter] Priesack, and Urs [Gutachter] Schmidhalter. "Measurements and modelling of energy and greenhouse gas fluxes from complex cropland ecosystems / Christoph-Josef Thieme ; Gutachter: Eckart Priesack, Urs Schmidhalter ; Betreuer: Eckart Priesack." München : Universitätsbibliothek der TU München, 2018. http://d-nb.info/1185069674/34.

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Förster, Christoph [Verfasser], Hans Peter [Akademischer Betreuer] Schmid, and Matthias [Akademischer Betreuer] Drösler. "Influence of management and restoration on greenhouse gas fluxes of a prealpine bog / Christoph Förster. Betreuer: Hans Peter Schmid. Gutachter: Matthias Drösler ; Hans Peter Schmid." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1082979961/34.

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Do, Phai Duy. "Quantifying organic carbon fluxes from upland peat." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/quantifying-organic-carbon-fluxes-from-upland-peat(f66901b0-b930-469e-8c33-2e480c4becd1).html.

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Present organic carbon fluxes from an upland peat catchment were quantified through measurement of in-situ direct and indirect greenhouse gas fluxes. To predict future greenhouse gas (GHG) fluxes, peat from eroded (E) and uneroded (U) site of an upland peat catchment was characterized.Composition of peat from E and U sites at the Crowden Great Brook catchment, Peak District Nation Park, UK that was characterized by Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC-MS) at 700 oC. Pyrolysis products of the peat were then classified using the Vancampenhout classification into 6 compound classes - viz. aromatic and polyaromatic (Ar), phenols (Ph), lignin compounds (Lg), soil lipids (Lp), polysaccharide compounds (Ps) and N-compounds (N). There was no significant difference in the composition between the eroded and uneroded sites within the study area or between peats from different depths within each site. Nevertheless, there was a significant difference between sites in the proportions of Sphagnum that had contributed to the peat. Pyrolysis products of the peat were also classified into pedogenic (Pd) and aquagenic (Aq) OC – the mean percentage of Pd in both eroded and uneroded peats was 43.93 ± 4.30 % with the balance of the OC classified as Aq.Greenhouse gas (GHG) fluxes were quantified directly by in-situ continuous measurement of GHG was carried out at the E and U sites of the catchment using a GasClam: mean in-situ gas concentrations of CH4 (1.30 ± 0.04 % v/v (E), 0.59 ± 0.05 % v/v (U) and CO2 (8.83 ± 0.22 % v/v (E), 1.77 ± 0.03 % v/v (U)) were observed, with both the CH4 and CO2 concentrations apparently unrelated to atmospheric pressure and temperature changes. Laboratory measurements of ex-situ gas production - for both CH4 and CO2 this was higher for U site soils than for E site soils. At the U site, maximum production rates of both CH4 (46.11±1.47 mMol t-1 day-1) and CO2 (45.56 ± 10.19 mMol t-1 day-1) were observed for 0-50 cm depth in soils. Increased temperature did not affect gas production, whilst increased oxygen increased gas production. The CH4/CO2 ratios observed in-situ are not similar to those observed in the ex-situ laboratory experiments; suggest that some caution is advised in interpreting the latter. However, the maximum OC loss of 2.3 wt. % observed after 20 weeks of ex-situ incubation is nevertheless consistent with the long-term degradation noted by Bellamy et al (1985) from organic-rich UK soils. Indirect greenhouse gas (GHG) fluxes were quantified through the mass flux of suspended organic carbon (SsOC) drained from studied catchments. The SsOC was quantified by interpolating and rating methods. Unfiltered (UF) organic carbon (OC) fluxes in 2010 were calculated to be 8.86 t/km2/yr for the eroded sub-catchment and 6.74 t/km2/yr for the uneroded sub-catchment. All the rating relationships have a large amount of scatter. Both UF OC and <0.2 µm fraction OC are positively correlated with discharge at the eroded site, whilst there is no discernable relationship with discharge at the uneroded site. SsOC is dominated by Pd type OC (95.23 ± 10.20 % from E; 92.84 ± 5.38 % from U) far more so than in sources of the peats, suggesting slower oxidation of Pd (cf. Aq) OC.

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Shrestha, Paliza. "Water Quality Performance And Greenhouse Gas Flux Dynamics From Compost-Amended Bioretention Systems & Potential Trade-Offs Between Phytoremediation And Water Quality Stemming From Compost Amendments." ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/851.

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Stormwater runoff from existing impervious surfaces needs to be managed to protect downstream waterbodies from hydrologic and water quality impacts associated with development. As urban expansion continues at a rapid pace, increasing impervious cover, and climate change yields more frequent extreme precipitation events, increasing the need for improved stormwater management. Although green infrastructure such as bioretention has been implemented in urban areas for stormwater quality improvements and volume reductions, these systems are seldom monitored to validate their performance. Herein, we evaluate flow attenuation, stormwater quality performance, and nutrient cycling from eight roadside bioretention cells in their third and fourth years of implementation in Burlington, Vermont. Bioretention cells received varying treatments: (1) vegetation with high-diversity (7 species) and low-diversity plant mixes (2 species); (2) proprietary SorbtiveMediaTM (SM) containing iron and aluminum oxide granules to enhance sorption capacity for phosphorus; and (3) enhanced rainfall and runoff (RR) to certain cells (including one with SM treatment) at three levels (15%, 20%, 60% more than their control counterparts), mimicking anticipated precipitation increases from climate change. Bioretention water quality parameters monitored include total suspended solids (TSS), nitrate/nitrite-nitrogen (NOx), ortho-phosphorus (Ortho-P), total nitrogen (TN) and total phosphorus (TP), which were compared among bioretention cells’ inflows and outflows across 121 storms. Simultaneous measurements of flow rates and volumes allowed for evaluation of the cells’ hydraulic performances and estimation of pollutant load and event mean concentration (EMC) removal. We also monitored soil CO2 and N2O fluxes, as they represent a potential nutrient loss pathway from the bioretention cells. We determined C and N stocks in the soil media and vegetation, which are critical design elements of any bioretention, to determine the overall C and N balances in these systems. Significant average reductions in effluent stormwater volumes and peak flows were reported, with 31% of the storms events completely captured. Influent TSS loads and EMCs were well retained by all cells irrespective of treatments, storm characteristics, or seasonality. Nutrient removal was treatment-dependent, where the SM treatments consistently removed P loads and EMCs, and sometimes N as well. The vegetation and RR treatments mostly exported nutrients to the effluent. We attribute observed nutrient exports to the presence of excess compost in the soil filter media. Rainfall depth and peak inflow rate undermined bioretention performance, likely by increasing pollutant mobilization through the filter media. While the bioretention cells were a source of CO2, they varied between being a sink and source of N2O. CO2 fluxes were orders of magnitude higher than N2O fluxes. However, soil C and N, and plant C and N in biomass was seen to largely offset respiratory CO2-C and biochemical N2O-N losses from bioretention soil. The use of compost in bioretention soil media should be reduced or eliminated. If necessary, compost with low P content and high C: N ratio should be considered to minimize nutrients losses via leaching or gas fluxes. In order to understand trade-offs stemming from compost amendments, we conducted a laboratory pot study utilizing switchgrass and various organic soil amendments (e.g., different compost types and coir fiber) to a sandy loam soil contaminated with heavy metals and studied potential nutrient leaching and pollutant uptake. Addition of organic amendments significantly reduced metal bioavailability, and improved switchgrass growth and metal uptake potential. While no differences in soil or plant metal uptake were observed among the amendments, significant differences in nutrient leaching were observed.

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Vanselow-Algan, Marion [Verfasser], and Eva-Maria [Akademischer Betreuer] Pfeiffer. "Impact of summer drought on greenhouse gas fluxes and nitrogen availability in a restored bog ecosystem with differing plant communities / Marion Vanselow-Algan. Betreuer: Eva-Maria Pfeiffer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://d-nb.info/1049281756/34.

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Vanselow-Algan, Marion Verfasser], and Eva-Maria [Akademischer Betreuer] [Pfeiffer. "Impact of summer drought on greenhouse gas fluxes and nitrogen availability in a restored bog ecosystem with differing plant communities / Marion Vanselow-Algan. Betreuer: Eva-Maria Pfeiffer." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2014. http://nbn-resolving.de/urn:nbn:de:gbv:18-66903.

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35

Tchiofo, Lontsi Rodine [Verfasser], Edzo Akademischer Betreuer] Veldkamp, Edzo [Gutachter] Veldkamp, and Dirk [Gutachter] [Hölscher. "The environmental impact of selective logging in southern Cameroon: soil disturbance, nutrient budget and greenhouse gas fluxes / Rodine Tchiofo Lontsi ; Gutachter: Edzo Veldkamp, Dirk Hölscher ; Betreuer: Edzo Veldkamp." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1205544836/34.

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Tchiofo, Lontsi Rodine [Verfasser], Edzo [Akademischer Betreuer] Veldkamp, Edzo Gutachter] Veldkamp, and Dirk [Gutachter] [Hölscher. "The environmental impact of selective logging in southern Cameroon: soil disturbance, nutrient budget and greenhouse gas fluxes / Rodine Tchiofo Lontsi ; Gutachter: Edzo Veldkamp, Dirk Hölscher ; Betreuer: Edzo Veldkamp." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1205544836/34.

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Tchiofo, Lontsi Rodine Verfasser], Edzo [Akademischer Betreuer] Veldkamp, Edzo [Gutachter] Veldkamp, and Dirk [Gutachter] [Hölscher. "The environmental impact of selective logging in southern Cameroon: soil disturbance, nutrient budget and greenhouse gas fluxes / Rodine Tchiofo Lontsi ; Gutachter: Edzo Veldkamp, Dirk Hölscher ; Betreuer: Edzo Veldkamp." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1205544836/34.

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Chan, Wai Nam 1964. "Quantificação e redução de emissões de gases de efeito estufa em uma refinaria de petroleo." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263805.

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Orientador: Arnaldo Cesar da Silva Walter
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-07T23:03:25Z (GMT). No. of bitstreams: 1 Chan_WaiNam_M.pdf: 1006705 bytes, checksum: 9353fc6b1ce1205a679d574738b25bfe (MD5) Previous issue date: 2006
Resumo: Queima de combustíveis fósseis é a principal contribuição humana para o aquecimento global. Neste trabalho foram investigadas oportunidades de redução das emissões de gases de efeito estufa (GEE) para uma refinaria brasileira de petróleo, através das seguintes etapas: levantamento das estratégias de enfrentamento do problema adotadas por algumas empresas; seleção de uma metodologia de estimativa de emissões de GEE para companhias de óleo e gás; elaboração do inventário da refinaria nacional através do programa aplicativo SANGEA; e proposição de opções para gestão das emissões de GEE dessa refinaria. Combustão e práticas de flaring e venting são os maiores contribuintes das emissões de GEE da cadeia produtiva. Quatro opções de mitigação estão sendo exploradas pelas empresas: aumento da eficiência energética, redução de flaring e venting, mudança para fontes energéticas menos intensivas em carbono e seqüestro de carbono. Neste estudo foi mostrado que o SANGEA é uma ferramenta de estimativa adequada, pois a emissão total de GEE obtida apresentou uma diferença de 1% em relação ao valor estimado pela Petrobrás. Melhoria da eficiência energética é a principal oportunidade de redução de emissões. Para a refinaria estudada foram descritos futuros projetos da área energética que apresentaram um potencial de emissão evitada de 270.000 t CO2 /ano. Por outro lado, a instalação de novas unidades para adequação dos teores de enxofre da gasolina e do diesel resultará na emissão adicional de 208.000 t CO2 /ano. Portanto, o sucesso dos esforços para economizar energia pode ser anulado pelas exigências ambientais para adequação da qualidade dos produtos. Isto ressalta a necessidade dos formuladores de política estabelecer um balanço entre as novas exigências para combustíveis (com impactos locais) e a política de abatimento de CO2 (com impactos globais)
Abstract: Fossil fuel burning is the main human contribution to global warming. In this study, opportunities for reducing greenhouse gas (GHG) emissions were investigated for a Brazilian oil refinery, according to the following steps: survey of climate change strategies adopted by some companies; selection of a methodology for calculating GHG emissions for the petroleum industry; development of an inventory for a national oil refinery by applying SANGEA software; and proposal of options for managing GHG emissions in this refinery. Combustion, flaring and venting are the largest contributors to GHG emissions in the production chain. Four mitigation options are being explored by companies: increasing energy efficiency, flaring and venting reduction, switching to less carbon-intensive sources of energy and carbon sequestration. It was demonstrated that SANGEA is a suitable estimation tool since the calculated total GHG emission showed 1% difference compared to Petrobras estimated value. Energy efficiency improvement is the main opportunity to reduce emissions. For the case study refinery future energy saving opportunities were described and their avoided emission estimation is 270,000 metric tonnes per year of CO2. On the other hand, new process units are required to comply with the gasoline and diesel stricter sulfur specifications, producing an additional emission of 208,000 metric tones per year of CO2. Thus, the successful energy saving efforts can be nullified by environmental requirements for fuel quality. This underlines the need for policy makers to strike a balance between new fuel requirements (with local impacts) and CO2 abatement policy (with global impacts)
Mestrado
Energia, Sociedade e Meio Ambiente
Mestre em Engenharia Mecânica

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Schützenmeister, Klaus [Verfasser], Dirk [Akademischer Betreuer] Gansert, and Hermann [Akademischer Betreuer] Jungkunst. "Effects of earthworms and tree species (Fagus sylvatica L., Fraxinus excelsior L.) on greenhouse trace gas fluxes in mixed deciduous broad-leaved forests / Klaus Schützenmeister. Gutachter: Dirk Gansert ; Hermann Jungkunst. Betreuer: Dirk Gansert." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://d-nb.info/1067626654/34.

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Müller, Anke Katrin [Verfasser], Edzo [Akademischer Betreuer] Veldkamp, Marife [Akademischer Betreuer] Corre, and Klaus [Akademischer Betreuer] Butterbach-Bahl. "Soil greenhouse gas fluxes under elevated nutrient input along an elevation gradient of tropical montane forests in southern Ecuador / Anke Katrin Müller. Gutachter: Edzo Veldkamp ; Marife Corre ; Klaus Butterbach-Bahl. Betreuer: Edzo Veldkamp." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1060246465/34.

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Fender, Ann-Catrin [Verfasser], Dirk [Akademischer Betreuer] Gansert, Christoph [Akademischer Betreuer] Leuschner, and Hermann [Akademischer Betreuer] Jungkunst. "The rhizosphere effects of Fagus sylvatica L. and Fraxinus excelsior L. saplings on greenhouse gas fluxes between soil and atmosphere / Ann-Catrin Fender. Gutachter: Dirk Gansert ; Christoph Leuschner ; Hermann Jungkunst. Betreuer: Dirk Gansert." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1044248874/34.

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Kreba, Sleem. "LAND USE IMPACT ON SOIL GAS AND SOIL WATER TRANSPORT PROPERTIES." UKnowledge, 2013. http://uknowledge.uky.edu/pss_etds/31.

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The consequences of land use choices on soil water and gas transport properties are significant for gas and water flux in agricultural environments. Spatial and temporal patterns and associations of soil water and soil gas characteristics and processes in different land uses are not well understood. The objectives of this study were to 1) characterize soil structure under crop and grass systems, 2) quantify spatial patterns and associations of soil physical characteristics in crop and grass systems, and 3) quantify spatial and temporal patterns and associations of CO2 and N2O fluxes. The research was conducted in a 60 by 80 m field divided into grass and crop systems. Sixty sampling points were distributed in four transects with 5- and 1-m spatial intervals between measurement points. Gas fluxes were measured, at two-week time intervals, 22 times during a year. Pore size distribution was more homogeneous and more continuous pores were found in the grass than in the crop system. The spatial variability of most selected soil physical characteristics was more structured in the crop than in the grass system, which reflected the impact of land use and soil structure on their spatial patterns. CO2 flux was dependent for a longer distance in the grass than in the crop system, however, the two land-use systems exhibited similar spatial ranges of N2O flux. Gas fluxes were temporally dependent for a longer period in the grass than in the crop system. The spatial associations between CO2 and N2O fluxes and selected biochemical and physical factors depended on the flux sampling season and land use. Soil temperature was the dominant controlling factor on the temporal variability of CO2 and N2O fluxes but not on the spatial behavior. Considering the spatial and temporal ranges and dependency strength of soil variables helps identify efficient sampling designs that can result in better time and resource management. Spatial and temporal relationships between the selected soil variables also improve understanding soil management and sampling soil variables. This study provides the baseline and recommendations for future investigations specifically for sampling designs, soil management, and predictions of different soil processes related to gas fluxes.

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Debouk, Haifa. "Assessing the effect of global change on plant functional structure, greenhouse gases, and soil functions in grasslands." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/436894.

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L'objectiu d'aquesta tesi és investigar el paper dels grups funcionals de plantes (GFP) en relació a l’estabilitat de la comunitat vegetal, els fluxos de GEH i les funcions del sòl, i com aquestes interaccions es regulen pel clima. La composició de GFP va influenciar els GEH i les funcions del sòl però les variables ambientals van regular aquest efecte. L’escalfament va afavorir la dominància d’espècies oportunistes i de creixement ràpid en detriment d’espècies més conservatives, causant una reducció en la diversitat específica. La composició i l’estructura funcional van tenir una major influencia en la productivitat i l’estabilitat de la comunitat que la diversitat específica. Els GEH es van reduir amb l’altitud, i incrementar durant l’estiu. La interacció entre GFP va afavorir l’assimilació de CH4 i N2O en comparació a la dominància d’un sòl GFP. Les interaccions entre GFP van també afavorir les funcions de sòl relacionades amb el cicle del N.
El objetivo principal de esta tesis fue investigar el efecto de los grupos funcionales de plantas sobre la estabilidad de la vegetación, los flujos de GEI y las funciones del suelo, y cómo las condiciones climáticas regulan sus interacciones. La estructura funcional de las plantas en pastos influyó la estabilidad de la vegetación, los flujos de GEI, la actividad y fertilidad del suelo, y ese efecto está regulado por el clima. El calentamiento causó la dominancia de especies oportunistas sobre las más conservadoras; reduciendo así la riqueza específica. Los rasgos funcionales tuvieron una mayor influencia en la productividad y estabilidad de las comunidades frente al efecto de la diversidad. Los flujos de GEI aumentaron en verano y disminuyeron con la altitud. La interacción entre grupos funcionales incrementó la absorción de CH4 y N2O respecto a grupos individuales. Las interacciones entre grupos funcionales favorecieron también las funciones de suelo relacionadas con el ciclo de N.
The main objective of this thesis is to investigate how plant functional types (PFT) affect vegetation stability, greenhouse gas (GHG) fluxes and soil functions, and how these interactions are regulated by climatic conditions. We found that plant functional structure strongly influences vegetation stability, GHG fluxes, and soil activity and fertility in grassland, but this relationship is regulated by climate. Warming lead to the dominance of acquisitive fast growing species over conservative species; thus reducing species richness. The functional traits structure in grasslands had greater influence on the productivity and stability of the community under warming, compared to diversity effects. GHG fluxes decreased with altitude- the colder the grassland site the lower the fluxes-, and increased during summer. The interaction between PFTs enhanced CH4 and N2O uptake compared to single PFTs. Also, PFT evenness and pairwise interactions between PFTs enhanced soil functions related to the N cycle.

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Koks, Josephus [Verfasser], Edzo [Akademischer Betreuer] Veldkamp, Alexander [Gutachter] Knohl, and Heinz [Gutachter] Flessa. "Tropical forest conversion to rubber and oil palm plantations: landscape-scale and inter-annual variability of soil greenhouse gas (GHG) fluxes and the contribution of tree-stem emissions to the soil GHG budget in Jambi province, Sumatra, Indonesia / Josephus Koks ; Gutachter: Alexander Knohl, Heinz Flessa ; Betreuer: Edzo Veldkamp." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2020. http://d-nb.info/1213096316/34.

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Gillespie, Lauren. "Impact of tree diversity and climate change on soil microbial functioning in European forests along a latitudinal gradient." Thesis, Montpellier, 2020. http://www.theses.fr/2020MONTG004.

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Les microorganismes du sol sont des acteurs principaux des cycles biogéochimiques terrestres car ils sont impliqués dans la séquestration du C dans les sols, la fertilité des sols ou l’émission de gaz à effet serre dans l’atmosphère. L’activité de ces microorganismes est fortement influencée par les caractéristiques des communautés des plantes, notamment leur abondance, composition et diversité. Cette influence des plantes est susceptible d’être modifiée par des conséquences du changement climatique comme par exemple des périodes de sécheresse qui sont prédites d’augmenter en fréquence dans l’avenir proche. Lors de cette thèse, j’ai cherché à comprendre comment le mélange des espèces d’arbres en interaction avec la sécheresse influence le fonctionnement microbien. J’ai comparé des communautés d’arbres dominées par une seule espèce avec des communautés composées de trois espèces dominantes d’arbres dans quatre types de forêt le long d’un gradient latitudinal en Europe.Avec différentes mesures d’activités microbiennes telles que l’utilisation de plusieurs substrats carbonés ou l’activité de dénitrification dans des sols échantillonnés dans ces forêts européennes, j’ai évalué l’impact du mélange des espèces d’arbres à travers des traits de litière et de racines absorptives sur le fonctionnement microbien. Des modèles linéaires généraux et des modèles d'équations structurelles ont montré que le fonctionnement microbien n’était pas systématiquement affecté par le mélange des espèces d’arbres, mais qu’il existait potentiellement des effets de cascades via la qualité de la litière et la colonisation des racines par les ectomycorhizes.Avec une expérience en microcosme à l’Ecotron Européen de Montpellier, j’ai testé comment des cycles d’asséchement et réhumectation (DRW) répétés affectent la diversité taxonomique et catabolique microbienne ainsi que le fonctionnement microbien, et si ces effets étaient modifiés par le mélange des espèces d’arbres. Malgré une large gamme de types de sol et de forêts, j’ai trouvé une association robuste entre les forêts mélangées et i) une résistance plus élevée de la respiration et de l’activité de dénitrification microbiennes ainsi que ii) des niveaux de stress des microorganismes du sol plus bas en réponse aux cycles DRW répétés, un scénario amené à devenir plus commun avec le changement climatique actuel.Ces résultats nous renseignent sur les mécanismes de l’impact du mélange des espèces d’arbres et des cycles de sécheresse sur le fonctionnement des communautés microbiennes du sol forestier et suggèrent qu’un mélange de différentes espèces d’arbres pourrait rendre les communautés microbiennes du sol et leur fonctionnement plus résistant face au changement climatique
Forest soil microorganisms are important drivers of biogeochemical cycling, influencing thus soil C sequestration, soil fertility, and the emission of greenhouse gases into the atmosphere. Microbial activity is strongly affected by plant communities, their composition and diversity, and the abundance of particular species. Climate change factors such as the predicted increased droughts are susceptible to modify these plant effects. In this PhD thesis, I aimed to understand how tree species mixing and increased drought interactively influence the activity of soil microbial communities. I compared forest communities dominated by one single tree species with communities co-dominated by three different tree species in four different European forest types along a climatic gradient.By measuring different microbial processes, such as the respiration induced by different carbon substrates or denitrification activity, in soil samples collected in the different European forests, I tested the relative influence of tree species mixing through litter traits and absorptive root traits on microbial functioning. Generalized mixed-effects linear models and structural equation models showed that the soil microbial functioning was not consistently affected by tree species mixing, but it potentially had cascading effects via litter quality and the colonization rate of roots by ectomycorrhizal fungi.I then used a microcosm experiment set up in the European Ecotron in Montpellier to test how repeated drying-rewetting (DRW) cycles affect taxonomic and catabolic diversity of soil microbial communities and their functioning, and whether tree species mixing modifies these effects. I found that tree species mixing had no influence on the composition of soil microbial communities. However, despite a wide range of soil and forest types, our results showed a robust and consistent association between mixed tree species forests and higher resistance of soil microbial respiration and denitrification, as well as with lower soil microbial stress levels in response to repeated DRW cycles, a scenario expected to become more common with ongoing climate change.These results help to better understand the underlying mechanisms of how tree species mixing and DRW, predicted to become more frequent under future climatic change, affect soil microbial communities and their functioning. The data suggest that microbial communities from mono-specific forest stands resist less to increased drought than those from mixed tree species forests which may thus mitigate drought effects

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D'Angelo, Benoît. "Variabialité spatio-temporelle des émissions de GES dans une tourbière à Sphaignes : effets sur le bilan carbone." Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2058/document.

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Les tourbières représentent 2 à 3% des terres émergées et stockent entre 10 et 25% du carbone des sols. Les tourbières sont soumises à des contraintes anthropiques et climatiques importantes qui posent la question de la pérennité de leur fonctionnement en puits de C et de leur stock. Une meilleure compréhension de ces écosystèmes est nécessaire pour déterminer les facteurs et les effets et interactions de ces facteurs sur les émissions de gaz à effet de serre (GES). Ce travail a consisté à suivre les émissions de GES et les facteurs contrôlant dans La tourbière de La Guette (Sologne) pour établir son bilan de C. En parallèle des expérimentations sur l’effet de l’hydrologie sur les flux ont été menées, enfin un suivi sur 4 sites a été réalisé pour étudier la variabilité à l’échelle journalière. Les résultats de ces travaux montrent que la tourbière de La Guette a fonctionné en source de C (-220 ± 33 gC m-2 an-1) et ce malgré un niveau de nappe élevé. Ils montrent également l’importance de la variabilité spatiale des flux estimés à l’échelle d’un site. Les expérimentations confirment l’importance de l’hydrologie et suggèrent à haut niveau de nappe d’eau des phénomènes liés au transport des gaz. Enfin l’étude de la variabilité journalière montre que la sensibilité de la respiration à la température peut être différente le jour et la nuit et que la synchronisation entre les températures du sol et la respiration peuvent améliorer la représentation de cette dernière
Peatlands cover only 2 to 3% of the land area but store between 10 and 25% of the soil carbon. The outcome of the anthropic and climatic pressure on these ecosystems is uncertain regarding their functions and storage. A better understanding of these ecosystems is needed to determine the factors and their interactions on greenhouse gas (GHG) emission. This work consist in monitoring GHG emissions and controlling factors in a Sphagnum peatland to estimate its carbon balance. Experimentation on mesocosms were carried out to explore the effect of hydrology on the fluxes and a monitoring on 4 sites was made to study the daily variability. Results show that La Guette peatland was a carbon source (-220 ± 33 gC m-2 an-1) in spite of the high water table level. The importance of the spatial variability measured in the site was also demonstrate. The hydrology effect was confirmed by the mesocosms experiments and high water table level shows that gas transport might have an effect. Finally the study of the daily variability show that the temperature sensitivity of the respiration might be different between day and night and that synchronizing soil temperatures and respiration can improve the respiration representation

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47

Liu, Tzu-Hua, and 劉子華. "Comparative Analyses for City Greenhouse Gas Inventories." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/94804106195985791047.

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碩士
國立交通大學
環境工程系所
103
Greenhouse gas (GHG) reduction has become an essential task for cities. Domestic and foreign cities are thus reporting their GHG inventories. However, these inventory reports are difficult to compare directly because of different guidelines, calculation methods, and selections of activity data. Therefore, this study was initiated to develop a method to compare the inventories and analyze their differences for discovering the benchmarks and exemplars in major sectors. GHG Inventory reports from domestic and foreign cities were collected. Inventory information and data were grouped by sector. Various differences were observed for every sectors. Adjusted and common emissions were determined by excluding the emissions from the items that were not commonly reported or had small quantities. Both adjusted and common emissions were used as bases for following benchmark analyses. First, the characteristics of cities and various GHG-related factors, including population density, employed population, average income, and electricity emission factors, were compared and analyzed. The amount of degree days, for analyzing climate effects on energy usages, were calculated, and regressive equations for domestic cites were established and applied to revise the benchmarks for those cities. Then, comparative analyses for each sector for their characteristics and GHG-related factors were implemented. For the industrial sector, its energy usage, employed population, gross production and water usage were analyzed. For the residential and commercial sector, its energy usage, employed population, gross production, water usage, number of households and the ratio for high-rise buildings were compared. For the transportation sector, its road area or length density, number of vehicles, vehicle kilometers traveled were analyzed. According to the results obtained from these comparative analyses and a preliminary aggregative analysis, the commercial employed population, population, number of households were selected as outputs, and the common emission was used as input, to establish indicators for evaluating the performance of major sectors in studied cities. Equations were established for determining the average and benchmark emissions of each city, the former is the typical target should be achieved and the latter is the goal to be pursued. Paradigm cities and sectors were identified based on the average and benchmark emissions. With the average and benchmark emissions and the paragons, how far their gaps to the emissions and paragons of each city were determined and discussed. Sectors with poor performance were also identified and possible policies or actions for reducing GHG emissions were suggested. The results are expected to facilitate the GHG reduction planning for cities in Taiwan.

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48

Glenn, Aaron James. "Greenhouse gas fluxes and budget for an annual cropping system in the Red River Valley, Manitoba, Canada." 2010. http://hdl.handle.net/1993/4286.

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Agriculture contributes significantly to national and global greenhouse gas (GHG) inventories but there is considerable control over management decisions and changes in production methods could lead to a significant reduction and possible mitigation of emissions from the sector. For example, conservation tillage practices have been suggested as a method of sequestering atmospheric carbon dioxide (CO2), however, many questions remain unanswered regarding the short-term efficacy of the production method and knowledge gaps exist regarding possible interactions with essential nutrient cycles, and the production of non-CO2 GHGs, such as nitrous oxide (N2O). Between autumn 2005 and 2009, a micrometeorological flux system was used to determine net CO2 and N2O exchange from an annual cropping system situated on clay soil in the Red River Valley of southern Manitoba. Four plots (4-ha each) were independently evaluated and planted to corn in 2006 and faba bean in 2007; in 2008, two spring wheat plots were monitored. As well, during the non-growing season in 2006-2007 following corn harvest, a second micrometeorological flux system capable of simultaneously measuring stable C isotopologue (12CO2 and 13CO2) fluxes was operated at the site. Tillage intensity and crop management practices were examined for their influence on GHG emissions. Significant inter-annual variability in CO2 and N2O fluxes as a function of crop and related management activities was observed. Tillage intensity did not affect GHG emissions from the site. After accounting for harvest removals, the net ecosystem C budgets were 510 (source), 3140 (source) and -480 (sink) kg C/ha/year for the three respective crop years, summing to a three-year loss of 3170 kg C/ha. Stable C isotope flux measurements during the non-growing season following corn harvest indicated that approximately 70 % and 20 – 30 % of the total respiration flux originated from crop residue C during the fall of 2006 and spring of 2007, respectively. The N2O emissions at the site further exacerbated the net global warming potential of this annual agroecosystem.

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Wang, Jonathan. "Methane Fluxes at a Temperate Upland Forest in Central Ontario." Thesis, 2012. http://hdl.handle.net/1807/33579.

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Methane fluxes were calculated from measurements carried out at a temperate upland forest in Central Ontario using the eddy covariance method over five months in the summer and fall seasons of 2011. Measurements were made by an off-axis integrated cavity output spectrometer Fast Greenhouse Gas Analyzer (FGGA) which simultaneously measured methane (CH4), carbon dioxide (CO2), and water at 10 Hz sampling rates. Observed methane fluxes showed net uptake of methane over the measurement period with an average uptake flux value (±standard deviation of the mean) of -2.7±0.13 nmol m-2 s-1. Methane fluxes showed a diurnal pattern of increased uptake during the day and increasing uptake with seasonal progression. There was also a significant correlation in methane fluxes with soil water content and wind speed. Comparison of the FGGA measurements to those using a static chamber method and canister sampling showed close agreement in flux and mixing ratio values respectively.

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Müller, Anke Katrin. "Soil greenhouse gas fluxes under elevated nutrient input along an elevation gradient of tropical montane forests in southern Ecuador." Doctoral thesis, 2014. http://hdl.handle.net/11858/00-1735-0000-0023-9920-3.

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Los suelos de los bosques tropicales desempeñan un papel importante en el clima de la Tierra mediante el intercambio con la atmosfera de grandes cantidades de gases de efecto invernadero (GEI). Sin embargo, esta importante función podría ser alterada por las actividades humanas causando el aumento en la deposición de nutrientes en los ecosistemas terrestres, especialmente en las regiones tropicales. Las causas de cómo el incremento de las cantidades de nutrientes está afectando los flujos de suelo de los GEI de los bosques tropicales es relativamente poco conocida, por ello los monitoreos de nutrientes in situ de los bosques montanos tropicales (BHT) son aún menos comprendidos. Ya que los BHT representan alrededor del 11-21% de la superficie forestal tropical, es de vital importancia predecir y cuantificar los cambios en los flujos de GEI del suelo en respuesta a la adición de nutrientes ya que podrían favorecer la retroalimentación a otros cambios globales. Esta tesis tiene como objetivo cuantificar el impacto de adición moderada de nitrógeno (N) y/o fósforo (P) en los flujos de tres GEI en suelo: dióxido de carbono (CO2), óxido nitroso (N2O) y el metano (CH4), a lo largo de un gradiente altitudinal (1000 m, 2000 m, 3000 m) de los BHT primarios en el sur de Ecuador. Desde hace más de cinco años, se ha medido los flujos de GEI del suelo en un experimento de manipulación de nutrientes (‘NUMEX’, por sus siglas en inglés), con replicas para control, y la adición de N (50 kg N ha-1 año-1), P (10 kg P ha-1 año-1) y N+P. Las mediciones in situ se realizaron mensualmente utilizando cámaras ventiladas estáticas, seguido por un análisis de cromatografía de gases para conseguir una perspectiva más profunda sobre los procesos implicados en el intercambio suelo-atmósfera de GEI. Se realizaron nuevas investigaciones incluyendo el monitoreo de factores básicos de control (i.e. temperatura del suelo, humedad y las concentraciones del N mineral), los diferentes componentes de los flujos de CO2 del suelo, tasas de reciclaje netos de N y fuentes de los flujos de N2O del suelo. Con este propósito, se utilizó la extracción de hojarasca y técnicas de excavación de zanjas (trenching technique), incubación de las muestras in situ (buried bag method) y el etiquetaje de 15N de corto plazo. Los flujos de GEI del suelo en los bosques que estudiados se mostraron en el rango de aceptado de los flujos de gases de otras BHT en elevaciones comparables, excepto para el N2O. Los flujos de N2O, que se derivan principalmente de la des nitrificación, fueron bajos para un TMF lo que se puede atribuir a los ciclos conservativos de N del suelo en nuestros sitios de estudios. Los suelos fueron fuentes de CO2 y N2O (la intensidad del recurso disminuye al aumentar la altitud) y en todas las elevaciones el CH4 es bajo. Encontramos efectos de los nutrientes en todos los flujos de GEI medidos en cada elevación. Las respuestas de los flujos de CO2 del suelo cambian con la duración y el tipo de nutrientes adicionado. En 1000 m, la adición del N no afecta los flujos de CO2 del suelo, mientras que las adiciones de P y N+P disminuyeron los flujos en el primer y cuarto a quinto año. En 2000 m., la adición de N y N+P incrementa los flujos de CO2 en el primer año; a partir de entonces, la adición del N disminuye los flujos mientras que la adición de N + P no mostro ningún efecto la adición de P carece de efectos. En 3000 m, la adición de N además incrementó los flujos de CO2 constantemente; la adición de P y N+P aumentaron los flujos sólo en el primer año a partir de entonces no existió ningún efecto. Los efectos diferenciales de los nutrientes estuvieron relacionados a un estatus del N y P y respuestas variadas de los componentes de la respiración del suelo. Las respuestas de los flujos de N2O y CH4 a la adición de nutrientes mostraron gran variabilidad entre años. Los flujos de N2O no se vieron afectados por la adición de tres a cinco años de N a pesar de las diferencias significativas observadas durante los dos primeros años del mismo experimento. Atribuimos la ausencia de las respuestas en años mas tardíos debido a los contenidos bajos de humedad del suelo en nuestro periodo de monitoreo 2010-2012. En todo el gradiente altitudinal, la adición de P disminuyó los flujos de N2O y las concentraciones de N mineral, presumiblemente debido a que alivió de la limitación del P en la producción primaria neta, lo que aumentó la captación de N a través de las plantas. La adición de N+P además mostró tendencias similares las respuestas a la adición de N solamente, pero con efectos menos fuertes debido a los efectos contrapuestos de la adición de P. Durante los dos primeros años de la adición de nutrientes, los flujos de CH4 no se vieron afectados en ninguna elevación, lo cual atribuimos a la combinación de cantidades moderadas de nutrientes añadidos, la fuerte inmovilización de nutrientes, y la separación de la más alta capacidad de absorción de CH4 en el subsuelo de la superficie del suelo donde se añaden fertilizantes. En el tercer a quinto año, la adición de nutrientes del suelo aumentaron la captación de CH4, aunque los efectos de N y P variaron a lo largo del gradiente altitudinal: en 1000 m, la adición de N y N+P aumentó la captación anual de CH4 a 20-60%; en 2000 m P y N+P incrementaron la captación a 21-50%; y en 3000 m la adición de P y N+P incrementó la captación de CH4 a 34-40%. Estos efectos diferenciales de la adición de nutrientes pueden estar relacionados con el estatus inicial de del suelo y respuesta diferenciales de otros componentes del ecosistema a la adición de nutrientes en cada elevación. Demostramos que los flujos de GEI del suelo y consecuentemente la red potencial de calentamiento global del suelo pueden cambiar considerablemente a lo largo de un gradiente de elevación, siguiendo una tendencia general de disminución con el aumento de la elevación. Los resultados indican además que la elevada deposición de N y P puede afectar los flujos de GEI del suelo en los BHT Andinos, pero las respuestas a los flujos de GEI a la adición de nutrientes depende del estatus inicial de los nutrientes del suelo, la duración de la adición de nutrientes y la variabilidad inter-anual de las condiciones climáticas. Puesto que los efectos de la adición de nutrientes fueron no lineares con el tiempo de exposición y a la par existen complejas interacciones con otros componentes del ecosistema, aún quedan muchas incertidumbres en la predicción exacta de los efectos de la deposición de nutrientes en los flujos de GEI. Sin embargo, ofrecemos los primeros datos sobre los efectos de nutrientes a medio plazo de N, P y N+P en los flujos de los tres principales gases de efecto invernadero del suelo a lo largo de un gradiente altitudinal de los BHT Andina. Nuestros resultados sugieren que la red potencial de calentamiento global de los suelos en todo el gradiente altitudinal podría aumentar ligeramente con la entrada contribución de N, mientras que podría disminuir con el aumento de la contribución de P y N+P.

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Dissertations / Theses on the topic 'Greenhouse gas inventories and fluxes'

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