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Title: Soil and environmental variables affecting the land-atmosphere exchange of methane
Author: Macdonald, J. A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1997
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Rates of methane (CH4) oxidation (-) and emission were measured from a range of soil types and land uses to investigate the soil and environmental variables which affected the land-atmosphere exchange of CH4. The influence of soil characteristics, land use, inputs of nitrogen (N) and sulphur (S) and temporal variations in soil water content and temperature on CH4 flux were examined in the field using a static chamber technique, and in the laboratory using soil cores. The flux of CH4 was measured from a range of sites in the UK, Cameroon and Borneo, including temperate and tropical forest, agricultural land, moorland and blanket bog. In mineral soils, rates of CH4 oxidation ranged from a maximum uptake of -27.2 ng m-2 s-1 in an undisturbed forest in Cameroon, to a small net emission of 0.8 ng m-2 s-1 from an agricultural field in Scotland. In peats, soil water content controlled the magnitude and direction of flux within sites by affecting the degree of anaerobicity of the peat and hence the depth of the CH4 oxidising layer. Other factors such as peat depth and substrate quality influenced inter-site variability. The contribution of CH4 produced by termites to the CH4 budget was investigated in undisturbed and disturbed forests in Cameroon and Borneo. In summary, rates of CH4 oxidation from mineral soils were low and covered a small range relative to CH4 emission rates from peat. Rates of CH4 oxidation were significantly inhibited by anthropogenic disturbance such as deforestation, conversion to agriculture, and inputs of N. Spatial variability was controlled by the bulk density of the soil, both in temperate and tropical climates, demonstrating the importance of the gaseous diffusion status of the soil and the secondary role of temperature in regulating oxidation rates. Seasonal variability affected both CH4 emission and oxidation rates. The relative influence of soil water content and temperature on the CH4 flux varied between sites and was dependent on the soil type.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available