Extended Abstract (188K)P1.13
Short-term changes in below-ground carbon dioxide concentrations
G. B. Drewitt, University of Guelph, Guelph, ON, Canada; and J. S. Warland
Soils are an important component of the carbon cycle in many agricultural and forest ecosystems. As part of a study examining the production and storage of CO2 within the soil, we obtained continuous measurements of below-ground CO2 concentrations in an agricultural field. Measurements were obtained at 10 and 20 cm below the soil surface of a conventionally-tilled corn field late in the growing season (Sep. 10 - Oct. 20, 2003) as well as during the coldest parts of the winter (Jan 8 - Feb 27, 2004). The sensors used in this study were Vaisala GMP CO2 probes enclosed in a suitable sampling apparatus to protect against moisture and provide a degree of spatial coverage. Measurements of concentration during the growing season demonstrated a temperature dependence and showed strong diurnal variability. Concentration measurements obtained in the winter, when soil temperatures were near-freezing, revealed much less CO2 storage and very little relationship with soil temperatures. During both measurement campaigns substantial short-term changes in below-ground CO2 were observed during periods of high windspeed. These changes in the quantity of CO2 stored in the soil pores are suspected to be caused by an increase in soil gas diffusivity from pressure fluctuations resulting in enhanced removal of CO2 from the soil surface. This poster will discuss the magnitude of these short-term changes in below-ground CO2 storage and their potential effect on micrometeorological measurements of CO2 flux.
Poster Session 1, Posters for the 26th Conference on Agricultural and Forest Meteorology
Wednesday, 25 August 2004, 5:30 PM-8:30 PM
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