Autori: Vasile E. Turcu and Dani Or

Editorial: AGU 2002 - Fall Meeting, 2002.

Rezumat:

Gaseous exchange between soil and atmosphere consist primarily of CO2 and O2 fluxes induced by concentration gradients resulting from respiration within the soil profile. Despite their crucial role in the biosphere, dynamics of CO2/O2 concentrations in soil and surface fluxes are rarely measured continuously. A new gradient-based method for continuous monitoring of soil CO2/O2 concentrations was tested in the laboratory and in the field and compared to closed-chamber measurements. In situ measurements were made in different plant communities within a semi-arid ecosystem. A one-dimensional vertical model for soil CO2/O2 fluxes that considers bio-geo-chemical and environmental factors within the basic governing equations for gaseous transport in porous media was developed. Comparisons between model simulations and continuous in-situ measurements of CO2 and O2 concentrations (and fluxes) were in reasonable agreement. Simultaneous measurements of soil CO2 and O2 concentrations provide insights on soil respiration characteristics such as the respiratory quotient (CO2/O2) that ranged from 0.7 to 1.2 and tended to remain remarkably stable under particular experimental conditions. Conversion of measured concentration gradients into surface fluxes was critically dependent on proper estimation of water content profile that affects soil diffusion coefficients. Continuous monitoring in the soil is particularly important following rainfall events where spatial (vertical) and temporal patterns of gaseous fluxes are complex and are unobservable by common surface chamber methods.

Cuvinte cheie: Soil respiration, modeling CO2 fluxes