Dynamic gas transport inside of forest soil and its couplings with the fluxes of water and heat
BMBF PT BEO 51-0339476 C BITÖK-N15
From 01/1995 to 04/1996Principal Investigator: Bernd Huwe
Staff: Matthias Haubold
Grant: 0339476 B Vorhersage und Erklärung des Verhaltens und der Belastbarkeit von Ökosystemen unter veränderten Umweltbedingungen
For the identification and quantification of essential subprocesses of the transport of gases in forest soils we used an approach consisting of laboratory experiments, field measurements and the development and application of simulation models. Laboratory experiments were used for parameter and process identification whereas simulation models served as tools for process analysis. Both, laboratory and field measurements showed only small pressure and concentration gradients in the gas phase. However, model calculations led to the conclusion that convective gas transport is by no means negligible. Further simulations provided reasons for the difficulties in direct measurements of the involved processes and showed that neglecting process coupling effects between water, heat and gas tranport may cause severe errors in results and interpretations. The critical parameter seems to be the tortuosity of pore space which may behave like a switch with regard to the transport of soil gases. Scarcely measurable pressure gradients at small airfilled porosities may already cause a convection dominated transport regime. Possible model simplifications thus depend on the actual site conditions and can not be derived in general.