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Gaseous Diffusion Evaluation in Forest Humus¹

ABSTRACT

Penman's ratio of direct length to effective diffusion path length, L/L_e, is not directly predictable from the air content of forest humus, probably because of anisotropic pore orientation. The diffusion coefficient of a gas in the unsaturated porous medium can be estimated from temperature, air pressure, porosity, water content, and an empirically determined value of L/L_e. A steady state CO₂ diffusion method is proposed for measuring L/L_e and gaseous diffusion coefficient in either loose or structurally intact forest humus samples.

¹ Contribution from the College of Forest Resources, University of Washington, Seattle. Based on part of the author's doctorate dissertation. Supported by NSF Grant GB 1357.

² Assistant Professor of Soil Science, University of British Columbia, Vancouver, Canada.

Received for publication November 19, 1969. Accepted for publication March 5, 1970.