Fig. 1. Log-transformed air permeability, log (k_a), and gas diffusivity, log (D_p/D₀), as a function of air-filled porosity, , for (a and c) field soils (Gjorslev and Mammen) and for (b and d) lysimeter soils (Rønhave, Foulum, and Jyndevad). The D_p/D₀ data are from Kawamoto et al. (2006).