Abstract: Macroscopic measurements and observations in two-dimensional soil-thin sections indicate that fungal hyphae invade pref-erentially the larger, air-filled pores in soils. This suggests that thearchitecture of soils and the microscale distribution of water are likelyto influence significantly the dynamics of fungal growth. Unfortunately,techniques are lacking at present to verify this hypothesis experimentally,and as a result, factors that control fungal growth in soils remain poorlyunderstood. Nevertheless, to design appropriate experiments later on, itis useful to indirectly obtain estimates of the effects involved. Suchestimatescan be obtainedvia simulation, basedondetailed micron-scaleX-ray computed tomography information about the soil pore geometry.In this context, this article reports on a series of simulations resultingfrom the combination of an individual-based fungal growth model, de-scribing in detail the physiological processes involved in fungal growth,and of a Lattice Boltzmann model used to predict the distribution of air-liquid interfaces in soils. Three soil samples with contrasting propertieswere used as test cases. Several quantitative parameters, includingMinkowski functionals,were used to characterize thegeometry ofpores,air-water interfaces, and fungal hyphae. Simulation results show that thewater distribution in the soils is affected more by the pore size distri-bution than by the porosity of the soils. The presence of water decreasedthe colonization efficiency of the fungi, as evinced by a decline in themagnitude of all fungal biomass functional measures, in all three sam-ples. The architecture of the soils and water distribution had an effect onthe general morphology of the hyphal network, with a ‘‘looped’’ config-uration in one soil, due to growing around water droplets. These mor-phologic differences are satisfactorily discriminated by the Minkowskifunctionals, applied to the fungal biomass.Key words: Fungal model, Lattice Boltzmann model, Minkowskifunctionals, Soil, X-Ray computed tomography.(Soil Sci 2012;177: 111Y119)