Coupled moisture and microbial dynamics in unsaturated soils

Abstract

A continuum-scale mathematical model which couples water flow and bacterial dynamics explores the process of biological clogging in unsaturated soils. The impact of biomass dynamics on soil water flow is assumed to take place through the changes in porosity and the structural properties of the medium by suitable modifications of the pore size distribution, water retention, and hydraulic conductivity functions. The feedback of soil moisture on biomass is taken into account by including the effect of water stress on microbial growth. The model is calibrated against existing laboratory experimental data for an artificial porous medium in saturated conditions, and it is used to analyze the hydraulic behavior of unsaturated soils when subject to biological clogging and plant water uptake. The results of this analysis show that this feedback may have a substantial impact on the net water flow, the soil water-holding capacity, and the soil moisture and biomass space-time distributions. Copyright 2007 by the American Geophysical Union.