Dynamic evolution of the soil pore size distribution and its connection to soil management and biogeochemical processes

Soil properties are determined by a complex arrangement of pores, particles, and aggregates, which may change in time as a result of both ecohydrological dynamics and land management processes. The soil pore size distribution (PSD), which typically is treated as a static component, is a key determinant of soil properties, and its accurate representation has the potential to improve hydrological and crop models. Following previous work by Or et al. (2000), a modeling framework is proposed for the time evolution of the PSD which takes into account processes such as tillage, consolidation, and changes in organic matter. A time-varying power law PSD is obtained as the solution of a special form of transport equation for the PSD, parameterized using data from the literature to capture, in a parsimonious and efficient manner, the changes in the PSD as a result of the soil processes considered. Alterations in soil properties brought about by tillage, consolidation, and organic matter are then discussed. The potential benefit of this method for determining soil properties over the more widely used pedotransfer functions (PTF) is that it allows for the history of the soil, rather than only its present state, to be taken into account when estimating soil properties, and it does so in a physically consistent manner, leading to the widely used power law expression for soil properties with few parameters.