Microbial decomposition of soil organic matter can be viewed as being causally related to the physical structure of the soil system, which consists of a network of functionally distinct sub-units. The heterogeneous distribution of water in this network creates variations in the diffusion rates of oxygen, nutrients, and organic substrates into and out of surrounding sub-units. As a result, soil becomes structured into distinct microenvironments that exhibit variation in oxygen supply, with resulting variation in carbon mineralization rates, redox potential, and the formation of greenhouse gases (e.g. CH₄, N₂O).  Differences in metabolic rates between functionally distinct soil volumes are often large enough to permit microenvironments with rapid mineralization rates to exist adjacent to such exhibiting slow mineralization rates, rendering a large scale representation of soil physiology in carbon turnover models difficult.

Solute flow patterns, which are based on pore structure, have been used to constrain soil structure by modeling the distribution of microbial communities and SOM mineralization rates. However, little scalable information is available about the relation between soil structure and the ability of the total soil environment to supply electron acceptors for carbon mineralization (oxidation).

Here we investigate the possibility to use indirect information about in situ metabolic activity to define the pore network and the resulting structural organization of the soil. To this end, we installed replicate platinum redox probes (n = 6 per depth increment) in a Willamette Valley soil with an epiaquic moisture regime and monitored redox potentials over time. The existence of scalable relationships between pore network characteristics (assessed using 3D computed tomography) and the distribution of metabolically distinct subunits (identified through their redox status) were investigated and will be discussed.