Soil water status is one of the
most important environmental factors that control microbial activity and rate of soil
organic matter (SOM) decomposition. Its effect can be partitioned into effect of water
energy status (water potential) on cellular activity, effect of water volume on cellular
motility, and aqueous diffusion of substrate and nutrients, as well as the effect of air
content and gas-diffusion pathways on concentration of dissolved oxygen. However,
moisture functions widely used in SOM decomposition models are often based on empirical
functions rather than robust physical foundations that account for these disparate
impacts of soil water. The contributions of soil water content and water potential vary
from soil to soil according to the soil water characteristic (SWC), which in turn is
strongly dependent on soil texture and structure. The overall goal of this study is to
introduce a physically based modeling framework of aerobic microbial respiration that
incorporates the role of SWC under arbitrary soil moisture status. The model was tested
by comparing it with published datasets of SOM decomposition under laboratory conditions.</p