Abstract
Abstract. 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.
Highlights
Soil moisture is one of the primary physical factors that control microbial activity (Harris, 1981)
We introduce a conceptual and mathematical model of soil organic matter (SOM) dynamics that accounts for the independent roles of matric potential, dissolved oxygen, and substrate accessibility
For all the soils investigated, the peak decomposition rate was approximately 60 % (Fig. 5) of the optimal rate that would occur if aqueous diffusion, gaseous diffusion, and water potential were not limiting
Summary
Soil moisture is one of the primary physical factors that control microbial activity (Harris, 1981). The relationship between the bulk soil water content and the corresponding volumetric-average matric potential – commonly referred to as soil water characteristic (SWC) or water retention curve (WRC) – is a macroscopic measure of hydrologically relevant pore-size distribution and surface area (Hillel, 1998). As such, it is a reflection of soil texture, which controls surface area and pore-size distribution, and structure, which controls total porosity and abundance of intra- and interaggregate porosity. The interaction of microbes with pore water is influenced by the concentration of chemical species that can lower the osmotic potential
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