On the role of soil water retention characteristic on aerobic microbial respiration

Abstract

Abstract. Soil water status is one of the most important environmental factors that control microbial activity and rate of soil organic matter decomposition (SOM). 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 effect of air content and gas-diffusion pathways on 10 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 modelling framework of 15 aerobic microbial respiration that incorporates the role of SWC under arbitrary soil moisture status. The model was tested by compariing it with published datasets of SOM decomposition under laboratory conditions.

Microbial dynamics and soil physicochemical properties explain large‐scale variations in soil organic carbon

“…Additional uncertainties are related to model structural assumptions and parameterizations. Specifically, soil moisture has been widely regarded as one of the primary physical factors that control microbial activity (Arnold, Ghezzehei, & Berhe, ; Ghezzehei, Sulman, Arnold, Bogie, & Berhe, ; Manzoni, Moyano, Kätterer, & Schimel, ); however, the soil moisture control over microbial dynamics is not used in the current parameterization of MIMICS. Soil structure (characterized by porosity or bulk density) determines soil O 2 availability and the accessibility of C particles to microbes (Davidson, Samanta, Caramori, & Savage, ; Lützow et al, ).…”

Zones of influence for soil organic matter dynamics: A conceptual framework for data and models

“…Neglecting this ‘dynamic soil structure’ in mechanistic models omits important soil responses and feedbacks to climate and land use drivers (Robinson et al, ), consequently mis‐estimating SOM dynamics as touched upon by Schmidt et al (). Including dynamic changes in soil structure, as triggered for example by climate change (Hirmas et al, ), will provide better representation of soil oxidation status and water holding characteristics that are primary controls of microbial activity and SOM decomposition (Ghezzehei, Sulman, Arnold, Bogie, & Berhe, ). Soil structural dynamics, driven for example by LUC, affect SOM protection, microbial activity and abundance through changes in the number and size of aggregates (Sutton & Sposito, ), though important questions remain on the extent to which microbes and geochemical interactions contribute to the stabilization of micro‐aggregates (Totsche et al, ).…”

Intensified Soil Moisture Extremes Decrease Soil Organic Carbon Decomposition: A Mechanistic Modeling Analysis

“…The influence of soil water change on heterotrophic respiration is dependent on different mechanisms, such as substrate accessibility, oxygen diffusion and microbial stress (Ghezzehei et al, 2019;Yan et al, 2018). These factors collectively shape the response of microbial respiration to soil water changes.…”