Modeling the Processes of Soil Moisture in Regulating Microbial and Carbon-Nitrogen Cycling

Soil moisture dynamics are required to reproduce C and N cycling in soils.

The Science

Soil moisture, temperature, and litterfall vary with time, but microbial models analyzing soil carbon and nitrogen cycling often don’t consider the effects of frequent changes in these parameters. Research from scientists at Oak Ridge National Laboratory shows that variation in soil moisture over time can critically affect soil respiration and carbon-nitrogen cycling.

The Impact

The dynamics of soil moisture must be considered to adequately model soil respiration and C-N cycling, and soil moisture is more sensitive to dynamics than temperature and litterfall. Dynamic data better represent real-world climate and environmental conditions, which could enable more realistic modeling and understanding of soil C and nutrient cycling in a changing world.

Summary

Soil moisture, litterfall, and temperature change seasonally and diurnally, but many microbial modeling analyses use yearly averages or time-invariant data as inputs. The effect of constant versus dynamic parameterization of soil moisture, temperature, and litterfall on microbially mediated carbon and nitrogen cycling in soils was investigated using an updated version of the Microbial-Enzyme Decomposition (MEND) model.  The study found that explicit, dynamic representation of soil moisture is critical to reproduce microbial respiration and C-N cycling processes because microbes can undergo dormancy under dry conditions and microbial enzyme activities also vary with soil moisture. The model was also able to faithfully reproduce the carbon-to-nitrogen ratio in soil organic matter and microbial biomass, and to reproduce nitrate and ammonia concentrations in soils.

Principal Investigator

Melanie Mayes
Oak Ridge National Laboratory
mayesma@ornl.gov

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
daniel.stover@science.doe.gov

Funding

This study was supported by the U.S. Department of Energy Office of Science, Genomic Science Program under Award Number DESC0004730, DE-SC001057, DE-SC0004601, DE-SC0014079, DESC0016247, and DE-SC0010715, and the Office of the Vice President for Research at the University of Oklahoma. This work was also supported by the U.S. Department of Energy (DOE) Office of Biological and Environmental Research through the Terrestrial Ecosystem Science Scientific Focus Area at Oak Ridge National Laboratory (ORNL). W.H. and G.Z. were supported by the National Natural Science Foundation of China (Grant Numbers 31670487, 41430529, and 31600353).

References

Wang, G., W. Huang, G. Zhou, and M. A. Mayes, et al. "Modeling the processes of soil moisture in regulating microbial and carbon-nitrogen cycling.” Journal of Hydrology". Journal of Hydrology 585 124777  (2020). https://doi.org/10.1016/j.jhydrol.2020.124777.