Uncertainty quantification of the soil moisture response functions for microbial dormancy and resuscitation

Abstract

Abiotic factors influence ecosystem functioning mainly through the biological mechanisms such as the shifts in microbial community structure and/or physiology. Sigmoidal shape soil moisture response functions (SMRFs) have been widely used to modify the dormancy and resuscitation rates in microbially explicit soil biogeochemical models. However, these SMRFs and their effects on microbial dormancy have not been well quantified with experimental data. Using observations from a three-year field experiment in subtropical forests, we conducted a comprehensive parameterization of typical sigmoidal SMRFs. We quantified uncertainties in the three parameters of these SMRFs: (i) the critical soil water potential (SWP) for microbes entering dormancy, φA2D=−0.46±0.03MPa (mean ± standard deviation); (ii) the ratio of the critical SWP for resuscitation to φA2D, τ=0.39±0.16; and (iii) the exponent in the SMRFs, ω=3.38±0.54. Our results show much higher uncertainty in the SMRF for microbial resuscitation than microbial dormancy, due to the parameter τ being included in microbial reactivation with larger uncertainty than that of φA2D and ω. In addition, the active microbes, rather than the total living microbes, were overwhelmingly controlled by soil moisture, leading to the stronger dependency of microbial respiration on soil moisture in the dry season than in the wet season. The SMRFs and their parameter values/uncertainties derived in this study could be directly incorporated into or used as a priori in ecosystem and Earth system models that account for microbial dormancy and resuscitation.