  Dormancy is an essential strategy for microorganisms to cope with
environmental stress. However, global ecosystem models typically ignore
microbial dormancy, resulting in major model uncertainties. To facilitate the
consideration of dormancy in these large-scale models, we propose a new
microbial physiology component that works for a wide range of substrate
availabilities. This new model is based on microbial physiological states and
is majorly parameterized with the maximum specific growth and maintenance rates
of active microbes and the ratio of dormant to active maintenance rates. A
major improvement of our model over extant models is that it can explain the
low active microbial fractions commonly observed in undisturbed soils. Our new
model shows that the exponentially-increasing respiration from
substrate-induced respiration experiments can only be used to determine the
maximum specific growth rate and initial active microbial biomass, while the
respiration data representing both exponentially-increasing and
non-exponentially-increasing phases can robustly determine a range of key
parameters including the initial total live biomass, initial active fraction,
the maximum specific growth and maintenance rates, and the half-saturation
constant. Our new model can be incorporated into existing ecosystem models to
account for dormancy in microbially-mediated processes and to provide improved
estimates of microbial activities.
