Modeling Dynamics of Hydrogen‐Oxidizing Bacteria Under Pulsing Soil Moisture Conditions

Abstract

Hydrogen‐oxidizing bacteria (HOB) are responsible for the dominant soil sink of atmospheric hydrogen (H ₂ ); however, models estimating this sink are yet to incorporate explicit representation of these biotic drivers. Here, we use a donor‐consumer model to examine how HOB and carbon‐decomposing bacteria (CDB) may jointly influence organic carbon decomposition and atmospheric H ₂ uptake as critically driven by hydroclimatic forcings and temporally varying soil moisture. Hydroclimatic forcing was investigated through three simulation setups: constant soil moisture, drying‐wetting sequences, and intermittent rainfall. Collectively, these simulations suggest the coexistence of both HOB and CDB, with each group predominantly contributing to microbial biomass in low and high soil moisture regions, respectively. Given the strong influence of soil moisture on H ₂ uptake identified in this study, our results further suggest that explicit representation of biotic drivers (HOB biomass and soil carbon) amplifies the oscillatory dynamics in soil H ₂ concentration, a feature not captured by the abiotic‐only model. We further examined the hypothesis that dormant microbes scavenge H ₂ as a survival mechanism by incorporating microbial dormancy into the HOB dynamics and showed that dormancy leads to a higher biomass contribution of HOB in arid regions (dryness index > 5). Finally, the model was applied to estimate H ₂ deposition velocity, showing improved agreement with measured data from a temperate forest and validating the importance of the explicit representation of biotic drivers. Model limitations and the potential integration with land‐surface models are also discussed.