4th UF Water Institute Symposium Abstract

Submitter's Name Debjani Sihi
Session Name Poster Session: Impact of changing drivers on water resources
Poster Number 6
Author(s) Debjani Sihi,  Graduate Student (Presenting Author)
  Stefan Gerbar,  Assistant professor
  Kanika Inglett, Research Assistant Professor
  Patrick Inglett, Associate Professor
  Inclusion of maintenance respiration alters temperature response in microbial soil organic matter decomposition model for wetlands
  The response of soil organic matter (SOM) decomposition to warming is hypothesized to be determined by microbial carbon use efficiency and enzyme activity. Current microbial-decomposition model for uplands parameterize carbon use efficiency crudely via simple growth respiration. An alternative formulation is respiration based on biomass (or nitrogen) as organisms are required to maintain their metabolism, i.e. maintenance respiration. Application of microbial decomposition models for wetlands require the consideration of oxygen supply to decomposers. However, existing SOM models in wetlands are not coupled with microbial physiological properties, yet at the same time it is pertinent to estimate warming response of microbial SOM decomposition. Our objective was to explore current SOM models to understand the response of SOM decay to changes in temperature and oxygen supply. We hypothesized that modeled warming response of SOM decomposition and microbial activity depends on how microbial respiration is formulated and the current SOM models can readily be adapted to wetland soils by incorporating oxygen limitation. The long-term responses for carbon pools (soil organic carbon and microbial biomass) showed similar pattern but model behaviors differed at transient stage of decomposition. Oscillation frequency of carbon pools was higher in wetlands compared to the upland models. Modeled respiration per unit of substrate was lower in wetlands compared to upland models. Low oxygen constraints can lead to dynamic breakdown of microbial population and decomposition in wetlands. Explicit representation of growth and maintenance respiration changes in decomposition models affects the transient response of decomposition to warming. The introduction of oxygen limitation renders the model and its applicability in wetlands to be very sensitive to the difference of the two not well constrained parameters (enzyme kinetic parameter and microbial turnover). Combining incubation experiments with microbial models requires consideration of microbial physiology and the models temporal dynamics (transient vs. long term response).