Terrestrial Wetland Function and Resilience Science Focus Area

Examining environmental effects on terrestrial wetland ecosystems, encompassing small-scale processes to large-scale ecosystem interactions

Overview brochure PDF

Principal investigator: Roser Matamala

Environmental change is intensifying hydrological regimes around the world, which will greatly impact the ecological and biogeochemical function and resilience of wetlands, including the production, consumption, and emission of greenhouse gases (GHGs). Wetland systems are currently not well represented in Earth system models (ESMs). Development and inclusion of new mechanistic and process-based representations of wetlands are necessary to improve the accuracy of ESM predictions.

To improve wetland representation in models, the Biological and Environmental Research (BER) program within the U.S. Department of Energy’s Office of Science supports the Terrestrial Wetland Function and Resilience Science Focus Area (SFA).

The Wetland Function SFA aims to develop a mechanistic understanding of how climatic conditions affect terrestrial wetland ecosystem function, particularly carbon (C) dynamics, with the goal of advancing predictive models at multiple scales. To achieve this goal, the SFA will integrate experiments, observations, and models. The SFA framework uses hydrogeomorphic (HGM) wetland classification, which provides a solid basis for investigating the transferability of process understanding across multiple wetland types.

Project Phases and Study Area

The SFA will progress through three phases. Phase I focuses on understanding mechanisms and processes across spatial and temporal scales and developing new components for inclusion in reactive transport models. Researchers initiated studies at the Cottonwood Lake Study Area located in the Prairie Pothole Region (PPR). The site represents a depressional wetland complex with variable hydro-biogeochemical drivers. Phase II will begin testing model transferability at adjunct sites within the PPR, and Phase III will collect data and test model transferability at wetlands outside the PPR.

Wetland Function SFA research focuses on the Upper Colorado River Basin (UCRB) and builds upon research at the East River while expanding into the Taylor River watershed. Both rivers are representative and vulnerable headwater systems within the UCRB, collectively forming the Gunnison River mainstem that accounts for just under half of the Colorado River’s discharge at the Colorado-Utah border. The Colorado River and its headwater tributaries supply water for municipal use to more than one in 10 Americans, irrigation for more than 5.5 million acres, and more than 4,200 megawatts of electrical-generating capacity for millions of people.

 

Research Objectives

Objective 1: Determine when and how heterogeneity must be considered when scaling wetland ecosystem function in models.

• Which hydro-biogeochemical factors most influence the response functions of GHG fluxes?
• How does the spatial variability of hydro-biogeochemical factors (e.g., soil properties, redox biogeochemistry, and microbial and plant communities) influence C dynamics and GHG fluxes?
• When and how do hot and cold moments and long-term temporal variability, including persistent flooding and drying conditions, influence C dynamics and GHG fluxes?

Objective 2: Identify generalized response functions of GHG emissions that can apply to multiple HGM wetland types.

• Are response functions of GHG fluxes conserved across wetland types?
• If not, can new response functions of GHG fluxes be generated using prior knowledge of interacting factors?

Research Design

The SFA is structured around three key themes, which organize research according to spatial/temporal scales and modeling approaches. Theme 1 advances understanding of fine-scale hydro-biogeochemical mechanisms that control C cycling and GHG emissions in wetland soils. Theme 2 identifies above- and belowground processes and interactions affected by these mechanisms. Theme 3 incorporates newly discovered emergent properties, underrepresented processes, and mechanistic understanding into fine- and intermediate-scale models that could be integrated with the land component of ESMs.

Theme 1: Microscale Mechanisms Affecting Greenhouse Gas Emissions

This theme focuses on examining microscale mechanisms controlling GHG fluxes under the spatially and temporally variable conditions within terrestrial wetlands. In the first 3 years, researchers are examining the effects of redox dynamics and organo-mineral interactions on C cycling and GHG emissions. The SFA explores soil structural controls on carbon dioxide and methane fluxes by studying the effects of pore-scale heterogeneity and mass-transport limitations.

Researchers also study microbially mediated hot and cold moments and their contributions to GHG emissions. The team employs laboratory batch reactors and microcosm experimental systems to uncover fundamental mechanisms that control GHG production and consumption at the microlevel, with implications for larger scales.

Theme 2: Macroscale Processes and Interactions Affecting Greenhouse Gas Emissions

This theme focuses on plant-driven mechanisms, plant-microbe interactions, and local wetland characteristics that impact wetland function and resilience as drivers of C cycling in wetlands at local to ecosystem scales. In the first 3 years, researchers are examining the role of plants and plant-microbe interactions as drivers of C cycling and GHG emissions in wetlands.

The SFA uses greenhouse mesocosm experiments to quantify plant-mediated gas fluxes and probe plant-microbe interactions under controlled hydrologic conditions. The team also examines how variations in wetland characteristics impact GHG fluxes by co-locating above- and belowground measurements of GHG fluxes, soil and porewater chemistry, and plant and microbial communities to assess the effect of hydro-biogeochemical conditions on overall ecosystem C and GHG emissions.

Theme 3: Model Development to Simulate Terrestrial Wetland Carbon Cycling and Greenhouse Gas Emissions

This theme focuses on developing mechanistic process models and continuum-scale reactive transport models (RTMs) to enable predictive simulation and investigation of processes governing GHG production, consumption, and release in terrestrial wetlands. In the first 3 years, researchers are developing biogeochemical process models and laboratory- and omic-informed reaction networks to be integrated with RTMs. Specifically, these include process models of organic matter–mineral surface interactions and the incorporation of microbial metabolic functions into RTMs.

The team is also developing multiphase transport processes in RTMs. Computational experiments incorporate new data as they are collected under Themes 1 and 2. Model parameter sensitivity studies and systematic assessment of model inadequacies are guiding experiment design and field measurement campaigns.