Combining Soil Chamber and Eddy Covariance Measurements to Better Constrain CO2 and CH4 Fluxes in a Restored Tidal Wetland
Abstract
Interpretation of net ecosystem exchange measurements of CO2 and CH4 in tidal wetland ecosystems is challenging due to effects from tidal activity and heterogeneous landscapes. In this study we are using eddy covariance and soil chamber measurements in a restored tidal wetland consisting of three land cover types: Spartina foliosa, Salicornia pacifica, and bare mudflats. We will use these data along with satellite imagery to better understand sources and sinks of CO2 and CH4 across the different landcover types, and improve partitioning algorithms. Two years of eddy covariance data have demonstrated the tidal marsh to be a consistently strong sink for CO2 and small source of CH4. Annual cumulative exchange of CO2 is -436.6 g C-CO2 m-2 yr-1 (sd=26.4 g C-CO2 m-2 yr-1) and of CH4 is 0.51 g C-CH4 m-2 yr-1 (sd=0.362 g C-CH4 m-2 yr-1). As the marsh is often flooded at night, nighttime ecosystem respiration is negligible, making partitioning of net ecosystem exchange of CO2 difficult. Average nighttime CO2 flux is -0.0261 g C-CO2 m-2 hr-1 (sd=0.0612 g C-CO2 m-2 hr-1). Soil chamber measurements show that average soil surface CO2 flux from S. foliosa is 7.3 mg C-CO2 m-2 hr-1, from S. pacifica is 25.6 mg C-CO2 m-2 hr-1, and from mudflats is 49.5 mg C-CO2 m-2 hr-1. Average soil surface CH4 flux is 0.212 mg CH4 C m-2 hr-1 from S. foliosa, 0.164 mg C-CH4 m-2 hr-1 from S. pacifica, and 0.0803 mg C-CH4 m-2 hr-1 from mudflats. On average, daytime soil fluxes from all landcover types are sources of CO2 and CH4, yet the land cover types contribute unequally to the total ecosystem flux. Soils in vegetated areas contribute more CH4, while bare mudflats contribute more CO2. We plan to use footprint analyses paired with satellite imagery to upscale the chamber data and inform estimates of soil respiration, which will be used to improve partitioning algorithms. Better constraint on ecosystem respiration, as well as the functional relationships between land cover type and CO2 and CH4 fluxes, will allow for improved understanding of the exchange of greenhouse gases in tidal wetlands. These data will be used to parameterize a process-based model and predict regional greenhouse gas budgets from restored wetlands in the California Bay-Delta region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB048.0008S
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0442 Estuarine and nearshore processes;
- BIOGEOSCIENCES;
- 0469 Nitrogen cycling;
- BIOGEOSCIENCES