Understanding photosynthesis in a salt marsh using observations of solar-induced chlorophyll fluorescence
Abstract
Forecasting the global carbon budget requires accurate estimates of vegetation-atmosphere exchanges of carbon dioxide (CO2) under various environmental conditions. Despite their small geographic extent, salt marshes serve as a large carbon sink, sequestering CO2 from the atmosphere through efficient photosynthesis and carbon burial. Quantifying gross primary production (GPP) in an intertidal marsh is complicated by tidal cycles because few methods can measure photosynthesis of plants both above and below the water surface. Previous studies using eddy covariance (EC) have concluded that photosynthesis decreases when salt marsh vegetation is inundated; however, EC cannot directly discern carbon uptake during high tides and additional and independent approaches are needed. Here, we use the solar-induced chlorophyll fluorescence (SIF) technique to study wetland photosynthesis, with SIF observations already having been shown to directly correlate with GPP in multiple ecosystem types. We describe concurrent measurements of SIF in the red (689 nm) and near-infrared (760 nm) regions using an automated spectrometer system and EC measurements for the 2020 growing season in a salt marsh on the Virginia Eastern Shore. We identify diurnal, tidal, and seasonal patterns in SIF and examine how these patterns are modulated by environmental factors including water depth, air temperature, photosynthetic photon flux density, and vapor pressure deficit. Our preliminary results have shown a clear diurnal pattern of SIF at 760 nm peaking at midday with maximum intensities reaching 1.5 mW m2 sr-1 nm-1. We also investigate relationships between SIF and EC-derived GPP during different stages of inundation in order to improve estimates of GPP at high tides when EC may not yield reliable results.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB006.0001M
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0452 Instruments and techniques;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES