Continuous Ground Measurement of Solar-Induced Chlorophyll Fluorescence and Its Link to Ecosystem-Level Photosynthesis in Wetland by High Resolution Spectrometer
Abstract
Remote sensing of solar-induced chlorophyll fluorescence (SIF) is motivated by its link to ecosystem-level photosynthetic activity as intended from satellite missions such as GOSAT and OCO series, and is now a representative for accurately estimating gross primary production (GPP) [Krause and Weis, 1991; Meroni et al., 2009; Frankenberg et al., 2011]. However, the SIF from field-based measurement in seasonal variations appear limited to understand the SIF-GPP relationship at finer temporal and spatial scale, which is not easily measured by satellites. It remains ambiguous to explicate a potential of SIF to evaluate terrestrial ecosystem GPP and dynamics of carbon dioxide uptake, especially for wetland where is a critical part of carbon sinks. In this research, continuous field-based measurement of canopy-top SIF was conducted in wetland field of northern Japan, Hokkaido, Bibai Mire (43°19'23''N, 141°48'38''E, 16 m above sea level), and compared to the eddy-covariance-based GPP [Ueyama et al., 2020] at the half-hourly and daily timescales during the growing season of 2020. QEPro spectroradiometer (range of wavelength 648-808 nm, the full width half maximum (FWHM) of 0.31 nm, Ocean Optics, Dunedin, FL, USA) and the spectral fitting method (SFM; Meroni and Colombo., 2006; Meroni et al., 2010; Mazzoni et al., 2012) were used for SIF retrieval at the oxygen absorption band (O2-A, centered around 760 nm). SIF was estimated from the spectra of downwelling and upwelling at the height of 2 meters above the ground by hemisphere spectroradiometer. The downward sun irradiance was captured by cosine corrector fiber (CC fiber) from field of view (FOV) at 180° and the upward canopy-reflected radiance was received by bare fiber FOV 25° and CC fiber FOV 180°. Preliminary results show GPP and top-of-canopy SIF have a positive correlation at both timescales. Moreover, a seasonal pattern of greenness quite significantly influences the diurnal peak of SIF intensity. Our result highlights the importance of SIF from ground-based measurement in seasonality to the relationship between SIF and GPP. Overall, our continuous ground measurement shows that SIF varies among seasons and links to GPP, broadening for better understanding the ecosystem-level photosynthesis and SIF-GPP relationship at global scale.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB006.0009T
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0452 Instruments and techniques;
- BIOGEOSCIENCES;
- 0476 Plant ecology;
- BIOGEOSCIENCES