Use of light response curve parameters to estimate gross primary production capacity from chlorophyll indices of global observation satellite and flux data

The photosynthetic rate has a nonlinear relationship with PAR during the day. We previously developed an algorithm for estimating GPP capacity, which is defined GPP under low-stress condition, using light response curves (LRCs). In this study, we studied the characteristics of LRC parameters of the initial slope and the maximum gross photosynthesis rate (Pmax), and formulas to calculate Pmax from the relationship between the chlorophyll index of the green and near-infrared (NIR) bands (CIgreen) and the GPP capacity at PAR = 2000 ?mol m–2 s–1 (GP2000) for nine vegetation types spanning tropical to subarctic climates on the Eurasian and North American continents using eddy covariance flux measurements and Moderate Resolution Imaging Spectrometer (MODIS) data. The slope of the relationship between CIgreen and GP2000 was highest for sites dominated by herbaceous plants such as open shrubland, savanna, and cropland (rice paddy); it was lower at sites dominated by woody plants. The yearly GPP/GPP capacity ratio was close to one in flux data. When the method was applied to satellite data, the daily GPP capacity exhibited a similar seasonal pattern to that of the Flux GPP and MODIS GPP products. Under high dryness conditions, Flux GPP showed the drop from the GPP capacity estimated from CIgreen and diurnal PAR data around noon, and they were nearly identical during the early morning and late afternoon. The instantaneous GPP capacity could be considered the baseline of the instantaneous GPP with stress-free conditions and important for quantifying midday depression at the sub-day scale.

This work was supported in part by JSPS KAKENHI grant (no. 16K00514); Environmental Research Projects from The Sumitomo Foundation grant (no. 193123); a grant for the Global Change Observation Mission (GCOM); nos. ER2GCF108 and ER3GCF107 of the Japan Aerospace Exploration Agency (JAXA); and the organization for the promotion of gender equality at Nara Women's University. MODIS datasets were provided by Land Processes DAAC and flux data were provided by FLUXNET Network of the Asia-Flux, Ameri-Flux, Fluxnet-Canada and GHG-Europe, and Forestry and Forest Products Research Institute Flux Observation Network (FFPRI FluxNet) in Japan. Funding for the Ameri-Flux data resources was provided by the Office of Science of the U.S. Department of Energy. The research leading to these results has received funding from the Seventh Framework Programme of European Community (FP7/2007–2013) under grant agreement no. 244122 GHGEurope. KM thanks A. Ozaki for the preliminary study of RU-YPF and RU-YLF sites that was performed during graduate training. ALB was supported by a Juan de la Cierva-Incorporación postdoctoral contract IJC2020-045630-I funded by MCIN/0041EI/10.13039/501100011033 and by European Union NextGenerationEU/PRTR. We thank the principal investigators and researchers of the EC observations for providing data and site information: L. Flanagan (CA-Let), K. Ono (JP-MSE), M. Cuntz (FR-Hes), M. Litvak (US-Ses, US-Wjs), S. Murayama (JP-TKY), A.R. Desai (US-Los), B. Kruijt (NL-Loo), (IT-Lav), A. Kotani (RU-YPF and RU-YLF), Y. Mizoguchi (JP-FJY), J. Limousin (FR-Pue), T. Maeda (TH-SKR), and the PI and researchers of JP-TMK and IT-Lav. We also thank the anonymous reviewers for their valuable comments and suggestions.

CIgreen

Eddy covariance flux

GPP

Light response curve

Published