Tracking Seasonal and Interannual Variability in Photosynthetic Downregulation in Response to Water Stress at a Temperate Deciduous Forest

He, L and Wood, JD and Sun, Y and Magney, T and Dutta, D and KAhler, P and Zhang, Y and Yin, Y and Frankenberg, C (2020) Tracking Seasonal and Interannual Variability in Photosynthetic Downregulation in Response to Water Stress at a Temperate Deciduous Forest. In: Journal of Geophysical Research: Biogeosciences, 125 (8).

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Abstract

The understanding and modeling of photosynthetic dynamics affected by climate variability can be highly uncertain. In this paper, we examined a well-characterized eddy covariance site in a drought-prone temperate deciduous broadleaf forest combining tower measurements and satellite observations. We find that an increase in spring temperature usually leads to enhanced spring gross primary production (GPP), but a GPP reduction in late growing season due to water limitation. We evaluated how well a coupled fluorescence-photosynthesis model (SCOPE) and satellite data sets track the interannual and seasonal variations of tower GPP from 2007 to 2016. In SCOPE, a simple stress factor scaling of Vcmax as a linear function of observed predawn leaf water potential (�pd) shows a good agreement between modeled and measured interannual variations in both GPP and solar-induced chlorophyll fluorescence (SIF) from the Global Ozone Monitoring Experiment-2 (GOME-2). The modeled and satellite-observed changes in SIFyield are ~30 smaller than corresponding changes in light use efficiency (LUE) under severe stress, for which a common linear SIF to GPP scaling would underestimate the stress reduction in GPP. Overall, GOME-2 SIF tracks interannual tower GPP variations better than satellite vegetations indices (VIs) representing canopy �greenness.� However, it is still challenging to attribute observed SIF variations unequivocally to greenness or physiological changes due to large GOME-2 footprint. Higher-resolution SIF data sets (e.g., TROPOMI) already show the potential to well capture the downregulation of late-season GPP and could pave the way to better disentangle canopy structural and physiological changes in the future.

Item Type:	Journal Article
Publication:	Journal of Geophysical Research: Biogeosciences
Publisher:	Blackwell Publishing Ltd
Additional Information:	The copyright of this article belongs to Blackwell Publishing Ltd
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	07 Sep 2020 06:56
Last Modified:	07 Sep 2020 06:56
URI:	http://eprints.iisc.ac.in/id/eprint/66487

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