Improving the Capability of the SCOPE Model for Simulating Solar-Induced Fluorescence and Gross Primary Production Using Data from OCO-2 and Flux Towers

Haibo Wang,Jingfeng Xiao

doi:10.3390/rs13040794

Abstract

Solar-induced chlorophyll fluorescence (SIF) measured from space has shed light on the diagnosis of gross primary production (GPP) and has emerged as a promising way to quantify plant photosynthesis. The SCOPE model can explicitly simulate SIF and GPP, while the uncertainty in key model parameters can lead to significant uncertainty in simulations. Previous work has constrained uncertain parameters in the SCOPE model using coarse-resolution SIF observations from satellites, while few studies have used finer resolution SIF measured from the Orbiting Carbon Observatory-2 (OCO-2) to improve the model. Here, we identified the sensitive parameters to SIF and GPP estimation, and improved the performance of SCOPE in simulating SIF and GPP for temperate forests by constraining the physiological parameters relating to SIF and GPP by combining satellite-based SIF measurements (e.g., OCO-2) with flux tower GPP data. Our study showed that SIF had weak capability in constraining maximum carboxylation capacity (Vcmax), while GPP could constrain this parameter well. The OCO-2 SIF data constrained fluorescence quantum efficiency (fqe) well and improved the performance of SCOPE in SIF simulation. However, the use of the OCO-2 SIF alone cannot significantly improve the GPP simulation. The use of both satellite SIF and flux tower GPP data as constraints improved the performance of the model for simulating SIF and GPP simultaneously. This analysis is useful for improving the capability of the SCOPE model, understanding the relationships between GPP and SIF, and improving the estimation of both SIIF and GPP by incorporating satellite SIF products and flux tower data.

Highlights

Introduction iationsSolar-induced chlorophyll fluorescence (SIF), emitted by vegetation in the pigment beds of photosystems, is an indicator of the efficiency by which photons are transmitted into photochemical reaction centers [1]
SIF has recently emerged as a novel tool for the estimation of terrestrial gross primary production (GPP), the amount of carbon fixed by terrestrial vegetation via photosynthesis [2,3]
We examined how well the simulated SIF by the optimized SCOPE model could be used to estimate GPP based on the relationship between these variables (Figure 13)

Summary

Introduction

Introduction iationsSolar-induced chlorophyll fluorescence (SIF), emitted by vegetation in the pigment beds of photosystems, is an indicator of the efficiency by which photons are transmitted into photochemical reaction centers [1]. SIF has recently emerged as a novel tool for the estimation of terrestrial gross primary production (GPP), the amount of carbon fixed by terrestrial vegetation via photosynthesis [2,3]. SIF is seen as a more promising proxy for GPP than the traditional vegetation indices that are derived from reflectance data [4,5,6]. GPP is a key component of the global carbon cycle, and its accurate estimation at region and global scales is vital for understanding the interactions between the terrestrial carbon cycle and climate change [7,8]. Previous studies have shown strong relationships between ecosystem SIF and GPP using SIF data from ground measurements (e.g., [9,10]), airborne imaging spectrometers (e.g., [4,11]), and satellite sensors such as the Greenhouse Gases.

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