SIFSpec: Measuring Solar-Induced Chlorophyll Fluorescence Observations for Remote Sensing of Photosynthesis.

Shanshan Du,Yongguang Zhang,Jiaochan Hu,Xinjie Liu,Jian Guo,Shaoqiang Wang,Liangyun Liu

doi:10.3390/s19133009

Abstract

Solar-induced chlorophyll fluorescence (SIF) is regarded as a proxy for photosynthesis in terrestrial vegetation. Tower-based long-term observations of SIF are very important for gaining further insight into the ecosystem-specific seasonal dynamics of photosynthetic activity, including gross primary production (GPP). Here, we present the design and operation of the tower-based automated SIF measurement (SIFSpec) system. This system was developed with the aim of obtaining synchronous SIF observations and flux measurements across different terrestrial ecosystems, as well as to validate the increasing number of satellite SIF products using in situ measurements. Details of the system components, instrument installation, calibration, data collection, and processing are introduced. Atmospheric correction is also included in the data processing chain, which is important, but usually ignored for tower-based SIF measurements. Continuous measurements made across two growing cycles over maize at a Daman (DM) flux site (in Gansu province, China) demonstrate the reliable performance of SIF as an indicator for tracking the diurnal variations in photosynthetically active radiation (PAR) and seasonal variations in GPP. For the O2–A band in particular, a high correlation coefficient value of 0.81 is found between the SIF and seasonal variations of GPP. It is thus concluded that, in coordination with continuous eddy covariance (EC) flux measurements, automated and continuous SIF observations can provide a reliable approach for understanding the photosynthetic activity of the terrestrial ecosystem, and are also able to bridge the link between ground-based optical measurements and airborne or satellite remote sensing data.

Highlights

Accurate estimation of the CO2 flux uptake by terrestrial vegetation photosynthesis, that is, gross primary production (GPP), is crucial in quantifying the gas exchanges between the biosphere and atmosphere [1]
This paper presents the detailsofof the system components, instrument installation and calibration, This paper presents the details of the system components, instrument installation and calibration, as well as data collection and processing for the automated in situ Solar-induced chlorophyll fluorescence (SIF) measurement (SIFSpec) system as well as data collection and processing for the automated in situ SIF measurement (SIFSpec) system produced by Bergsun Inc. (Beijing, China) and used in the ChinaSpec network, along with two years produced by Bergsun Inc. (Beijing, China) and used in the ChinaSpec network, along with two years of continuous SIF measurements on a maize crop at the Daman (DM) site
The automated and long-term in situ SIF measurement system—SIFSpec used in the ChinaSpec network—was presented

Summary

Introduction

Accurate estimation of the CO2 flux uptake by terrestrial vegetation photosynthesis, that is, gross primary production (GPP), is crucial in quantifying the gas exchanges between the biosphere and atmosphere [1]. The development of high-resolution sensors deployed on aircraft [2,3] and satellites [4,5,6,7,8,9,10] especially has opened the door to detecting SIF signals at regional and global scales. Several ground-based flux observation networks have been established to combine the ground-based instruments and to define the calibration protocols and data processing procedure, which is crucial to the comparison of the flux measurements across different sites. FLUXNET is a network including hundreds of flux sites distributed across the world and is used to measure the exchange of CO2 and water between the biosphere and atmosphere [19]

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