Modeling Transpiration with Sun-Induced Chlorophyll Fluorescence Observations via Carbon-Water Coupling Methods

Huaize Feng,Ziwei Xu,Zhongli Zhu,Kebiao Mao,Linna Chai,Xinlei He,Tongren Xu,Shaomin Liu,Jingxue Zhao,Liangyun Liu,Sha Zhou

doi:10.3390/rs13040804

Abstract

Successfully applied in the carbon research area, sun-induced chlorophyll fluorescence (SIF) has raised the interest of researchers from the water research domain. However, current works focused on the empirical relationship between SIF and plant transpiration (T), while the mechanistic linkage between them has not been fully explored. Two mechanism methods were developed to estimate T via SIF, namely the water-use efficiency (WUE) method and conductance method based on the carbon–water coupling framework. The T estimated by these two methods was compared with T partitioned from eddy covariance instrument measured evapotranspiration at four different sites. Both methods showed good performance at the hourly (R2 = 0.57 for the WUE method and 0.67 for the conductance method) and daily scales (R2 = 0.67 for the WUE method and 0.78 for the conductance method). The developed mechanism methods provide theoretical support and have a great potential basis for deriving ecosystem T by satellite SIF observations.

Highlights

Evapotranspiration (ET) is a pipeline of the water cycle in the air, and an important influence factor of energy balance as a carrier of latent heat
The sun-induced chlorophyll fluorescence (SIF) data of the Harvard Forest (HF) site were retrieved from FluoSpec deployed about 5 m above the canopy on top of a tower and extracted by spectral fitting methods at 760 nm [20]
Scatter diagrams of modeled T ((a,d) TSLR estimated by the simple linear regression (SLR) method, (b,e) TWUE

Summary

Introduction

Evapotranspiration (ET) is a pipeline of the water cycle in the air, and an important influence factor of energy balance as a carrier of latent heat. Total ET is mainly composed of plant transpiration (T) and soil evaporation (E). T could account for 95% of the total ET [3]. T, the water flux from plants, is closely coupled with the carbon assimilation through stomata [4]. An accurate understanding of the spatiotemporal variations of T is crucial for understanding the mass and energy interactions between land surface and atmosphere. It is still a challenge deriving T, especially at a large scale [3]

Methods

Results

Conclusion