• Noda, H. M.
;
• Kosugi, Y.
;
• Kikosaka, K.
;
• Tsujimoto, K.
;
• Yoshida, Y.
;
• Oshio, H.
;
• Matsunaga, T.

Abstract

Optical remote sensing is a powerful tool to monitor the temporal and spatial variations in the canopy structure and physiological traits of terrestrial vegetation. Especially those observation is helpful to understand the phenological changes in the carbon flux of the vegetation. Several studies have shown that the evergreen forest also shows clear seasonal dynamics in gross primary production (GPP). However, vegetation indices, such as NDVI, of the evergreen forest do not show such seasonality because the foliage structure is relatively stable throughout a year. In recent years, solar induced chlorophyll fluorescence (SIF) have been utilized for carbon cycling studies. Since the chlorophyll fluorescence is the weak radiation emitted by chlorophyll in the process of photosynthesis, SIF signal enable us to understand the photosynthetic activity of the vegetation. SIF might be useful to monitor the phenological changes in physiological traits of evergreen species.

Kiryu Experiment Watershed ("Kiryu site") is a warm-temperate evergreen coniferous forest dominated by Japanese cypress (Chamaecyparis obtusa) located near Kyoto, Japan. Kiryu site is one of AsiaFlux site and Phenological Eyes Network (PEN) and flux measurement by eddy covariance methods and in-situ optical remote sensing have been conducted. We started continuous measurement of in-situ SIF at the site from the end of March 2017. GPP of Kiryu site shows seasonal change; increase from sprig to summer and decrease autumn to winter. In-situ SIF also similar seasonal changes. In present paper, we will discuss the phenological changes in the relationship between GPP and SIF in Kiryu site. We also show the seasonality of satellite-based SIF retrieved from by GOSAT data in western part of Japan, mainly dominated by evergreen forest and introduce SIF product of our new satellite GOSAT-2, the successor of GOSAT.