[A-CG37] Biogeochemical Cycles in Land Ecosystem

[ACG37-07] Evaluation of plant physiological functions of multi-layered forests by active and passive chlorophyll fluorescence observations

*Tomoki Morozumi¹, Hibiki M Noda¹, Tomomichi Kato², Hiroyuki Muraoka³ (1.National Institute for Environmental Studies, 2.Hokkaido University, 3.Gifu University)

Keywords:optical remote sensing, photosynthesis

In temperate regions, forests often exhibit a distinct layer structure; trees in overstory, shrubs, herbs, and grasses in understory. Although the understory is characterized by a low light environment, it is expected that the plants inhabiting there have an important role in the carbon fixation of the whole forest. Thus, the light utilization of leaves of each layer and the vertical structure of the forest would be key to understanding the consequences between the structure and functions of forest ecosystems. A lot of studies have focused on the understory of dense tropical forests and not enough studies have been done in temperate forests. In the present study, we focused on temperate forests to investigate the photosynthetic activity of the understory. Active and passive chlorophyll fluorescence (chlF) was used to assess the plant physiological state of light use. This study aims to evaluate the functions of the understory by detecting the temporal change of fluorescence yield through two different approaches. The active chlF was detected by the pulse amplitude modulation method; the passive chlF (i.e., Solar-Induced chlF: SIF) was retrieved from the Fraunhofer-line approach using field spectroscopy measurements of oxygen A absorption band (760 nm wavelength). The preliminary results include leaf and canopy fluorescence yield at the dwarf bamboo understory in the deciduous broad-leaved forest in the northern Gifu region in spring-fall 2023. This measurement approach will be applied to the other forest types in the future to investigate the structural effect on carbon cycling over a broader scale.