1) ブナ林における生理生態学とガス交換
植物の周囲を取り巻く環境への機能的な応答,特に,光合成能力に関するパラメータ(Vcmax, Jmax, Rd…)及び蒸散を含む生理的なパラメータの季節変化を連続的に調査しています.季節変動を明らかにするために,定期的な野外観測及び自動観測システムを用いたデータ取得を行っています.また,季節変動における制御ファクターを特定するために,内的・外的要因を詳細に調査しています.例として,グラニエセンサによる樹液流の計測を通した立木の蒸散の観測,高頻度での形態的な特徴や光合成能力に関するパラメータの計測を行っています.

2) ハイパースペクトルリモートセンシング及び放射伝達モデル
反射されたスペクトルに関与する生物物理学,生化学及び生理的なメカニズムを明らかにするために多くのリモートセンシングによる研究がなされています.分光反射特性は群葉における光の吸収特性との関連性が強いため,分光反射特性から生化学及び生物物理学的なパラメータを推定することができます.そこで,生化学パラメータ(e.g. Vcmax, gs…)との関連性がある指標を開発することに取り組んでいます.また,葉及びキャノピーでの放射伝達モデルは,様々なスケールにおける吸収,透過及び反射をシミュレーションするために用いることができます.このモデルを用いることによって,構造的なパラメータだけでなく,生化学,生物物理学的なパラメータの光への感度を明らかにすることができ,リモートセンシングデータと生態生理的なパラメータをリンクさせる基礎となりえます.

3) リモートセンシングの応用

4) 乾燥地における研究

1) Ecophysiology and gas exchanges in beech forests
Functional responses of plants to ambient environmental factors with the special attention on the seasonal trajectories of physiological parameters include photosynthetic capacity parameters (Vcmax, Jmax, Rd…) and transpiration are continuously investigated. Periodic field measurements and automatic monitoring systems were applied to gather time series data for retrieving seasonal patterns. Both internal and external factors are examined in detail for identifying the controlling factors on seasonal patterns. Photosynthetic capacity parameters as well as leaf morphological characteristics were mainly based on frequently periodic field measurements using either detached or intact leaf samples, while tree level transpiration was mainly monitored through Granier sap flow sensors. In addition, ecosystem scale gas exchange is monitored using eddy covariance system.

2) Hyperspectral remote sensing and radiative transfer models
A number of remote sensing activities is currently ongoing for revealing the underlying biophysical, biochemical and physiological mechanisms of reflected spectra. Hyperspectral information contains subtle absorption features from foliar and can be used to study the correlations of these minor absorption features with biochemical and biophysical parameters, from which they can be retrieved inversely. Special attentions are paid for identifying indices that have close relationships with biochemical parameters (e.g. Vcmax, gs…) at different temporal scales and their underlying links are investigated by inverse reflectance models. On the other hand, radiative transfer models of both leaf and canopy will be used to simulate absorption, transmission and reflection in various scales. Inverse models are applied to investigate the sensitivities of biophysical and biochemical as well as structure parameters to light distribution, which further provide physical and physiological bases for linking remote sensing data with ecophysioloigcal parameters.

3) Remote sensing applications
Satellite-born remote sensing data suffers serious atmospheric and topographic effects preventing the direct applications on them. This is even getting more serious in rugged terrain due to the complex redistribution of radiation and other climate conditions. Radiative transfer models coupling with DEM are used for corrections and in situ measurements are providing validation data sets. Thoroughly corrected remote sensing data will be used for land cover classification and change detection, and both empirical and inverse models will be used to derive LAI from remote sensing data with the challenge in rugged terrains.

4) Researches on dry areas

We are studying environmental preservation and carbon fixing, in the context of natural vegetation growing in various dry regions. Main sites are located in central Asia including China and Tajikistan. Research approaches include plant physiology, modeling, and remote sensing technology. With these studies, we would like to develop new monitoring techniques on carbon and water cycles in xeric ecosystems.