TY - JOUR
T1 - The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy
AU - Kume, Atsushi
AU - Nasahara, Kenlo N.
AU - Nagai, Shin
AU - Muraoka, Hiroyuki
N1 - Funding Information:
Acknowledgments We thank K. Kurumado and Y. Miyamoto of the Takayama field station of Gifu University for their support of field investigations. We also thank Dr. Takeshi Motohka of University of Tsukuba for his assistance in the field observation and the data analysis. This study was supported by the Ministry of Environment, Japan, as Global Environment Research Fund (S-1: Integrated Study for Terrestrial Carbon Management of Asia in the 21st Century Based on Scientific Advancement), JSPS 21st Century COE Program (Satellite Ecology) and KAKENHI(19688012; Grant-in-Aid for Young Scientists A by JSPS) and the Japan Aerospace Exploration Agency, Global Change Observation Mission (GCOM). Support for technical advice and data collection at the Takayama site was provided by the Phenological Eyes Network (PEN; http://www.pheno-eye.org/).
PY - 2011/1
Y1 - 2011/1
N2 - The daily total photosynthetically active radiation (400-700 nm, PAR) and near-infrared radiation (700-1000 nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt (R2 = 0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 (R2 = 0.97). We conclude that seasonal changes in fAPAR (= 1 - PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy.
AB - The daily total photosynthetically active radiation (400-700 nm, PAR) and near-infrared radiation (700-1000 nm, NIR) were measured in the understory beneath the canopy (PARt and NIRt) and above the canopy (PARi and NIRi) of a Japanese cool-temperate deciduous broad-leaved forest during the snow-free period (May to November). The integration of spectral radiation for NIR and that for PAR, and the daily integrations of instantaneous NIR and PAR, reduced the noises from the optical difference in spectrum and from canopy structure heterogeneity, sky condition and solar elevation. PARi/PARt was linearly related to NIRt/PARt (R2 = 0.96). The effect of cloudiness was negligible, because the fluctuation of NIRi/PARi was quite small regardless of season and weather conditions compared with the range of NIRt/PARt in the forest. The ratio of NIRt/PARt beneath the canopy was log-linearly related to the in situ leaf area index (LAI) with a wide range from 0 to 5.25 (R2 = 0.97). We conclude that seasonal changes in fAPAR (= 1 - PARt/PARi) and LAI of a canopy can be estimated with high accuracy by transmitted NIRt and PARt beneath the canopy.
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U2 - 10.1007/s10265-010-0346-1
DO - 10.1007/s10265-010-0346-1
M3 - Article
C2 - 20428920
AN - SCOPUS:78650510653
SN - 0918-9440
VL - 124
SP - 99
EP - 106
JO - Journal of Plant Research
JF - Journal of Plant Research
IS - 1
ER -