The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy
The ratio of transmitted near-infrared radiation to photosynthetically active radiation (PAR) increases in proportion to the adsorbed PAR in the canopy
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DOI：
10.1007/s10265-010-0346-1
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发表时间：
2011-01-01
影响因子：
2.8
通讯作者：
Muraoka, Hiroyuki
中科院分区：
文献类型：
--
作者：
Kume, Atsushi;Nasahara, Kenlo N.;Muraoka, Hiroyuki
在无雪期（5 ~ 11月），测定了日本冷温性落叶阔叶林冠层下（PARt和NIRt）和冠层上（PARi和NIRi）的日光合有效辐射总量（400-700 nm，PAR）和近红外辐射（700-1000 nm，NIR）。近红外光谱辐射和PAR光谱辐射的积分以及瞬时近红外光谱辐射和PAR光谱辐射的日积分，降低了光谱光学差异、冠层结构异质性、天空条件和太阳高度等噪声。PARi/PARt与NIRt/PARt呈线性相关（RA（2）A = 0.96）。云量的影响可以忽略不计，因为与森林中NIRt/PARt的范围相比，无论季节和天气条件如何，NIRi/PARi的波动都很小。冠层下NIRt/PARt比值与叶面积指数（LAI）呈对数线性关系，相关范围为0 ~ 5.25（RA（2）A = 0.97）。我们的结论是，季节变化的fAPAR（= 1 - PARt/PARi）和叶面积指数的冠层可以估计与高精度的传输NIRt和PARt下冠层。
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 (RA(2)A = 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 (RA(2)A = 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.