Experimental study on utilization of remote sensed data for assessing ecophysiological condition of vegetation

为了建立遥感技术评价植被生态生理状况的方法，通过田间和室内试验，阐明了叶片和冠层尺度上光合行为特征与光谱反射率特性之间的关系。田间试验在滋贺县的Kiryu试验流域和兵库县的Akoh试验场进行。采用涡旋相关法，结合各微气象观测资料，进行了多季节CO_2/H_2O通量观测。在此观测结果的基础上，建立了描述林冠与大气间CO_2/H_2O交换的大叶型数值模型，该模型能合理地估算林分的热通量、水汽通量和CO_2通量的季节变化，并能计算林分的年同化速率。在Akoh站点进行了通量观测，重点研究了冠层结构对通量的影响。本实验建立的模型可以预测辐射、风速、热量、CO_2和H_2O通量的垂直分布。利用高分辨率多光谱仪和便携式光合作用仪，对盆栽常绿阔叶树进行了室内实验。结果表明，利用叶片光谱反射率得到的NDVI并不总是与光合作用行为相对应，这表明即使在单个叶片尺度上，也需要利用远红外反射率作为地表温度指标来远程感知光合作用的实时响应。

In order to establish the methodology for assessing ecophysiological conditions of vegetation using remote sensing technique, field and laboratory experiments were conducted to clarify the relationship between characteristics of photosynthetic behavior and properties of spectral reflectance in leaf and canopy scale. The field experiments were conducted at the Kiryu Experimental watershed in Shiga prefecture and the Akoh experimental site in Hyogo prefecture. Multi-seasonal CO_2/H_2O flux observations were carried out using eddy correlation method with various micro meteorological measurements in the Kiryu sites. Based on the experimental results in this observation, a big leaf type numerical model describing the CO_2/H_2O exchanges between canopy and atmosphere was developed, The model could reasonably estimate the seasonal variations of heat, vapor and CO_2 fluxes, and could calculate the annual assimilation rate of forest stands. The flux observations in the Akoh site were conducted focusing on the influences of canopy structure. The model developed for this experiments can predict the vertical distributions of radiation, wind speed, heat, CO_2 and H_2O fluxes. The laboratory experiments were operated on several broad-leaf evergreen trees planted in pots using a high-resolution multi-spectral meter and a portable photosynthesis meter. The results shows that the NDVI derived from spectral reflectance of leaves did not always correspond to photosynthetic behaviors, This suggests that utilization of the far infrared reflectance as a surface temperature index is required to sense remotely the real-time responses of photosynthesis even for individual leaf scale.