抄録
To understand global climate change, it is important to monitor the temporal and spatial distributions of vegetation. Digital cameras are relatively inexpensive to operate, and have small labor requirements, allowing the detection of subtle seasonal variation at high spatial resolution. Recent studies have reported camera-based indices that are calculated from the digital values of blue, green and red are useful to grasp the seasonal variation of vegetation phenology such as leaf expansion or fall. To examine this possibility, we investigated the characteristics of seasonal variation of camera-based indices for Larix kaempferi. Our camera adjusts the white balance automatically so that the 3 color components are modified by the lighting conditions. By normalizing respective components with their arithmetic mean, the dispersion becomes smaller than the raw digital value. However, the influence of solar radiation remains. We surveyed the relationship between the 3 components and solar radiation, and developed new vegetation indices independent of solar radiation by utilizing the normalized components. These indices are very useful for the analysis of seasonal change of Larix kaempferi.
