 The Green-Red Vegetation Index, GRVI, was evaluated as a phenological indicator based on multi-year stand-level observations in Japan, showing relationships between GRVI values and seasonal changes in vegetation and ground surface with high temporal resolution. GRVI has advantages as a phenological indicator, including being a site-independent single threshold for detecting early leaf green-up and autumn coloring, and showing a distinct response to subtle disturbance and ecosystem types. This article was authored by Takishi Motoka, Kenlo Nishida-Nasahara, Satoshi Sachida, and others.