2019 年 35 巻 p. 1-30
This study examines the role of traditional calendars in regulating agriculture in a tropical monsoon climate in Western Sumba Island, Indonesia. Our findings indicate that Podu, which marks the end of the dry season and the start of land crop agriculture, and Nyale, which marks the late rainy season and the start of rice planting, are cardinal points at which local calendars are synchronized to the luni-solar cycle. Analyses of 391 normalized difference vegetation index (NDVI) images that were issued every 16 days from 2000 to 2017 revealed that the timing of Podu and Nyale did not correspond with specific vegetation levels across different years due to fluctuations influenced by extreme weather events. However, time-series analyses of the same images disclosed that Podu and Nyale represented the bottom and the peak of “standard” seasonal vegetation changes, respectively, suggesting that these calendars represent Western Sumbanese adaptations to the unstable monsoon climate.