Exploration of Global Spatiotemporal Changes of Fall Foliage Coloration in Deciduous Forests and Shrubs Using VIIRS Phenology Product

Abstract:

Foliage senescence is a slow development process that has a significant impact on ecosystem carbon and water balance, climate change, animal migration, and human sightseeing activities worldwide. Studies of land surface phenology concentrating on the onset dates of senescence and dormancy are insufficient to reveal the full details of the complex process. The aim of this study is to explore the detailed changes of foliage senescence across the globe by dividing the senescence process into six coloration statuses, including little/no coloration, low coloration, moderate coloration, high coloration, peak coloration, and post-peak coloration. The onset date and duration of each coloration status are estimated by the linear relationship between senescence phenology and temporally-normalized brownness index (TNBI) using VIIRS 500 m phenology product from 2013 to 2018, and then evaluated using species-based leaf color observations. Specifically, the onset date and duration of each coloration status show obvious gradient along latitude. Peak coloration has the longest duration with largest anomaly during the 6 years, while low coloration is on the contrary. The inter-annual variation of each onset date of coloration status decreases as foliage senescence development. The result from this study improves the understanding of foliage coloration development across the globe.