Observing fall foliage with PACE pigment indices

Abstract

Autumn senescence represents an important seasonal event in the deciduous forests of eastern North America. PACE’s repeated hyperspectral observations provide a new view of seasonal fall foliage change based on pigment indices related to the key pigments involved in leaf colour, greens from chlorophyll, reds from anthocyanin, and yellows to oranges from carotenoids. Phenologies of the ratios of the PACE anthocyanin index to chlorophyll index and carotenoid index to chlorophyll index were shown to be related to the perceived redness of forest canopies as indicated by the red chromatic coordinate (RCC) calculated from phenocam images. Spatial patterns of PACE derived pigment ratios over eastern North America clearly identify some specific ecoregions based on timing of onset of fall colours.