Utility of commercial high‐resolution satellite imagery for monitoring general flowering in Sarawak, Borneo

Abstract

AbstractGeneral flowering (GF), irregular synchronous mass flowering of multiple tree species across multiple families, is a unique biological phenomenon of the mixed lowland dipterocarp forest in Southeast Asia. Characterizing the spatial extent and temporal dynamics of GF is essential for an improved understanding of climate–vegetation interactions and the potential climate change impact on this species‐rich rainforest. We investigated the utility of newly available high‐temporal (daily) and high‐spatial (3–4 m) resolution remote sensing by the PlanetScope commercial satellite constellation for detecting flowering trees in a dipterocarp rainforest at Lambir Hills National Park, Sarawak, Malaysia. Our study was focused on the latest GF event known to have occurred in the region in the year 2019. PlanetScope successfully acquired 13 clear‐sky or minimally cloud‐contaminated scenes over the park during a study period of January 1, 2019 to August 31, 2019 encompassing the 2019 GF event. In situ phenology observations verified that the PlanetScope images detected the flowering crowns of tree species that turned into white or orange. This multitemporal image dataset also captured the flowering peak and species differences. The correlation coefficients between the multitemporal image signatures and in situ phenology observations were moderate to very strong (0.52–0.85). The results indicated that the 2019 GF event was a whole‐park phenomenon with the flowering peak in May. This study reports the first successful satellite‐based observations of a GF event and suggests the possibility of regional‐scale characterization of species‐level phenology in the dipterocarp forest, key information for biodiversity conservation in Southeast Asia.