Response of Photochemical Reflectance Index to Microclimate Variables in Oil Palm Plantation

Extreme climate events such as drought and high temperature are occurring increasingly frequently in Thailand. The drought negatively affects crops and their productivity. A reflectance-based remote sensing photosynthetic parameter called the photochemical reflectance index (PRI) is a widely used for monitoring vegetation health. This index can capture the xanthophyll cycle activity resulting from drought-induced down-regulation in photosynthesis. Therefore, this paper aims to study the key microclimate factors affecting the PRI of oil palms in the south of Thailand during 2018–2021. We found that microclimate variations led to severe drought in the dry season during 2020. As a results, the drought response in oil palm can be captured with the PRI reduction. The PRI is mainly controlled by vapor pressure deficit (VPD) and moderately controlled by air temperature and soil water content. The PRI is one of the best candidates for the understanding of the oil palm adaption under future climate change.