Use of satellite-derived hyperspectral indices to identify stress symptoms in anAustrocedrus chilensisforest infested by the aphidCinara cupressi

Abstract

We explore the suitability of vegetation indices derived from satellite hyperspectral data for identifying stress symptoms induced by the invasion of cypress aphid (Cinara cupressi Buckton complex) in a Ciprés de La Cordillera (Austrocedrus chilensis (D. Don) Pic.Serm. & M.P. Bizzarri) forest, located in the Andes mountain range of central Chile. A set of 11 indices related to leaf physiology was retrieved from the processing of a Hyperion image of the study area. The indicies were correlated with the percentage of chlorosis and necrosis of the crown foliage of infested trees estimated visually in the field. The strongest correlations were recorded for two anthocyanin reflectance indices and the photochemical reflectance index. Vegetation indices sensitive to foliage quantity were weakly correlated with field data, likely due to the influence of wind-induced defoliation. Even when tree stands presented fairly similar levels of chlorosis and necrosis, as well as moderate vegetation cover, the results indicate that vegetation indices derived from hyperspectral images are potentially very useful in the detection, assessment and monitoring of the damage caused by the aphid.