Novel integration of high resolution satellites with drone flights improves monitoring of tree-crown scale autumn leaf phenology

Abstract

Autumn leaf phenology signals the end of leaf growing season and shows large inter-crown variability in response to global climate change, which strongly regulates the carbon, water, and nutrient cycles from individual tree-crowns up to ecosystems. However, critical challenges remain with the monitoring of tree-crown scale autumn leaf phenology over large spatial coverage due to the lack of spatially explicit information of individual tree-crowns and high-quality and high-resolution time-series observations. Traditional field and proximate remote sensing methods (eg field observations, phenocam measurements and UAV flights) are the commonly-used means to monitor crown-scale leaf phenology, but are constrained to a very limited footprint and time span. Satellite remote sensing might provide another alternative solution, but most satellites remain too coarse spatial resolution to resolve individual tree-crowns.