How does canopy height regulate autumn photosynthetic phenology in the Northern Hemisphere?

Abstract

<p>Autumn photosynthetic phenology strongly regulates the length of growing season and terrestrial carbon cycle, providing feedbacks to climate change. While the climatic drivers of autumn photosynthetic phenology have received considerable attention, the regulation by forest structural features is frequently overlooked. Here, we used spaceborne LiDAR observations of canopy height, two sets of canopy height products, and satellite solar-induced chlorophyll, to characterize the role of canopy height in autumn photosynthetic phenology from 2001 to 2020. We found strong dependencies of autumn photosynthetic phenology on canopy height in 65.2% of the northern forest. Taller trees tend to end the growing season later, likely due to the enhanced acquisition of solar radiation associated with increased canopy height. Additionally, taller trees have deeper root system to maintain strong hydraulic transport capacity and higher resistance to water stress. This study highlights the importance of forest structure in regulating vegetation phenology and contributes to enhancement of phenological models and carbon cycle simulations.</p>