Forest structure and dynamics are changing rapidly around the world as a consequence of climate-change-related pests, droughts and wildfires, and human use. It is critical to understand these changes at the process level (e.g. demographic performance of trees) to accurately predict subsequent forest responses, including impacts on carbon and water cycles, surface-atmosphere energy dynamics, and ecological communities. Remote sensing may offer a critical tool to assess and understand these changes at large scales if it can connect observations of forest canopies to underlying biological processes such as demography. Too be effective such an approach must be able to assess the full spectrum of forest demographic groups, including those that fall primarily in the shade of larger trees. Here we ask whether recent advances can answer this challenge by reconstructing high-resolution canopy structure in 3D from airborne LiDAR data and then associating LiDAR derived leaf area strata and leaf area light environments with the stem frequency, biomass and performance of trees in different demographic groups.
Results/Conclusions
ocusing on Amazonian forests, we demonstrate that forest structure (e.g., size distributions) can be retrieved by accounting for tree architecture over light environments. Furthermore, by linking LiDAR derived light environments with LiDAR derived (or ground measured) size classes, we show that even a single LiDAR survey can help reveal forest dynamics, while multiple LiDAR surveys across years allow for direct assessment of the role of canopy light environments in demographic dynamics. We show that estimates of canopy functional traits and biophysical environments in three dimensions can improve estimates of forest ecosystem and community dynamics revealed with this approach, including across scales utilizing remote measurements of structure from tree plot to space-borne scales. We conclude that this approach can inform ecosystem and community demographic models that explicitly represent forest dynamics and vertical canopy structure, and thereby significantly advance our understanding of forest disturbance and its consequences in the Anthropocene.