Reaching for new heights: canopy laser scanning in the Peruvian Amazon

Large trees are vital for the functioning of tropical forests. They house a wide range of organisms, making them true biodiversity hotspots and play a key role in forest biomass storage.The Life On Trees (LOT) project is a research program in which all eukaryotic organisms on individual trees are surveyed, including plants, fungi, animals and protists. One of the goals of the research program is to explore the link between the distribution of the occurring organisms and the tree architecture of those large trees. To accurately quantify the structure of such trees and investigate the interplay between the tree and its surroundings, terrestrial laser scanning is currently used as a state-of-the-art technology. Terrestrial laser scanning (TLS) generally uses a laser scanner to scan trees from multiple viewpoints from the ground. In dense tropical forests, the tree canopy often reaches a height of 50 m or more. Due to the large distance between the scanner and the tree crown, even the best laser scanners have difficulty getting a clear view of the top of the canopy. For those large, colossal trees, data is limited and suffers a lot of occlusion. Since all scans are taken from the ground, data on the upperpart of branches is nonexistent. To assess this limitation of TLS, we explore how much additional 3D information is gained from the tree structure by collecting 3D scans inside the tree crown. With the aid of professional climbers, we lifted a RIEGL vz-400 laser scanner into a Dussia tree in Rio Abiseo National park located in the Peruvian Amazon. The selected tree is quite spectacular, it reaches a height of 50 m and a width of 45 m, and is covered with vegetation including many orchids and epiphytes hosting a wide variety of life forms. The first results of this project will be presented, focusing on the tree architecture with its impressive volume and branch length, and the benefits and challenges of scanning inside the tree crown.