Treetop leaf sampling ( canopy foliar sampling) at forested NEON (The National Science Foundation’s National Ecological Observatory Network ) field sites just got a whole lot easier. We’ve added a new tool to our kit: an unmanned aerial vehicle (UAV), or drone. Drone-based foliar sampling has been added as an official NEON protocol for forested sites. The UAV will also be available for use in the Assignable Assets program.
Faster, Safer Canopy Sampling with UAVs
The NEON program has been experimenting with drone-based foliar sampling since 2019, when we conducted a pilot programwith Outreach Robotics, the creators of the DeLeaves tree sampling tool. Since then, DeLeaves has made significant improvements in range, portability, and ease of use for the system.
After training additional pilots in 2021, we decided to invest in a UAV of our own. The Matrice 300 RTK commercial drone is about 2′ by 2.5′ and has a payload capacity of ~3 kg, enough to support the DeLeaves sampling arm, camera, and a foliar sample. It can also be outfitted with other types of equipment, such as a lidar system or spectrometer.
This is the first UAV purchased by the NEON project, though previous flights have been performed at NEON sites using Battelle-owned drones as part of a series of internal research and development (IRAD) grants aimed at improving drone research capabilities across the organization. Battelle operates the NEON program on behalf of the National Science Foundation (NSF).
Tree foliar sampling is the first drone-based protocol to be added to NEON’s sampling design. NEON collects foliar samples from as close to the canopy top as possible, and does chemical analyses of these samples, to provide ground-truthing for the hyperspectral data from the Airborne Observation Platform (AOP).
Previously, field staff used line launchers to collect leaf samples from the tree canopy—a process that is both time-consuming and imprecise. The line launchers collect leaf samples from the sides of the tree instead of the top of the canopy. This matters because leaves from lower in the canopy do not get as much sunlight as leaves at the top, resulting in different chemical makeup and growth patterns. As a result, it is harder to correlate hyperspectral data from with chemical analysis of foliar samples for ground truthing.
Using drones to collect samples from the canopy tops is safer, faster, and easier than other methods. Using a UAV and the DeLeaves sampling tool, it is possible to precisely target samples from the very top of the canopy—the part of the canopy viewed by the AOP—for better ground truthing data. In addition, the drone protocol saves considerable time in the field.
Dave Durden, a senior research scientist for the NEON program and the primary investigator for the drone project, says, “Canopy sampling is conducted at peak greenness for each site, which is already a tremendously busy time for our field scientists. Anything that gives our field science team some time back is a big win. This has greatly reduced the time needed for canopy sampling.” Using the drone, the team was able to cut time for canopy sampling at mixed forest sites from 3-4 weeks per site to just 1-1.5 weeks per site.