Trees grow via photosynthesis, a process where light energy is converted into carbohydrates. Light is absorbed by leaves, which is why characterizing canopy foliage is critical to understanding tree functionality. This is also why structural traits such as the plant area index (PAI), that quantify canopy foliage, have found widespread use. Recently, Vicent Ribas Costa and Dr Jon Atherton, from the Optics of Photosyntesis Laboratory within Ecosystem Processes group at the Department of Forest Sciences, developed a new drone method to estimate important structural traits such as the PAI throughout the depth of tree canopies.
Though possible for individual plants, destructively measuring leaf area is extremely time consuming. For this reason, indirect optical methods such as hemispherical photography are usually used instead. Hemispherical photography involves taking wide angle pictures of tree crowns from the forest floor, which are subsequently run through image processing software. If sufficient care is taken these methods work well, but they are restricted to places accessible on foot. Dr Atherton said that: “we had an old problem of how to estimate foliage in the crowns, not below them” and added “we previously dismissed the use of drones to do this due to the problem of flying heavy equipment within the trees, until we stumbled across the potential of panoramic imagery”.
Most smart phones have a panorama mode and so do some off-the-shelf drones. Just like the fisheye photos collected by traditional hemispherical systems, panoramic imagery can also be run through image processing software to produce estimates of plant area. The researchers were able to use this knowledge to capture vertical profiles of leaf area through the depth of pine, spruce and birch canopies. Because they use a small, mass-produced drone, the new method has a low barrier to entry just like hemispherical photography. The new method is described in detail and published online in the New Phytologist (available also throug the group's webpage).
YouTube video showing the drone flying, and Jon Atherton explaining the technique : Using drones to measure leaf area index
Research group's website explains some of the science behind the use of panoramic photography (does not cover drones): https://cano.fi/
YouTube video showing the drone flying, and Jon Atherton explaining the technique : Using drones to measure leaf area index
Research group's website explains some of the science behind the use of panoramic photography (does not cover drones): https://cano.fi/
YouTube video showing the drone flying, and Jon Atherton explaining the technique : Using drones to measure leaf area index
Research group's website explains some of the science behind the use of panoramic photography (does not cover drones): https://cano.fi/
YouTube video showing the drone flying, and Jon Atherton explaining the technique : Using drones to measure leaf area index
Research group's website explains some of the science behind the use of panoramic photography (does not cover drones): https://cano.fi/