Lidar data capture fuel and consumption across scales
Light Detection and Ranging (lidar), also known as laser scanning, is a type of remote sensing data collection system that captures three-dimensional data about vegetation and fuel structure, both of which are relevant to wildfire research and management. What makes lidar data valuable, you might ask? Well, it can be used to show the fuel load in a forest at a particular point in time as well as fuel consumption by a fire (if data are obtained both before and after a fire). This lidar data can then be combined with ground-truthed measurements of fuels to improve maps of fuels and fuel consumption. These maps are in high demand from the USDA Forest Service and other fuel and fire management agencies to more accurately estimate smoke emissions and plan revegetation activities.
Lidar systems can be mounted on a tripod, the ground, a mobile backpack unit, an aircraft, or even the International Space Station, making it a flexible option. However, it is important to validate the accuracy of the data in different situations. Our recent research demonstrated that terrestrial and mobile scanning lidars perform comparably well for distinguishing fuel layers in a forest, which include tree canopy, shrub understory, grasses, and downed woody debris and litter (needles and leaves) on the forest floor. In contrast, we also found that airborne lidar collected overhead from aircraft (whether piloted or not) has less sensitivity to fuels and consumption on the ground because the tree canopy obstructs the signal.
Some of our latest research showed that when a fire burns through a forest where field plots and lidar coverage already exist, then it is possible to estimate fuel consumption directly from that data, which is more accurate than other methods. This means that having better access to pre-fire lidar data would help researchers and managers accurately estimate smoke emissions and effects of both wildfires and prescribed fires.
Luckily, the Forest Service and other agencies are spearheading increasingly widespread airborne lidar acquisitions nationally, and lidar data are also being collected from the International Space Station. Access to this new data will increase the accuracy with which researchers and managers can work together to monitor forest fuel biomass and reduce the uncertainty around fuel biomass losses and emissions caused by fires. The three-dimensional fuel maps derived from lidar can also offer better fuel load information inputs into fire behavior and smoke models, which managers need to answer questions about where to install fuel treatments in order to mitigate high severity fires and fire effects.
This research was possible thanks to the Fire And Smoke Model Evaluation Experiment (FASMEE), funded by the Joint Fire Science Program during the planning phase (Phase 1), and then by the USFS during the measurements phase (Phase 2).