LIDAR Deployed to Help Save Forests

Researchers at the University of Arkansas have begun a program using cutting-edge spatial technologies to study the aftermath of an insect infestation that has devastated red oak populations in Arkansas and Missouri. Dr. Fred Stephen, a professor of entomology and Dr. Jason Tullis, a geosciences professor are using light detection and ranging (LIDAR), to accurately map a forested area of the Ozark National Forest where many trees succumbed to red oak borers.

The LIDAR instrument, mounted in an airplane, shoots about 50,000 near-infrared laser pulses per second at the earth. Depending on the path of a given laser pulse, up to four return pulses are recorded by the instrument's receiver. On a typical red oak tree, return pulses originate from leaves, branches, the trunk and the ground.

Using GPS, gyroscopes and other instrumentation, the location where each LIDAR return pulse originated is computed, allowing the researchers to study a three-dimensional “point cloud," an example of which is shown above, representing forest structure and terrain. This information will be used in conjunction with field studies to try to find patterns that might help explain what trees are vulnerable to infestation, and thereby help help foresters shape forest management practices to protect them.

The red oak borer, lived in relative obscurity in red oak trees in the Ozark Mountains until 1999. Then foresters began noticing oaks dying in droves. When Professor Stephen and his students examined the trees, they found them filled with borers. In 2005, the red oak borer population fell back to normal levels.

Researchers are trying to understand why the sudden infestation happened, and to keep it from happening again. “GIS and remote sensing can help find a pattern, and this can help us understand the underlying science of the ecosystem,” Dr. Tullis said.