Assessing Insect-Induced Tree Mortality Across Large Areas with High-Resolution Aerial Photography in a Multistage Sample

Randy Hamilton, Kevin Megown, Jim Ellenwood, Henry Lachowski, and Paul Maus

USDA Forest Service Remote Sensing Applications Center (1, 2, 4, 5) and Forest Health Technology Enterprise Team (3)

In recent years, unprecedented tree mortality has occurred throughout the National Forests due to insect infestations and disease outbreaks. The magnitude and extent of mortality, coupled with the lack of routine monitoring in some areas, has made it difficult to assess the damage and associated ecological impact and fire hazard in a timely and cost effective manner. To aid forest managers in assessing the damage, a cost effective multistage sampling method, using high-resolution digital aerial photography, was developed to estimate overall mortality across large areas. The method was tested within a 332,000-acre piñon/juniper woodland west of Flagstaff, Arizona, within the Kaibab National Forest. Severe piñon pine mortality has occurred in this area in recent years. Piñon mortality was assessed (sampled) using high-resolution digital aerial photographs within vegetation-type and percent-cover strata. The sample revealed that dead trees covered 7±0.3% of the study area. As a percentage of total tree cover, 20±0.5% mortality had occurred. The cost to obtain this estimate was approximately $0.04 per acre. A second study area covering the entire subalpine fir/Engelmann spruce cover type of the Bighorn National Forest, west of Sheridan, Wyoming, is currently under investigation.

Monitoring Methods Session - Tuesday Afternoon

corresponding author:

Randy Hamilton
USDA Forest Service
Remote Sensing Applications Center
2222 West 2300 South
Salt Lake City, UT  84119
801-975-3845
randyhamilton@fs.fed.us