Assessing Insect-Induced Tree Mortality across Large Areas with High-Resolution Aerial Photography in a Multistage Sample
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, 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, AZ, within the Kaibab National Forest. Piñon pine mortality caused by piñon ips bark beetles (Ips confusus (LeConte)) was assessed from high-resolution digital aerial imagery within percent-cover strata using a digital dot grid. The sample revealed that dead trees covered 7.0 ±0.3 percent of the study area. As a percentage of total tree cover, 20.0 ±0.8-percent mortality had occurred. The cost to obtain this estimate was approximately $0.04 per acre.
- Introduction : Over the past century, stand density and fuel loading have increased in forests and rangelands throughout the United States, leading to a general decline in ecosystem health.
- Assessing Piñon Pine Mortality : Beginning around 2002, extensive piñon pine (especially Pinus edulis and P. monophylla) mortality appeared throughout the Western United States.
- Conclusions : Forests and rangelands throughout the United States are at risk of severe insect and disease outbreaks and catastrophic wildfires.
Encyclopedia ID: p3357
