Aerial Detection Monitoring
Insects and diseases are integral components of forest ecosystems. They play a critical role in shaping forest lands, nutrient recycling, and small-scale disturbance. Disturbances result in changes in the ecosystem function which often means mortality of trees. Tree mortality and other forest damage is detected by annual aerial surveys over forested lands. The primary purpose of the aerial survey is to create sketch maps of areas containing current year conifer and hardwood mortality, defoliation, and other damage. Number of trees and acres with damage are calculated for areas surveyed and reported annually using the methodology described below.
Recent tree mortality and currently active non-mortality damage is sketch mapped on a mobile device by an aerial observer flying in a small fixed wing aircraft at ≈1000’ AGL searching for visibly dried and discolored foliage, typically yellow to reddish brown. Generally, two observers are onboard the aircraft surveying on opposite sides with about a two-mile swath width for each surveyor.
Drawn polygons are then attributed with the following: a) damage type, mortality or one of several non-lethal damage types (topkill, defoliation, branch flagging, die back or discoloration) b) percentage category of forest area affected, c) affected tree species and d) probable damage-causing agent (root disease, bark beetles, etc.).
Percent of Forest Area Affected is expressed as a severity class. VL very light 13%, L light 4-10%, M moderate 11-29%, H high 30-50% and VH Very Heavy >50%
Generally, areas with <1% of Forested Area Affected of mortality is considered to have "background" or "normal" levels of mortality and are not usually mapped as polygons during the flight. However, they may be mapped as point data especially if low levels of mortality are indicative of a localized pest-related event. Point data is also broken down into 5 classes: 1 Tree, 2-5 Trees, 6-15 Trees, 16-30 Trees and >30 Trees affected. All other attribute information is identical to polygon data.
Affected tree species is recorded to species level if possible (Sugar Pine and White Fir), or to genus level (pine, fir). Damage occurring on any tree species should be mapped.
Multiple damage types can be listed for each polygon, though more typically overlapping portions of polygons are double or even triple attributed in the overlapping areas. Thus, in areas where two or more tree species affected or two or more damage types occur, the surveyor will typically draw two or more different polygons reflecting the actual location and extent of mortality for each different host or damage type. During editing, the overlapping portions will then be multi-attributed. Likewise, point data can overlap polygon data.
Aerial Survey Results
Special Survey: Early Season Drought