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-52001:T
INVENTORY OF BARK BEETLE MORTALITY IN CONIFEROUS FORESTS
WITH COLOR AND COLOR IR PHOTOGRAPHY
by
William M. Ciesla and William H. Klein
Forest Insect and Disease Management
Methods Application Group
USDA Forest Service
Davis, California, USA
Abstract
Coniferous bark beetles are among the most destructive forest insect pests in
North. America. They periodically reach epidemic proportions, causing extensive
loss to forest resources. Timely, accurate inventories on status of outbreaks
and magnitude of loss are needed for management decisions. Sampling systems
using color and color IR aerial photography are an effective means of acquiring
inventory data.
Data requirements for reporting forest insect and disease losses have been
defined at two managerial levels, the resource manager who must make "on-the-
ground" management decisions, and the national or Regional program manager
where quantitative summaries are required to establish priorities and allocate
funds for forest pest management activities.
In 1977, we designed and conducted surveys in lodgepole and ponderosa pine
forests in Idaho and South Dakota to quantify annual timber mortality by
mountain pine beetle, Dendroctonus ponderosae. These surveys were designed
to provide in-place information needed by the resource manager and statistical
summaries required at the national level. Aerial sketch mapping combined
with large-scale color photography and ground sampling were used to obtain
the required data. We are currently evaluating high-resolution, small-scale
reconnaissance photography (1:30,000) for stratification of outbreaks into
intensity classes and allocation of second stage samples.
Introduction
The bark beetles of the family Scolytidae are among the most damaging insects
in North American coniferous forests. Insects of the genera Dendroctonus,
Ips, and Scolytus periodically reach outbreak proportions and cause extensive
tree mortality. Available data indicate that coniferous bark beetles are
responsible for up to 90% of the insect-caused tree mortality in the United
States (USDA 1958).
Bark beetles are an integral part of the coniferous forest ecosystem in North
America. They can be instrumental in conversion of pure stands of one
Species to mixed species forests, or in combination with wildfire create
conditions favorable for regeneration of vast areas of pure stands of a
single species. Bark beetle outbreaks undoubtedly have occurred long before
man made significant use of the forest, and sketchy records of bark beetle