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Excerpt from Natural Regeneration 10 Years After a Douglas-Fir Tussock Moth Outbreak in Northeastern Oregon Forest managers feared that natural regeneration would not be adequate to reforest the larger patch kills of grand fir and Douglas-fir and consequently planted many of the areas after clearcut and partial cut salvage logging (seidel and Head After the outbreak there were also questions about adequacy, timing, and species of natural regeneration and on environmental factors responsible for success or failure of regeneration establishment. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.
Tree damage occurring immediately after an outbreak of Douglas-fir tussock moth, Orgyia Pseudotsugata McD., and stand conditions 10 years later are described. Because of increased radial growth and ingrowth in the 10-year postoutbreak period, good evidence indicates that tree damage caused by the tussock moth may not be as severe in the overall stand dynamics as previously pictured. The insect probably plays a key role as a phytophagous regulator of primary production in some second-growth white fir stands in California and elsewhere.
Case histories of five tussock moth outbreaks that occurred in California and Oregon between 1935 and 1965 are discussed. Information is given on the size and duration of the outbreaks, the presence of natural control agents and the damage caused. Most of the outbreaks were eventually treated with DDT. However, enough information was available from untreated portions to show the probable trend of natural events in the absence of direct control. Repeated patterns observed in each of the outbreaks enabled certain generalizations to be made about natural population behavior and tree impact. All infestations followed a 3-year cycle with inconspicuous to minimal defoliation the first year, severe foliage loss the second year, and ultimate collapse of the population by the end of the third year. The most severe tree damage occurred in the second year. Additional loss of foliage before population collapse in the third year was usually of minor importance in terms of total impact. Although other natural factors were involved, a virus disease appeared to be the principal cause of insect mortality during collapse.