Some factors affecting colonization and distribution of bark-beetles within selectively logged areas
Creators: name: Reid, Robert William
Publisher: name: University of British Columbia
Year: 2012

description: Forest insect populations, like many other animal populations, are not uniformly distributed throughout an area but are found in various degrees of concentration regionally and locally. Bark-beetles constitute a major group of economically important forest insects and the causes of their variable concentrations are only partially understood. Among the important circumstances with which variable bark-beetle populations are associated are those encountered in forest stands undergoing cutting practices. In such stands, the conditions affecting bark-beetles vary according to different cutting methods which coincidentally produce different quantities of food in the form of slash, and expose that food, as well as the environment generally to altered micro - and meso - climates. The present investigation was undertaken to determine and explain some of the major factors underlying the variability in concentration of certain bark-beetles in a forest stand cut in certain selected ways. An investigation of this nature may be carried out in an area chosen for this purpose alone, or may be coordinated with a programme already designed for silvicultural purposes. There are advantages and disadvantages either way. The requirements for entomological experimentation are not necessarily best provided by the experimental design which is adequate for silvicultural purposes. On the other hand, the results from such a coordinated study carry the weight of authenticity for representing an actual forestry condition, and not merely a hypothetical case. In addition, the use of the materials provided by a silvicultural study make possible an entomological study which would otherwise be too costly of time and effort. Indeed, one of the chief obstacles to this type of study, heretofore, has been the lack of selectively cut stands. In 1952 the Dominion Forest Service initiated studies on selective cutting of lodgepole pine (Plnus contorta Dougl.) in the foothills region of Alberta. The opportunity was here presented for getting the special forestry conditions for the desired entomological study. The entire entomological Investigation, of which this study is a part, had a broad basis. Ultimately, it is desired to know something of the make-up of the insect complex associated with stands selectively cut in different ways, to learn something of the factors responsible for the variation of concentration, and to observe the effect of the insect population on the forest. The present investigation is an initial study to determine the manner in which the bark-beetles disperse within newly logged regions, and to relate their type of dispersal with the factors common to the environment. The insect complex was made up chiefly of Scolytids, Cerambycids, and Buprestids. Among the species, Ips pini Say. formed the most important component and the one which provided the most suitable data for analytical study. Accordingly the data concerning this species form the basis for the conclusions arrived at in this study.