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UBC Theses and Dissertations

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UBC Theses and Dissertations

Distribution, Management, Variability and Economics of Sitka spruce (Picea sitchensis (Bong.) Carr.) in coastal British Columbia Mac Siúrtáin, Máirtín Pádraig

Abstract

Two major aspects of Sitka spruce (Picea sitchensis (Bong.) Carr.) in coastal British Columbia were investigated: 1. The factors which influence the management of the Species; 2. The quantification of the variability of naturally regenerated stands and plantations of the species. Factors analysed were natural distribution, ecological classification, the white pine weevil (Pissodes strobi Peck.), current management, genetic improvement, volume producing potential and economic importance of the species. The major factor influencing the management of Sitka spruce, within its natural range, has been and will continue to be the white pine weevil. The impact of the white pine weevil on the management of Sitka spruce has resulted in avoidance of the species in reforestation programs throughout a very large part of the natural range. Consequently, the natural distribution of Sitka spruce in coastal British Columbia is much greater than the range within which the species can be economically managed, therefore a distinction must be made between the natural and economic range of the species. In effect, management of Sitka spruce, in coastal British Columbia, is confined to the northern and western extremes of Vancouver Island, the mainland mid-coast regions, the lower Nass and Skeena River Valleys and the Queen Charlotte Islands. Analysis of variability of plantation grown Sitka spruce indicated that the species has very rapid establishment potential on ecologically suitable weevil free sites. Wide variation in plantation performance prompted the preliminary development of a simple, objective method for assessing average juvenile total height growth of Sitka spruce plantations in the Vancouver Forest, Region. The assessment system was derived from the relationship between total age and total height, and involved selecting and computing confidence limits for the best interpretive mathematical model that could be derived from the data. The proposed system permits probability to be assigned to the assessment, thus the term Probability Assessment System. Preliminary development of this assessment system indicated that the system was straightforward, and would be quick and inexpensive to apply in the forest, however, it was recommended that the system undergo further development and testing before being used operationally. The variability within naturally regenerated stands in coastal British Columbia reflects an underutilization of Sitka spruce in comparison to the intensively managed Sitka spruce plantations of Great Britain and Ireland. Higher average productivity in Great Britain and Ireland was attributed to the higher level of intensive forest management practiced by British and Irish foresters. It was established that there is more area of Sitka spruce in Great Britain and Ireland than in coastal British Columbia, and of even greater significance is that by the turn of the century Great Britain and Ireland will surpass coastal British Columbia in annual production of Sitka spruce. Analysis of variability and economics indicated the substantial volume and value producing potential of Sitka spruce. A management strategy likely to maximize volume and value through wide spacing and control of stocking and stand density has been presented. Finally, suggestions for increasing funding for intensive forest management of Sitka spruce and other high yielding species in coastal British Columbia, by revision of the present restrictive log export policy, were made.

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