SOME OBSERVATIONS ON THINNING FORESTS IN THE COASTAL REGION OF BRITISH COLUMBIA

Thinning is a potential forest practice awaiting economic evidence of its merit. In the south coast zone of British Columbia, nearly 2 million acres of immature Douglas fir and western hemlock forests offer the possibility of making thinnings to maximize the productive capacity of sustained yield units. The commercial feasibility of any one thinning should not overrule the silvicultural attributes of repeated thinnings to mould the stands in a forest to a desired structure. There is no economic or biological necessity to clearcut immature stands on short rotations rather than adopt thinning regimes within a rotation twice as long. Careful attention to location of skid trails, landings and roads should precede the marking job. If thinnings become widely applied, the need for mechanization of yarding processes to cope with difficulties of terrain may probably give rise to thinning schemes which alternate thinned patches with clearcut patches. Management, engineering and silvicultural aspects are very much in need of integrated research on a scale large enough to entertain sustained yield objectives and realistic costs. The application of crown thinnings meets economic and biological requirements. Experience rather than science must still underlie marking techniques until facts are available concerning the growth performance and intrinsic wood qualities of particular phenotypes in relation to tree-spacing. As a result of tending plantations since they were 13 years old, the gross and merchantable volumes per acre at 21 years of age are lower in a plot having 400 free-growing stems than in a plot with 1,200 competitors, but different stand development is expected in the next decade as the degree of competition becomes a more important influence. There is evidence that a thinning which yields #3 logs to an 8″ top and/or poles and piling will return a small profit, terrain and transportation permitting, and that when a thinning yields only pulpwood or the larger percentage of the total thinning yield is pulpwood, that it will not usually meet the costs of the operation.