Canadian Forest Service Publications
Canada's oldest permanent sample plots - thinning in white and red pine. 1998. Burgess, D.M.; Robinson, C.F. The Forestry Chronicle 74(4): 606-616.
Issued by: Pacific Forestry Centre
Catalog ID: 5054
Availability: Order paper copy (free)
Two of the oldest permanent sample plots (PSPs) in Canada were set up at Petawawa, Ontario (45o 57'N, 77o 34'W) to examine the effect of thinning on the development of natural white (Pinus strobus L.) and red pine (Pinus resinosa Ait.). Field data were collected periodically, starting in 1918 when the stand was 40 years old and continuing for 71 years. Six thinning treatments were completed, beginning in 1918, and then in 1933, 1941, 1959, 1969 and 1989. The intensity of thinning varied through time with 14, 27, 38, 8, 30 and 7% of the basal area removed. The sawlog volume mean annual increment for the thinned plot remained stable at about five m3/ha/yr, but the sawlog volume periodic annual increment for the control declined markedly during the last 10-year measurement period to less than 2 m3/ha/yr. The residual volume was higher in the control; but, if the harvested sawlog volume (264.5 m3/ha) was added to the residual sawlog volume (301.3 m3/ha) for PSP one, then the sawlog production on the thinned plot has been about the same and its residual volume concentrated on fewer, larger and more valuable trees. The level of natural mortality in the control plot (129.7 m3/ha of sawlog volume) was greater than 10 times that in the thinned plot, thereby adding more coarse woody debris to improve wildlife habitat. These two approaches had a major influence on stand development. The approach used will depend on specific stand-level management objectives.