Thinning and pruning: Demonstrations Plots (EP 204-205)


The project was established in 1931 in a 20-year-old naturally regenerated stand of Douglas fir, near Lake Cowichan, primarily as a demonstration plots for visitors to the newly established Cowichan Lake Research Station. Please review a brief history of the establishment of the Cowichan Lake Research Station.


  1. Demonstrations plots.
  2. Provide growth and yield data under pruning and thinning.


The 2 plots were 0.4 ha with a 9.14 m surround.  About 60 dominant trees per acre (150/ha) were marked as crop trees and pruned to a height of 14 feet (4.3 m).  These crop trees were subsequently pruned up to 34 feet (10 m) at 36-years to provide 2 short log lengths or one log length of clear lumber.  At the same time, a light thinning removing the dead, dying and suppressed trees reduced the stand from 1200 stems/acre (3000/ha) to 750 spa (1850/ha).  Since establishment, the plots have been thinned 6 times. In 1945, 13 crop trees were replaced with substitutes from adjacent numbered trees.  In 1957, a number of crop trees were felled for a veneer recovery study.  Since then, dead and dying trees affected by root rot have been removed.


Inactive due to heavy root rot.  In winter of 1993/94 plots were combined into one, and all plot trees and ingrowth trees were retagged, measured and stem-mapped to examine rate of spread of root rot.  


  • Warrick, G. 1948. Thinning and pruning of second-growth Douglas-fir in the coastal region of British Columbia. B.C. Min. For., Victoria, B.C. Res. Note 13.