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Juvenile-spacing Trials in the BC Interior (EP 922)


Beginning in 1982, a series of long-term experiments were established by the BC Ministry of Forests, Forest Science Program to document the growth and yield impacts of a wide range of post-thinning stand densities in early- and mid-rotation, fire- and harvest-origin lodgepole pine and Douglas-fir stands in the BC interior. A total of 14 installations (11 Pl; 3 Fd) are distributed among seven Forest Districts and five biogeoclimatic zones (ICH, IDF, MS, SBPS, SBS). Stand ages ranged from 7 to 60 years old at the time of trial establishment. (map)


To determine the effects of different levels of post-thinning density on the growth and development of various interior tree species growing under a variety of age, site, and stand conditions.


Seven of the trials include five post-thinning densities (500, 1000, 1500, 2000, 2500 st/ha) and an unthinned control. The 500 st/ha treatment is replaced with a 3000 st/ha treatment at one location. Six of the installations test 3 or 4 of the post-thinning densities and an unthinned control. All trials contain the 1000 and 1500 st/ha levels, plus controls. Eight of the trials contain two replicates of each treatment. Each treatment is replicated three times at six study sites.

At 13 of the 14 sites, thinned plots vary in size (0.03 to 0.20 ha) depending on post-thinning stand density. At one site, all plots are the same size (0.25 ha).

Thinned treatment plots at most study sites contain 100 trees (10 rows of 10 trees). Treatment plots at three study sites contain 144 trees (12 rows of 12 trees). At the site where a fixed plot size is used, treatment plots contain between 121 and 361 trees depending on the level of post-thinning density.

All of the installations are re-measured at 5-year intervals.

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Installation 1 (Pl) - unthinned control, age 22 Installation 1 (Pl) - 1500 sph, age 22
15 years after thinning



Johnstone, W.D. and F. J. van Thienen. 2004. A summary of early results from recent lodgepole pine thinning experiments in the British Columbia interior. B.C. Ministry of Forests, Victoria. Technical Report 016.


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Last Modified: 2007 APR 20.  Ministry contact: Frank van Thienen