Weyerhaeuser Company installed a trial in south central British Columbia to monitor changes in stand density and species composition of natural regeneration (ingress) of trees occurring after salvaging fire-killed timber. The trial included three sites, each sampled with six randomly located clusters of sixteen 1 x 1 m sample plots. The fires occurred in the summer of 2003 and the timber was salvaged in the winter logging season of 2003/04. The regenerating trees were counted in the sample plots to estimate stand density and species composition after the 2005 and 2007 growing seasons (two and four growing seasons after salvage). Heights were also measured and brush stems counted in the 2007 measurement. Site 1 regenerated to almost pure Douglas-fir (Fd) estimated at 256,000 trees/ha (98% Fd) after the 2005 growing season and 183,000/ha (99% Fd) after the 2007 season (29% reduction). After the 2007 season, the Fd was about 19 cm in height in 2007 and was overtopped by about 34,000 stems/ha of willow with average height about 50 cm. About 800/ha of aspen (At) had also regenerated.
Site 2 regenerated to about 441,000 trees/ha after two growing seasons and decreased 9% two years later to 402,000/ha. The 2007 species mix was western larch (Lw) 58%, Fd 20%, ponderosa pine (Py) 14%, interior spruce (Sx) 7%, and 1% At. The At was estimated at 20 cm in height, Lw 43 cm, and 53,000/ha willow at 40 cm.
Site 3 regenerated to almost pure lodgepole pine (Pl) estimated at 143,000/ha (83% Pl) after two growing seasons and 191,000/ha (76% Pl) after four seasons (33% increase over the two years). The Pl density increased by 22% but most ingress was At that increased from 11,000 to 33,000/ha. Willow also invaded the site with an estimated 108,000 stems/ha. The Pl regeneration was about 27 cm in height compared to At about 45 cm and willow 75 cm. The cutblocks containing these study sites will soon require juvenile spacing and brushing to meet BC Government free-growing regulations. This report recommends leaving the plots and a surrounding buffer area untreated, with continued remeasurements on two-year intervals
until stand dynamics slow.