Espacement trials of Mixed Douglas-fir and Western Red Cedar on Coastal Sites (EP 1130)


Douglas-fir and western redcedar are recommended for planting together on many sites throughout the Coastal Western Hemlock zone in British Columbia (Green and Klinka, 1994).  The two species have very different growth characteristics: Douglas-fir has rapid early height growth that is typical of a shade intolerant species while western redcedar has a slow early height growth typical of a shade tolerant species.  Decisions about planting mixtures require an understanding of how the different species respond when grown together.  Information is needed about the optimum spacing and management regimes of the species mixtures.


To determine if the productive capacity of a site is increased over that of pure species stands by mixing Douglas-fir and western red cedar, such that the total volume of mixed stands is greater that total volume of pure stands at 3 different densities.


This experiment was established in 1992 at MacDonald Lake near Sooke, B.C.  The experiment examines the effects on growth and development of Douglas-fir and western redcedar when grown at 500, 1000 and 1500 sph in Douglas-fir:western redcedar mixes of 1:0, 1:1, 1:3 and 0:1. Plot size is variable, consisting of 8 x 8 rows with a 2 tree-wide buffer on all sides. The trees in the 1:1 mixture were planted in an alternating pattern; the trees in the 1:3 mixture were planted as 1 row of a 1:1 mixture and the adjacent row as pure western redcedar.