Western white pine
Western white pine (Pw) - Pinus monticola
Western white pine is a medium- to large-sized (exceptionally >70 m tall) evergreen conifer. At maturity, it has a sparse, variable crown, short branches (except for cone bearing branches which are long), and dark gray bark broken into small, scaly plates. It is an important timber species; its wood is desired for sash, frames, doors, interior paneling, building construction, match wood, and other products.
|Geographic Range||Geographic element:
Western North American/mainly Cordilleran and less Pacific
Distribution in Western North America:
central and (south) in the Pacific region, central and south in the Cordilleran region
subalpine boreal - cool temperate - cool mesothermal
submontane - montane - subalpine
Occurrence in biogeoclimatic zones:
(lower southern MH), (lower southern ESSF), MS, wetter IDF, ICH, (CDF), CWH
The tolerance of western white pine for dry and cold climates is lower than that of interior common douglas. However, western white pine occurs in the lower, southern MH and ESSF zones.
Range of soil moisture regimes:
(moderately dry) - slightly dry - fresh - moist - very moist - wet
Range of soil nutrient regimes:
(poor) - medium - rich - very rich; calciphytic
Western white pine does not grow in very acid peat bogs, but it may grow on wet sites that are slightly acidic to neutral (e.g., skunk cabbage sites).
Western white pine grows well in calcium-rich soils or on seepage sites. It was found experimentally that the requirements of western white pine for calcium and magnesium are fairly high (Krajina 1969). When deprived of calcium, western white pine is first affected strongly by calcium dieback of its root system. Western white pine does not readily develop new roots when the older roots are killed. Therefore, calcium deficiency becomes a strong factor in the survival of western white pine.
Many young western white pine trees are eliminated in strongly leached calcium-poor soils, such as in the CWH zone. In the ICH zone, this elimination takes place when trees are much older and is therefore more easily noticed. When the trees (i.e., their roots) are already affected by calcium deficiency, they may be readily killed by drought. Plants experimentally inflicted with calcium deficiency frequently appear to wilt, even when water is available. In other cases of calcium deficiency, western white pine collapses more slowly - from the top of the crown down - by a process of chlorosis and later necrosis.
|Root System Characteristics||Approximately 65 percent of the total root system occurs in the uppermost 30 cm of soil. The root system of mature trees can spread 8 m laterally from the root collar with verticals descending off the lateral system. Roots of western white pine are associated with both ecto- and endo-mycorrhizae.|
|Associated tree species and successional role||In British Columbia, western white pine grows predominantly in even-aged, post-fire, mixed-species stands with a variety of species, and usually persists to late seral stages. It associates as a scattered species with a great number of species such as: Pacific silver fir, Grand fir, Subalpine fir, Western larch, Engelmann spruce, Common douglas, Western redcedar, and Western hemlock. It is present in early, mid-, and late stages of secondary succession; a minor component in the old-growth stands in cool temperate and mesothermal climates.|
|Genetics||Western white pine is different in genetic variation from most of other conifers. There is little geographical or ecological variation in western white pine populations. Work on blister rust indicated considerable heritability of resistance.|
|Notes||Western white pine is a very productive and desirable species considering its rapid growth, clean bole with minimum taper, narrow crown, and non-resinous wood. The major hazard limiting its wider application is blister rust. More detailed silvics information is given by:
Graham, R.T. 1990. Pinus monticola. Pp. 385-394 in R.M. Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol. 1. Agri. Handbook 654, USDA For. Serv., Washington, D.C.