Arbutus (Ra) - Arbutus menziesii
- Geographic range and ecological amplitudes
- Tolerances and damaging agents
- Silvical characteristics
- Genetics and notes
Pacific madrone is a tall shrub to small or medium-sized (< 30m tall), evergreen broad-leaved tree, at maturity with an irregular, commonly short, umbrella-like shaped crown, leaning and crooked stem, and smooth, thin, reddish-brown bark, peeling in papery flakes and strips in summer to reveal olive green beneath. The bark is scaly at maturity. Pacific madrone is not grown for timber production; its wood utilization potential is very low.
Western North American/mainly Pacific and less Cordilleran
Distribution in Western North America:
central and south in the Pacific region; (central) and (south) in the Cordilleran region
cool and warm mesothermal
submontane - montane
Occurrence in biogeoclimatic zones:
Range of soil moisture regimes:
very dry - moderately dry - slightly dry - (fresh)
Range of soil nutrient regimes:
very poor - poor - medium - (rich); oxylophytic
On the basis of field studies, Krajina (1969) concluded that the nutritional requirements of Pacific madrone for nitrogen, calcium, magnesium, potassium, and phosphorus are low; no plant indicators of available soil nitrate-N grow in the understory of Pacific madrone-dominated ecosystems.
Root system characteristics
The root system of Pacific madrone exhibits large variations in pattern and length. 50-year-old trees often have a well-developed root burl from which a spreading root system composed of deep-spreading lateral roots develops. Roots are associated with ericoid mycorrhizae.
|Tolerance to||Tolerance class||Comments|
|low light||L||high tolerance in the seedling stage|
|frost||L||very sensitive to frost|
|heat||H||tolerates insolated sites|
|water deficit||H||very frequent on water-deficient sites|
|water surplus||L||absent on water-surplus sites|
|nutrient (mainly N) deficiency||H||tolerates acid, leached, very poor soils|
|Damaging agent||Resistance class||Comments|
|snow||M||snowpack is infrequent in submaritime cool mesothermal climates|
|wind||M||firmly rooted, even on rock outcrops|
|fire||H||a major damaging agent|
|insect||L||not a serious concern|
|fungi||M||not a serious and major concern; leaf spots, leaf rust, tar spot, cankers (madrone canker), root disease|
Associated tree species and successional role
In British Columbia, Pacific madrone grows in small, open to closed-canopy stands or, more often, mixed with common douglas, less often, with lodgepole pine, and rarely with Garry oak, on warm-aspect, water-deficient sites in southwestern coastal B.C., typically on rocky shores. It is often a pioneer species in primary succession on rock outcrops, and is present in early, mid-, and late (old-growth) stages of secondary succession.
|reproduction capacity||H||fruit (drupe) production after 5 years; reproduces vegetatively by sprouting from numerous dormant buds formed at or just above the root collar|
|seed dissemination capacity||H||distributed by birds and animals|
|potential for natural regeneration in low light||L||higher, providing the presence of exposed mineral soil|
|potential for natural regeneration in the open||H||providing the presence of exposed mineral soil|
|potential initial growth rate (<5 years)||H||when originated from sprouts|
|response of advance regeneration to release||na||advance regeneration does not develop in the absence of adequate light and seedbeds|
|self-pruning capacity in dense stands||M||dense stands are infrequent|
|crown spatial requirements||L||develops an irregular crown|
|light conditions beneath closed-canopy, mature stands||H||closed-canopy stands are infrequent; associated with well-developed understory vegetation|
|potential productivity||na||non-crop species; site index functions have not been determined|
|longevity||M||occasionally >500 years|
No natural varieties or hybrids of Pacific madrone are known.
Pacific madrone is the only broad-leaved evergreen tree species of British Columbia. Although not grown commercially for timber production, scattered native trees and stands are valued scenic assets in wildlands, parks, and urban areas with its limited B.C. range. More detailed silvics information is given by:
McDonald, P.M. and J.C. Tappeiner, II. 1990. Arbutus menziesii. Pp. 124-132 in R.M. Burns and B.H. Honkala (technical coordinators) Silvics of North America, Vol. 2. Agri. Handbook 654, USDA For. Serv., Washington, D.C.