Water birch
Betula occidentalis Hook.
Introduction
Water birch occurs as a deciduous shrub or small tree growing in riparian, wooded communities. Most of these sites have high water tables, and the shallow rooting of the trees on such sites regularly results in windfall. The species grows on a wide variety of soil textures and has high nutritional requirements. Water birch often occurs in dense stands, which provide good cover, forage and nesting opportunities for many wildlife species. Water birch is suitable for revegetating disturbed riparian sites and for stabilizing stream banks, due to its dense root system (Uchytil 1989).
Water birch has a very scattered distribution in the western half of North America. It is found from southern Alaska to southern Manitoba, North Dakota, southern California and New Mexico (Little 1979). It is absent along the Pacific Coastal mountain ranges. Even within British Columbia, its range is markedly scattered, the areas of high occurrence in our survey being clearly separated from each other by areas where it is completely absent.
Distribution and Protected Areas – from Hamann et.al. 2005
Conservation Status Summary – from Chourmouzis et.al. 2009
“Water birch occurs in many zones, but in low numbers. It is most common in the IDF zone. It is under-protected in several zones, but is identified as a species of concern and is recommended for verification only in the IDF and in the northern part of its range in the BWBS zone, where calculated protection levels are near zero.”
Reproduction
Water birch is wind pollinated and its small seeds are wind dispersed. The interval between good seed crops is typically two years (Banerjee et al. 2001). Due to its scattered and wide ranging distribution, populations may be physically isolated and genetically differentiated.
Genetic structure
In eastern Washington, northeastern Oregon, western Idaho, and southern British Columbia, water birch hybridizes with paper birch (Betula papyrifera) producing many intermediate forms, which appear to be well established locally (Hitchcock and Cronquist 1964).
Resource management and seed transfer
No information available.
REFERENCES
Hamann, A., Smets, P., Aitken, S. N. and Yanchuk, A. D. 2005. An ecogeographic framework for in situ conservation of forest trees in British Columbia. Can. J. For. Res. 35:2553-2561. View online resources for this report.
C. Chourmouzis, A.D. Yanchuk, A. Hamann, P. Smets, and S.N. Aitken. 2009. Forest Tree Genetic Conservation Status Report 1: In situ conservation status of all indigenous BC species. Centre for Forest Conservation Genetics, Forest Genetics Council of BC, and BC Ministry of Forests and Range, Forest Science Program, Victoria, BC Technical Report 053. www.for.gov.bc.ca/hfd/pubs/Docs/Tr/Tr053.htm
Banerjee, S. M., Creasy, K. and Gertzen, D. D. 2001. Native woody plant seed collection guide for British Columbia. Crown Publications, Victoria. 147 p.
Hitchcock, C. L. and Cronquist, A. 1964. Vascular plants of the Pacific Northwest, part 2: Salicaceae to Saxifragaceae. University of Washington Press, Seattle, WA. 597 p.
Little, E., L., Jr. 1979. Checklist of United States trees (native and naturalized). In: U.S. Department of Agriculture, Agriculture Handbook 541. Washington, DC, 375p.
Uchytil, R. J. 1989. Betula occidentalis. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (2002, January). Fire Effects Information System. [Online]. Available: http://www.fs.fed.us/database/feis/ [January 2002].