Red alder often occurs in mixture with other tree species. Red alder does not reproduce in the absence of soil disturbance. Its roots fix atmospheric nitrogen via symbiosis with the actinomycete, Frankia. Red alder can maintain or improve soils via rapid input of organic matter and nitrogen. Red alder is a pioneer species that establishes rapidly in openings created by forest disturbance it commonly invades newly bared soils after landslides, logging, or fire. In mixed stands, red alder are usually grouped. Both pure and mixed-species stands are predominantly even-aged. Trees of intermediate or suppressed-crown classes do not survive long. Red alder is intolerant of shade, and it must maintain a dominant or codominant canopy position. Also, very little red alder is sold from public lands, although substantial inventory occurs there. A significant portion of the red alder resource is not available for harvest forest practices rules constrain timber management in riparian areas where red alder is most abundant. The greatest volume occurs in the Puget Sound and Northwest Oregon subregions. The current inventory of about 7.4 billion cubic feet of red alder comprises 60 percent of the total hardwood volume in the Northwest ( Appendix 1, Table 1). Historical inventories indicate that the abundance of red alder has increased about 20-fold since the 1920s, though this trend may be reversed by modern forest practices, which favor conifers. Red alder is common at low elevations throughout the Coast and north Cascade ranges but is restricted to riparian areas or moist microsites farther south. The range of red alder extends from southeastern Alaska (lat 60°N) to southern California (lat 34°N), generally within 125 miles of the ocean. The root system of red alder is shallow and spreading where limited by poor drainage a deep-root system develops on soils with better drainage. Open-grown trees form broadly conical crowns and highly tapered boles, often with large forks and branches. In forest stands, red alder develops a clear (60 to 70 percent of total height), slightly tapered bole with a narrow, domelike crown. Red alder are mature at 60 to 70 years they seldom survive beyond 100 years. Mature red alder trees are typically 70 to 120 ft in height (130 ft maximum) and 10 to 34 in. It is also the most common and important of the hardwoods in the Pacific Northwest. Of the ten species of Alnus native to the United States, red alder is the only one that reaches commercial size and abundance. Oregon State University, Forest Research Laboratory General CharacteristicsĪlders are members of the birch family (Betulaceae). This information was originally published in Hardwoods of the Pacific Northwest, S.S.
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