In : Silvicultural systems for the maJor forest types of the United Red Alder States, DC: Dean S. DeBell Pac((ic Northwest Forest a11d Ra11Re Experime11t Statioll Thomas C. Turpin Pac((ic Northwest Re[iioll 445. Washington ' Department of Agriculture·' 1983: 26-28. w_as cr Red alder (Alnus rubra Bong.) is the most widely distributed hardwood type in the coastal Pacific Northwest, occupying more than 3 million acres (1.2 million ha) of commercial forest land in Oregon and Washington. This type is identical to Society of American Foresters cover type 221 of the same name (4). The type is found from southern California to southeastern Alaska, but stands seldom occur east of the Cascade Range or the Sierra Nevadas. Red alder stands grow on a wide range of soil and site conditions, varying from well-drained gravels and sands to poorly drained clays and organic soils (17). Because red alder can tolerate poorly drained conditions and some flooding in the growing season, it prevails on soils of restricted internal drainage, along streams, and on swampy or marshy areas. The most productive stands are usually found on deep, well-drained Ioams or sandy Ioams derived from marine sediments or alluvium; some very good stands also grow on residual or colluvial soils of volcanic origin. Rapidly growing red alder stands occur on hillsides as well as along streams at elevations below I ,500 feet (460 m) in coastal areas of northern Oregon , Washington, and British Columbia. At mid-elevations in the Cascade Range, stands of commercial dimensions are limited mainly to stream bottom sites. Climate in the type's range is humid or superhumid, with most precipitation occurring as rain during winter. Summers are cool and dry, sometimes with considerable morning fog. Annual precipitation and temperature extremes are 16 to 220 inches (405 to 5590 mm) and -22° to 115° F (-30.0° to 46. I o C) , respectively. Most stands , however, are found where annual precipitation exceeds 40 inches (1015 mm) and winter temperatures are relatively mild. Red alder occurs in both pure and mixed stands. Common tree associates include coast Douglas-fir (Pseudotsuga menziesii (Mirb. ) Franco var. menziesii), western hemlock (Tsuga heterophylla (Raf.) Sarg.) , western redcedar (Thuja plicata Donn ex D. Don), Sitka spruce (Picea sitchensis (Bong.) Carr. ), black cottonwood (Populus trichocarpa Torr. & Gray) , bigleaf maple (Acer macrophyllum Pursh), and willow (Salix spp). Red alder regenerates most commonly by natural seeding. It has also been established by direct seeding and planting in several research and pilot-scale trials (17). Survival of both bare-root and container seedlings has been excellent (3). Red alder will sprout vigorously from the stump wl)en young and has been repeatedly coppiced on short cycles (6). Stumps of pole- and sawlog-size trees may sprout, but prouts rarely 1 persist. Individual trees reach sexual maturity at 3 to 4 years, and most dominant trees in a stand will begin to produce seed at 6 to 8 years (II). Red alder is a prolific seeder, with moderate seed crops produced almost annually. Bumper crops occur at 3- to 5-year intervals, and seed crop failure is unusual. Seed dispersal begins soon after ripening in late summer , but most seeds are shed during fall and winter. Dissemination is primarily by wind, and sufficient seed for 26 Agric. Handb. About This File: ted by scanning the printed pLibli ation . Mls cans ldentlfle by the software have been correcte d; however, some mistakes may . / remain. : T is file • . U.S. ) natural regeneration is usually present throughout the species' range (17). Germination and early growth is best on moist mineral soil and in full sunlight. The species is a common pioneer on landings , skidtrails, road cuts , and other areas where mineral soil has been freshly exposed. Seeds will also germinate on soil organic horizons and on rock-surfaced logging roads, but the newly developing roots must quickly penetrate a moist, nutritious substrate if the seedlings are to survive. Some early mortality has been observed after girdling by meadow mice or cutting by mountain beaver, but its extent is unknown. Red alder is moderately intolerant of shade. Seedlings will survive in partial shade for several years, but full sunlight is required for normal development. Compared with most of its associates, red alder is relatively tolerant of flooding and salinity. Windthrow is not common except along exposed cutting boundaries or where root systems have been undermined by flooding or erosion. Mortality , stem breakage, and other top damage have been observed in natural stands after ice storms and unseasonable frosts (3, 17). Red alder is the only commercial tree species native to western North America that fixes atmospheric nitrogen symbioti­ cally in its root nodules; both content and availability of nitrogen are increased in soils beneath red alder stands. Accretion rates varying from about 40 to more than 300 pounds of nitrogen per acre (45 to 335 kg/ha) per year have been reported for alder stands of 50 years and less (12, 13). Soil organic matter is higher and bulk density is lower in red alder stands than in conifer stands of comparable history (12). Red alder has therefore been proposed for site improve­ ment purposes, either by itself or in crop rotations and mixtures with other species. Young stands of red alder may be very dense , having more than 100,000 stems per acre (247 100 stems/ha) at 1 and 2 years (2). Self-thinning or suppression-related mortal­ ity begins at an early age in such stands, but they remain too dense for optimum growth without management. Spacing control or thinning in previously unmanaged stands is effec­ tive in stimulating growth if done before age 15 to 20. Thinning in overly dense, older stands can salvage mortality but is of questionable value for increasing growth on selected crop trees (10, 15). Young alder trees grow rapidly. On favorable sites, seedlings grow 3 feet (0.9 m) or more in the first year; they may attain 30 feet (9.1 m) by age 5 and more than 80 feet (24.4 m) by age 30 (16). Good growth rates are maintained from establishment to at least age 25; during this period, growth of red alder surpasses that of any conifer or other hardwood species in the Pacific Northwest, with the excep­ tion of black cottonwood on its best sites. Growth thereafter slows, and the decrease begins earlier and is greater on poor than on good sites. Growth and yield information is available for natural, unmanaged stands of red alder ( l , 2, 10, 13, 14, 16). On . i well-stocked sites of the highest quality, mean annual incre­ ment (total stem) may approach 150 cubic feet per acre (10.5 m3/ha) for 20- to 40-year rotations; a comparable value for sites of average quality is 120 cubic feet per acre (8.4 m3/ha). Projections based on early performance of experimental plantings, results of thinning trials, and gains obtained with spacing control of other species suggest that yields of managed red alder stands will be much higher than natural stands (2). For example, coppice stands can be grown on cutting cycles of 2 or more years, and pulpwood-size (6-inch (15 em) diameter at breast height (d.b.h.)) trees can be produced in lO to 15 years on good sites. Sawlog- and veneer Jog-size trees (12-inch (30 em) d.b.h.) can probably be grown in 25 to 35 years on such sites. Annual total stem yields are estimated at 170 to 210 cubic feet per acre (11.9 to 14.7 m3 /ha). Rotations longer than 40 years are not recom­ mended for timber production because of increased disease problems and reduced growth of red alder at older ages (3, 13, 17). Young, vigorous stands of red alder appear relatively free from serious insect and disease problems, but such pests could become more evident or serious as the species becomes more widely managed (17). Insect damage observed in alder stands include twig girdling by flatheaded borers, defoliation by tent caterpillars and sawflies, and infestation by bark beetles. Red alder is susceptible to several canker-causing fungi and foliage and catkin diseases, but none have signifi­ cant economic importance. A white heart rot is the major cause of defect in older trees, and many other fungi species have been identified on alder as secondary invaders of dead or dying tissues. Red alder is resistant to laminated root rot (Phellinus weirii (Murr.) Gilb.), and therefore is a suitable, non-susceptible species for growing on sites severely infested with the fungus (5). Fire rarely damages red alder stands-in fact, the species has been planted as a fire break (17). The low fire hazard is due to scarcity of flammable understory and organic debris in closed alder stands and because natural alder stands commonly occur on wet sites. Fire may be an important site preparation tool in red alder management. Dense understories of shrub species develop in older, unmanaged red alder stands with less than full stocking, particularly on the more productive sites. Such shrub species may take over the site following harvest and thereby prevent successful regenera­ tion of alder or other commercial tree species, unless special site preparation measures are taken. Tractor scarification is rather expensive and is inappropriate on many red alder sites because of steep terrain or excessive soil moisture. Broadcast burning is usually difficult because of moist conditions, green underbrush, and the non-resinous, light slash of such s ands (17). Coupled with preparatory applications of herbi­ Cides and/or desiccants, however, broadcast burning can be a suitable method for ameliorating the brush encroachment problem following harvest cuts on such sites (9). Although natural stands of red alder occupy about 15 percent of commercial forest lands in western Oregon and Western Washington, foresters have had little experience in managing the species. Historically, red alder has been regarded primarily as a weed species limiting production of more highly valued conifers. Stumpage values for red alder are very low; available supplies far exceed present demand (7). There is growing interest, however, in regeneration and management of red alder because of its rapid juvenile growth and bility to fix atmospheric nitrogen and improve other hem1cal and physical properties of soils. Recent expansions lfl use of the species in solid wood, paper, and other reconstituted fiber products as well as recognition of its . Potential contributions in multiple-use situations have also aided the developing interest in red alder management. Because of the dearth of operational experience with the species, present management recommendations are based primarily on extrapolation of results from limited research trials as well as management experience with other species having similar biological traits. Silvical characteristics and regeneration requirements of red alder mandate a silvicultural system adapted to even-aged management, specifically, clearcutting, seedtree, or shelterwood. Of the three, clearcutting provides the greatest flexibility in use of site lpreparation techniques to control brush and to expose mineral soil. Natural seeding from adjacent uncut stands, direct seeding, and planting of container or bare-root seedlings have all resulted in satisfactory establishment of new alder stands in clearcut areas (3, 17). Stocking in naturally established stands, however, is commonly either clumpy with much unoccupied growing space or extremely ·dense. Thus, planting may be preferable in situations where red alder is managed primarily for wood production. In most cases, clearcutting is probably the most effective silvicultural system, followed, if necessary, by scarification or some other form of site preparation. Clearcutting is also the appropriate method to use in short-rotation management systems for fiber and energy production (2, 6). No attempts to reproduce red alder by the seedtree method have been documented. Only in rare cases does seed supply limit natural regeneration of red alder after clearcutting; seedbed condition is more likely to be the limiting factor. Leaving a few seed trees per acre, however, might provide a more uniform distribution of seedlings where cutting units are exceptionally large or where there are few adjacent uncut red alders. The shelterwood system might also be used to regener­ ate red alder, but there is little documented information to recommend it. Seed is usually produced every year, and established seedlings grow best in full sunlight. Moreover, juvenile growth rate of red alder is so rapid that, even in areas of high esthetic value, the overstory would probably have to be removed in less than 2 years; excessive damage to the young reproduction would otherwise be expected. Because red alder can become established naturally in abundance, precommercial thinning will probably be an essential feature of management programs--especially those that entail natural regeneration. There are several reports of enhanced growth of the species following early spacing control (10, 15); such cutting also provides opportunities to favor stems of superior form. Uniform spacing may also reduce the sweep or lean characteristic of red alder in unmanaged, irregularly spaced stands (2). Maintenance of the red alder type is no problem; the estimated acreage occupied by red alder in western Oregon and western Washington has more than tripled in the past quarter century. Recent emphasis on conversion of red alder stands to conifers, however, has resulted in an unbalanced distribution of age classes in some areas. Individual alder stands begin to break up by age 60 to 70; intact stands more than 80 years old are rare. Much evidence points to maxi­ mum rotation ages of 40 years or less if wood production is the primary objective of management. Mixed stands of red alder and other species are more common than pure red alder stands in many parts of the species range. These mixtures are both even- and uneven­ aged, and may include most of the previously listed associ­ ated tree species. There is no specific management experi­ ence and little research data for most of these mixtures; the intention of' most forest owners and managers is to convert such stands to pure conifers after harvest of the existing stands. There are some exceptions, however, and interest in 27 mixed-species management has increased substantially in the last decade. For example, mixed stands of Douglas-fir and red alder have been established on an experimental basis and such mixtures are now being considered for limited opera­ tional use on some nitrogen-deficient soils. Interplanting alder seedlings in a 4-year-old Douglas-fir plantation at a ratio of nearly two alders to one Douglas-fir, increased soil nitrogen and soil organic matter and lowered bulk density (12); it also enhanced growth of Douglas-fir (8). Similar benefits might be obtained with a lower ratio of red alder to Douglas-fir. Mixed red alder -Douglas-fir stands are pre­ scribed on the Siuslaw National Forest for soils that are low in nitrogen but are otherwise productive (site index class II). Current management plans for these sites call for leaving some naturally established red alder when Douglas-fir planta­ tions are precommercially thinned at about age 10 (14). The red alder will be removed in a commercial thinning at about age 40. It is assumed that nitrogen accumulated in the soil during the period of alder's occupancy will enhance Douglas­ fir growth in the remaining years of the conifer rotation. Red alder stands can be established and managed for purposes other than, or in addition to, wood production. Because of the species' tolerance of poor drainage and flooding, alder is sometimes recommended for management in riparian zones. It can be especially useful in the ameliora­ tion of coal mine spoils, landslides, and other eroded or low fertility areas. Although red alder is not a preferred browse species, its presence in pure stands, small clumps or stringers, and mixed stands within extensive conifer forests provides edges and adds structural diversity; it may therefore be used to enhance the forest habitat for many wildlife species. Esthetically, red alder stands provide variety in a landscape covered mainly by stands of conifers, and its rapid juvenile growth rate permits its use where rapidly established tree cover is desired for protection or enhancement of visual resources. 3. DeBell. D. S.; Harrington, C. A. Mini-monograph on Alnus ruhra. In: Documents, Technical consultation on fast-growing plantation broadleaved trees for Mediterranean and temperate zones: 1979 October 16 -20· Lisbon, Portugal. Volume I. Invited Papers. Food and Agricultu Organization of the United Nations: 1979: 169-186. 4. Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 1980. 148 p. 5. Hansen, E. M. Survival of Phellinus weirii in Douglas-fir stumps after logging. Can. J. For. Res. 9(4):484-488; 1979. 6. Harrington, C. A.; DeBell, D. S.: Strand. R. F. An experiment in biomass production: Results from three consecutive harvests of cotton­ wood and alder. In: Proceedings of Solar '79 Northwest. U.S. Seattle, WA: U.S. Department of Energy and others: 1979:363-366. 7. McGillivray, R. Alder survey. Pullman, WA: State of Washington Department of Natural Resources; 1981. 24 p. 8. Miller, R. E.; Murray, M. D. The effects of red alder on growth of Douglas-fir. In: Briggs, D. G.; DeBell, D. S.; Atkinson, W. A.. comps. Utilization and management of alder. Gen. Tech. Rep. PNW-70. Portland, OR:U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station: 1978: 283-306. 9. Newton, M. Herbicides in alder management and control. In: Briggs, D. G.; DeBell, D. S.; Atkinson, W. A., comps. Utilization and management of alder. Gen. Tech. Rep. PNW-70. Portland, OR:U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station; 1978: 223-230. 10. Smith, J. H. G. Growth and yield of red alder: Effects of spacing and thinning. In: Briggs, D. G.; DeBell, D. S.; Atkinson, W. A.. comps. Utilization and management of alder. Gen. Tech. Rep. PNW-70. Portland, OR: U.S. Department of Agriculture, Forest Service. Pacific Northwest Forest and Range Experiment Station; 1978: 245-263. II. Stettler, R. F. Biological aspects of red alder pertinent to potential breeding programs. In: Briggs, D. G.; DeBell, D. S.; Atkinson, W. A., comps. Utilization and management of alder. Gen. Tech. Rep. PNW-70. Portland, OR:U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station; 1978: 209-222. 12. Tarrant, R. F.; Miller, R. E. Accumulation of organic matter and soil nitrogen beneath a plantation of red alder and Douglas-fir. Soil Sci. Soc. Amer. Proc. 27(2): 231-234; 1963. I3. Trappe, J. M.; Franklin, J. F.; Tarrant, R. F.; Hansen, G. M., eds. Biology of alder. Portland, OR:U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station; 1968. 292 p. I4. Turpin, T. C. Managing red alder on the Siuslaw National Forest. In: Proceedings, National Silviculture Workshop--Hardwood Management; I981 June 1-5; Roanoke, VA. Washington, DC:U.S. Department of Literature Cited Agriculture; Forest Service, Timber Management; 1981: 268-272. I. Chambers, C. J. Empirical yield tables for predominantly alder stands in western Washington. Report No. 31. Olympia, WA: State of Washing­ ton Department of Natural Resources; 1974. 70 p. Columbia Forest Service, Research Division; 1964. 7 p. 16. Worthington, N. P.; Johnson, F. A.; Staebler, G. R.; Lloyd, W. J. 2. DeBell, D. S.; Strand, R. F.; Reukema, D. L. Short-rotation production Normal yield tables for red alder. Res. Pap. 36. Portland, OR: U.S. of red alder: Some options for future forest management. In:Briggs, D. Department of Agriculture, Forest Service, Pacific Northwest Forest G.; DeBell, D. S.; Atkinson, W. A., comps. Utilization and manage­ and Range Experiment Station; 1960. 29 p. ment of alder. Gen. Tech. Rep. PNW-70. Portland, OR: U.S. 17. Worthington, N. P.; Ruth, R. H.; Matson, E. E. Red alder: its Department of Agriculture, Forest Service, Pacific Northwest Forest management and utilization. Misc. Pub. 881. Washington, DC:U.S. and Range Experiment Station; 1978:231-245. Department of Agriculture; 1962. 44 p. .. \ l 28 15. Warrack, G. C. Thinning effects in red alder. Victoria, BC: British