Recovery Plan for the Northern Spotted Owl - DRAFT

C. FertilizationThinning or other disturbance also aids the development of shrubs (Long andTurner 1975) (see Figure G.3). Vine maple clones spread by layering as theyare pinned to the ground by falling trees (O'Dea 1991). Shrubs like salmonberryand salal spread from increased rhizome extension and seedling establishmentin thinned stands flappeiner et al. 1991, Huffman 1991). Too densea layer of shrubs or forbs will prevent the establishment of conifers and hardwoodsin the understory (Isaac 1938). Bigleaf maple seedlings become establishedas the overstory is thinned to about 70 to 80 percent cover or less, butbefore a layer of shrubs or forbs is formed (Fried et al. 1988). Where layers ofshrubs occur in the understory, some treatment to reduce their density may beneeded to establish trees to provide the stand structure used by owls.Fertilization has been shown to increase the rate of stand development instands 15 to 110 years old. For example, 90-year-old (Miller and Harrington1979) and 110-year-old (Harrington and Miller 1979) Douglas-fir standsincreased basal area and diameter growth rates following application of nitrogenfertilizer as urea or ammonium nitrate. Increased growth occurred inthinned and unthinned stands and on a range of sites and stand ages lessthan 90 years (Miller et al. 1979, Miller and Tarrant 1983). Fertilization alsoincreased diameter and height growth in thinned and unthinned 15-year-oldwestern red cedar stands (Harrington and Wierman 1990).D. Historical Stand Management PracticesThe primary silvicultural system for Douglas-fir and western hemlock forests inthe coastal forests and western Cascades of Oregon and Washington has beeneven-age management. This is an efficient way to manage these forests fortimber production primarily because a) the major conifers can be regeneratedin open conditions following disturbance, b) steep topography on many sitesprecludes tractor logging or makes it prohibitively expensive and likely to causeserious soil erosion, and c) cost of setting up cable logging equipment and roadbuilding in steep terrain makes it most efficient and least expensive to clearcut.Under the even-age system, stands most often are regenerated using theclear-cutting method, followed by site preparation, planting nursery-grownseedlings, and some level of control of herbs, shrubs, or hardwoods. Theshelterwood method also has been used on some sites where wind is not aserious problem (Williamson 1973).Early in the development of silvicultural practices in this region, Kirkland andBrandstrom (1936) recommended partial cutting and group selection as a wayto manage Douglas-fir. Isaac (1956) reviewed the early trials of this type of"selection management" in old-growth forests and recommended that Douglasfirforests be managed under even-age systems. His recommendations werebased on observations that a) there was little natural regeneration occurringafter selection cutting, b) understory trees were damaged by logging, c) therewas blowdown (few trees, but lots of volume), and d) the old trees generally didnot increase their growth rates after cutting. Isaac (1956) recognized severalcases where selection cutting (uneven-age management) appeared to be reasonable:a) dry sites with more open stands, b) stands with a high proportionof young trees, and c) salvage of mortality. It is important to note that hisrecommendations were based mainly on experience in old stands, not youngstands (less than 100 to 120 years). These recommendations considered onlynatural regeneration without well-planned site preparation prior to planting ornatural seeding, followed by vegetation control. Also, advances in logging501