Recovery Plan for the Northern Spotted Owl - DRAFT

Douglas-fir forests. Fire (or some other disturbance) is, however, important tohelp conifers maintain dominance over hardwoods in mixed evergreen forests(Thornburgh 1981, Hoover 1988).Pathogens (such as black stain and annosus root rot) and insects (such aswestern and mountain pine beetle, fir engraver beetle) are most likely to causeconifer mortality on dry interior sites. Insects are particularly likely to affectdense stands where poor tree vigor may predispose stands to attack, especiallyin periods of drought. Root disease also may make stands susceptible toinsects. Ice storms and wet snow can uproot large, broad-leaved evergreentrees in the mixed evergreen forests.Wind can be a major factor on coastal sites, especially when large individualtrees are left in shelterwoods. Hemlock, Douglas-fir, redwood, sugar pine, andponderosa pine are susceptible to windthrow, which is locally important oninterior sites and most likely to occur on ridge tops, saddles, and in coniferstands on shallow soils or infected with root diseases. Pocket gophers andbrowsing deer and livestock, which are important factors in the establishmentand growth of planted and natural conifers, may have major effects on reforestationin some areas.Four to five decades of fire suppression and timber harvesting have influencedtoday's forests. Fire suppression likely has favored the development of theunderstory of tanoak, a shade-tolerant hardwood, which is a climax species inthe tanoak association and an important component of the Douglas-fir, whitefir, and western hemlock associations. Fire exclusion also has favored thedevelopment of hemlock and white fir understories on some mesic sites,Douglas-fir understory on dry sites, and a tanoak understory beneath redwood.To the extent that a well-developed understory is important for owlhabitat, fire exclusion probably has improved owl habitat. Recent large,variable-intensity fires have increased the structural and species diversity ofmixed evergreen and mixed conifer forests in northwestern California(Thornburgh 1991).2. Forest Management and Stand DevelopmentLogging in this area began about 1830. Large-scale commercial harvestingbegan about 1915, but was confined to gentle terrain (Walstad 1992). Cuttingrapidly increased after 1945. Effects of logging varied tremendously. In somecases, only certain species were cut and large trees of nonmerchantable specieswere left (partial cutting). Also, shelterwood methods and, more recently, clearcuttingwere employed. Partial cutting and shelterwood regeneration methodprobably have favored the establishment and growth of Pacific madrone andwhite fir and the growth of established tanoak. In general, the types of standspresent today include: a) old-growth stands undisturbed, except for fire suppression;b) stands composed of varying numbers and species of conifers andhardwoods released by logging, residual old-growth trees, and natural regenerationof conifers, hardwoods, and shrubs following logging; and c) relativelyuniform young stands that contain shrubs, hardwoods, and other conifers thathave been established by natural seeding and planting.C. East Cascades of Oregon and WashingtonThe forests in the east Cascades, inhabited by northern spotted owls, generallyare composed of mixed conifer stands in the Douglas-fir and grand fir plantassociations. Under natural fire regimes these forests had intense fire, atpossibly centuries-long intervals, and light underburns at about 10- to 20 -495