Recovery Plan for the Northern Spotted Owl - DRAFT

western hemlock, and sometimes other conifers, occurs among planted seedlingsand dramatically increases stocking (700 + trees per acre). Foreststands, especially plantations established for timber production, often willproceed through a stem exclusion stage (Oliver 1981) in which shrubs andhardwoods die or become substantially suppressed by a dense conifer overstory.Most of the understory plants likely will die if hemlock is the main overstorytree (Alaback 1982), because its foliage is denser (high leaf area index)compared to Douglas-fir (Waring et al. 1978). Thus, plantations, because of theirlack of large trees and snags from the previous stand, and regular, close spacing,may develop stands that are quite different from young natural stands (Spies et al.1988).On coastal sites, red alder stands frequently have become established. Thesestands often have salmonberry or salmonberry-sword fern understories whichprevent conifer establishment. The shade from the salmonberry and browsingfrom mountain beaver often found in salmonberry-dominated communitiesprevent conifer regeneration. Alder stands with salmonberry in the understory,unless treated to establish conifers, are unlikely to produce conifer standscapable of developing owl habitat because the salmonberry will form a dense,persistent shrub layer as the alder dies and will retard invasion of conifers(Tappeiner et al. 1991).B. Northern California and Southwestern Oregon1. Natural Forest DevelopmentThe vegetation comprising owl habitat in southwestern Oregon and northernCalifornia is quite diverse. It includes redwood forests (Zinke 1977), mixedevergreen forests (both hardwood and conifers) (Sawyer and Thornburgh1977a) and mixed conifer forests (Sawyer and Thornburgh 1977b). Atzet et al.(1992) have classified the vegetation of southwestern Oregon into 16 series andeach series usually is subdivided into several plant associations (more than200 total). The most common series are white fir, western hemlock, Douglasfir,tanoak, and mountain hemlock. These vegetation series and their includedassociations vary by elevation and aspect and occur on a variety of soil types,including soils of volcanic and metasedimentary material. There is generallyless precipitation in this area, except near the coast, than there is in thewestern Cascades and northern coastal forests. Climate is Mediterranean,with strong coastal and continental influences. In northern California, themost common vegetation series include redwood, Douglas-fir, tanoak, andwhite fir.Fire occurs in forests of all vegetation series. Natural fire return intervals varyfrom 20 to 200 years (Atzet and Wheeler 1982) (Appendix F). More frequentand less intense fires generally occur on drier sites at lower elevation, with lessfrequent stand-replacement fires at higher elevations or near the coast. SeeWalstad (1992) for a discussion of recent fire history. Accidental ignition andpurposeful use of fire by Indians and European settlers also has had a majorimpact on the forests.Factors which affect natural succession and management of landscapes andindividual stands in this region include fire, wind, insects, pathogens, andbrowsing by animals. Chance of ignition is high on interior sites due to lightningand human causes. Fires are likely to be intense because of the summerdrought, steep terrain, and accumulation of fuels due to fire suppression andlogging slash. The likelihood of fire and its effects vary by forest type. Fire isnot expected to be a severe problem in most of the redwood forests or coastal494