Recovery Plan for the Northern Spotted Owl - DRAFT

formed during the initial meeting to address this task. A working principle ofthe committee was that the recovery plan should take advantage of opportunitiesto benefit other species and ecosystem function. In the long term, a planthat adheres to this principle will be more sound ecologically and be a moreefficient and cost-effective approach than a series of conservation measuresaimed at single species.Description of Older Forest EcosystemsConiferous forests in the Northwest succeed through three biological stages ofdevelopment: young, mature, and old-growth. Precise definition of the latterstage is difficult because characteristics are influenced by a number of variablesincluding species composition and climate. However, an interagencytask group developed interim definitions for old-growth Douglas-fir and mixedconifer forests (USDA 1984). The task group suggested that the transition frommature forest to old-growth begins at about 175 or 200 years of age for Douglas-firforests, with continuing change until these forests are much older.Specific characteristics vary with site but include: (a) two or more species oftrees with a wide range of ages and sizes of large trees, usually Douglas-fir,with diameters 30 inches or ages older than 200 years: (b) multilayeredcanopy: (c) one to four conifer snags per acre with diameters greater than 20inches and heights greater than 15 feet; and (d) 10 to 15 tons of down logs peracre with two to four per acre having diameters greater than 24 inches andlengths greater than 50 feet. The special significance of old-growth forests liesin the combination of characteristics they possess, rather than in any uniqueattribute. This was recognized explicitly in the interim definition of old-growthforests (USDA 1986) and the use of multiple criteria rather than single attributesto characterize these forests. Species composition and specific structuralattributes vary with location. In northern California, mixed-conifer andmixed-evergreen forests contain Douglas-fir, white fir, sugar pine, and ponderosapine in addition to deciduous species such as tanoak, Pacific madrone,and canyon live oak. In Oregon and Washington, Douglas-fir, western hemlock,Sitka spruce, and Pacific silver fir are common.Throughout much of the region, total precipitation is high and the climate ismoderate. Within old-growth stands, the climate is especially moderate, andmany of the organisms that inhabit these forests cannot tolerate extreme heator dryness. The combination of mild climate and year-round food suppliesresults in a high level of plant and animal diversity.Historically, these forests did not extend across the landscape in an unbrokenexpanse of old-growth trees. Within the region there are mountainous areasthat typically are dissected heavily by streams and rivers, as well as largeexpanses of less rugged terrain. Also, natural disturbances such as fire, wind,insect infestations, diseases, and volcanic eruptions created a mosaic ofdifferent-aged stands. This disturbance regime resulted in a patchy landscapeand a diverse variety of habitats for animals. Natural disturbances differedsignificantly from clear-cut harvesting of timber. Intervals between fires westof the Cascades typically were much greater than those between harvests, andfires did not result in the relatively fine-grained fragmentation of habitatsassociated with clear-cut harvesting. The amount of coarse woody debris leftafterward is the most significant difference between natural disturbance andlogging. Far more wood is removed by harvesting than by fire, which maydestroy only a few large trees and consume less than 20 percent of the coarsewoody debris (Spies and Cline 1988).Many attributes within these forests are important for wildlife. These forestsare dominated by exceptionally long-lived conifer trees, and, in the absence of334