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3 OLD GROWTH FORESTS /NTRODUCT/ON Issues surrounding old-growth forests are at the very center of discus- sions about forest management in the Pacific Northwest. Terms such as "overmature," "late successional," "ancient forest," "forest primeval," as well as "old growth," often are used interchangeably, adding to the confusion of these discussions. Furthermore, public perceptions of what an old-growth forest is might not jibe with quantitative definitions of forest scientists and managers (Ribe 1989~. This chapter describes the attributes that characterize old-growth forests. Variations among forest types are described with respect to those attributes, as wed as variations in the age at which forests acquire particular characteristics after disturbance. The characteristics impart several unique ecological features of old-growth forests, such as complexity and high biodiversity, low susceptibility to disturbance, and mesic microclimate. WHAT /S VEGETATIVE SUCCESS/ON? Succession implies structural and compositional change in the species that dominate a plant community (and frequently an animal community as well). Fire, wind, disease, and other disturbance processes of varying intensity and frequency select for adaptions in a landscape's biota, making some species more resistant to and other species more resilient to effects of disturbance; some species have evolved to become depend- 44

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Old-Growth Forests 45 enton disturbance. A landscape can tee viewed as a collection of patches of varying size and undergoing changes influenced by disturbance, as well as by the patches that surround it, and at any time, different parts of a forested lancEscape will be at different successional stages. A Pacific Northwest forest could comprise an evenly aged stand of red alder that eventually is replaced by Douglas-fir, which might then be replaced by hemlock or cedar. WHAT IS AN 0! D-GROWTH FOREST? Late-successionai, or late-seral, has commonly referred to forests in which shade-tolerant tree species, such as western hemlock and grand fir, begin to attain dominance (Spurr and Barnes 1973~. FEMAT (1993) defined late-successional quite differently, as the period from first merchantibility to culmination of mean annual increment. As traclition- ally defined (e.g., by Spurr and Barnes), late-successional conditions in Pacific Northwest forests occurred rarely, only after many years in the old-growth condition and in the absence of significant disturbances that maintained dominance of less shade-tolerant species (most commonly Douglas-fir or ponderosa pine). Under FEMAT's definition, however, late-successional has nothing to do with dominance by shade-tolerant species, but rather is a stage of development of all forests that occurs well before, rather than in the later stages of, old-growth conditions. Unless noted otherwise, our use of late-successional will follow Spurr and Barnes (1973~. in the absence of fire or other disturbance, Douglas-fir ~ moderately moist Westside forests is gradually replaced over many centuries by shade-tolerant species, most commonly western hemlock. However, because of intermittent fires, shade-tolerant species rarely replace Douglas-fir altogether (Agee 1993~. Similarly, frequent fires maintained dominance by ponderosa pine throughout most of the low- and micl- elevation forests in the interior of the Pacific Northwest; hence, forests dominated by shade-tolerant species were a minor component of the region. Late-successional forests have been more common at higher elevations in interior Oregon and Washington. Old-growth forests are forests that have accumulated specific characteristics related to tree size, canopy structure, snags and woolly

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46 Pacific Northwest Forests debris, and plant associations. Ecological characteristics of old-growth forests emerge through the processes of succession. Certain fea- tures presence of large, old trees, multilayered canopies, forest gaps, snags, woody debris, and a particular set of species that occur primarily In old-growth forestsclo not appear simultaneously, nor at a fixed time in stand development. Old-growth forests support assemblages of plants and animals, environmental conditions, and ecological processes that are not found in younger forests (younger than 150-250 years) or in small patches of large, old trees. Specific attributes of old-growth forests develop through forest succession until the collective properties of an older forest are evident. The U.S. Forest Service (USES) Old-Growth Definition Task Group (1986) defined old-growth forests as the third of three basic stages in forest development. These forest stages are young, mature, and old; or, as sometimes distinguished by foresters, immature, mature, and overmature. In Douglas-fir forests of the Pacific Northwest, maturation typically occurs at 80 to 110 years. The mature - torest represents a relatively stable stage with substantial continued growth and biomass accumulation, albeit at a slower rate than in the young forest. Transition from the mature to the oid-growth stage is gradual. Douglas-fir stands do not begin to show the characteristics usually associated with old- growth until hey are 175 to 200 years old. Ecological characteristics of old-growth forests vary from one forest type to another (Tables 3-1 and 3-2) (Franklin and Spies, 199Ja; Spies and Franklin, 1991), and therefore, no single definition of old growth is appropriate. Increasingly, definitions rely on indexes of successional development based on multiple forest characteristics (e.g., Spies 1991~. USES interim definitions for all types involve specific values or states for five criterianumber of large, old trees; variation In tree diameter; degree of tree decadence; amount of large, dead wood; and characteris- tics of the canopy architecture (USFS 1993b; Williams 1992~. Number of large, old trees. The minimum density of large, old trees necessary for a stand to qualify as old growth varies from 16 to 50 per O/~-growth forests are forests that have accumu/ated specific characteristics re/atec/ to tree size, canopy structure, snags ant/ Woody debris, and plant associations.

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O/~-Growth Forests 51 ha, depending on forest type, with minimum sizes ranging from 52 cm diameter et breast height (dbh) on less-productive sites (generally in the interior) to 92 cm dbh on more-productive sites west of the Cascade crest. Old-growth forest might have 2 to 3 times that density of large, old trees. Minimum ages for these large dominant trees range from 150 years for the major interior forest types to 200 years for forests in western Oregon and Washington. Old-growth Douglas-fir and ponderosa pine stands typically contain trees some 700 years old, and in some cases, more than 1,000 years. Old- growth Douglas-fir in western Oregon and Washington most commonly range from 350 to 700 years of age (Franklin et al. 1981~. Under some circumstances, forests younger than 150-200 years produce trees that meet minimum size requirements, but those trees do not have character- istics of old-growth trees, such as thick, deeply incised bark and various manifestations of decadence as discussed below (Spies and Franklin 1991~. Variation in tree diameter. Variation in tree diameters is greater in old-growth forests than in younger forests. For example, in the western hemlock zone of western Oregon and Washington, the standard deviation of tree diameters in stands 200 years or older is 2 to 3 times that of younger stands. In many forest types, that difference in diameter reflects the increasing abundance of shade-tolerant tree species in the understory as forests age. In other cases, such as ponderosa pine, it is due to small patches of young pine regenerating within the old-growth matrix. Tree decadence. In western Oregon and Washington, stands of Douglas-fir that are considered old growth have greater numbers of trees with broken tops, excavated bole cavities, root collar cavities, and bark resinosis than either young or mature stands (Spies and Franklin 1991~. Those characteristics are typical of old trees throughout the region; old grand fir trees, for example, are commonly infected with a heart rot called Indian Paint fungus (Echinodontium tinctorium). Presence of large dead! wood. Large, standing snags and fallen tree boles typify all types of old-growth forests. On average, 25-35% of the standing boles in old-growth Douglas-fir stands are snags comparable in size to living trees, with more than half of the snags larger than 50 cm diameter (Franklin and Spies 1991 b). Large logs are also common on the forest floor (termed "down wood") in Douglas-fir old growth forests, as

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52 Pacific Northwest Forests well as in high-elevation forest types. Down wood occurs in dry forest types, such as ponderosa pine, but less commonly than in more mesic forests. Snags and logs are important structural features of old-growth forests in providing wildlife habitat (Maser et al. 1979; Thomas et al. 1979; Harmon et al. 1986~. In the Blue Mountains, for example, 39 bird and 23 mammal species use snags, and 179 vertebrate species make at least some use of down wood (Thomas et al. 1979; Maser et al. 1979~. Young, naturally established stands also can have large dead wood as legacies from the previous stand. Hence, presence of large, dead wood does not distinguish an old-growth forest as reliably among natural stands of different ages as does the number of large trees (Franklin and Spies 199Ib; Spies and Franklin 1991~. Cano By architecture. Large variation in tree diameters in old-growth forests is accompanied by a high degree of structural complexity in the forest canopy. Old-growth forests contain multiple tree-canopy layers (in addition to herb and shrub layers), a feature common to all types except ponderosa pine, lodgepole pine, and Eastside Douglas-fir. That layering reflects the growth of saplings (mostly shade-tolerant trees) into midcanopy strata as stands age. O1~-growth forests in western Oregon and Washington also tend to have greater shrub and herb cover than younger stands (Spies and Franklin 1991~. That is largely a function of overstory canopy density, inasmuch as open-grown younger stands generally have abundant shrub cover. Frequent ground fires retard understory growth in ponderosa pine and Eastside Douglas-fir forests. A typical old-growth forest also has areas with little or no understory, resulting in a patchy spatial structure. Patchiness is a distinguishing characteristic of old-growth ponderosa pine, in which small islands (roughly 0.25-0.5 ha) of regenerating pine occur scattered through a matrix of oilier trees. Viewed from above, the pattern of canopy cover in old-growth stands is distinct from younger stands. Cohen et al. (1990) used {ow-altitude remote images from the central Oregon Cascades to calculate semivariance, a geostatistical technique that quantifies average patterns of variance. Different age classes of forests were easily distinguished visually using the red bands of the spectrum. Nel et al. (1994) assessed the value of remote imagery of canopy reflection to identify old growthin spruce-fir forests of the interior West. They found the same general patterns as Cohen et al. (1990) but concluded that although remote imagery was a useful guide to old-growth stands, it was not sufficient to identify old-growth stands with certainty.

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Outgrowth Forests Time Required for O/~-Growth Development 53 Development of old-growth characteristics forests is progressive and varies among forest types. Some characteristics first appear about a century after a disturbance that destroys a forest stand (Table 3-3~. Across the region, many old-growth characteristics develop during the second century of stand development, but forests do not typically display all of the properties described above before they are 200 years old. Rates of succession differ from site to site depending on environmen- tal conditions, nutrient and moisture availability, and residual forest components from the previous stand. To deal with the spatial and temporal variability in succession, Franklin and Spies (1991 b) developed a continuously varying index of old growth based on the following five criteria for naturally established stands in the Oregon coast range, Cascades, and the southern Washington Cascades: density of large trees (e.g., more than SOcm Dbh) density of shade-tolerant trees amount of crown decadence (e.g., broken tops and multiple tops) density of large snags log biomass (using 60 Mg per ha as the base value) On the Westside, Douglas-fir stands younger than 200 years generally have a low old-growth index (Franklin and Spies 1 99Jb). Forests in that region have been classified as old growth at ages ranging from 150-250 years (Franklin and Spies 1991b; Johnson et al. 1991; Bonnicksen 1993; FEMAT 1993; Bolsinger and Waddell 1993~. There is, however, consider- able change in old-growth features across that age span. In the Franklin and Spies (199lb) study region, the old-growth index averaged a little more than 2.0 for stands younger than 100 years (range, 0-6.0), 3.0 for stands between 100 and 300 years (range, 0.3-5.0), and 6.0 for stands older than 300 years (range, I.0-10.0) (Spies and Franklin 1991~. O/~-Growth Landscapes Ideas about how forests developed following major natural disturbances

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54 Cal .~ be o .$ CD a' U) o a' o On .= . - a) o 5- o o Ct ED EM a; . A_ o .5 En ~ in E-U~ ~ a; Ed a; ., ~ .= C, .5 ~ ~ ~ AS ~ ~ Ct Cal o O ~ O ~ ~ c7N ~ ~ ~ Lf, ~ (Sx au ~ ~ ~ ~ ~ ~ ~ Cal Cal ~ ~ Cal .~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 _ _ _ ~ ~ A= ~ ~ ~ of of of of Ed ~ ~ ~ ~ ~1 ~ ~h ~ ~h ~ Dow ~ ~h p _ cr) - oo t-~ ~ O LE~ O Lo c-I Lo Z C~ ~ ~ C~ ~ ~ C~ o z ~ tn ~ ~n ~ cn ~ a; au ~ ~ a; 0 0 t~ <~- o 8 ~ ~ ~ * ~ E~ oo ~ o o o o o o o o U~ o o o o oo 'N oo ~ oo ~ oo ~ * ~ ~ ~ ~ ~ ~ ~ p =r ~ \o -~ ~ ~ o ~ ~ ~ ~ ~ ~ o ~ U, o ,,, ~ cn U~ ~ ~ ~ ~ ~ ~ ~ ~ o~ ~ ~ ~ ~ ~ ~ ~

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62 Pacific Northwest Forests increased presence of coarse wood) and a higher amount of woody debris in streams and terrestrial areas. Old-growth forests are also less susceptible to large-scale disturbances and pest outbreaks, and they have a Tower incidence of root-rot problems. Old-growth forests have unique microclimates and might have an effect on regional climate as wed. Species Diversity The Scientific Analysis Team (SAT 1993) listed 80 terrestrial vertebrate species (16 amphibians, 38 birds, and 26 mammals) that were "closely associated" with old-growth stands in the range of the northern spotted owl, along with 99 invertebrate species and Ill vascular plant species. In his analysis of forests in western Oregon and Washington, Harris (1984) estimated that I18 terrestrial vertebrate species used old growth as primary habitat, 135 species used young forests (before canopy closure), and 90 species used mature forests. He also noted that "all of the species that meet their primary habitat requirements in...early stage forests find abundant habitat throughout the western Cascades and are generally common. Forty of the species finding primary habitat...in old- growth or mature forest cannot meet their habitat requirements outside this forest type." Thomas et al. (1979) found somewhat different patterns in the Blue Mountains of eastern Oregon and Washington. In all forest types in the Blue Mountains, more terrestrial vertebrate species reproduced in mature and old-growth stands than in early-successional stands, but little difference was seen between old-growth and mature stands. The Blue Mountains and the Cascades have significantly different environ- ments and hence, different patterns of forest development. Arthropods and other small or inconspicuous organisms account for the bulk of diversity but have been largely overlooked until recently (Parsons et al. 1991), despite their importance in terms of numbers, species diversity, and functional importance. Lattin (1990) estimated that 8,000 arthropod species are found in the H.~. Andrews Experimental Forest in the central Cascades, compared with 143 vertebrate species and 460 vascular plant species. Many of those arthropods live either in

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Outgrowth Forests 63 canopies or soils, the least studied subsystems in forests. Schowalter (2000) compiled data from 9 forest, grassland, desert, and marsh ecosystems where extensive species inventories are available to show that arthropods commonly account for at least 70-90% of all species present. The few studies that have been completed found striking differences between old-growth and younger forests in epiphyte, arthropod, and lichen communities. For example, one of the distinguishingcharacteris- tics of old-growth Douglas-fir forests is the abundance of epiphytic plants (mosses and lichens), especially the nitrogen-fixing lichen Lobana oregona. J obaria occurs in younger stands but not nearly as abundantly as In o1~-growth forests (Franklin et al. 1981~. Arthropod communities in old-growth canopies are significantly more diverse than in young plantations. Schowalter (1989, 1995) measured more than 70 species of arthropods associated with Douglas- fir and western hemlock foliage in old-growth forests in the central Cascades and only 15 species associated with Douglas-fir in 7- to 11- year-old stands. Diversity was 5-6 times greater in old-growth stands than in younger stands, with some of the most striking differences occurring in the diversity of predatory arthropods, such as spiders (Schowalter 1995~. Moreover, the structure of arthropod communities differed significantly between young and old forests. In the former, the biomass of phytophages (largely aphids) was 800% greater than that of predators (e.g., ants, wasps, and spiders), while in the latter, the biomass of plant eaters (largely defoliators) was only 20% greater than that of predators. That pattern suggests more effective internal controls over plant eaters in old-growth stands than in younger stands. The dominance of hardwoods and shrubs in young forests in part reflects the suppression of conifers by insects and pathogens at this stage. Conifers become re-established after populations of insects and pathogens have been reduced because they have so few conifer hosts (Goheen and Hansen 1 993~. The pines, western larch, western red cedar, Engelmann spruce, and western hemlock have higher tree mortality associated with root disease in early stages of stand development (younger than 30 years), but mortality decreases thereafter (Hagle and Goheen 1988~. Indigenous insects and diseases might have important roles in stand

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64 Pacific Northwest Forests development by mitigating the effects of biomass accumulation and competitive stress Trough natural pruning, thinning, and cycling nutrients. Old-growth forests generally have higher populations of predatory insects than younger forests; those insects might help maintain populations of herbivorous insects at lower levels than in young stands (Schowalter 1989, 1995~. Management practices that focus on short rotations or plantations of single species result in an overall loss of predators. Pests also are better able to find their hosts in such managed forests, and the systems become more susceptible to insect outbreaks (Hagle and Schmaltz 1993, Schowalter 1995~. togs and Woocly Debris Much of the influence of old-growth forests on environmental condi- tions is conferred by their large persistent structures. Whereas younger or smaller trees decompose relatively quickly (Harmon et al. 1986), large boles of old trees contain terpenoid and phenolic compounds in the heartwood that inhibit decay and provide structure and resources for soil and aquatic systems for centuries after tree death and fall (Harmon et al. 1986; Schowalter et al. 1992; Schowalter et al. 1998; Progar 2000~. Logs decomposing on slopes stabilize soils, retain moisture during dry periods (often more than 200% of wood dry weight, especially after a period of decay has increased porosity), and provide organic matter and nutrients that are tapped by mycorrhizae and roots penetrating wood from surrounding plants (Harmon et al. 1986; Schowalter et al.1992~. Logs falling into streams create the pool-and-riffle structure that contributes to aquatic biodiversity. Logs are essential components of salmon habitat, slowing erosion from upsIope and minimizing scouring of streambeds that degrade salmon habitat. Although amounts of woody debris that can function in conserving mycorrhizal inoculi are highest in late-successional forests (Vogt et al. 1995), the actual diversity and biomass of mycorrhizai fungi may peak in the early stages of stand development. Only limited data exist on the pattern of mycorrhizal development with stand age (Vogt et al. 1992), but existing information suggests that the number of mycorrhizal species and the associated sporocarp biomass peak at canopy closure. Thus, total diversity of mycorrhizal fungi may be more closely tied to

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Outgrowth Forests 65 the net prunary production of a forest than to structural components such as coarse wood. In contrast, the diversity of certain groups, such as the truffle farmers, is higher in old-growth stands than in young stands (Amaranthus et al. 1994~. The number of sites for mycorrhizal fungal colonization of root tips is maximal at canopy closure (Vogt et al. 1983~. The peaking of mycorrhizal fungi in early states of stand development might indicate a carbon cost to plants to maintain mycorrhizal associations (Vogt et al. 1991~; hence, less carbon might be available to sustain all plant parts after that stage (Grier and Logan 1977~. All Pacific Northwest forest tree species have a good complement of different mycorrhizal species that are capable of colonizing tree-root systems (e.g., almost 1,000 species of mycorrhizal associates have been reported for Douglas-fir (Perry et al. 1992~. Many of the trees share similar species of mycorrhizal associations. Insects and pathogens are instrumental in directing succession Outgrowth forests are more resistant to crown fires than are through their selection of younger forests.... plant species. Although tree characteristics have been emphasized in most studies of succession, insects, pathogens, and other taxa influence seed production and dispersal, tree growth and survival, nutrient cycling, and soil-fertility patterns, and therefore affect the rate and direction of successional transformation. For example, several insects and root pathogens that kill Dougias-fir trees are instrumental in accelerating the transition to hemlock or cedar forest but also might provide litter accumulation sufficient to fuel a stand replacement fire (Goheen and Hansen 1993~. Insects and root diseases responsible for stand replacement also can retard germination and growth of young conifers after disturbances. Suscepribi/ity to Disturbance Old-growth forests are more resistant to crown fires than are younger forests, perhaps because of high humidity and litter moisture (Perry 98Sa; Franklin et al. 1989; Chen et al. 1993~. The hardwood and shrub species in the old-growth understory also appear to inhibit fire spread

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66 Pacific Northwest Forests and to protect interspersed conifers. Young, evenly aged conifer forests are the most flammable ancE are particularly vulnerable to reburns (Agee 1993~. Old-growth forests might be most vulnerable to fire where adjacent younger, drier, and more flammable forests provide the necessary heat and fuels to carry flames into the forest canopy. However, the heterogeneous structure of old-growth forests and the water-saturatecl logs provide barriers to fire spread, allow trees to survive, and provide open spaces for growth of understory (Perry 198Sa; Paiazzi et al. 1992~. AQUATIC ECOSYSTEMS Streamsicle disturbance and flooding have important impacts on virtually all components of aquatic ecosystems (Reiter and Beschta 1995~; however, no component has received more attention than salmon and trout. Seven species of salmon exist in the Pacific Ocean, and five occur on the North American continent: chinook (Oncorhynchus tschawylscha), coho (O. kisutch), chum (O. keta), pink (O. gorbuscha), and sockeye salmon (O. nerka). in addition, there are anadromous trout, steelhead or rainbow trout (O. mykiss), coastal cutthroat trout (O. cZarki), and DoEy Varden trout (SaZveZinus maZma). Those salmonid species cto not obligately require old-growth forests for survival, but they dicI evolve across a geographic range that closely overlaps that of the Northwestern coniferous forests. Anadromous salmon and trout spawn in freshwater streams. Fry and juveniles rear in streams and rivers (sockeye in lakes), migrate to the ocean, spend varying amounts of time (depending on species and stocks), return as adults to their natal streams, spawn, and die. All Pacific salmon die after spawning, but a small fraction of anadromous trout are capable of repeated ocean migration and spawning. All eight species of the anadromous salmon and trout spend a portion of their lives in freshwater habitats in forested areas of the Pacific Northwest. As a result, their survival and production are closely linked to the forest ecosystem and are influenced by changes caused by forest practices (NRC 1996~. Disturbance, which is a critical feature of streams and rivers, strongly influences the survival of salmon and trout. Floods are a natural and

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Outgrowth Forests 67 essential component of rivers. Streams are shaped by floods, and rivers are more productive after flooding. Although productivity might decline immediately after flooding, flooding in streams creates pools, cleans gravels, and delivers dissolved and particulate nutrients. Refuges, such as deep pools, boulders and logs, off-channelL habitats on flooclplains, and stems and roots of streamside forests, are required for aquatic organisms to survive frequent disturbances. Over short- and long-term scales, old-growth forests along streams and floodplains create sizes and amounts of woody debris Mat cannot be provided by younger forests. Floodplain habitats' large woody debris, and pool habitats have declined substantially in recent years, and conversion of old-growth forests to younger stands is one of the causes of habitat losses related to the decline of Pacific salmon (NRC 1996~. Many processes mediated by old-growth trees can be provided in riparian reserves or stream-management zones, but riparian management must be integrated with watershed conditions and land-use practices. EXTENTAND STATUS OF OLD-GROWTH FORESTS Differences in estimates of the past and present extent of old-growth forest in the Pacific Northwest reflect differences in the definitions used in each study: the time frame (e.g., presettlement, early settlement, pre- World War IT, or current), the geographic area (e.g., states, Eastside forests, or Westside forests), land-use types (e.g., forest lands only or combinations of forest, agricultural, residential, and urban lands), and type of ownership (e.g., public, private, or national park). Eight studies have attempted to evaluate the current extent of old-growth forest in the Pacific Northwest, and eight studies have attempted to reconstruct the past distribution (Table 3-4~. When allowances are made for the factors above, the study results are much the same. Regional patterns of forest age classes and structure before logging resulted from the frequency and severity of natural disturbances, primarily fire, and to a lesser degree, wind, insects, and pathogens. The natural fire regime is closely linked to climate and, as a result, historic patterns of forest succession have varied within the region. Estimates of the extent of oid-growth before logging in the Douglas-fir

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68 Pacific Northwest Forests TABLE 34. Comparison of Studies of the Historical Extent of 015- Growth Forests in the Pacific Northwest . . . Study Timeframe Region Landbase Extent Bonnicksen Pre-1850 W OR, Public and private 42% 1993 W WA forest land 77% Boothl991 Pre-1850 W OR, Public and private 62% W WA forest land Teensmaet 1890 CoastalOR Public end private 46% al. 1991 forest land Morrison Pre-1850 WOR,WWA Public end private 66% 1991 forest land Morrison 1200-1990 Central Public forest land 25%- and Swanson Cascades, OR only 49% 1990 Andrews Mid-1930s WOR,W WA, Public end private 44% and Cowlin NW CA forest land 1940 Cowlin et al. 1936 E OR, E WA Public and private 73% 1942 (excludes 2 forest land counties) Lehmkuhl et 1932-1959 E OR, E WA Public forest only Mean- al. 1994 (6 national 8.8% forests) Bolsinger mid-1950 E OR Public land only 44% and Berger (Ochoco National 1975 Forest) Hemsbom 1980 Mt. Rainer Public forest land 65% and Franklin (represents National Park only 1982 historical) region west of the Cascades crest, inferred largely from fire histories, range from 5.6 million ha to nearly ~ million ha, or 54-70% of the commercial forest area (Andrews and Cowlin 1940; Franklin and Spies 1984; Norse 1990; Booth 1994~. The first inventory of Pacific Northwest

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Outgrowth Forests 69 forests on the west side of the Cascades, conducted in the m~-1930s after a period of heavy logging in the lowlands and severe logging- related fires, recorded old-growth forests covering 4 million ha, or 44% of the commercial forest (Andrews and Cowlin 1940~. In southwestern Oregon, where little logging had occurred by the 1930s, old-growth trees of various species accounted for 73% of the commercial forest (Cowlin et al. 1942~. In the Oregon Cascades and eastern coast range, only S% of forests had been cut by the m~-1930s, and 57% remained in old-growth stands. In western Washington, 18% of the commercial forest had been logged by the 1930s, leaving 45% in old-growth stands. Most reconstructions of presettlement conditions estimate that oIc[- growth forests covered 54-70% of the forest area in western Washington and Oregon. Timber harvest and development have reduced this to 13- 18% (Table 3-5~. Using a landscape simulation mode} driven by climate change and its coupling to fire, Wimberly et al. (2000) estimated that old-growth forest coverage in the Oregon Coast Range varied from25-75% curing the past 3000 years. The earliest quantitative estimate for the Oregon coast range was that old-growth trees covered 33% of the commercial forest in the mid-1930s (Andrews ancE Cowlin 1940~. By that time, a significant amount had been logged, and large areas of old-growth trees had been destroyed by rampant wildfires. If logged areas and the TilIamook burn are added to the 1930s inventory, estimates of old-growth stands in presettlement coast range forests rises to 47%, which is consistent with the Teensma et al. (1991) estimate of 46% in 1890. Slightly more than one-third of coast range forests were between 90 and 200 years old in the 1930s survey. Because of logging-related fires, estimates of fire patterns based on wildfires during the past century are likely to overestimate presettlement fire frequency and, thus, underestimate the original extent of old-growth forests. At the time of the 1930s survey, an additional 2.5 million ha in western Oregon and Washington were 90- to 160-year-old stands that had been established by fire. About 50% of those stands had trees averaging 50 cm dbh or more and were beginning to take on old-growth characteristics. Thus, by the 1930s, despite extensive logging, 68% of commercial forest land in western Oregon and Washington remained in what FEMAT (1993) classified as "late-successional/old-growth" (stands 80 years of age or older). Based on that figure, when Euro-Americans

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70 Pacific Northwest Forests TABLE 3-5. Comparison of Studies of the Existing Extent of Old-Growth Forests in the Pacific Northwest Study Timeframe Region Landbase Extent . . Morrison Mid 1980s W OR, W Public and 13% 1991 WA private forest land Lehmkuhl et 1985-1990 E OR, E WA Public forest Mean- al. 1994 only FEMAT 1993 1990 W OR, W Public forest <20% WA, NW CA only Hann et al. 1992 W MT Public forest 3%-21% 1994 only (Beaverhead N.F.) Bolsinger and 1992 W OR, W Public and 18% Waddell 1993 WA, NW CA private forest lands arrived in the area in the 1800s, as much as 80% of the forests in western Oregon and Washington were older than 80 years and about two-thirds were older than 200 years. Forests of interior Oregon and Washington were also dominated by old-growth stands. The first comprehensive survey of forest resources in eastern Oregon and Washington (excluding northeastern Washington) was completed in 1936, at which time "the area of commercial forest land twas] characterized by a high proportion of old- growth" (Cowlin et al. 1942~. The 1936 survey found that old-growth forests of ah types made up 89% of the sawTog-sized stands and 73% of all commercial forest in eastern Oregon and Washington. Nearly two- thirds of Eastside forest lands covered by the 1936 survey were dominated by ponderosa pine, which, even after a period of heavy cubing that began in the early 1920s, was still mostly old-growth. If adjustments are made for logging before 1936, the original low-and midelevation ponderosa pine forests were nearly 90% old growth. Those stands typically contained trees up to 60-70 in dbh with most of the stand volume concentrated in trees 20-44 in dish (Cowlin et al. 1942~.

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O/~-Growth Forests 71 In the late 1800s on what is now the Ochoco National Forest, surveyors recorded ponderosa pine at 93% of the section corners in all but the wettest forest lopes (north slopes above 5,000 feet in elevation). Various tree species other than ponderosa pine dominated forests at higher elevations and on moist sites at m~delevations in the interior. In the 1936 survey, those species were classified as either large or small rather than as old-growth or second-growth, which was the case with ponderosa pine and Douglas-fir. In 1936, 71-96% of species other than ponderosa pine were classified as large, which almost certainly would fit within current definitions of old-growth for these types. In 1936, 11% of Eastside forest lands were lodgepole pine, a pioneer tree species that colonizes sites after wildfire. Most of those stands were classified as medium-sized and probably were not old-growth. No comprehensive early surveys exist for Idaho, western Montana, and extreme northeastern Washington. Forest types of central Idaho are quite similar to those in the Blue Mountains of Oregon and Washington, and historic patterns are unlikely to have differed substantially between the two areas. In contrast, forest types in northeastern Washington and northern Idaho are unlike other Eastside forests, having higher proportions of Douglas-fir and a representation of species such as western hemlock and western red cedar that are more typical of Westside forests. Historically, northeastern Washington and northern Idaho had extensive stands of western white pine that were probably mostly old growth. These have either been logged or killed by white pine blister rust (an introduced pathogen). The moist western red cedar stands, common in northeastern Washington and northern Idaho, probably had a relatively large proportion of old growth, because fires were infrequent and of a low intensity that seldom killed large overstory trees. The most extensive and recent analysis of the current extent of old- growth forest included all federal, state, and private forest lands in western Washington, western Oregon, and northern California (Bolsinger and Waddell 1993~. Old-growth forests were estimated to occupy IS% of the existing forest lands in the area. That analysis was based on recent maps and interpretations by the array of institutions and ownerships that have been responding to the debate over old- growth stands during the past 2 decades.

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72 Pacific Northwest Forests Conditions of Eastside forests were reviewed by the Eastside Forests Scientific Pane} (Henjum et al. 1994), which concluded that approximately 25% of the land on eight national forests in eastern Washington and Oregon was old-growth forest. When public and private lands are considered, that proportion decreases to less than 20 %, which is consistent with the distribution of old growth estimated for Westside forests (Bolsinger and Wadded 1993~. The composition of Pacific Northwest forests has changed dramatically over the past 10,000 years since the last ice age. Thus, the distribution and amount of old-growth forests before settlement represents only one point along a continuum of natural forest change. in some prehistoric periods, old-growth coniferous forests made up less than Me 60-70% of the forest that settlers encountered when they first came to the Northwest (Brubaker et al. 1992; Whitiock 1992~. Regardless of the extent that old-growth forest might have increased and decreased naturally over thousands of years, the reduction of old-growth over the past century is a more abrupt change than the forests have undergone since the last ice age. SUMMARY Because the ecological characteristics of old-growth forests vary from one forest to another, no single definition of old growth is appropriate. However, as knowledge has progressed, various indexes of successional development have been developed to characterize forests. Old-growth forests are bioticaDy complex, win some species depending on unique features of old growth to survive, and the biological functioning of old- growth and late-successional forests is important to management of terrestrial and aquatic ecosystems. Fifty percent of Pacific Northwest land is forested. Depending on locality, late-successional and old-growth forests originally made up from54-70% of the forests, but now they are only 10-~%. Harvest since 1850 has removed more than 80% of the late-successional and old- growth forests of the Pacific Northwest; nonetheless, more than 80% of the remaining old-growth forests occur in national forests.