|FEIS Home Page|
|Figure 1. Western swordfern in the forest understory. Photo courtesy of Hansen's Northwest Native Plant Database (http://www.nwplants.com).|
Western swordfern is closely related to Polystichum imbricans based on morphologic  and electrophoretic  analysis.
Hybrids: Hybridization and polyploidy have contributed to morphological diversity and taxonomic complexity in the widespread genus Polystichum . At least 1 or 2 hybrid plants are expected in large, mixed Polystichum populations, and several sterile interspecific hybrids have been reported. Hybrids between western swordfern and P. andersonii, P. californicum, P. scopulinum, P. braunii, P. kruckebergii, P. dudleyi, and P. lemmonii have been reported (review by ). According to Hickman , hybrids with P. dudleyi are called P. californicum. Polystichum munitum × P. andersonii and P. munitum × P. lemmonii hybrids are described by Soltis and others .SYNONYMS:
|Figure 2. Western swordfern distribution in the United States and Canada. Map courtesy of USDA, NRCS. 2012. The PLANTS Database. National Plant Data Team, Greensboro, NC. (2012, 29 February).|
Western swordfern occurs along the Pacific Coast from southeastern Alaska south to Baja, California [81,100,126,183], with disjunct populations in northeastern Washington, northern Idaho, northwestern Montana, northeastern Oregon [130,189], and the west Kootenays in British Columbia . Western swordfern is most abundant and widespread in coastal areas from central Vancouver Island and the adjacent mainland southward , throughout the western Coast and Cascade ranges [81,100], and into northwestern California . Its latitudinal distribution is described as low-subarctic, high-temperate .
Western swordfern occurs in the following states and provinces as of 2014:
United States: AK, CA, ID, MT, OR, PA, SD, WA
Canada: BC , YT 
In Mexico, western swordfern occurs on Guadalupe Island [58,98]. According to NatureServe , it occurs in Yukon Territory, is nonnative in Pennsylvania, and may be extirpated in South Dakota. It is naturalized in Europe .
SITE CHARACTERISTICS AND PLANT COMMUNITIES:
Western swordfern is widespread in the understory of mesic coniferous and moist mixed-evergreen forests at low to middle elevations (sea level to 7,200 feet (0-2,200 m)) along the northern Pacific Coast [36,58,100,121,126,170,189]. It is among the most common herbaceous species and is often dominant on nitrogen-rich or moist sites in forest habitats where western hemlock and/or coast Douglas-fir (hereafter, Douglas-fir) are characteristic species. These forests occur throughout low-elevation western Washington and on the western slopes of the Cascade Range, around the margins of the Willamette Valley, and in the Coast Ranges . Western swordfern sometimes codominates the understory of oak and dry Douglas-fir forests and woodlands west of the Cascade Range in the Puget Lowlands, Willamette Valley, and Klamath Mountains. It is especially common on sites that formerly supported grasslands and savannas in these areas . Western swordfern may dominate the herb layer in lowland riparian areas west of the Cascade Crest from British Columbia south into northwestern California. These habitats are typically comprised of tall (6-30 feet (2-9 m)), deciduous shrublands, woodlands or forests, or some mosaic of these. Red alder is the most widespread tree species .
Climate: Western swordfern thrives in humid coastal climates with mild winters. It also occurs in areas of moist, relatively mild continental climate in northern Idaho, northwestern Montana, and adjacent areas of British Columbia, but in these areas it tends to be restricted to shaded, moist, northern aspects [74,154]. Its frequency and abundance decrease with increasing elevation and continentality [41,121,175].
Western swordfern is among the most typical and abundant understory plants in Sitka spruce  and redwood  forests along the Pacific Coast. Sitka spruce forests are limited to a relatively narrow oceanside strip characterized by mild winters, cool summers, and abundant moisture throughout the growing season . Extremes in moisture and temperature are rare; the climate is uniformly wet and mild. Precipitation averages about 80 to 120 inches (2,000-3,000 mm) , but may reach 220 inches (5,600 mm) in some areas of Alaska and British Columbia . Frequent fog and low clouds add moisture during the relatively drier summer months . Climate in the redwood forest zone is similarly characterized as moist and temperate , with high rainfall and dense, dripping fog . Annual precipitation averages nearly 60 inches (1,500 mm), of which 10% to 25% falls in the warmest months and 60% to 70% from December to March . Plants in redwood forests depend on fog absorbed through foliar uptake to stay hydrated during the relatively dry summer . The high foliar uptake capacity of western swordfern may allow it to rely completely on fog water during the summer, when fog exposure is frequent (, but see Other Management Considerations). Western swordfern's foliar uptake capacity and morphological characteristics vary with latitude in the redwood forest zone (Table 1), with its greatest foliar uptake capacity in the central part of the zone and no foliar uptake capacity at the southern end .
|Table 1. Mean (SD) size and abundance of western swordfern crown and fronds measured inside plots at each of 7 old-growth redwood forest sites in California where western swordfern was the understory dominant. Sites are listed from northernmost to southernmost .|
|Frond length (cm)|
|Prairie Creek||5.4 (1.3)ab*||22.8 (20.6)a||123.0 (42.8)a||86.6 (19.7)a|
|Humboldt Redwoods||6.5 (3.0)a||14.5 (11.4)bc||94.2 (27.0)a||74.3 (21.1)b|
|Angelo Reserve||6.1 (1.9)a||18.9 (13.7)ab||115.3 (44.8)a||60.2 (11.9) cd|
|Hendy Woods||7.8 (2.6)a||13.9 (9.3) bc||108.1 (27.0)a||62.1 (12.9)c|
|Grove of Old Trees||6.8 (1.5)a||15.2 (12.6)bc||103.2 (26.0)a||56.7 (15.0) d|
|Roy's Redwoods||5.5 (2.0)ab||16.2 (10.8)bc||88.9 (32.5)a||51.4 (16.9) e|
|Big Basin||2.9 (1.9)b||11.5 (8.8)c||33.5 (29.7)b||48.1 (15.7)e|
|*Values followed by different letters within a column are significantly different (P<0.05).|
The climate in the western hemlock forest zone is wet and mild but varies with latitude, elevation, and location in relation to mountain massifs. Moisture and temperature extremes are greater farther inland . Precipitation occurs mainly during the winter, with brief summer droughts [64,173], and averages about 30 to 170 inches (800-4,400 mm) annually. Precipitation falls mostly as rain or cloud drip, with minimal snow accumulations [169,173,181]. While western swordfern's evergreen fronds are presumably somewhat resistant to frost, they may limit its ability to survive in areas with cold winters . It is not common on sites where snow pack is deep [81,131], and western swordfern associations typically occur where little snow falls (e.g., ).
Site characteristics: Western swordfern tolerates a range of site characteristics, from the coastal fog belt to montane and subalpine sites . It is an indicator of mesic and moist, nutrient-rich environments in western hemlock and Douglas-fir forests in western Oregon and Washington [4,39,81,94,131], and it is an indicator of moist, nutrient-rich, humus-rich forests and shaded slopes in British Columbia [121,175]. Plant associations where western swordfern is an understory dominant typically occur at low elevations on productive soils, especially those enriched by surface flow of fine organic materials . Soils typically remain saturated throughout the year due to subsurface water from upslope [81,131], flat topography with impeded soil drainage [118,169], near proximity to surface water, high precipitation, high humidity, or frequent fog (see Moisture relationships for more information).
Western swordfern associations often occur on sites with high timber productivity; these sites are frequently logged [64,161]. The western hemlock zone includes some of the most productive forest land in the Pacific Northwest [64,82,208], and communities where western swordfern dominates the understory are some of the most productive among these [64,65,71,95,97,198,208]. Impressive stands of Douglas-fir, western hemlock, and western redcedar are possible , with sparse shrub layers and well-developed herb layers that are often described as lush or luxuriant, because of abundant western swordferns [53,62,64]. High moisture availability and nutrient-rich soils contribute to the high productivity of these sites [64,119]. In British Columbia, for example, these sites typically occur on valley bottoms and relatively flat alluvial terraces close to rivers. Soils are from base-rich parent materials and have loamy textures with high soil moisture holding capacity, few coarse fragments, and good drainage .
Western swordfern may reach its best growth and greatest abundance in undisturbed, old-growth stands, especially those dominated by western hemlock or Sitka spruce (Table 2); lush growth of western swordfern may indicate late-successional or relatively undisturbed sites. Western swordfern accounted for almost all understory cover in the central, protected valleys of Sucia Island, Washington, where vegetation is undisturbed, wind is minimal, summer temperatures are low, and soil moisture is high. Its fronds had a spread of nearly 7 feet (2 m) .
|Table 2. Western swordfern cover and site characteristics in remnant old-growth forests in the North Coast Range of Oregon .|
|Plant association||Western swordfern cover (%)||Elevation (feet)||Precipitation (inches)||Moisture group*||Slope (%)||Aspect (degrees)||Slope position|
|Sitka spruce/redwood-sorrel||40.0||1,200||110||41||73||slope, upper 3rd|
|Sitka spruce/redwood-sorrel||16.7||1,500||112||30||297||slope, upper 3rd|
|western hemlock/redwood-sorrel||34.0||1,180||118||wet||59||150||slope, lower 3rd|
|western hemlock/vine maple/western swordfern||40.0||1,320||110||wet||71||181||slope, lower 3rd|
|western hemlock/vine maple/western swordfern||28.3||1,400||107||mesic||41||200||bench|
|western hemlock/salal||13.7||480||105||mesic||52||215||slope, lower 3rd|
|western hemlock/Pacific rhododendron-salal||1.4||1,300||88||mesic||54||215||slope, middle 3rd|
|western hemlock/dwarf Oregon-grape-salal||6.0||1,570||97||mesic||59||133||slope, middle 3rd|
|western hemlock/vine maple-California hazelnut||4.3||2,030||90||dry||49||154||slope, upper 3rd|
|grand fir/California hazelnut/white insideout flower||18.3||1,100||61||dry||41||329||slope, upper 3rd|
|grand fir/California hazelnut/white insideout flower||3.0||1,200||65||dry||31||29||rounded ridge top|
|*Identified only for Douglas-fir-dominated stands >200 years old.|
Western swordfern tolerates disturbance and is common in second-growth forests after logging and other disturbances (see Successional Status), and sometimes occurs even in highly disturbed areas. For example, it was common along electrical transmission rights-of-way in western Washington and Oregon, where it ranged in cover from 2% to 55% . It was noted as particularly common along roadside clearings in southern coastal British Columbia .
The following discussion describes common site characteristics of western swordfern communities and gives examples showing its range of site tolerances. This information comes almost exclusively from vegetation classifications, although a few studies were available (as of 2015) that examined western swordfern site affinities. For example:
See the following vegetation classifications for details about western swordfern plant communities: [6,53,64,65,94,95,97,208]. See the following vegetation classifications for descriptions of western swordfern communities in specific locations: [16,53,94,95,99,143,208].
Elevation, landform, topography: Western swordfern is most common at low elevations, but it occurs from sea level to about 7,200 feet (0-2,200 m) . It is widespread in the western hemlock zone in the Pacific Northwest, which occurs from about 490 to 1,800 feet (150-550 m) in wet environments, such as the western slopes of the Olympic Mountains , and from sea level up to about 4,000 feet (1,200 m) in relatively drier environments [64,97,181]. Western swordfern is most common up to about 2,500 feet (760 m) on the Olympic National Forest . In California, it occurs below 5,200 feet (1,600 m) . It rarely occurs above 3,000 feet (900 m) in southwestern British Columbia, or above 300 feet (100 m) on the northern coast of British Columbia . Plants at high elevations near the coast may be stunted or sparse (e.g., at 6,300 feet (1,920 m) in the northern Cascade Range [49,50]). Inland populations occur at relatively higher elevations; for example, western swordfern's range in Montana is from 3,500 to 5,000 feet (1,070-1,500 m) .
Western swordfern communities in the western hemlock zone are most common on lower slopes and flats such as toe slopes, benches, and stream terraces, although occurrence on steeper slopes at any aspect is possible. For example, the western hemlock-Port-Orford-cedar/western swordfern-redwood-sorrel community occurs mostly on flats but sometimes on slopes up to 35%, mostly with northern aspects . In the western hemlock zone of the central western Cascade Range in Oregon, western swordfern communities tended to occur on slopes with north aspects, ranging from 18 to 45 degrees . The western hemlock/western swordfern association in Mt Rainier National Park occurs mostly on low slopes or sloping benches with southerly aspects, but it can be found on slopes of 70% or more with any aspect . Western swordfern was strongly correlated with aspect, favoring north- and east-facing slopes, in successional red alder stands in the Alsea River drainage of the Central Coast Ranges in western Oregon .
In redwood forests, western swordfern associations occur on both slopes and flats, and western swordfern cover may be greater near the coast than farther inland. In old-growth redwood stands in the Coast Ranges of northern California, western swordfern cover was greater on coastal sites than inland sites. Its cover was similar on slopes and flats near the coast, but it occurred only on flats inland . Western swordfern occurred in all streamside redwood sites studied in northwestern California . In southern Monterey County, the redwood/western swordfern-Pacific trillium ecological type occurs on mesic, moderate to very steep (50-100%), lower slopes. Most stands face north to north-northwest and are 50 to 175 feet (15-53 m) from the nearest stream .
Soils: Western swordfern grows on a variety of soils and parent materials including exposed bedrock, but the most luxuriant growth is found on deep, loamy soils, especially those developed on fluvial parent materials (e.g., [53,64,97]). Western swordfern is characteristic of moist but strongly drained, deep soils in northwestern Washington  and Canada , although western swordfern associations may indicate relatively shallow soils in some sites (e.g., [43,94,97]). Many western swordfern associations occur on moderately deep to deep (effective rooting depths of 3 feet (1 m) or more), well-drained but moist soils with fine to moderately fine (silty clay loam to sandy loam) surface textures [16,53,64,91,97,99,169]. Soils range from relatively stone free [53,94] to moderately stony (5-30% coarse fragments) or stonier [53,65,94]. Parent materials include alluvium, colluvium, outwash, and glacial till [53,97] derived from andesite, basalt, sandstone, siltstone, tuffs, breccias, lahar, or tephra deposits [53,65,95]. Western swordfern occurs only occasionally on rock , such as shaded talus slopes , cliffs, outcrops [98,192], and terraces adjacent to the ocean . On Junipero Serra Peak in California, western swordfern occurred in Coulter pine and sugar pine stands on rock outcrops .
Western swordfern is nitrophytic  and grows best on nutrient-rich soils. It is a characteristic understory species on soils that are moderately to very rich in nutrients (e.g., [81,97,118,120,123,131,169,175]). Abundant and vigorous growth of western swordfern may indicate nutrient-rich sites . In Canadian forests, presence of western swordfern indicates base-rich parent materials  or nitrogen-rich sites. It has greater frequency and cover on soils with relatively high pH and mineral nitrogen and relatively low carbon:nitrogen ratio .
Soils in western swordfern communities are often rich in organic matter (e.g., ), and western swordfern can grow on decaying stumps . In redwood/western swordfern forests, soils are Ultisols; base saturation is low, but organic matter content is high . In cool mesothermal forests in southern British Columbia, western swordfern occurs on a variety of organic substrates, but it is an indicator of moder and mull humus forms [123,175], which are differentiated by a layer of organic materials with more than 17% organic carbon overlying mineral soil . A comparison of vegetation on stumps and on the ground in coniferous (Douglas-fir-western hemlock-western redcedar) and deciduous (red alder) forest sites in Olympia, Washington, showed that western swordfern had similar stem density in each forest type, and had higher stem density on ground microsites in both forests (P<0.005). It sometimes occurred on stumps in the deciduous forest, but not in the coniferous forest .
Moisture relationships: Western swordfern associations are characteristically found in moist or shaded locations, where drainage is good but little moisture stress is encountered. In western hemlock forests, western swordfern is most often dominant in moist and wet communities  (e.g., see Table 3). For example, the western hemlock/western swordfern-redwood-sorrel association typically occurs on very moist streamside slopes, and the western hemlock/western swordfern association occupies toe slopes and northern aspects . On the Olympic National Forest, the Sitka spruce/western swordfern-redwood-sorrel association occurs along toe slopes or in areas of high precipitation, high humidity, or fog . The western hemlock/Pacific rhododendron/western swordfern association on the Siuslaw National Forest is the moistest of the Pacific rhododendron associations .
|Table 3. Examples of western swordfern associations in the western hemlock forest zone on the Gifford Pinchot National Forest on a moisture gradient from wet to dry (Topik and others 1986 as cited by )|
|Wet group||Moist group||Mesic group||Dry group|
|devils club-western swordfern||
|dwarf Oregon-grape-western swordfern||-none-|
The 2 most important understory or groundlayer species in western hemlock and Douglas-fir forests are western swordfern on relatively moist sites and salal on slightly drier sites [16,41,62,63]. In Douglas-fir/western hemlock forests in the eastern portion of the Olympic Peninsula, for example, forest understories are dominated by dense salal on the drier west- and south-facing slopes, and by western swordfern, twinflower, oneleaf foamflower, and northwestern twayblade on north- and east-facing slopes . Western swordfern and salal may codominate on intermediate, mesic sites [64,150]. On alluvial landforms of the McKenzie River valley, Oregon, 2 topoedaphic climaxes were identified. Understories were dominated by western swordfern and redwood-sorrel on terraces with fine, sandy loam to silt loam soils derived from silty river alluvium; and by dwarf Oregon-grape and salal on rockier soils with coarser alluvium or glacial outwash. Sites with finer-textured soils had greater late summer moisture availability . Western swordfern is an indicator of relatively cool, moist sites in Douglas-fir forests on the HJ Andrews Experimental Forest, Oregon , and in tanoak-redwood and tanoak-vine maple associations in southwestern Oregon [13,14].
In British Columbia, western swordfern is most abundant in ecosystem associations with moderately well-drained to poorly drained soils [118,140]. Western swordfern is sporadic to scattered on water-shedding sites, and plentiful to dominant on water-receiving and colluvial sites enriched by surface flow of fine organic materials . In the coastal Douglas-fir zone of southern Vancouver Island, where summer moisture deficits are common, western swordfern occurs only where seepage water augments soil moisture supply. In wetter climates it is less restricted by soil moisture .
In drier forest zones, western swordfern presence or abundance may indicate relatively moist sites. In the Willamette Valley, the Oregon white oak/California hazelnut/western swordfern forest community was the most mesic and occurred on moderate to steep, sheltered slopes. Western swordfern cover averaged 34% but reached 80% with fronds >3 feet (1 m) tall on the best sites. In progressively drier communities, frequency, cover, and height of western swordfern declined (Table 4), and in the Pacific poison-oak community it grew "only as a sporadically distributed, depauperate plant" .
|Table 4. Western swordfern cover and frequency (%) in Oregon white oak plant communities listed from mesic to xeric |
|California hazelnut/western swordfern||sweet cherry/common snowberry||Saskatoon serviceberry/common snowberry|
In the Selway-Bitterroot Wilderness in Idaho, western swordfern is a common understory species in "older-aged" grand fir-western redcedar forests on creek bottoms and smaller stream ravines .
Plant communities: Western swordfern is widespread, abundant, and often an understory dominant in the maritime forests along the northern Pacific coastline; it also occurs in some inland forest types. Maritime forests occur between the ocean shore and the crest of the Coast Ranges and are variously dominated by western hemlock, Sitka spruce, redwood, western redcedar, and Douglas-fir [62,136]. It is an understory dominant in some Port-Orford-cedar, Pacific silver fir, Oregon white oak, and tanoak communities, and it often occurs in the understory of successional red alder communities. Western swordfern also occurs in drier forest zones, and at higher elevations near the Pacific Coast but is less often an understory dominant .Information compiled from vegetation classification literature from Oregon and Washington shows the average cover and frequency of western swordfern in plant communities in each of 5 forest zones (Table 5). Western swordfern is most common in the western hemlock zone, where it is most prominent in communities on cold, wet sites. It is well suited to the moist and wet climates in the Pacific silver fir zone but uncommon in the drier sites of that zone. Western swordfern is present in the warmer-drier Douglas-fir zone, but cover is low. It is infrequent in the mountain hemlock zone and absent or rare in the subalpine fir zone .
|Table 5. Average cover and frequency of western swordfern by selected forest associations in 5 forest zones in the Pacific Northwest |
|Forest zone/association||western swordfern frequency (%)||western swordfern cover (%)|
|Subalpine fir zone|
|Mountain hemlock zone|
|big huckleberry-Alaska blueberry||---||---|
|Pacific silver fir zone|
|Western hemlock zone|
|vine maple/sweet after death||100||9|
|Pacific dogwood/vine maple||73||4|
|western swordfern-threeleaf foamflower||100||39|
|dwarf Oregon-grape-western swordfern||100||26|
|Pacific rhododendron-western swordfern||82||22|
|Pacific rhododendron-dwarf Oregon-grape||70||10|
|creambush oceanspray-dwarf Oregon-grape||78||2|
|creambush oceanspray-baldhip rose||76||3|
Western hemlock zone forests: The regional climatic climax for the western hemlock zone in the Oregon Coast Ranges is thought to be the western hemlock/western swordfern association . Shrub layers are not well developed in these habitats, although vine maple or dwarf Oregon-grape may dominate. Lush herbaceous understories are common in western hemlock/western swordfern habitats. Foamflowers, twinflower, deer fern, lady fern, and several lilies are among the numerous succulent herbs that cover the forest floor in these rich habitats . See Appendix B for a list of western swordfern associations that occur in western hemlock forests and are described in regional vegetation classifications.
Sitka spruce zone forests: Western swordfern is a common understory species in the long, narrow Sitka spruce zone along the Pacific coastline from southeastern Alaska to southern Oregon. Coniferous forest stands in this zone are typically dense, tall, and among the most productive in the world. Western hemlock-Sitka spruce forests are mostly restricted to a narrow coastal band but may occur as much as 50 miles (80 km) inland on cool, moist slopes, along stream bottoms, and around lake margins where fog is prevalent during the growing season. Western swordfern, redwood-sorrel, and red huckleberry are common in these optimum conditions . Western swordfern and redwood-sorrel are the most important understory species in old-growth forests dominated by Sitka spruce and western hemlock in the very heavy rainfall area on the western slopes of the Olympic Mountains. These forests have distinctive characteristics including massive trees, numerous canopy levels, evergreen dominants, a profusion of epiphytes, an abundance of bigleaf maple and vine maple, abundant nurse logs, and "an intangible overall quality of growth" . See Appendix B for a listing of Sitka spruce/western swordfern associations described in regional vegetation classifications.
Western swordfern is less common in Alaska and was mentioned in only a few vegetation classification publications from there. Details were lacking in all but one of these. In the Stikine area of Southeast Alaska it occurred at low frequency and cover in closed-canopy forests (60-100% canopy cover) dominated by western hemlock, Sitka spruce and/or western redcedar, and in open-canopy (25-59% canopy cover) western hemlock forests. Its greatest frequency was in western hemlock/blueberry/spreading woodfern communities (22%), where its cover ranged from 1% to 6%; and in Sitka spruce-western hemlock/American skunkcabbage/sphagnum communities (33%), where its cover ranged from 3% to 10% .
Pacific silver fir forests: Western swordfern is an understory dominant in Pacific silver fir forests on the Olympic Peninsula (see Appendix B). In the Cascade Range of Oregon and southern Washington, western swordfern occurs on warm sites in the Pacific silver fir series [26,93] but typically has low cover (about 1-2%) [53,93].
|Redwood forests: Redwood forests occur in a narrow strip from southwestern Oregon to Santa Cruz and are characterized by pure stands of redwood on floodplains and with a mixed lower tree stratum on hillsides. Western swordfern is one of the most abundant plants in redwood forests [20,25,41,205], especially in old-growth stands [21,23] on moist sites  such as alluvial flats and lower slopes . See Appendix B for a list of redwood/western swordfern associations.|
|Figure 3. Western swordfern growing under towering redwoods on the Simpson Reed Grove Trail, Redwood National Park. Photo courtesy of the National Park Service, www.nps.gov|
Tanoak forest: Western swordfern is among the most common ferns in the tanoak series of the Siskiyou Region of southwestern Oregon. It is most abundant in coastal associations such as tanoak-coast redwood and tanoak-vine maple [13,14] (Appendix B).
Other community types: Western swordfern may be an understory dominant or indicator species in Oregon white oak, canyon live oak, and coyotebrush communities. The Oregon white oak/California hazelnut/western swordfern association occurs on moist sites in the Willamette Valley, Oregon [194,203], and western swordfern was characteristic of the Oregon white oak/common snowberry woodland type in the Bald Hills oak woodlands in Redwood National Park, California . A coyotebrush/western swordfern association is described in California northern coastal sage scrub . A Douglas-fir/canyon live oak/western swordfern association was described in the northern Sierra Nevada , and western swordfern occurs with low cover in mature canyon live oak forest on the San Bernardino National Forest in southern California .
Riparian: Western swordfern is a common to dominant species in many riparian communities throughout its range. It is a characteristic species in widespread and highly productive black cottonwood-willow riparian forests occurring on bottomlands, riverbars, streambanks, and meadows along the Pacific coast ; and in black cottonwood riparian forests in bottomlands, floodplains, gravelbars, and banks of perennial streams in northern coastal California . In northwestern Oregon, western swordfern occurs in several plant communities on cobble bars and low floodplains, and may reach 17% to 25% cover in some, though it is not a named community dominant. Western swordfern also occurs in swamp communities, such as the red alder/slough sedge-American skunk cabbage community, where it may be abundant on logs and stumps and reach 45% cover . In California, western swordfern is common in riparian forests dominated by Port-Orford-cedar in ravines and draws, along streams, and on mesic, protected slopes with a strong maritime influence .
Eastern Washington and Oregon: Western swordfern is rare in eastern Washington and Oregon, though it occurs as an understory dominant in the relatively warm, moist grand fir series in the Blue Mountains  with wild ginger and oak fern . A grand fir/western swordfern-wild ginger potential vegetation type occurs on cool, very moist site types . These communities typically occur on lower slopes or riparian areas and may exist as residual stringers that do not burn as often as associated uplands .
Western swordfern is classified as a facultative wetland species in eastern Washington, where it occurs in several riparian and wetland communities with low cover, including those in the Pacific silver fir, western hemlock, and black cottonwood series . It also occurs in small amounts in old-growth western redcedar-western hemlock forest , Pacific ponderosa pine (hereafter, ponderosa pine) communities, the grand fir-Oregon boxwood association, the western hemlock-Oregon boxwood association, and the western redcedar-devil's-club association .
Idaho: Western swordfern is not widespread in Idaho but is most abundant in western redcedar [37,163], grand fir [37,56,163], and western hemlock communities . It may also occur in riparian habitats . In northern Idaho, western swordfern dominated the diverse understory in a western redcedar/northern maidenhair habitat type along Nylon Creek north of Dworshak Reservoir. Western swordfern commonly occurs in the western redcedar/wild ginger habitat type and may occasionally dominate the forb layer in the grand fir/wild ginger habitat type . Western swordfern occurred with low cover at all stages of succession in the Rocky Mountain juniper/red-osier dogwood habitat type in eastern and southern Idaho .
Montana: Western swordfern is rare in Montana. It was recorded in late-seral to climax stands of the western hemlock/oak fern habitat type with an average cover of 1% . Populations have been recorded in the Bitterroot and Sapphire ranges; a population at Charles Waters Memorial Campground was extirpated by collectors .
South Dakota: According to a flora published in 1977 , western swordfern occurred in moist places in the Black Hills. However, it was listed among the rare plants of South Dakota in 1985, with its status "undetermined" and this comment: "Recently reported but population has apparently been extirpated" .See Appendix B for a list of western swordfern association described in vegetation classifications, or the Fire Regime Table for a list of plant communities in which western swordfern may occur and information on the fire regimes associated with those communities.
|Figure 4. Western swordfern frond. Photo courtesy of Hansen's Northwest Native Plant Database, http://www.nwplants.com.|
Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [10,58,98,100,106,126,130,170,183]). Morphological similarity among Polystichum species may make identification difficult .
Western swordfern populations consist mostly of sporophytes; gametophytes are extremely rare , and no description of western swordfern gametophytes was found in the literature. The following description applies to sporophytes.
Western swordfern is a medium-sized, perennial, long-lived, evergreen fern [170,189] with many leaves (fronds), sometimes 75 to 100 , clustered on a short, vertical rhizome . Stems are erect or ascending and fronds arch outward [58,126], forming a crown [36,155,170,175]. Fronds are leathery and stay evergreen for several years; withered fronds remain attached to the rhizome . Frond size varies depending on location and site conditions and may range from about 8 to 98 inches (20-250 cm) long [36,58,74]. Fronds are usually at the smaller end of this range in northern [7,106,170] and inland  parts of western swordfern's distribution, and in sunny places . Plants with fronds >3 feet (1 m) long typify western swordfern where it is an understory dominant [100,170,216]. Petioles are one-eighth to one-fourth the length of the frond, densely scaly, and gradually diminishing in size distally. Leaflets are 0.4 to 6 inches (1-15 cm) long. Those of shade-growing plants occur in 1 plane; those of sun-growing plants are twisted or contorted . Sori are large and circular  and occur in 1 to several rows  on leaflets (Figure 6).
Western swordfern is closely related to narrowleaf swordfern based on morphologic  and electrophoretic analysis ; it is possible that some of the older literature misidentified these species. When western swordfern plants are subjected to increased insolation (e.g., after canopy removal, in rocky outcrops, or at high elevations), the fronds become dwarfed and more erect, and the leaflets become crisped and more crowded, such that it more closely resembles narrowleaf swordfern .
Western swordfern rhizomes are stout, woody, and scaly [36,170], often covered with old stipe bases and ending in a crown of new fronds . Rhizomes are short , and plants grow in separate, individual clumps  but often form extensive populations . Populations can cover very large areas and consist of thousands of individuals. Disjunct populations east of the Cascade Range are typically smaller, consisting of a few hundred individuals .
Characteristics of western sword plants (clonal fragments) were described on 3 sites on the Olympic Peninsula occupied by densely stocked, second-growth forests, 40 to 60 years after clearcutting (Table 6). Clonal fragments consisted of all live plant parts (rhizomes, stolons, roots, buried apical buds, and aerial shoots) connected to an initially selected, undamaged aerial shoot. Most western swordfern clonal fragments consisted of a single rhizome segment that thickened with the production of new fronds, although 5% had more than one ramet emerging from a branched rhizome. Perennating buds were shallow, ranging in depth from about 0.2 to 1.8 inches (0.5-4.5 cm). Roots were wiry and densely branched, mostly occurring in the top 8 to 12 inches (20-30 cm) of soil and spreading laterally in the upper organic horizon; maximum root depth was about 28 inches (72 cm). Soils were silt loams and very gravelly sandy loams, and the thickness of the organic horizon ranged from about 0.4 to 2 inches (1-5 cm) .
|Table 6. Characteristics* of western swordfern rhizomes, roots, and shoots in young coniferous forests on the Olympic Peninsula, Washington (n=20 western swordfern clonal fragments) |
|Total length (cm)||Max. diam (mm)||Lateral spread (cm)||Max. length (cm)||Max. spread (cm)**||No. of ramets||Plant height (cm)***|
|*Values are means with ranges in parentheses.
**Maximum root spread is the greatest horizontal distance from the junction of a root and rhizome to the farthest root tip.
***Maximum height to stem or leaf.
At the start of the growing season western swordfern rosettes of the previous year are flattened by rain or snow, but new fronds grow fast, reaching about 3 feet (1 m) by mid-May on sites in western Washington . In Oregon, western swordfern fronds were partially unfurled on 26 May, and by 28 July the fronds were mature and spores were nearing maturity (Stewart 1976 as cited by ). Western swordfern maintained relatively constant cover throughout the growing season in western Oregon . Western swordfern spores mature in August , and sporangia dehisce in early to midsummer, releasing thousands of spores . The plant's evergreen fronds persist for several years. Evergreen ferns like western swordfern retain some spores over winter and release them the following spring .
|Figure 5. Early spring fiddleheads. Photo courtesy of Hansen's Northwest Native Plant Database, http://www.nwplants.com.||Figure 6. Western swordfern sori. Photo courtesy of Hansen's Northwest Native Plant Database, http://www.nwplants.com.|
Western swordfern populations consist mostly of mature plants, with small, juvenile plants present in low numbers; gametophytes are extremely rare. Reproduction in western swordfern is mostly by sexual means. High levels of genetic variation in western swordfern suggest that spores disperse away from parent plants (sporophytes) and that gametophytes usually cross with other gametophytes rather than self-fertilize. Vegetative reproduction is limited ; it can regenerate from rhizomes after top-kill but does not spread vegetatively .
Pollination and breeding system: The mating systems of Polystichum species are outcrossing, and western swordfern is highly outcrossing [189,190]. Rates of intragametophytic selfing in western swordfern range from 0% to 3% .
Hybrids are frequent where 2 or more Polystichum species occur. Sterile hybrids are recognized by their misshapen sporangia .
Spore production: Most medium-sized forest ferns such as western swordfern begin to produce spores between 1 and 5 years of age, and spore production takes place very regularly from year to year. Most ferns similar in size to western swordfern produce tens of millions of spores on each frond .
Spore dispersal: Western swordfern spores are primarily wind-dispersed  but are also dispersed by other means [35,74]. The tiny spores are ejected into the air when mature and are carried away by gravity, wind, water, or animals. Fern spores can travel thousands of miles, but in forests there may be a lack of air current to carry them aloft. Airborne spores are often brought down during rainstorms .
Spore banking: No information was available in the literature regarding western swordfern spore persistence under field conditions. Under ideal conditions (e.g., dry storage), fern spores may remain viable for 2 to 4 years, but viability and speed of germination decrease with age. Fern spores in a dry, resting state are resistant to physical extremes. They can withstand intense radiation and very low temperatures but are reportedly very sensitive to temperatures above 131 °F (55 °C) (review by ).
Germination: Fern spores usually germinate only after being soaked in water. Spores of western swordfern germinate best when exposed to light, but some germination occurs in darkness (review by ). In the laboratory, western swordfern spore germination rate was >20% in light and 2% to 10% in the dark .
Gametophyte establishment and plant growth: Very little information was available regarding western swordfern gametophyte establishment (as of 2015). One source says that gametophytes are extremely rare in western swordfern populations . Another source notes that western swordfern and other ferns establish from spores on fresh alluvium following deep sediment deposition in redwood forests on alluvial terraces; the new alluvium is rich in nutrients and is an excellent seedbed .
Vegetative regeneration: Vegetative reproduction in western swordfern is limited ; it can regenerate from rhizomes after top-kill but does not spread vegetatively. Fronds have determinant growth and do not grow back. New fronds emerge from rhizomes early each growing season  and after top-kill or removal. Heavy cropping of western swordfern does not reduce cover for long; new fronds quickly regain cover after old ones have been removed .
Western swordfern rhizomes may become highly branched with age but are not creeping or spreading [74,189]. Most western swordfern plants studied on the Olympic Peninsula consisted of a single rhizome segment supporting a single ramet; 5% of the plants had more than one ramet emerging from a branched rhizome  (see Botanical Description). Although the species often occurs in pure, uniform stands, these stands probably represent populations of individual sporophytes rather than colonies .
Western swordfern is typically present during most stages of stand development . It can establish in primary succession, such as after deglaciation or volcanic eruption, and in early secondary succession, but typically reaches its best growth and greatest abundance in mid- to late-successional forests .
|Figure 7. Western swordfern reflecting lightspots in the forest understory. Photo courtesy of Hansen's Northwest Native Plant Database, http://www.nwplants.com.|
Shade tolerance: Western swordfern has a high tolerance for shade but can also grow in the open [35,95,100]. Western swordfern communities often occur in the understory of closed-canopy forests, but western swordfern plants can persist following canopy-opening disturbances . Some authors have noted that western swordfern may have lower cover in dense shade and grows best in "lightspots" under dense canopies [16,192]. Carey  notes that western swordfern grows rapidly when forest canopies are even moderately open and forms dense carpets that can shade out other plants.
Although it tolerates a wide range of light conditions, western swordfern seems to have optimal growth under relatively low light conditions, and its response to increased light depends a lot on site moisture availability. In the coastal redwood region, western swordfern's optimum light requirement (where it reached its highest cover at about 2%) was less than 3%, but it grew in areas having up to 40% of full sunlight . Many examples in the literature demonstrate that western swordfern persists after canopy-opening disturbances (see Secondary succession); however, its abundance and vigor may depend on site conditions and disturbance severity (i.e., moisture availability, size and pattern of canopy openings, and degree of soil disturbance). In clearcut areas, for example, western swordfern often prefers protected, shaded locations. This probably reflects sensitivity to high evoptranspirative losses rather than intolerance of light itself , and it may be more pronounced in clearcuts on south-facing slopes (e.g., ). When plants of western swordfern are subjected to increased insolation through removal of overstory shade, the fronds can become dwarfed and more erect, and the pinnae become crisped [74,181] (see Botanical Description).
Western swordfern communities commonly occur in the understory of old-growth and late-successional forests, indicating shade tolerance of the species. Stands typical of the western hemlock/western swordfern association in the western Cascade Range, Oregon, have a relatively dense overstory averaging 70% to 80% canopy cover [53,64]. In the western hemlock zone of the central western Cascade Range, western swordfern communities tended to occur on sites with >100% cover of mature trees . In a Douglas-fir/vine maple/western swordfern community at Monument Peak, Oregon, "only the most shade-tolerant species", such as western swordfern or mosses, grew under the dense vine maple canopy . In 4 redwood stands studied at Humboldt Redwoods State Park, California, western swordfern and redwood-sorrel dominated the forest floor on 2 well shaded lowland sites that had only occasional sunlight breaks .
On the southeastern Olympic Peninsula, the western hemlock/salal/western swordfern association occurs in matrix forests among anthropogenically fire-maintained beargrass savannas that have grown into forests with fire exclusion. Former savanna plots have some western swordfern, but western swordfern is less abundant than in the forest matrix , suggesting that it spreads into the savanna slowly, after trees establish.
Primary succession: During primary succession on the foreland of Coleman Glacier on Mt Baker in northwestern Washington, western swordfern was uncommon but was most prevalent about 95 to 180 years after deglaciation. Vegetation in this age class had the highest tree canopy cover and was dominated by Pacific silver fir and western hemlock. Soils were volcanic ash and colluvium over glacial till; under forest canopies, the mineral soil was covered by an organic horizon up to 12 inches (30 cm) thick .
|Table 7. Average cover of western swordfern during primary succession on the foreland of Colman Glacier in northwestern Washington .|
|Approximate time since deglaciation (years)||0-24||70-95||95-180||300|
|Mean western swordfern cover (%)||0||0.32||2.93||0.54|
In a study comparing primary successional uplands to refugia (habitats where plants survived as rootstock) after the 1981 eruption of Mt Saint Helens, plants in the blast zone were inventoried in the summers of 1993 and 1994. Before the eruption vegetation in the area was a patchwork of forested and clearcut areas, typical of the Pacific silver fir zone in Washington. After the eruption, wind-dispersed invasive species dominated. Western swordfern was infrequent to common throughout the area in both primary successional habitat and refugia .
Secondary succession: Western swordfern associations occur in late-successional and old-growth forests with natural disturbance regimes typified by very infrequent large-scale and infrequent small-scale disturbances. The most common contemporary disturbances in many western swordfern habitats are logging and associated slash disposal and site preparation. The impact of these and other disturbances on western swordfern populations depends on light and moisture conditions in the postdisturbance understory environment. Reviews suggest its response to logging is variable, although western swordfern generally persists, and no studies report dramatic postlogging increases or decreases of its abundance or cover. Western swordfern probably maintains or increases its cover and vigor only on microsites without severe soil disturbance or significant summer moisture stress (reviews by [35,74]). In the absence of severe soil disturbance, western swordfern usually persists or reestablishes from surviving rhizomes following overstory mortality at most scales. Exceptions may be found on exposed and/or dry sites where moisture stress is severe  and at the extremes of its range, where sites may already be marginal for western swordfern and become less habitable with soil and canopy disturbance.
The following summary of the literature describes western swordfern's role in secondary succession following canopy opening disturbances and is organized by forest type. It includes several studies where vegetation response was monitored after canopy removal, almost entirely after logging, especially clearcutting, as well as general descriptions of secondary succession, such as those found in vegetation classifications that do not usually specify disturbance type, stating only, "after fire or logging". Specific examples of western swordfern response to fire and examples of successional changes in western swordfern communities following wildfires or prescribed fires other than slash burning are included in the discussion on Fire Effects and Management.
Western hemlock and Douglas-fir forests: Western swordfern is a common dominant in old-growth forests in the western hemlock zone. Prior to European settlement, these forests were mostly late successional and old growth with very large trees, dense canopies, infrequent, small-scale disturbances from windfall, insects, or disease; and less frequent, larger disturbances from landslides, blowdown, fluvial action, and fire. Although changes of ground cover in old-growth stands are relatively slow, they are constantly taking place. Understory and ground layer plants respond to canopy gaps in various ways; western swordfern response depends largely on moisture conditions .
Lush growth of western swordfern may indicate late-successional, old-growth, or relatively undisturbed sites. The regional "climatic climax" for the western hemlock zone in the Oregon Coast Ranges is thought to be the western hemlock/western swordfern association . Stands typical of the western hemlock/western swordfern association in the western Cascade Range, Oregon, are generally made up of old-growth Douglas-fir and western hemlock; western swordfern is the only constant herbaceous species, with an average cover of 25% [53,64]. In the western hemlock zone of the Gifford Pinchot National Forest, Washington, old-growth stands of the western hemlock/western swordfern-redwood-sorrel association have huge, widely-spaced Douglas-firs, western hemlocks, and western redcedars towering over a lush carpet of redwood-sorrel interspersed with western swordfern . Other old-growth types include the western hemlock/western swordfern-threeleaf foamflower association in the northern Cascade Range  and Olympic Peninsula; and the western hemlock/salal-western swordfern association on the Olympic Peninsula [159,166]. The western redcedar-Douglas-fir-western hemlock/western swordfern-spreading woodfern community is a late-successional community that develops in forests with infrequent stand-replacing fires (~150-200 years) and occasional mortality from windthrow, insects, or disease (leading to gap dynamics and multiage structure) in coastal British Columbia . The Oregon white oak/California hazelnut/western swordfern community occurs on the least disturbed sites in the Willamette Valley , and the western redcedar-grand fir/western swordfern community occurs in undisturbed locations on the moistest sites in interior valleys of the San Juan Islands, whereas areas disturbed by logging commonly support red alder communities . See Table 2 for western swordfern cover and site characteristics in remnant old-growth forests in the northern Coast Range of Oregon , and Appendix B for more examples of late-successional western hemlock communities in which western swordfern is a dominant species.
Western swordfern occurs in Douglas-fir forests on Mount St Helens . Following the 1980 eruption, it was associated with scorched forest but not with clearcut or blowdown forest . It occurred in the habitats with the greatest plant cover, usually in organic soil such as the area around a stump base . The maximum tephra depth from which western swordfern was excavated was 3.5 inches (9 cm), 13 to 15 months after the eruption. The authors concluded that western swordfern rarely produces buds in tephra . Most of the area was salvage logged between 1982 and 1984, then planted with noble fir. Western swordfern presence and abundance corresponded with litter depth and downed woody debris, which were greater on unsalvaged plots. In July of 2003 western swordfern cover and frequency averaged 0.05% and 28%, respectively, on salvage logged sites, compared with 0.4% and 80% on unlogged sites .
Postlogging succession: Because much of the western hemlock zone in the Pacific Northwest  and the majority of forests in the coastal Douglas-fir zone in British Columbia  have been logged during the last 2 centuries, much of the information available on succession in these communities comes from studies of plant community changes after logging and site preparation. The remainder of this subsection includes information from such studies as it may pertain to postfire succession. Timber harvesting operations in the western hemlock zone historically involved clearcut logging followed by slash burning under prescribed conditions to reduce fire hazard, prepare the seedbed for planting, and reduce shrub cover . According to Garrison and Smith , western swordfern is among the species in Douglas-fir forests of Oregon and Washington that "suffer the most loss in crown cover" from the accumulation of heavy slash and soil disturbance after clearcutting. Burning of logging waste causes additional changes . Although its abundance may be reduced initially, on sites where moisture is not limiting western swordfern recovers in early succession, and it may be an understory dominant or codominant in seral stands that develop after logging disturbances . For example, Douglas-fir/western swordfern and red alder/western swordfern community types are considered relatively young stands in the western hemlock/western swordfern association in Mt Rainier National Park .
Western swordfern occurs throughout postharvest succession in western hemlock and Douglas-fir forests, but it is generally most abundant in middle to late succession [17,18,46,122,160], with the exception of dense, closed-canopy stands, where its abundance drops off and it most frequently occurs in light spots (see Shade tolerance).
Post-harvest succession and the abundance of western swordfern follow some general patterns in the western hemlock forest zone, but vary depending largely on predisturbance community composition, site characteristics (especially available moisture), and disturbance type, timing, and severity, including postharvest site preparation. The general sequence begins with an herbaceous stage dominated by nonresident annual and perennial herbs, which typically lasts 4 or 5 years; residual herbs, such as western swordfern, may contribute substantial cover during this stage. A shrub stage follows, as residual shrubs develop in canopy openings, and continues until the shrubs are overtopped by tree saplings, after about 10 to 25 years .
On sites with greater available moisture, western swordfern recovers more rapidly [39,52], and red alder is likely to dominate early forest succession [39,62]. In the Oregon Coast Ranges, herbaceous species surviving from the predisturbance stand, especially western swordfern, often constitute an important component of the early-seral vegetation following logging; however, residual species such as western swordfern, broadleaf starflower, and redwood-sorrel are reported to be of only minor importance during the first 10 to 25 years of succession in the relatively drier Cascade Range (review by ). On relatively xeric sites in the HJ Andrews Experimental Forest in the western Cascade Range of Oregon, western swordfern cover was reduced by at least half in the first year  and maintained very low cover for at least 10 years after clearcutting and slashburning. The author suggested that western swordfern "apparently found survival difficult or impossible under clearcut conditions" on the steep, south-facing slopes in the study area . Following the period of shrub dominance, stands may go through a red alder stage on moist, productive sites such as western swordfern habitats . Red alder is among the first trees to establish on moist sites, and pure stands are common in the Oregon and Washington coastal mountains and parts of the Puget Sound region. Red alder is gradually replaced by Douglas-fir and western hemlock but may dominate for up to 90 years .
Western swordfern communities tended to have greater resilience than other community types in the HJ Andrews Experimental Forest. A series of studies used long-term sampling of permanent plots before and after clearcutting and slash burning in 100- to 500-year-old Douglas-fir forest [52,77,78]. Initial understory in the western swordfern community was richer and more structurally complex than in most other communities, and surviving perennial herbs and shrubs were abundant, resulting in relatively rapid community recovery. The resilience of the western swordfern community was attributed to the ability of dominant herb and shrub species to sprout from subterranean structures following slash burning, and western swordfern "regenerated continuously from surviving rhizomes or stem bases" [77,78]. Abundance of understory dominants, including western swordfern, was reduced during the first 2 years after slash burning, when wind-dispersed annuals such as tall annual willowherb and nonnative woodland ragwort dominated. This was followed by increases of initially subordinate (e.g., sweetscented bedstraw) and dominant (e.g., western swordfern) forest herbs. Shrubs began to dominate 14 years after disturbance. Trees did not dominate until after 20 years [52,78]. See the Research Project Summary of these studies for more information.
Western swordfern response varies with timing and severity of disturbance during logging and especially site preparation [52,78]. Techniques that remove the plant from the ground can nearly eliminate the species from the site. Brush bale scarification totally eliminated western swordfern from a study site in Oregon; scarification of several sites near Vancouver left western swordfern only on undisturbed microsites . In a comparison of the effects of chemical, fire, and mechanical site preparation in an area that was repeatedly logged, western swordfern frequency was similar among all but scarified sites, where soil was severely disturbed, and western swordfern was reduced from about 25% to 0% frequency .
Slash burning may alter succession and decrease western swordfern abundance compared to unburned, logged sites (e.g., [16,152,182]). Some authors note that western swordfern was initially reduced or eliminated on slash-burned sites compared to unburned sites [107,152,199]. Although western swordfern can survive severe fire, plants may be restricted to unburned patches and aboveground structures may be absent for several years following slash burning (reviews [35,74]). Western swordfern abundance may remain low and even decline as succession proceeds on slash-burned sites exposed to intense insolation, low humidity, and low soil moisture (e.g., [69,107,116]). If left unburned, residual species such as western swordfern can dominate early succession; if slash is burned, native and nonnative annual herbaceous species that establish from windborne or soil-banked seed, tend to dominate. In areas where mineral soil is exposed by logging activities, successional patterns may resemble those on burned sites .
Sitka spruce forests: Western swordfern is a common dominant in old-growth forests in the Sitka spruce zone of North America (for examples, see Table 2 and Appendix B). Old-growth Sitka spruce associations include the Sitka spruce/western swordfern association [159,166] and the Sitka spruce/western swordfern-redwood-sorrel association  on the Olympic Peninsula, and the Sitka spruce/western swordfern association in coastal British Columbia . Areas typical of the Sitka spruce/western swordfern-redwood-sorrel association on the Olympic Peninsula have burned very seldom in the last 500 years . Western swordfern was present in late-successional forest dominated by western hemlock, Sitka spruce, and western redcedar in Southeast Alaska, but was not mentioned as an important species in second-growth forests .
Early successional trends following fire or logging in the Sitka spruce zone are similar to those in the western hemlock zone, although dense shrub communities are more common in the Sitka spruce zone because of more favorable growing conditions [62,64], and young stands in the Sitka spruce zone are more likely to be dominated by western hemlock and Sitka spruce than by Douglas-fir. Red alder is also more abundant after logging in the Sitka spruce zone due to the preponderance of moist and wet sites [29,62]. Shrub communities can develop quickly after canopy-opening disturbances in these forests [62,64]. Several of these seral communities have been described and mapped along the northern Oregon coast, including the salmonberry-western swordfern, vine maple-western swordfern, and salal-red huckleberry types . In many cases, western swordfern is the major early-seral understory species after clearcutting in the Sitka spruce/western swordfern association on the Siuslaw National Forest; these sites are generally resilient to fire effects (review by ).
Western swordfern is usually present even in young stands of the Sitka spruce/western swordfern-redwood-sorrel association on the Olympic Peninsula, and it is often conspicuous by the time of crown closure (about 15 years). Western swordfern abundance becomes relatively stable by about 100 years . A chronosequence study on the Olympic Peninsula in the Sitka spruce-western hemlock zone showed that western swordfern had high frequency (50%-67%) but low cover (0.7%-6.25%) in all age classes from 0 to >199 years. Percent cover of western swordfern increased steadily with forest age, but differences were not significant among age classes (P>0.05) .
Redwood forests: Western swordfern occurs throughout succession in redwood forests but may be more abundant in second-growth stands. In Redwoods State Park, the redwood-Sitka spruce/evergreen huckleberry-western swordfern and Sitka spruce/western swordfern-salmonberry associations occur in cutover forests . Riparian forests in adjacent watersheds at Redwood National Park were studied to understand structural and compositional differences between old-growth and unmanaged second-growth forests about 40 to 50 years old. Old growth was dominated by redwood, and second growth was dominated by red alder, Douglas-fir, and redwood. Western swordfern, deer fern, and lady fern dominated the understory in both old-growth and second-growth forests. Western swordfern had the highest importance value and the highest relative cover of all understory plants for both old-growth and second-growth stands, 52.3% and 71.2%, respectively . Loya and Jules  identified 4 stages of postlogging development in redwood forests: initiation, closure, mature, and old growth; western swordfern was an indicator of the closure stage . Similarly, western swordfern was associated more with recently harvested sites than sites with longer times since harvest (P<0.05) in riparian redwood forests ranging from 10 to 110 years since harvest. In 0- to 30-year-old forests, overstory canopy cover was about 35%, and in >100-year-old forests, canopy cover was about 70% . Ten years after logging in redwood forests in the Santa Cruz Mountains, western swordfern was commonly found in canopy gaps created by logging .
Red alder forests: Seral stands dominated by red alder, particularly those with western swordfern dominating the herb layer, are most common in wetter parts of the western hemlock zone, (i.e., the northern Washington Cascade Range, the west side of the Olympic Mountains, and in the Coast Ranges) and in the Sitka spruce zone. Understory vegetation in red alder stands is most frequently dominated by salmonberry in the shrub layer and western swordfern in the herb layer . As the short-lived red alder dies, many of these stands may become dominated by a dense cover of salmonberry and western swordfern that can persist and slow establishment of conifers (review by ).
Western swordfern occurs throughout succession in red alder stands but tends to increase with stand age and reach its greatest abundance in middle to late succession. In the Alsea River drainage of the central Coast Ranges in western Oregon, Carlton  studied 44 red alder stands ranging in age from 7 to 87 years, and originating from different types of disturbance: mostly logging, but also fire, slides, debris flows, and unstable ravel soils. Western swordfern was most abundant in middle age classes and still a prominent component of older stands, along with salmonberry and vine maple. Five understory communities were identified in these red alder stands: 1) a western swordfern community was most characteristic of young red alder stands but also occurred under dense, middle-aged stands on moderate to steep slopes with low light levels in the understory; 2) a western swordfern-mixed shrub community occurred under middle-aged red alder stands; 3) a western swordfern-salmonberry community occurred in many middle-aged red alder stands; 4) a salmonberry community occurred on flat terraces or stream bottoms under middle-aged stands where western swordfern was present but much less abundant; and 5) a vine maple community where western swordfern was a codominant under most stands of old, senescing and several middle-aged red alder stands. None of the communities was restricted to only one age class of red alder . Fifteen red alder stands on river-bottom, alluvial soils in the Oregon Coast Ranges, ranging in age from 2 to 64 years, were evaluated between 1 August and 7 September 1969. Succession in the understory proceeded from a grass-herb to shrub-fern understory over a 60- to 70-year period. Western swordfern crown cover and frequency generally increased with stand age and were highest in stands aged 39 to 64 years, with cover ranging from 4% to 37% and frequency ranging from 18% to 92%. In stands younger than 35 years, cover ranged from trace to 4% and frequency from 4% to 22% . On steep terrain in the western hemlock zone of the central Oregon Coast Range, a debris flow deposited material containing western swordfern rhizomes onto the valley floor of a second order stream watershed. Western swordfern reproduced from rhizomes and increased rapidly. Its abundance increased steadily over time, from 4% frequency the first growing season after the deposition to 30% 9 years later .
Floodplains and river terraces: Western swordfern communities often indicate later stages of succession on floodplains and river terraces in the Pacific Northwest. The California bay-Douglas-fir/vine maple/western swordfern community in the Umpqua River valley in the Oregon Coast Ranges is an old-growth association on the highest floodplain terrace . A riparian chronosequence spanning more than 3 centuries along the Queets River, Olympic National Park, showed that the western swordfern/redwood-sorrel plant community occurred on the oldest sites in the study area (60-330 years old), on soils with relatively finer surface textures (38%-57% silt and clay), and on the highest terraces (6.2-8.5 feet (1.9-2.6 m)) above the low flow channel, mostly above the reach of annual floods . In 29 plots on floodplains of 2 rivers on the west coast of Vancouver Island, western swordfern was among the species "typical of rich climax ecosystems". Western swordfern was absent from the pioneer seral stage, averaged 12% cover in the young seral stage, and 23.5% cover in the mature climax stage of floodplain succession. The climax stage was dominated by Sitka spruce with an understory of salmonberry, coastal hedgenettle, threeleaf foamflower, and western swordfern .
On alluvial landforms of the McKenzie River Valley, Oregon, 2 topoedaphic climaxes were identified: the western hemlock/western swordfern-redwood-sorrel association on terraces with fine, sandy loam to silt loam soils derived from silty river alluvium; and the western hemlock/dwarf Oregon-grape-salal association occurring on rockier soils with coarser alluvium or glacial outwash. Three early seral communities (willow, red alder, and black cottonwood) were identified (Table 8). Western swordfern established during the red alder seral stage on relatively fine-textured soils. Dominants in the herb layer of the black cottonwood association include western swordfern and several other herbaceous species common to the grand fir association. Western swordfern reached its highest cover in the Douglas-fir/beaked hazelnut/western swordfern association; however, individuals were chlorotic and thin-leaved compared to those growing in stands of the western hemlock/western swordfern-redwood-sorrel association. The western hemlock/western swordfern-redwood-sorrel association was the most extensive in the area .
|Table 8. Western swordfern cover and frequency in successional communities on alluvial landforms in the McKenzie River Valley, Oregon .|
|Plant community dominants||Site characteristics||Cover (%)||Frequency (%)|
|willow||recent alluvium||no data||no data|
|red alder||Establishes following deposition of 20-30 cm gravelly sand, which increases terrace elevation; red alder is typically replaced within 30 to 50 years||1||40|
|black cottonwood||If little elevation of the floodplain occurs (through either sedimentation or downcutting of the river), black cottonwood replaces red alder||no data||no data|
|grand fir||Replaces red alder in areas with deeper fine sediment deposits, usually within 30 to 70 years||15||100|
|western hemlock/western swordfern-redwood-sorrel||Stands were 200-500 years old; most areas of this association had probably been through one or more fires||22||100|
|Douglas-fir/California hazelnut/western swordfern||Develops on sites that have burned within the last 100 to 200 years||26||100|
|Western hemlock/dwarf Oregon grape-salal||Develops on shallow to moderate cobbly loams to cobbly sandy loams on terraces and glacial outwash plains, at about 450-500 years||no data||no data|
|Douglas-fir/dwarf Oregon-grape-salal||Develops on shallow to moderate cobbly loams to cobbly sandy loams on terraces and glacial outwash plains||1||36|
Fonda  described 5 plant communities along the Hoh River in Olympic National Park, (Table 9). Western swordfern occurred in all of these communities and was most abundant in 400- to 750-year-old communities on 1st and 2nd terraces and rockslides. This study also describes soil characteristics for each community, noting a strong relationship between terrace age, soil moisture, and soil profile development. The younger land surfaces are substantially drier than the older terrace, which may affect western swordfern abundance .
|Table 9. Western swordfern cover and frequency in 5 plant communities representing 5 successional stages along the Hoh River in Olympic National Park |
|Plant community||Location||Stand age (years)||Cover (%)||Frequency (%)|
|red alder-Scouler willow||gravel bars||80-100||1.5||40|
|Sitka spruce-bigleaf maple-black cottonwood||1st terraces||400||22.3||88|
|bigleaf maple||rockslides where 2nd terrace meets valley wall||<750||19.0||100|
|Sitka spruce-western hemlock||2nd terraces||750||22.4||76|
|western hemlock||3rd terraces||>750||2.6||30|
Immediate fire effect on plant: Western swordfern is top-killed by fire , and rhizomes likely survive where soil heating is not severe and soil remains intact. No observations of wildfire effects on western swordfern were found in the current literature (2015), but observations after clearcutting and slash burning in Oregon revealed that western swordfern regenerated "continuously" from surviving rhizomes or stem bases [77,78].
Survival of rhizomes likely depends on fire severity (depth of burn) and postfire site conditions. Although this is not explicitly documented in the current literature (as of 2015), western swordfern rhizomes are less likely to survive where severe fire consumes the organic surface horizons. Only one study describing the burial depth of western swordfern roots and rhizomes was found. Rhizomes ranged in depth from about 0.2 to 1.8 inches (0.5-4.5 cm) in the upper organic horizon , where they would likely be killed by fire that consumes all or part of the organic horizon. Most western swordfern roots occurred in the top 8 to 12 inches (20-30 cm) of soil, and maximum root depth was about 28 inches (72 cm) ; roots are unlikely to be damaged by wildfire at these depths.
Postfire reductions in western swordfern abundance may indicate that fire killed western swordfern individuals. Greater reductions in severely burned areas compared to lightly burned and unburned areas  may also indicate that mortality is related to fire severity. For example, western swordfern was more frequent on unburned than slash-burned plots after clearcutting on sites throughout Washington and Oregon [16,152]. Immediately after logging and slash burning at HJ Andrews Experimental Forest, western swordfern occurred to a limited extent in disturbed areas; some individuals occurred on lightly burned areas, but none occurred on severely burned areas [51,52].
No information was available regarding the effects of fire on western swordfern spores; however, Haeussler and Coates  report that fern spores are generally very sensitive to temperatures above 131 °F (55 °C).
Postfire regeneration strategy (adapted from ):
Surface rhizome and/or a chamaephytic root crown in organic soil or on soil surface
Rhizomatous herb, rhizome in soil
Ground residual colonizer (on site, initial community)
Initial off-site colonizer (off site, initial community)
Secondary colonizer (on- or off-site spore sources)
Fire adaptations and plant response to fire:
Fire adaptations: Few direct references to western swordfern's fire adaptations were found in the literature (as of 2015); however, many observations of western swordfern sprouting after top-kill suggest that it is adapted to survive fires of low to moderate severity and is likely to increase in abundance during postfire succession under favorable conditions. Under less favorable conditions, such as sites at the extremes of its range or droughty, exposed, south-facing slopes, recovery of western swordfern after fire may proceed more slowly or not at all. High-severity fire may kill western swordfern (see Immediate fire effect on plant).
According to a review by Smith and Fischer , western swordfern sprouts from woody rhizomes and colonizes from off-site spores after fire; the source of this information is not cited. In their study of vegetation succession after wildfire in managed forests, Kayes and others  classified western swordfern as a "sprouting residual species", and a fire "endurer" that dominated "higher severity" sites.
Although western swordfern can survive severe fire, plants may be restricted to unburned patches, and aboveground structures may be absent for several years following slash burning (reviews [35,74]).
Plant response to fire: Information on response of western swordfern to fire was limited. Response depends on fire severity and site conditions, especially soil moisture availability. Severe fires on dry or shallow soils are more likely to eliminate or dramatically reduce swordfern cover and frequency (review by ). Plants may survive and sprout soon after fire (e.g., [60,77,124]), although cover may be reduced or lacking for several years (reviews [35,74,187]). Because western swordfern occurs in plant communities characterized by infrequent wildfire, most information about its response to fire comes from studies on the effects of slash burning following logging. Slash burning effects on western swordfern depend on fire severity, soil moisture , and severity of logging and related soil disturbance (e.g., [35,114]).
The few studies that record observations on response of western swordfern to wildfires suggest that it can sprout soon after fire, but the rate and magnitude of recovery vary among sites. Western swordfern sprouted within the first year after a wildfire in a red alder-black cottonwood-bigleaf maple riparian forest on Whatcom Creek in Bellingham, Washington . After 2 overlapping wildfires (the 1987 Silver Fire and the 2002 Biscuit Fire ) in mixed-evergreen forest in southwestern Oregon, western swordfern had 0.7% cover on unburned stands, was absent from once burned stands, and had 0.4% cover on twice burned stands 2 growing seasons after the 2nd fire . A chronosequence study in western hemlock-Douglas-fir/western swordfern communities in the Olympic Mountains examined different stages of postfire succession on sites burned by wildfires 2 to 515 years prior. Stands had similar aspect, elevation, and slope, and all were over 300 years old (old-growth stage) at the time of fire. Fires were of mixed severity, with extensive overstory mortality. Annuals tended to dominate early postfire years, but they were replaced by perennial herbs including ferns by year 19, when western swordfern reached its peak frequency (Table 10). As the canopy closed, the herb and shrub components, including western swordfern, were less prevalent. Western swordfern was 1 of 2 species observed in all study areas . See Agee and Huff  for a description of fuel characteristics and potential fire behavior at each stage of postfire succession in these stands.
|Table 10. Western swordfern frequency on forest plots of increasing postfire age |
|Fire name||Hoh||Hoh||Queets||North Fork||Mineral Creek||Olympus Guard|
|Stem exclusion||Understory reinitiation||Old
|Time since fire (years)||2||3||19||110||118||515|
|Western swordfern frequency (%)||5||21||37||19||19||10|
In the western hemlock zone on the Willamette National Forest in central western Oregon, fourteen 2-storied stands of remnant trees (>300 years old) over younger trees (65 to 125 years old) that established after wildfire were compared to 65- to 125-year-old stands without remnant trees. Mean species richness and cover of shrubs and herbs did not differ between stands with and without remnant trees. Western swordfern cover was not correlated to remnant tree density, basal area, volume or crown area, but it was negatively correlated with Douglas-fir abundance and positively correlated western hemlock abundance (P≤0.05)). The positive correlation with western hemlock may indicate greater available moisture. Western swordfern tended to be more abundant on plots with more coarse woody debris, which helps retain soil moisture and stand humidity and also helps maintain mycorrhizal associates through succession . Wildfire burned an area of dense conifer forest, the Tillamook Burn area, in 1933, 1939, and again in 1945. Sixteen years after the 3rd fire, western swordfern was frequent in all plant communities but had lower average cover on drier sites (Table 11) .
|Table 11. Western swordfern frequency and cover in 6 plant communities in the Tillamook Burn area in the winter of 1961-1962 (16 years after the last fire) . No data were given from before the fire or from unburned sites.|
|Plant community||Site characteristics||Western swordfern frequency (%)||Western swordfern average cover (%)|
|red alder/western swordfern||Steep, north-facing lower slope positions, <1,200 feet elevation, stony soils with silt loam or loam surface textures; dense, closed canopy||100||64|
|red alder/thimbleberry||Steep, lower and middle, north-facing slopes at 800-1,200 feet elevation; soils typically extremely gravelly||100||40|
|vine maple/western swordfern||Steep lower and middle slopes, all aspects but mostly south and east facing, 700-2,100 feet, high water availability; stony colluvial soils||100||24|
|thimbleberry/broadleaf starflower||1,200 to >1,800 feet, all aspects, slopes generally >60%, predominantly upper slopes and ridgetops; extremely gravelly, shallow, poorly developed soils||100||6|
|red huckleberry/salal||Upper, convex, 40%-60% slopes and exposed ridgetops from 800-1,900 feet||66||1|
|western bracken fern/big deervetch||Upper or middle slope positions, 60% slopes, all aspects, generally <1,200 feet, deeply weathered soils||100||<1|
In unburned alpine krummholz at about 6,200 feet (1,900 m) in North Cascades National Park, Washington, western swordfern had 1% frequency and only trace cover. It was absent from burned krummholz and from both burned and unburned heath in an area burned by wildfire 29 years earlier .
A comparison of logged areas with and without slash burning may provide additional insights into the postfire response of western swordfern, although the effects of wildfires without precedent logging are likely to be quite different with regard to the degree of canopy opening, soil disturbance, and a greater likelihood of postfire establishment of nonnative plants . Studies from the western hemlock forest zone indicate that western swordfern may recover more rapidly after logging when slash is left unburned (see Secondary succession for details of particular studies). On unburned sites, residual species such as western swordfern tend to dominate early succession; if slash is burned, species absent from the preharvest understory, such as nonnative annual herbaceous species that establish from windborne or seed banked seed, tend to dominate (review ). Western swordfern was one of the first plants to sprout after an herbicide and burn operation in a red alder brushfield in the Sitka spruce zone of the Oregon Coast Ranges. Sprouts began appearing within 2 to 3 weeks after the fire. Western swordfern codominated the herbaceous layer before burning. Its prefire frequency was 82% in June, burning was conducted in August, and its postfire frequency was 78% in September and 64% the following August .FUELS AND FIRE REGIMES:
Fire regimes: Western swordfern is a common understory dominant in Douglas-fir, western hemlock, and Sitka spruce forests that have fire regimes characterized by long-interval, stand-replacement and mixed-severity fires. However, it is also a dominant in communities that historically had more frequent surface and mixed-severity fires, such as redwood forests and Oregon white oak woodlands (Appendix B, Appendix C).
Western swordfern is a dominant or indicator species in several associations in coastal forests of the Pacific Northwest. Due to low lightning incidence and high fuel moisture content year-round, conditions favorable for large wildfires develop only briefly every few years during severe drought. Strong, dry, east (foehn) winds occasionally blow in western Washington and Oregon, causing severe fire conditions. Thunderstorms are uncommon but concentrated in some years over mountainous terrain . British Columbia's coastal temperate rainforests have a wet climate and are rarely impacted by stand-replacing fire. This results in a structurally complex, multiage, multicanopy, old-growth forest with large volumes of living and dead wood . Large lightning fires in Olympic National Park are usually associated with low relative humidity, prolonged drought, short-term dry spells before and after ignition, and locally strong winds .
A fire history of the Olympic Mountains indicates that lightning fires were responsible for most of the ignitions prior to 1850, and human-caused fires were likely prevalent during the period of European settlement, 1880 to 1910. Forests on the east side of the Olympics are generally younger than those on the west side. Most of the east side was thought to have burned about 300 years ago, while the west side consists of vast expanses of forest greater than 300 years old. The west side is less prone to burning due to its wetter climate . Western swordfern is a common understory dominant in plant communities on the Olympic National Forest (Table 12), and it is usually present in all ages of stands with average cover often exceeding 20%, although it may be inconspicuous or absent in second growth .
|Table 12. Fire and other disturbances in forested plant associations of the Olympic National Forest where western swordfern is a named understory dominant .|
|Plant association||Fire and other disturbance history|
|western hemlock/dwarf Oregon-grape/western swordfern||The typical area of this type has burned once or twice in the last 500 years, although most old stands of this type have been logged. Most old growth that remains is either about 280 or 450 years old.|
|western hemlock/Pacific rhododendron/western swordfern||The typical area of this type has burned once or twice in the last 300 years. Most areas have been logged or burned, so little old growth remains, and most stands are less than 80 years old.|
|western hemlock/western swordfern-redwood-sorrel||Little of this type has burned in the last 500 years, and most stands are very old. Some younger stands have originated from windstorms or small fires.|
|western hemlock/western swordfern-foamflower||The typical area of this type has burned once or twice in the last 700 years. Western swordfern is usually present in all ages of stands, although it may be inconspicuous or absent in densely stocked second growth.|
|Pacific silver fir/western swordfern||The typical area of this type has burned once or twice in the last 500 years.|
|Pacific silver fir/western swordfern-redwood-sorrel||The typical area of this type has burned very seldom in the last 500 years, and most stands are very old. Some younger stands have originated from windstorms or small fires.|
The following examples of fire regime information from other areas where western swordfern occurs demonstrate the range of fire regime characteristics with which this species may be associated. The western hemlock/western swordfern-redwood-sorrel association was the most extensive successional community on alluvial landforms in the McKenzie River Valley, Oregon. Stands were 200 to 500 years old, and evidence suggested that most areas of this association had been through 1 or more fires. The Douglas-fir/California hazelnut/western swordfern associations occurred on sites that had burned within the last 100 to 200 years . On Yellow Island, San Juan County, Washington, which had not been logged or grazed, western swordfern was a dominant understory species in Douglas-fir forest. The fire rotation for the island was estimated at 83 years; this frequency was probably influenced by humans . Western swordfern is a typical understory dominant in Oregon white oak forests in the Willamette Valley, where wildfires were common prior to European settlement. After European settlement in the mid-1800s, fires became less frequent and Oregon white oak savannas developed into forests . In the Blue Mountains of northeastern Oregon, western swordfern occurs in cool, moist grand fir stands, where long fire-return intervals and moderate-severity fires may be typical. Most of these locations are lower slopes or near riparian areas and may exist as residual stringers that do not burn as often as associated uplands .
At the extremes its range, soil and canopy disturbance may make sites uninhabitable for western swordfern, so it is more common in communities with long intervals between disturbances. For example, in western redcedar-western hemlock forests of northern Idaho, western swordfern had low frequency (1%-2%) on plots in seral shrub communities (2 to 60 years old) regardless of disturbance history (logging with and without pile or broadcast burning), but it occurred in only trace amounts on plots burned multiple times . In northern Idaho, western swordfern seems to be most common in communities with long fire-return intervals. It is an "important forb" in warm, dry to moderate interior Douglas-fir, grand fir, and ponderosa pine habitat types with presettlement fire regimes of frequent, low- or mixed-severity fire and occasional stand-replacing fire. It "occurs widely" in moderate and moist grand fir habitat types with variable presettlement fire regimes ranging from high-severity fires followed by persistent shrub fields, to areas where evidence of historic fire is difficult to find. It is "common" in mature and late-successional stands in moderate and moist western redcedar and western hemlock habitat types, where stand-replacing fires probably occurred at intervals of 200 to 250 years (review by ).
See the Fire Regime Table for additional information on fire regimes of vegetation communities in which western swordfern may occur. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find Fire Regimes".
FIRE MANAGEMENT CONSIDERATIONS:
Western swordfern is generally resilient to canopy-opening disturbance and fire effects (see Secondary succession and Plant response to fire), and it is present in most stages of succession in the forests where it occurs as an understory dominant. However, it may be reduced or eliminated after severe soil disturbance . Therefore, while it is likely to persist following wild or prescribed fire in most of its main habitats, it may be sensitive to fire suppression activities that disturb the soil. This is especially true at the extremes of its range where it occurs in lower abundance or is more sensitive to environmental extremes and is more likely to be stressed.
Slash burning has variable effects on western swordfern, depending mostly on site conditions, soil disturbance, and fire severity (see Secondary succession). A series of studies on the HJ Andrews Experimental Forest found that recovery of western swordfern declined as disturbance severity increased, whether by burning or mechanical damage, and cover of western swordfern tended to increase gradually with time since disturbance [52,78]. Disturbance severity was evaluated and sites were classified according to degree of soil disturbance: undisturbed; disturbed-unburned (litter removed or mixed with mineral soil, but little or no evidence of fire); lightly burned (surface litter was charred by fire but not completely removed); and heavily burned (surface litter completely consumed) . Immediately after logging and slash burning, western swordfern was most abundant on undisturbed sites and occurred to a limited extent in disturbed areas. Some plants occurred on lightly burned areas, but none on severely burned areas [51,52]. On undisturbed sites, fireweed dominated early succession, followed by dramatic but temporary release of the residual trailing subshrub common whipplea, which was followed by recovery of the initially dominant western swordfern. In contrast, heavily burned sites were dominated initially by annuals such as nonnative woodland ragwort, tall annual willowherb, and Siberian springbeauty; secondarily by biennials and small-statured perennials; and subsequently by tall woody perennials such as snowbrush ceanothus, redstem ceanothus, and thimbleberry. Western swordfern was not abundant on these sites . See the Research Project Summary of these studies for additional details. For detailed planning and operational considerations for slash burning, including determining site and/or community sensitivity and advantages and disadvantages to burning in different seasons, see Hawkes and others .
On the Clearwater National Forest, northern Idaho, western swordfern is among several plant species that have been identified as indicators of sites with high risk of mass movement because they are also indicators of high levels of soil moisture. Mass movement is more likely to occur on these sites following canopy-opening disturbances such as fire (review by ).Western swordfern is an important plant in mountain beaver habitat, and postfire changes in plant community composition may have negative impacts on mountain beavers in some areas. In October 1995, a wildland fire burned about 12,400 acres (5,000 ha) on the Point Reyes Peninsula, California. Postfire surveys (2 to 6 months after the fire) in coastal sage scrub indicated that mountain beaver burrow openings were fully exposed, and only 0.4% to 1.7% of mountain beavers within the burned area survived the fire and immediate postfire period. The fire initially reduced vegetation to a few charred skeletons of the larger shrubs and the charred bases of western swordferns, and in some areas vegetation changed from dense western swordfern before the fire to stands of thimbleberry and blackberry. Even where mountain beavers survived the fire, little or no recovery of mountain beaver populations was detected 5 years later .
|Figure 8. Mountain beaver snacking on western swordfern near Seattle. Photo courtesy of https://shawncita.wordpress.com/.|
FEDERAL LEGAL STATUS:
Information on state- and province-level protection status of plants in the United States and Canada is available at NatureServe.
IMPORTANCE TO WILDLIFE AND LIVESTOCK:
Several mammals eat western swordfern, including elk, black-tailed deer, mountain beavers, American black bears (review by ), and mountain goats . Western swordfern communities also provide habitat for several bird species (e.g., [159,180,220], Table 13). Western swordfern was apparently not eaten by domestic sheep in a Douglas-fir plantation in the Oregon Coast Ranges . However, another study in coastal Douglas-fir plantations found that domestic sheep consumed a lot of ferns, although it was unclear how much of their forage consisted of western swordfern .
A review suggests that American black bears sometimes forage on western swordfern , and a study from Olympic National Park identified western swordfern in mountain goat fecal pellets collected in late winter or spring . However, most information regarding wildlife use of western swordfern concerns elk, black-tailed deer, and mountain beaver.
Western swordfern is an important elk food in Douglas-fir forests  and other habitats in Oregon and Washington [87,97,102,109,148]. Jenkins and Starkey  provide a summary of Roosevelt elk use of western swordfern throughout the Pacific Northwest. The elk consumed an abundance of ferns, including western swordfern, during winter and spring . On the Olympic Peninsula, western swordfern is seasonally important for elk [97,102]. Western swordfern was one of the 10 most frequently used elk foods in the southern Oregon Coast Ranges, and the western swordfern-redwood-sorrel habitat type provided much of the food for elk in both clearcuts and undisturbed forests .
Western swordfern is a moderately important food for black-tailed deer year-round [38,74]. Western swordfern made up 13% of the annual diet of black-tailed deer at one site (review ), and was found in 27 of the 178 stomach samples from black-tailed deer in western Washington . Western swordfern was among the most common species browsed by mule deer in the western hemlock/salal/western swordfern and the Pacific silver fir/western swordfern-redwood-sorrel associations on the Olympic National Forest. Deer sign was frequently observed, and recent activity was noted in late summer . Klein  observed heavy spring use of western swordfern by mule deer on Coronation Island in southeast Alaska, despite its apparent low palatability.
Western swordfern is an important plant in mountain beaver habitat from British Columbia to California, providing both food and cover [55,74,81,94,137,176]. Mountain beavers as young as 7 weeks old eat western swordfern . Mountain beaver may be abundant in western swordfern sites in western Oregon , where western swordfern is an important winter food . Western swordfern is a favorite mountain beaver food on the Siuslaw National Forest, and mountain beaver populations may be especially large in the moist stands of the western hemlock/Pacific rhododendron/western swordfern association .
Western swordfern communities provide habitat for several species of birds. In the Sitka spruce and western hemlock zones on the Olympic Peninsula and in the North Cascade Range, western swordfern is an understory dominant in old-growth forests providing northern spotted owl habitat . In western Washington, it is among the dominant understory species in second-growth Douglas-fir forests (after logging and fire) that serve as drumming sites for Pacific ruffed grouse. The 2 dominant species of ground vegetation at drumming sites are western swordfern and salmonberry (the abundance of one correlates with the scarcity of the other). Ruffed grouse select drumming logs that are higher than surrounding growth of western swordfern . A census in coniferous forests of the central Oregon Cascade Range showed that several species of birds used the 3 habitats shown in Table 13, which all contain substantial western swordfern cover.
|Table 13. Population density (individuals/km²) of breeding bird species recorded in a June 1972 census in the central Oregon Cascade Range |
Plant community (western swordfern cover)
|Douglas-fir/creambush oceanspray (8%)||western hemlock/Pacific rhododendron/dwarf Oregon-grape (3%)||western hemlock/vine maple/western swordfern-redwood-sorrel (22%)|
Palatability and nutritional value: Information on palatability and nutritional value of western swordfern was very limited in the available literature (2015). One source rated western swordfern as moderately palatable to big game  and another characterized it as having low palatability to slugs .
Klein  provides information on nutritional content of western swordfern collected on 2 dates from Coronation Island, Alaska. Western swordfern had the lowest protein content among deer forage species analyzed . In samples collected between 15 January and 15 February in the White River drainage of western Washington, it averaged 29% in vitro dry-matter digestibility and 11% crude protein .
Palatability and nutritional value of western swordfern may differ between logged and unlogged forests. On southern Vancouver Island, western swordfern growing in a recently logged area was described as "still struggling for survival in the newly logged and burned area" and was seldom eaten until winter (when preferred browse was less available). Conversely, western swordfern growing on an older burn site was preferentially selected and eaten by black-tailed deer in summer . Happe and others  provide information on nutrient content and astringency in current annual growth of western swordfern and other browse species collected in old-growth forest and 5- to 15-year-old clearcuts on the Olympic Peninsula during summer, fall, winter, and spring.
Cover value: Western swordfern habitats may provide cover for large and small animals. Mule deer and elk use of the western hemlock/vine maple/western swordfern association on the Willamette National Forest is moderately high, mostly for thermal cover. The dense shrub layer also provides good hiding cover . In the western hemlock zone of the Gifford Pinchot National Forest, the western hemlock/devil's-club/western swordfern association provides exceptional hiding cover for big game . On one plot in the western hemlock/western swordfern-foamflower association on the Olympic National Forest, a newborn elk was observed, indicating that the site was used as a calving area .
Western swordfern was used as bedding material in winter dens by American black bears in coastal British Columbia. One American black bear habitat was dominated by large Douglas-fir and western redcedar with an understory characterized by western swordfern, foamflower, sweet after death, and lady fern .
Mountain beaver and vagrant shrews may prefer western swordfern habitats. Western swordfern provides both food and cover for mountain beaver from British Columbia to California (see Importance to Wildlife). The western hemlock/vine maple/western swordfern association on the Siuslaw National Forest is prime mountain beaver habitat. Mountain beaver were present in over 40% of the plots in that type . In 40-year-old western redcedar and western hemlock stands in British Columbia, the vagrant shrew favored mesic habitats under western redcedar, where western swordfern provided understory cover (review by ).
VALUE FOR REHABILITATION OF DISTURBED SITES:
Western swordfern was recommended as a good ground cover to control erosion for conservation planting in the Northeast . Vegetative reproduction of western swordfern can occur through rhizome division .
Commercial harvesting of floral greens, including western swordfern , began in 1915 and remains one of the most enduring and stable year-round nontimber forest products industries in the Pacific Northwest [54,211]. Enormous quantities of western swordfern leaves are gathered for backgrounds in floral displays; the evergreen leaves keep well in cold storage and are even exported to Europe . Western swordfern requires partial shade to grow in forms acceptable for commercial harvest (with deep green, broad, spreading leaves). See Table 5 for information on which forest zones have the greatest potential for western swordfern production .
Western swordfern is used extensively for landscaping .
American Indians used western swordfern for a variety of purposes, including household tasks and applications, food, and medicine. Northwest coastal peoples used western swordfern leaves to line pits for cooking [54,81,170,210], to layer between food in baskets, drying racks, and storage boxes [170,210,221], and to cover floors and beds [81,170,210]. Western swordfern leaves were used in a traditional game known as pala-pala . The species also played a part in Kwakiut'l mythology and so was used in rituals . The large, basal clump of leaves and the rhizomes of western swordfern were used as food by several tribes. They were roasted or steamed, peeled, and eaten [81,170,210,221]
Traditional medicinal uses of western swordfern include rhizomes eaten to cure diarrhea , young leaves chewed and swallowed for sore throat or tonsillitis, an infusion of boiled rhizome used on sores and to ease pain, and a tea from boiled stems used in labor . Aerial parts of western swordfern are used to stimulate digestion in ruminants .
OTHER MANAGEMENT CONSIDERATIONS:
Western swordfern is among several forest products in the Pacific Northwest that may require special management considerations to be sustainable. For example, repeated harvesting of western swordfern fronds reduces frond length and plant survival considerably (review, ).
The presence of seeps or super-saturated soils typical in western swordfern habitats indicates that these areas are susceptible to soil compaction or erosion .
Because western swordfern may interfere with post-logging regeneration, it has been the object of herbicide applications. Information on studies pertaining to that topic can be found in these references: [35,74,149,195].
Climate change: Fog frequency has declined over the past 50+ years along the Pacific Coast of the western United States (Johnstone 2008, as cited by ), which has reduced the frequency of summertime leaf-wetting events. Considering the demonstrated importance of fog water for redwood forest plants, including western swordfern (see Climate in the Site Characteristics section), it seems likely that levels of plant water stress will increase in coastal communities as this important water subsidy is lost .
SPECIES: Polystichum munitum
|Appendix A. Scientific and common names of plant species associated with western swordfern and/or mentioned in this review|
|Common name||Scientific name|
|bigleaf maple||Acer macrophyllum|
|black cottonwood||Populus balsamifera subsp. trichocarpa|
|California bay||Umbellularia californica|
|canyon live oak||Quercus chrysolepis|
|coast Douglas-fir||Pseudotsuga menziesii var. menziesii|
|Coulter pine||Pinus coulteri|
|grand fir||Abies grandis|
|interior Douglas-fir||Pseudotsuga menziesii var.glauca|
|mountain hemlock||Tsuga mertensiana|
|noble fir||Abies procera|
|Oregon white oak||Quercus garryana|
|Pacific dogwood||Cornus nuttallii|
|Pacific ponderosa pine||Pinus ponderosa var. ponderosa|
|Pacific silver fir||Abies amabilis|
|red alder||Alnus rubra|
|Rocky Mountain juniper||Juniperus scopulorum|
|Sitka spruce||Picea sitchensis|
|subalpine fir||Abies lasiocarpa|
|sugar pine||Pinus lambertiana|
|sweet cherry||Prunus avium|
|western hemlock||Tsuga heterophylla|
|western redcedar||Thuja plicata|
|Alaska blueberry||Vaccinium alaskensis|
|baldhip rose||Rosa gymnocarpa|
|big huckleberry||Vaccinium membranaceum|
|California hazelnut||Corylus cornuta subsp. californica|
|common snowberry||Symphoricarpos albus|
|common whipplea||Whipplea modesta|
|creambush oceanspray||Holodiscus discolor|
|dwarf Oregon-grape||Berberis nervosa|
|evergreen huckleberry||Vaccinium ovatum|
|Oregon boxwood||Paxistima myrsinites|
|ovalleaf huckleberry||Vaccinium ovalifolium|
|Pacific poison-oak||Toxicodendron diversilobum|
|Pacific rhododendron||Rhododendron macrophyllum|
|red huckleberry||Vaccinium parvifolium|
|red-osier dogwood||Cornus sericea|
|redstem ceanothus||Ceanothus sanguineus|
|Saskatoon serviceberry||Amelanchier alnifolia|
|snowbrush ceanothus||Ceanothus velutinus|
|vine maple||Acer circinatum|
|American skunkcabbage||Lysichiton americanus|
|big deervetch||Lotus crassifolius|
|broadleaf starflower||Trientalis borealis subsp. latifolia|
|California manroot||Marah fabaceus|
|coastal hedgenettle||Stachys chamissonis var. cooleyae|
|garden vetch||Vicia sativa|
|northwestern twayblade||Listera caurina|
|oneleaf foamflower||Tiarella trifoliata var. unifoliata|
|Pacific trillium||Trillium ovatum subsp. ovatum|
|Siberian springbeauty||Claytonia sibirica var. sibirica|
|sweet after death||Achlys triphylla|
|sweetscented bedstraw||Galium triflorum|
|tall annual willowherb||Epilobium brachycarpum|
|threeleaf foamflower||Tiarella trifoliata|
|white insideout flower||Vancouveria hexandra|
|wild ginger||Asarum caudatum|
|woodland ragwort*||Senecio sylvaticus|
|youth on age||Tolmiea menziesii|
|Anderson's hollyfern||Polystichum andersonii|
|Braun's hollyfern||P. braunii|
|California swordfern||P. californicum|
|deer fern||Blechnum spicant|
|Dudley's swordfern||P. dudleyi|
|Kruckeberg's hollyfern||P. kruckebergii|
|lady fern||Athyrium filix-femina|
|Lemmon's hollyfern||P. lemmonii|
|mountain hollyfern||P. scopulinum|
|narrowleaf swordfern||P. imbricans|
|northern maidenhair||Adiantum pedatum|
|oak fern||Gymnocarpium dryopteris|
|spreading woodfern||Dryopteris expansa|
|western bracken fern||Pteridium aquilinum|
|slough sedge||Carex obnupta|
|feather moss||Hylocomium spp.|
|goose neck moss||Rhytidiadelphus loreus|
|Appendix B. Western swordfern associations described in vegetation classifications from areas where it is a community dominant. Associations are grouped by corresponding Potential Natural Vegetation Groups (PNVGs) and Biophysical Settings (BpSs).|
|Douglas-fir-western hemlock (wet mesic) PNVG
BpSs 0111780, 0211780, 0711780, 0110390, 0210390, 0310390, 0710390, 0110420, 0210420, 0710420
|Vegetation||Geographic area(s) (vegetation classification)|
|western hemlock/western swordfern association||Cascade Range, Oregon|
|Oregon Coast Ranges |
|southwestern Oregon |
|Mt Rainier National Park |
|Mt Hood National Forest |
|Gifford Pinchot National Forest |
|central portion of the western Cascade Range, Oregon |
|Siuslaw National Forest, Oregon |
|Willamette National Forest |
|western hemlock/western swordfern-redwood-sorrel association||Cascade Range, Oregon |
|Coast Ranges |
|Olympic National Forest |
|Gifford Pinchot National Forest |
|Mt Hood National Forest |
|central portion of the western Cascade Range in Oregon |
|western hemlock/vine maple/western swordfern association||Watershed 10, HJ Andrews EF |
|central portion of the western Cascade Range, Oregon |
|Siuslaw National Forest, Oregon |
|western hemlock/vine maple/western swordfern-redwood-sorrel association||western Cascade Range of Oregon and Washington |
|western hemlock/western swordfern-threeleaf foamflower association||Olympic National Forest |
|western hemlock/devil's club/western swordfern association||Gifford Pinchot National Forest |
|Mt Rainier National Park |
|western hemlock/dwarf Oregon-grape/western swordfern association||Mt Hood National Forest |
|Gifford Pinchot National Forest |
|Olympic National Forest |
|western hemlock/salal/western swordfern association||southwestern Oregon |
|western hemlock/evergreen huckleberry/western swordfern association||southwestern Oregon |
|western hemlock/ovalleaf huckleberry/western swordfern association||north coastal Oregon |
|western hemlock/western swordfern-northern maidenhair association|
|western redcedar/dwarf Oregon-grape/western swordfern association||southwestern Oregon |
|western redcedar/western swordfern||coastal British Columbia |
|western redcedar-western hemlock/western swordfern|
|western redcedar-Douglas-fir-western hemlock/western swordfern-spreading woodfern community||coastal British Columbia |
|western redcedar-grand fir/western swordfern community||interior valleys of the San Juan Islands |
|Sucia Island in Puget Sound |
|Port-Orford-cedar/western swordfern community||northern part of Port-Orford-cedar's range |
|Port-Orford-cedar-western hemlock/western swordfern||southwestern Oregon |
|western hemlock-Port-Orford-cedar/western swordfern-redwood-sorrel community||Oregon and northern California |
|Douglas-fir-western hemlock (dry mesic) PNVG
BpSs 0110350, 0210350, 0710350, 0111740, 0211740, 0711740, 0110370, 0210370, 0710370
|western hemlock/salal/western swordfern association||Olympic National Forest |
|southeastern Olympic Peninsula |
|western hemlock/Pacific rhododendron/western swordfern association||Siuslaw National Forest, Oregon |
|Olympic National Forest |
|coast Douglas-fir-western swordfern alliance||coastal British Columbia |
|coast Douglas-fir/western swordfern-feather moss association||southwestern British Columbia |
|coast Douglas-fir/western swordfern-foamflower association|
|Douglas-fir/salmonberry/western swordfern association||southwestern Oregon |
|Douglas-fir/dwarf Oregon-grape/western swordfern|
|western redcedar-grand fir-Douglas-fir/threeleaf foamflower-western swordfern||coastal British Columbia (Krajina 1969 as cited by )|
|western redcedar-grand fir-Douglas-fir/common snowberry/threeleaf foamflower-western swordfern|
|western redcedar-Douglas-fir/western swordfern-sweet after death|
|Douglas-fir/western swordfern||Cedar River Drainage in the Cascade Range of western Washington |
|red alder/western swordfern|
|Douglas-fir/Pacific poison-oak/western swordfern association||interior valleys of the Umpqua River Basin, Oregon |
|western redcedar-Douglas-fir-Oregon white oak/common snowberry/western swordfern||coastal British Columbia (Krajina 1969 as cited by )|
|Sitka spruce-western hemlock PNVG
BpSs 0110360, 0210360, 0310360
|Sitka spruce-western swordfern association||Siuslaw National Forest |
|coastal British Columbia |
|Sitka spruce/western swordfern-redwood-sorrel association||Olympic National Forest |
|Sitka spruce-western hemlock/western swordfern association||coastal British Columbia |
|western redcedar-Sitka spruce/western swordfern association|
|western redcedar-Sitka spruce-Pacific silver fir-Douglas-fir/western swordfern||coastal British Columbia (Krajina 1969 as cited by )|
|western swordfern-thimbleberry||Oregon coastal prairie |
|Pacific silver fir (low elevation) PNVG
BpSs 0110420, 0210420, 0710420, 0111740, 0211740, 0711740
|Pacific silver fir/western swordfern association||Olympic National Forest |
|Pacific silver fir/western swordfern-redwood-sorrel association|
|Coast redwood PNVG
BpSs 0210150, 0310150, 0410150
|redwood/western swordfern alliance (Becking 1967 as cited by )||northern part of redwood's range|
|redwood/western swordfern association|
|redwood-western hemlock/western swordfern association [20,142]|
|redwood-western hemlock/salmonberry/western swordfern association|
|redwood-western redcedar/western swordfern association|
|redwood-Douglas-fir/western swordfern association|
|redwood-grand fir/salal/western swordfern association|
|redwood-tanoak/western swordfern association (Jimerson and Jones 2000 as cited by )|
|redwood-western hemlock-evergreen huckleberry-western swordfern coastal forest||Siskiyou Mountains, Oregon and California |
|redwood-Douglas-fir/tanoak-Pacific rhododendron/evergreen huckleberry-western swordfern association||Redwoods State Park (Mendonca, unpublished data, as cited by )|
|redwood-western hemlock-Sitka spruce/western swordfern association|
|redwood/western swordfern-evergreen huckleberry-redwood-sorrel association|
|red alder-Sitka spruce/salmonberry-western swordfern association|
|redwood/western swordfern-Pacific trillium ecological type||Southern Monterey County, California |
|redwood/California manroot-garden vetch ecological type|
|Oregon coastal tanoak PNVG
BpSs 0210430, 0310430
|tanoak-bigleaf maple-canyon live oak/western swordfern||southwestern Oregon |
|tanoak-western hemlock/evergreen huckleberry/western swordfern|
|Douglas-fir/tanoak/western swordfern-herb community type||Illinois River area, Oregon |
|California bay-Douglas-fir/vine maple/western swordfern community||Umqua River valley in the Oregon Coast Ranges |
|Oregon white oak and Oregon white oak-ponderosa pine PNVGs
BpSs 0110600, 0210600, 0710600, 0810600, 0210290, 0710290, 0110080, 0210080, 0710080, 0111200, 0211200, 0711200
|Oregon white oak/California hazelnut/western swordfern association||Willamette Valley, Oregon [194,203]|
|beaked hazelnut/western swordfern group||northwestern Oregon |
|salmonberry/youth on age-redwood-sorrel-western swordfern phase|
|salmonberry/western swordfern association|
|Fire regime information on vegetation communities in which western swordfern may occur. This information is taken from the LANDFIRE Rapid Assessment Vegetation Models , which were developed by local experts using available literature, local data, and/or expert opinion. This table summarizes fire regime characteristics for each plant community listed. The PDF file linked from each plant community name describes the model and synthesizes the knowledge available on vegetation composition, structure, and dynamics in that community. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Pacific Northwest Grassland|
|Alpine and subalpine meadows and grasslands
|Pacific Northwest Woodland|
|Oregon white oak||Replacement||3%||275|
|Surface or low||78%||12.5|
|Oregon white oak-ponderosa pine||Replacement||16%||125||100||300|
|Surface or low||81%||25||5||30|
|Pacific Northwest Forested|
|California mixed evergreen (northern California and southern Oregon)||Replacement||6%||150||100||200|
|Surface or low||64%||15||5||30|
|Douglas-fir (Willamette Valley foothills)||Replacement||18%||150||100||400|
|Surface or low||53%||50||20||80|
|Douglas-fir-western hemlock (dry mesic)||Replacement||25%||300||250||500|
|Douglas-fir-western hemlock (wet mesic)||Replacement||71%||400|
|Lodgepole pine (pumice soils)||Replacement||78%||125||65||200|
|Mixed conifer (southwestern Oregon)||Replacement||4%||400|
|Surface or low||67%||22|
|Oregon coastal tanoak||Replacement||10%||250|
|Pacific silver fir (low elevation)||Replacement||46%||350||100||800|
|Pacific silver fir (high elevation)||Replacement||69%||500|
|Sitka spruce-western hemlock||Replacement||100%||700||300||>1,000|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Coastal sage scrub||Replacement||100%||50||20||150|
|Coastal sage scrub-coastal prairie||Replacement||8%||40||8||900|
|Surface or low||62%||5||1||6|
|California oak woodlands||Replacement||8%||120|
|Surface or low||91%||10|
|California mixed evergreen||Replacement||10%||140||65||700|
|Surface or low||32%||45||7|
|Surface or low||98%||20|
|Mixed conifer (north slopes)||Replacement||5%||250|
|Surface or low||88%||15||10||40|
|Mixed conifer (south slopes)||Replacement||4%||200|
|Surface or low||80%||10|
|Mixed evergreen-bigcone Douglas-fir (southern coastal)||Replacement||29%||250|
|Northern and Central Rockies|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Northern and Central Rockies Forested|
|Douglas-fir (warm mesic interior)||Replacement||28%||170||80||400|
|Mixed-conifer upland western redcedar-western hemlock||Replacement||67%||225||150||300|
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [83,127].
1. Agee, James K. 1993. Fire ecology of Pacific Northwest forests. Washington, DC: Island Press. 493 p. 
2. Agee, James K. 1996. Fire in the Blue Mountains: a history, ecology, and research agenda. In: Jaindl, R. G.; Quigley, T. M., eds. Search for a solution: sustaining the land, people and economy of the Blue Mountains. Washington, DC: American Forests: 119-145. 
3. Agee, James K.; Dunwiddie, Peter W. 1984. Recent forest development on Yellow Island, San Juan County, WA. Canadian Journal of Botany. 62(10): 2074-2080. 
4. Agee, James K.; Huff, Mark H. 1987. Fuel succession in a western hemlock/Douglas-fir forest. Canadian Journal of Forest Research. 17(7): 697-704. 
5. Alexander, Susan J.; McLain, Rebecca J. 2001. An overview of non-timber forest products in the United States today. Journal of Sustainable Forestry. 13(3-4): 59-66. 
6. Aller, Alvin R. 1956. A taxonomic and ecological study of the flora of Monument Peak, Oregon. The American Midland Naturalist. 56(2): 454-472. 
7. Anderson, J. P. 1959. Flora of Alaska and adjacent parts of Canada. Ames, IA: Iowa State University Press. 543 p. 
8. Antos, Joseph A.; Zobel, Donald B. 1985. Plant form, developmental plasticity and survival following burial by volcanic tephra. Canadian Journal of Botany. 63(12): 2083-2090. 
9. Anzinger, Dawn; Radosevich, Steven R. 2008. Fire and nonnative invasive plants in the Northwest Coastal bioregion. In: Zouhar, Kristin; Smith, Jane Kapler; Sutherland, Steve; Brooks, Matthew L., eds. Wildland fire in ecosystems: fire and nonnative invasive plants. Gen. Tech. Rep. RMRS-GTR-42-vol. 6. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station: 197-224. 
10. Applegate, Elmer I. 1939. Plants of Crater Lake National Park. The American Midland Naturalist. 22(2): 225-314. 
11. Asada, Taro; Warner, Barry G.; Pojar, Jim. 2003. Environmental factors responsible for shaping an open peatland forest complex on the hypermaritime north coast of British Columbia. Canadian Journal of Forest Research. 33(12): 2380-2394. 
12. Atzet, Thomas; White, Diane E.; McCrimmon, Lisa A.; Martinez, Patricia A.; Fong, Paula Reid; Randall, Vince D., tech. coords. 1996. Field guide to the forested plant associations of southwestern Oregon. Tech. Pap. R6-NR-ECOL-TP-17-96. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. Available online: http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5319837.pdf [2015, April 1]. 
13. Atzet, Tom; Wheeler, David; Smith, Brad; Riegel, Gregg; Franklin, Jerry. 1984. The tanoak series of the Siskiyou region of southwest Oregon [part 1]. Forestry Intensified Research Report. Medford, OR: Oregon State University, Extension Service, Southwest Oregon Forestry Intensified Research Program. 6(3): 6-7. 
14. Atzet, Tom; Wheeler, David; Smith, Brad; Riegel, Gregg; Franklin, Jerry. 1985. The tanoak series of the Siskiyou region of southwest Oregon [part 2]. Forestry Intensified Research Report. Medford, OR: Oregon State University, Extension Service, Southwest Oregon Forestry Intensified Research Program. 6(4): 6-10. 
15. Bailey, Arthur W.; Poulton, Charles E. 1968. Plant communities and environmental interrelationships in a portion of the Tillamook Burn, northwestern Oregon. Ecology. 49(1): 1-13. 
16. Bailey, Arthur Wesley. 1966. Forest associations and secondary succession in the southern Oregon Coast Range. Corvallis, OR: Oregon State University. 166 p. Thesis. 
17. Bailey, John D.; Mayrsohn, Cheryl; Doescher, Paul S.; St. Pierre, Elizabeth; Tappeiner, John C. 1998. Understory vegetation in old and young Douglas-fir forests of western Oregon. Forest Ecology and Management. 112(3): 289-302. 
18. Bailey, John D.; Tappeiner, John C. 1998. Effects of thinning on structural development in 40- to 100-year-old Douglas-fir stands in western Oregon. Forest Ecology and Management. 180(1-2): 99-113. 
19. Barbour, Michael G. 1994. SRM 204: North coast shrub. In: Shiflet, Thomas N., ed. Rangeland cover types of the United States. Denver, CO: Society for Range Management: 14-15. 
20. Barbour, Michael G.; Keeler-Wolf, Todd; Schoenherr, Allan A., eds. 2007. Terrestrial vegetation of California. 3d ed. Berkeley, CA: University of California Press. 712 p. 
21. Bingham, Bruce B.; Sawyer, John O. 1988. Volume and mass of decaying logs in an upland old-growth redwood forest. Canadian Journal of Forest Research. 18(12): 1649-1651. 
22. Blair, Brent C.; Letourneau, Deborah K.; Bothwell, Sara G. 2010. Disturbance, resources, and exotic plan invasion: gap size effects in a redwood forest. Madrono. 57(1): 11-19. 
23. Boe, Kenneth N. 1975. Natural seedlings and sprouts after regeneration cuttings in old-growth redwood. Res. Pap. PSW-111. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 17 p. 
24. Borchert, Mark; Segotta, Daniel; Purser, Michael D. 1988. Coast redwood ecological types of southern Monterey County, California. Gen. Tech. Rep. PSW-107. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station. 27 p. 
25. Bowcutt, Frederica S. 1999. A floristic study of Sugarloaf Ridge State Park, Sonoma County, California. Aliso. 18(1): 19-34. 
26. Brockway, Dale G.; Topik, Christopher; Hemstrom, Miles A.; Emmingham, William H. 1983. Plant association and management guide for the Pacific silver fir zone: Gifford Pinchot National Forest. R6-Ecol-130a. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 122 p. 
27. Brown, Ellsworth R. 1961. The black-tailed deer of western Washington. Biological Bulletin No. 13. Olympia, WA: Washington State Game Commission. 124 p. 
28. Carey, Andrew B. 2002. Globalization of flora: inviting worldwide ecosystem disaster. Renewable Resources Journal. 20(1): 13-17. 
29. Carlton, Gary C. 1988. The structure and dynamics of red alder communities in the central Coast Range of western Oregon. Corvallis, OR: Oregon State University. 173 p. Thesis. 
30. Cates, Rex G.; Orians, Gordon H. 1975. Successional status and the palatability of plants to generalized herbivores. Ecology. 56(2): 410-418. 
31. Chappell, Christopher B.; Kagan, Jimmy. 2001. 1. Westside lowlands conifer-hardwood forest. In: Chappell, Christopher B.; Crawford, Rex C.; Barrett, Charley; Kagan, Jimmy; Johnson, David H.; O'Mealy, Mikell; Green, Greg A.; Ferguson, Howard L.; Edge, W. Daniel; Greda, Eva L.; O'Neil, Thomas A. Wildlife habitats: descriptions, status, trends, and system dynamics. In: Johnson, David H.; O'Neil, Thomas A., managing directors. Wildlife-habitat relationships in Oregon and Washington. Corvallis, OR: Oregon State University Press: 24-26. 
32. Chappell, Christopher B.; Kagan, Jimmy. 2001. 2. Westside oak and dry Douglas-fir forest and woodland. In: Chappell, Christopher B.; Crawford, Rex C.; Barrett, Charley; Kagan, Jimmy; Johnson, David H.; O'Mealy, Mikell; Green, Greg A.; Ferguson, Howard L.; Edge, W. Daniel; Greda, Eva L.; O'Neil, Thomas A. Wildlife habitats: descriptions, status, trends, and system dynamics. In: Johnson, David H.; O'Neil, Thomas A., managing directors. Wildlife-habitat relationships in Oregon and Washington. Corvallis, OR: Oregon State University Press: 26-28. 
33. Chappell, Christopher B.; Kagan, Jimmy. 2001. 23. Westside riparian-wetlands. In: Chappell, Christopher B.; Crawford, Rex C.; Barrett, Charley; Kagan, Jimmy; Johnson, David H.; O'Mealy, Mikell; Green, Greg A.; Ferguson, Howard L.; Edge, W. Daniel; Greda, Eva L.; O'Neil, Thomas A. Wildlife habitats: descriptions, status, trends, and system dynamics. In: Johnson, David H.; O'Neil, Thomas A., managing directors. Wildlife-habitat relationships in Oregon and Washington. Corvallis, OR: Oregon State University Press: 94-96. 
34. Clement, C. J. E. 1985. Floodplain succession on the west coast of Vancouver Island. The Canadian Field-Naturalist. 99(1): 34-39. 
35. Coates, D.; Haeussler, S. 1986. A preliminary guide to the response of major species of competing vegetation to silvicultural treatments. Land Management Handbook No. 9. Victoria, BC: Ministry of Forests, Information Services Branch. 88 p. 
36. Cody, William J.; Britton, Donald M. 1989. Ferns and fern allies of Canada. Ottawa, ON: Agriculture Canada, Research Branch. 430 p. 
37. Cooper, Stephen V.; Neiman, Kenneth E.; Roberts, David W. 1991. Forest habitat types of northern Idaho: a second approximation. [Revised]. Gen. Tech. Rep. INT-236. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 143 p. 
38. Cowan, Ian McTaggart. 1945. The ecological relationships of the food of the Columbian black-tailed deer, Odocoileus hemionus columbianus (Richardson), in the coast forest region of southern Vancouver Island, British Columbia. Ecological Monographs. 15(2): 110-139. 
39. Cromack, K.; Swanson, F. J.; Grier, C. C. 1979. A comparison of harvesting methods and their impact on soils and environment in the Pacific Northwest. In: Youngberg, Chester T., ed. Proceedings: forest soils and land use: 5th North American forest soils conference; 1978 August 6-9; Fort Collins, CO. Fort Collins, CO: Colorado State University: 449-476. 
40. Curtis, Robert O.; DeBell, Dean S.; Harrington, Constance A.; Lavender, Denis P.; St. Clair, J. Bradley; Tappeiner, John C.; Walstad, John D. 1998. Silviculture for multiple objectives in the Douglas-fir region. Gen. Tech. Rep. PNW-GTR-435. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 123 p. 
41. Daubenmire, R. 1969. Ecologic plant geography of the Pacific Northwest. Madrono. 20(3): 111-128. 
42. Daubenmire, Rexford F.; Daubenmire, Jean B. 1968. Forest vegetation of eastern Washington and northern Idaho. Tech. Bull. 60. Pullman, WA: Washington State University, Agricultural Experiment Station. 104 p. 
43. Davidson, Eric Duncan. 1967. Synecological features of a natural headland prairie on the Oregon coast. Corvallis, OR: Oregon State University. 78 p. Thesis. 
44. Davis, Helen. 1996. Characteristics and selection of winter dens by black bears in coastal British Columbia. Burnaby, BC: Simon Fraser University. 147 p. Thesis. 
45. DeBell, Dean S. 1980. Black cottonwood-willow. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 100-101. 
46. del Moral, Roger; Long, James N. 1977. Classification of montane forest community types in the Cedar River drainage of western Washington, U.S.A. Canadian Journal of Forest Research. 7(2): 217-225. 
47. Donato, Daniel C.; Fontaine, Joseph B.; Robinson, W. Douglas; Kauffman, J. Boone; Law, Beverly E. 2009. Vegetation response to a short interval between high-severity wildfires in a mixed-evergreen forest. Journal of Ecology. 97(1): 142-154. 
48. Dorn, Robert D. 1977. Flora of the Black Hills. Cheyenne, WY: Robert D. Dorn and Jane L. Dorn. 377 p. 
49. Douglas, George W.; Ballard, T. M. 1971. Effects of fire on alpine plant communities in the North Cascades, Washington. Ecology. 52(6): 1058-1064. 
50. Douglas, Geroge W.; Taylor, Ronald J. 1970. Contributions to the flora of Washington. Rhodora. 72(789): 496-501. 
51. Dyrness, C. T. 1965. The effect of logging and slash burning on understory vegetation in the H. J. Andrews Experimental Forest. Res. Note PNW-31. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 13 p. 
52. Dyrness, C. T. 1973. Early stages of plant succession following logging and burning in the western Cascades of Oregon. Ecology. 54(1): 57-69. 
53. Dyrness, C. T.; Franklin, J. F.; Moir, W. H. 1974. A preliminary classification of forest communities in the central portion of the western Cascades in Oregon. Bulletin No. 4. Seattle, WA: University of Washington, Ecosystem Analysis Studies, Coniferous Forest Biome. 123 p. 
54. Emery, Marla; O'Halek, Shandra L. 2001. Brief overview of historical non-timber forest product use in the U.S. Pacific Northwest and Upper Midwest. Journal of Sustainable Forestry. 13(3-4): 25-30. 
55. Fellers, Gary M.; Pratt, David; Griffin, Jennifer L. 2004. Fire effects on the Point Reyes mountain beaver at Point Reyes National Seashore, California. The Journal of Wildlife Management. 68(3): 503-508. 
56. Ferguson, Dennis E.; Johnson, Frederic D. 1996. Classification of grand fir mosaic habitats. Gen. Tech. Rep. INT-GTR-337. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 16 p. 
57. Fites-Kaufmann, Josephine. 1997. Historic landscape pattern and process: fire, vegetation, and environment interactions in the northern Sierra Nevada. Seattle, WA: University of Washington. 175 p. Dissertation. 
58. Flora of North America Editorial Committee, eds. 2015. Flora of North America north of Mexico, [Online]. Flora of North America Association (Producer). Available: http://www.efloras.org/flora_page.aspx?flora_id=1. 
59. Fonda, R. W. 1974. Forest succession in relation to river terrace development in Olympic National Park, Washington. Ecology. 55(5): 927-942. 
60. Fonda, R. W. 2001. Postfire response of red alder, black cottonwood, and bigleaf maple to the Whatcom Creek fire, Bellingham, Washington. Northwest Science. 75(1): 25-36. 
61. Fonda, R. W.; Bernardi, J. A. 1976. Vegetation of Sucia Island in Puget Sound, Washington. Bulletin of the Torrey Botanical Club. 103(3): 99-109. 
62. Franklin, Jerry F. 1979. Vegetation of the Douglas-fir region. In: Heilman, Paul E.; Anderson, Harry W.; Baumgartner, David M., eds. Forest soils of the Douglas-fir region. Pullman, WA: Washington State University, Cooperative Extension Service: 93-112. 
63. Franklin, Jerry F. 1988. Pacific Northwest forests. In: Barbour, Michael G.; Billings, William Dwight, eds. North American terrestrial vegetation. New York: Cambridge University Press: 103-130. 
64. Franklin, Jerry F.; Dyrness, C. T. 1973. Natural vegetation of Oregon and Washington. Gen. Tech. Rep. PNW-8. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 417 p. 
65. Franklin, Jerry F.; Moir, William H.; Hemstrom, Miles A.; Greene, Sarah E.; Smith, Bradley G. 1988. The forest communities of Mount Rainier National Park. Scientific Monograph Series No. 19. Washington, DC: U.S. Department of the Interior, National Park Service. 194 p. 
66. Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. 1977. No. 27--The redwood ecosystem. In: Garrison, George A.; Bjugstad, Ardell J.; Duncan, Don A.; Lewis, Mont E.; Smith, Dixie R. Vegetation and environmental features of forest and range ecosystems. Agric. Handb. 475. Washington, DC: U.S. Department of Agriculture, Forest Service: 31. 
67. Garrison, George A.; Smith, Justin G. 1974. Habitat of grazing animals. In: Cramer, Owen P., ed. Environmental effects of forest residues management in the Pacific Northwest: A state-of-knowledge compendium. Gen. Tech. Rep. PNW-24. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station: 1-10. 
68. Gashwiler, Jay S. 1959. Small mammal study in west-central Oregon. Journal of Mammalogy. 40(1): 128-139. 
69. Gashwiler, Jay S. 1970. Plant and mammal changes on a clearcut in west-central Oregon. Ecology. 51(6): 1018-1026. 
70. Gray, Andrew N.; Monleon, Vicente J.; Spies, Thomas A. 2009. Characteristics of remnant old-growth forests in the northern Coast Range of Oregon and comparison to surrounding landscapes. Gen Tech. Rep. PNW-GTR-790. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 45 p. 
71. Green, R. N.; Marshall, P. L.; Klinka, K. 1989. Estimating site index of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) from ecological variables in southwestern British Columbia. Forest Science. 35(1): 50-63. 
72. Grier, Charles C.; Logan, Robert S. 1977. Old-growth Pseudotsuga menziesii communities of a western Oregon watershed: biomass distribution and production budgets. Ecological Monographs. 47(4): 373-400. 
73. Habeck, James R. 1972. Fire ecology investigations in Selway-Bitterroot Wilderness, historical considerations and current observations. Contract No. 26-2647, Publication No. R1-72-001. Missoula, MT: University of Montana, Department of Botany. 119 p. 
74. Haeussler, S.; Coates, D.; Mather, J. 1990. Autecology of common plants in British Columbia: a literature review. FRDA Report 158. Victoria, BC: Forestry Canada, Pacific Forestry Center; British Columbia Ministry of Forests, Research Branch. 272 p. 
75. Hall, Frederick C. 1974. Key to some common forest-zone plants of northwestern Washington. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 34 p. 
76. Halpern, C. B. 1989. Early successional patterns of forest species: interactions of life history traits and disturbance. Ecology. 70(3): 704-720. 
77. Halpern, Charles B. 1988. Early successional pathways and the resistance and resilience of forest communities. Ecology. 69(6): 1703-1715. 
78. Halpern, Charles B.; Franklin, Jerry F. 1990. Physiognomic development of Pseudotsuga forests in relation to initial structure and disturbance intensity. Journal of Vegetation Science. 1(4): 475-482. 
79. Halpern, Charles B.; Frenzen, Peter M.; Means, Joseph E.; Franklin, Jerry F. 1990. Plant succession in areas of scorched and blown-down forest after the 1980 eruption of Mount St. Helens, Washington. Journal of Vegetation Science. 1(2): 181-194. 
80. Halpern, Charles B.; Harmon, Mark E. 1983. Early plant succession on the Muddy River mudflow, Mount St. Helens, Washington. The American Midland Naturalist. 110(1): 97-106. 
81. Halverson, Nancy M., comp. 1986. Major indicator shrubs and herbs on national forests of western Oregon and southwestern Washington. R6-TM-229. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 180 p. 
82. Halverson, Nancy M.; Topik, Christopher; Van Vickle, Robert. 1986. Plant association and management guide for the western hemlock zone: Mt. Hood National Forest. R6-ECOL-232A. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 111 p. 
83. Hann, Wendel; Havlina, Doug; Shlisky, Ayn; [and others]. 2010. Interagency fire regime condition class (FRCC) guidebook, [Online]. Version 3.0. In: FRAMES (Fire Research and Management Exchange System). National Interagency Fuels, Fire & Vegetation Technology Transfer (NIFTT) (Producer). Available: http://www.fire.org. 
84. Hansen, Paul L.; Hall, James B. 2002. Classification and management of USDI Bureau of Land Management's riparian and wetland sites in eastern and southern Idaho. Corvallis, MT: Bitterroot Restoration. 304 p. 
85. Hansen, Paul L.; Pfister, Robert D.; Boggs, Keith; Cook, Bradley J.; Joy, John; Hinckley, Dan K. 1995. Classification and management of Montana's riparian and wetland sites. Misc. Publ. No. 54. Missoula, MT: The University of Montana, School of Forestry, Montana Forest and Conservation Experiment Station. 646 p. 
86. Happe, Patricia J.; Jenkins, Kurt J.; Starkey, Edward E.; Sharrow, Steven H. 1990. Nutritional quality and tannin astringency of browse in clear-cuts and old-growth forests. The Journal of Wildlife Management. 54(4): 557-566. 
87. Harper, James A. 1969. Relations of elk to reforestation in the Pacific Northwest. In: Black, Hugh C., ed. Wildlife and reforestation in the Pacific Northwest: Proceedings of a symposium; 1968 September 12-13; Corvallis, OR. Corvallis, OR: Oregon State University, School of Forestry: 67-71. 
88. Harris, A. S. 1980. Sitka spruce. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 101-102. 
89. Hawk, G. M.; Zobel, D. B. 1974. Forest succession on alluvial landforms of the McKenzie River Valley, Oregon. Northwest Science. 48(4): 245-265. 
90. Hawk, Glenn M. 1979. Vegetation mapping and community description of a small western Cascade watershed. Northwest Science. 53(3): 200-212. 
91. Hawk, Glenn Martin. 1977. Comparative study of temperate Chamaecyparis forests. Corvallis, OR: Oregon State University. 195 p. Dissertation. 
92. Hawkes, B. C.; Feller, M. C.; Meehan, D. 1990. Site preparation: fire. In: Lavender, D. P.; Parish, R.; Johnson, C. M.; Montgomery, G.; Vyse, A.; Willis, R. A.; Winston, D., eds. Regenerating British Columbia's forests. Vancouver, BC: University of British Columbia Press: 131-149. 
93. Hemstrom, Miles A.; Emmingham, W. H.; Halverson, Nancy M.; Logan, Shiela E.; Topik, Christopher. 1982. Plant association and management guide for the Pacific silver fir zone, Mt. Hood and Willamette National Forests. R6-Ecol 100-1982a. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 104 p. 
94. Hemstrom, Miles A.; Logan, Sheila E. 1986. Plant association and management guide: Siuslaw National Forest. R6-Ecol 220-1986a. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 121 p. 
95. Hemstrom, Miles A.; Logan, Sheila E.; Pavlat, Warren. 1987. Plant association and management guide: Willamette National Forest. R6-Ecol 257-B-86. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 312 p. 
96. Henderson, Jan A. 1978. Plant succession on the Alnus rubra/Rubus spectabilis habitat type in western Oregon. Northwest Science. 52(3): 156-167. 
97. Henderson, Jan A.; Peter, David H.; Lesher, Robin D.; Shaw, David C. 1989. Forested plant associations of the Olympic National Forest. R6-ECOL-TP 001-88. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 502 p. 
98. Hickman, James C., ed. 1993. The Jepson manual: Higher plants of California. Berkeley, CA: University of California Press. 1400 p. 
99. Hines, William Wester. 1971. Plant communities in the old-growth forests of north coastal Oregon. Corvallis, OR: Oregon State University. 146 p. Thesis. 
100. Hitchcock, C. Leo; Cronquist, Arthur. 1973. Flora of the Pacific Northwest. Seattle, WA: University of Washington Press. 730 p. 
101. Holland, Robert F. 1986. Preliminary descriptions of the terrestrial natural communities of California. Sacramento, CA: California Department of Fish and Game. 156 p. 
102. Houston, D. B.; Schreiner, E. G.; Moorhead, B. B.; Krueger, K. A. 1990. Elk in Olympic National Park: will they persist over time? Natural Areas Journal. 10(1): 6-11. 
103. Houston, D. B.; Stevens, V.; Schreiner, E. G. 1994. Habitat relations, social behavior, and physiological ecology. In: Houston, Douglas B.; Schreiner, Edward G.; Moorhead, Bruce B., eds. Mountain goats in Olympic National Park: biology, and management of an introduced species. Scientific Monograph NPS/NROLYM/NRSM-94/25. Denver, CO: U.S. Department of the Interior, National Park Service: 84-97. 
104. Houtcooper, Wayne C.; Ode, David J.; Pearson, John A.; Vandel, George M., III. 1985. Rare animals and plants of South Dakota. Prairie Naturalist. 17(3): 143-165. 
105. Huff, Mark Hamilton. 1984. Post-fire succession in the Olympic Mountains, Washington: forest vegetation, fuels, and avifauna. Seattle, WA: University of Washington. 235 p. Dissertation. 
106. Hulten, Eric. 1968. Flora of Alaska and neighboring territories. Stanford, CA: Stanford University Press. 1008 p. 
107. Isaac, Leo A. 1940. Vegetative succession following logging in the Douglas-fir region with special reference to fire. Journal of Forestry. 38(9): 716-721. 
108. Jenkins, Kurt J.; Starkey, Edward E. 1991. Food habits of Roosevelt elk. Rangelands. 13(6): 261-265. 
109. Jenkins, Kurt J.; Starkey, Edward E. 1993. Winter forages and diets of elk in old-growth and regenerating coniferous forests in western Washington. The American Midland Naturalist. 130(2): 299-313. 
110. Johnson, Charles G., Jr.; Clausnitzer, Roderick R.; Mehringer, Peter J.; Oliver, Chadwick D. 1994. Biotic and abiotic processes of eastside ecosystems: the effects of management on plant and community ecology, and on stand and landscape vegetation dynamics. Gen. Tech. Rep. PNW-GTR-322. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 66 p. 
111. Jones, Chad C.; del Moral, Roger. 2005. Patterns of primary succession on the foreland of Coleman Glacier, Washington, USA. Plant Ecology. 180(1): 105-116. 
112. Kartesz, J. T.; The Biota of North America Program (BONAP). 2015. Taxonomic Data Center, [Online]. Chapel Hill, NC: The Biota of North America Program (Producer). Available online: bonap.org. [maps generated from Kartesz, J. T. 2010. Floristic synthesis of North America, Version 1.0. Biota of North America Program (BONAP). (in press)]. 
113. Kayes, Lori J.; Anderson, Paul D.; Puettmann, Klaus J. 2010. Vegetation succession among and within structural layers following wildfire in managed forests. Journal of Vegetation Science. 21(2): 233-247. 
114. Kelpsas, B. R. 1978. Comparative effects of chemical, fire, and machine site preparation in an Oregon coastal brushfield. Corvallis, OR: Oregon State University. 97 p. Thesis. 
115. Kennedy, Peter G.; Quinn, Timothy. 2001. Understory plant establishment on old-growth stumps and the forest floor in western Washington. Forest Ecology and Management. 154(1-2): 193-200. 
116. Kienholz, Raymond. 1929. Revegetation after logging and burning in the Douglas-fir region of western Washington. Illinois State Academy of Science. 21: 94-108. 
117. Klein, David R. 1965. Ecology of deer range in Alaska. Ecological Monographs. 35(3): 259-284. 
118. Klinka, K. 1977. Guide for the tree species selection and prescribed burning in the Vancouver Forest District: Second approximation. Vancouver, BC: Ministry of Forests, Forest Service Research Division, Vancouver Forest District. 56 p. 
119. Klinka, K.; Carter, R. E. 1980. Ecology and silviculture of the most productive ecosystems for growth of Douglas-fir in southwestern British Columbia. Land Management Report Number 6. Victoria, BC: Province of British Columbia, Ministry of Forests. 12 p. 
120. Klinka, K.; Green, R. N.; Courtin, P. J.; Nuszdorfer, F. C. 1984. Site diagnosis, tree species selection, and slashburning guidelines for the Vancouver Forest Region, British Columbia. Land Management Report No. 25. Victoria, BC: Ministry of Forests, Information Services Branch. 180 p. 
121. Klinka, K.; Krajina, V. J.; Ceska, A.; Scagel, A. M. 1989. Indicator plants of coastal British Columbia. Vancouver, BC: University of British Columbia Press. 288 p. 
122. Klinka, K.; Scagel, A. M.; Courtin, P. J. 1985. Vegetation relationships among some seral ecosystems in southwestern British Columbia. Canadian Journal of Forestry. 15(3): 561-569. 
123. Klinka, K.; Wang, Q.; Carter, R. E. 1990. Relationships among humus forms, forest floor nutrient properties, and understory vegetation. Forest Science. 36(3): 564-581. 
124. Klinka, Karel; Qian, Hong; Pojar, Jim; Meidinger, Del V. 1996. Classification of natural forest communities of coastal British Columbia, Canada. Vegetatio. 125(2): 149-168. 
125. Kovalchik, Bernard L.; Clausnitzer, Rodrick R. 2004. Classification and management of aquatic, riparian, and wetland sites on the national forests of eastern Washington: series description. Gen. Tech. Rep. PNW-GTR-593. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 354 p. 
126. Lackschewitz, Klaus. 1991. Vascular plants of west-central Montana--identification guidebook. Gen. Tech. Rep. INT-227. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 648 p. 
127. LANDFIRE Rapid Assessment. 2005. Reference condition modeling manual (Version 2.1). Cooperative Agreement 04-CA-11132543-189. Boulder, CO: The Nature Conservancy; U.S. Department of Agriculture, Forest Service; U.S. Department of the Interior. 72 p. On file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 
128. LANDFIRE Rapid Assessment. 2007. Rapid assessment potential natural vegetation groups (PNVGs): associated vegetation descriptions and geographic distributions. Washington, DC: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Lab; U.S. Geological Survey; Arlington, VA: The Nature Conservancy. 84 p. 
129. Lans, Cheryl; Turner, Nancy; Khan, Tonya; Brauer, Gerhard; Boepple, Willi. 2007. Ethnoveterinary medicines used for ruminants in British Columbia, Canada. Journal of Ethnobiology and Ethnomedicine. 3(11): [1-22]. 
130. Layser, Earle F. 1980. Flora of Pend Oreille County, Washington. Pullman, WA: Washington State University, Cooperative Extension. 146 p. 
131. Lesher, Robin D.; Henderson, Jan A. 1989. Indicator species of the Olympic National Forest. R6-ECOL-TP003-88. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 79 p. 
132. Lezberg, Ann L.; Antos, Joseph A.; Halpern, Charles B. 1999. Belowground traits of herbaceous species in young coniferous forests of the Olympic Peninsula, Washington. Canadian Journal of Botany. 77(7): 936-943. 
133. Limm, Emily B.; Dawson, Todd E. 2010. Polystichum munitum (Dryopteridaceae) varies geographically in its capacity to absorb fog water by foliar uptake within the redwood forest ecosystem. American Journal of Botany. 97(7): 1121-1128. 
134. Limm, Emily Burns; Simonin, Kevin A.; Bothman, Aron G.; Dawson, Todd E. 2009. Foliar water uptake: a common water acquisition strategy for plants of the redwood forest. Oecologia. 161(3): 449-459. 
135. Lorenz, David G.; Sharp, W. Curtis.; Ruffner, Joseph D. 1991. Conservation plants for the Northeast. Program Aid 1154. [Washington, DC]: U.S. Department of Agriculture, Soil Conservation Service. 43 p. 
136. Lotan, James E.; Alexander, Martin E.; Arno, Stephen F.; French, Richard E.; Langdon, O. Gordon; Loomis, Robert M.; Norum, Rodney A.; Rothermel, Richard C.; Schmidt, Wyman C.; van Wagtendonk, Jan. 1981. Effects of fire on flora: A state-of-knowledge review: National fire effects workshop: Proceedings. 1978 April 10-14; Denver, CO. Gen. Tech. Rep. WO-16. Washington, DC: U.S. Department of Agriculture, Forest Service. 71 p. 
137. Lovejoy, Bill P.; Black, Hugh C.; Hooven, Edward F. 1978. Reproduction, growth, and development of the mountain beaver (Aplodontia rufa pacifica). Northwest Science. 52(4): 323-328. 
138. Loya, David T.; Jules, Erik S. 2008. Use of species richness estimators improves evaluation of understory plant response to logging: a study of redwood forests. Plant Ecology. 194(2): 179-194. 
139. Luoma, Daniel L.; Frenkel, Robert E.; Trappe, James M. 1991. Fruiting of hypogeous fungi in Oregon Douglas-fir forests: seasonal and habitat variation. Mycologia. 83(3): 335-353. 
140. MacKinnon, A.; Meidinger, D.; Klinka, K. 1992. Use of the biogeoclimatic ecosystem classification system in British Columbia. Forestry Chronicle. 68(1): 100-120. 
141. MacKinnon, Andy. 2003. West coast, temperate, old-growth forests. The Forestry Chronicle. 79(3): 475-484. 
142. Mahony, Thomas M.; Stuart, John D. 2007. Status of vegetation classification in redwood ecosystems. In: Standiford, Richard B.; Giusti, Gregory A.; Valachovic, Yana; Zielinski, William J.; Furniss, Michael J., technical editors. Proceedings of the redwood region forest science symposium: What does the future hold; 2004 March 15-17; Rohnert Park, CA. Gen. Tech. Rep. RSW-GTR-194. Albany, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 207-214. 
143. McCain, Cindy; Christy, John A. 2005. Field guide to riparian plant communities in northwestern Oregon. Tech. Pap. R6-NR-ECOL-TP-01-05. [Portland, OR]: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 357 p. 
144. McKenzie, Donald; Halpern, Charles B.; Nelson, Cara R. 2000. Overstory influences on herb and shrub communities in mature forests of western Washington, U.S.A. Canadian Journal of Forest Research. 30(10): 1655-1666. 
145. Mead, Bert R. 2002. Constancy and cover of plants in the Petersburg and Wrangell Districts, Tongass National Forest and associated private and other public lands, southeast Alaska. Res. Pap. PNW-RP-540. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 112 p. 
146. Meidinger, Del; Pojar, Jim. 1991. Ecosystems of British Columbia. Special Report Series 6. Victoria, BC: British Columbia Ministry of Forests. 330 p. 
147. Merrill, Evelyn H. 1994. Summer foraging ecology of wapiti (Cervus elaphus roosevelti) in the Mount St. Helens blast zone. Canadian Journal of Zoology. 72(2): 303-311. 
148. Merrill, Evelyn; Raedeke, Kenneth; Taber, Richard. 1987. Population dynamics and habitat ecology of elk in the Mount St. Helens blast zone. Seattle, WA: University of Washington, College of Forest Resources, Wildlife Science Group. 186 p. 
149. Miller, Daniel L.; Kidd, Frank A. 1983. Shrub control in the Inland Northwest--a summary of herbicide test results. Forestry Research Note RN-83-4. Lewiston, ID: Potlatch Corporation. 49 p. 
150. Minore, Don. 1980. Western hemlock-Sitka spruce. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 103. 
151. Minore, Don. 1983. Western redcedar--a literature review. Gen. Tech. Rep. PNW-150. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 70 p. 
152. Morris, William G. 1958. Influence of slash burning on regeneration, other plant cover, and fire hazard in the Douglas-fir region: a progress report. Res. Pap. PNW-29. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 49 p. 
153. Morris, William G. 1970. Effects of slash burning in overmature stands of the Douglas-fir region. Forest Science. 16(3): 258-270. 
154. Mueggler, Walter F. 1965. Ecology of seral shrub communities in the cedar-hemlock zone of northern Idaho. Ecological Monographs. 35(2): 165-185. 
155. Munz, Philip A.; Keck, David D. 1973. A California flora and supplement. Berkeley, CA: University of California Press. 1905 p. 
156. Narog, Marcia G.; Wilson, Ruth C.; Paysen, Timothy E. 1993. Invertebrate responses to thinning and understory burning in a canyon live oak forest. In: ICFVM, Proceedings of the international conference on forest vegetation management. Report No. 1. Auburn, AL: Auburn University School of Forestry: 209-213. 
157. NatureServe. 2007. Thuja plicata - Pseudotsuga menziesii - Tsuga heterophylla / Polystichum munitum - Dryopteris expansa forest. Ecological association comprehensive report, [Online]. NatureServe Explorer: An online encyclopedia of life. Version 7.1. Arlington, VA: NatureServe (Producer). Available: http://explorer.natureserve.org/servlet/NatureServe?searchCommunityUid=ELEMENT_GLOBAL.2.788002 [2015, April 7]. 
158. NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life, [Online]. Version 7.1. Arlington, VA: NatureServe (Producer). Available: http://www.natureserve.org/explorer. 
159. North, Malcolm P.; Franklin, Jerry F.; Carey, Andrew B.; Forsman, Eric D.; Hamer, Tom. 1999. Forest stand structure of the northern spotted owl's foraging habitat. Forest Science. 45(4): 520-527. 
160. North, Malcom; Chen, Jiquan; Smith, Gordon; Krakowiak, Lucy; Franklin, Jerry. 1996. Initial response of understory plant diversity and overstory tree diameter growth to a green tree retention harvest. Northwest Science. 70(1): 24-35. 
161. Nuszdorfer, F. C.; Klinka, K.; Demarchi, D. A. 1991. Coastal Douglas-fir zone. In: Meidinger, Del; Pojar, Jim, eds. Ecosystems of British Columbia. Special Report Series 6. Victoria, BC: British Columbia Ministry of Forests: 81-94. 
162. Pabst, Robert J.; Spies, Thomas A. 2001. Ten years of vegetation succession on a debris-flow deposit in Oregon. Journal of the American Water Resources Association. 37(6): 1693-1708. 
163. Patterson, Patricia A.; Neiman, Kenneth E.; Tonn, Jonalea. 1985. Field guide to forest plants of northern Idaho. Gen. Tech. Rep. INT-180. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 246 p. 
164. Pearson, Dean E. 1999. Small mammals of the Bitterroot National Forest: a literature review and annotated bibliography. Gen. Tech. Rep. RMRS-GTR-25. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 63 p. 
165. Peinado, M.; Aguirre, J. L.; Delgadillo, J. 1997. Phytosociological, bioclimatic and biogeographical classification of woody climax communities of western North America. Journal of Vegetation Science. 8(4): 505-528. 
166. Peter, David H.; Harrington, Constance A. 2010. Reconstructed old-growth forest stand structure and composition of two stands on the Olympic Peninsula, Washington state. Res. Pap. PNW-PW-583. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 22 p. 
167. Peter, David; Shebitz, Daniela. 2006. Historic anthropogenically maintained bear grass savannas of the southeastern Olympic Peninsula. Restoration Ecology. 14(4): 605-615. 
168. Pillers, Michael D.; Stuart, John D. 1993. Leaf-litter accretion and decomposition in interior and coastal old-growth redwood stands. Canadian Journal of Forest Research. 23(3): 552-557. 
169. Pojar, J.; Klinka, K.; Demarchi, D. A. 1991. Coastal western hemlock zone. In: Meidinger, Del; Pojar, Jim, eds. Ecosystems of British Columbia. Special Report Series 6. Victoria, BC: British Columbia Ministry of Forests: 95-112. 
170. Pojar, Jim; MacKinnon, Andy, eds. 1994. Plants of the Pacific Northwest coast: Washington, Oregon, British Columbia and Alaska. Redmond, WA: Lone Pine Publishing. 526 p. 
171. Powell, David C.; Johnson, Charles G., Jr.; Crowe, Elizabeth A.; Wells, Aaron; Swanson, David K. 2007. Potential vegetation hierarchy for the Blue Mountains section of northeastern Oregon, southeastern Washington, and west-central Idaho. Gen. Tech. Rep. PNW-GTR-709. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 87 p. 
172. Raunkiaer, C. 1934. The life forms of plants and statistical plant geography. Oxford, England: Clarendon Press. 632 p. 
173. Reukema, Donald L. 1980. Douglas-fir--western hemlock. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 107-108. 
174. Rhodes, Bruce D.; Sharrow, Steven H. 1990. Effect of grazing by sheep on the quantity and quality of forage available to big game in Oregon's Coast Range. Journal of Range Management. 43(3): 235-237. 
175. Ringius, Gordon S.; Sims, Richard A. 1997. Indicator plant species in Canadian forests. Ottawa, ON: Natural Resources Canada, Canadian Forest Service. 218 p. 
176. Roberts, Catherine Anne. 1975. Initial plant succession after brown and burn site preparation on an alder-dominated brushfield in the Oregon Coast Range. Corvallis, OR: Oregon State University. 90 p. Thesis. 
177. Rogers, Deborah L. 2000. Genotypic diversity and clone size in old-growth populations of coast redwood (Sequoia sempervirens). Canadian Journal of Botany. 78(11): 1408-1419. 
178. Russell, Will. 2009. The influence of timber harvest on the structure and composition of riparian forests in the coastal redwood region. Forest Ecology and Management. 257(5): 1427-1433. 
179. Russell, Will; Terada, Sayaka. 2009. The effects of revetment on streamside vegetation in Sequoia sempervirens (Taxodiaceae) forests. Madrono. 56(2): 71-80. 
180. Salo, Leo J. 1978. Characteristics of ruffed grouse drumming sites in western Washington and their relevance to management. Annales Zoologici Fennici. 15(4): 261-278. 
181. Schlosser, William E.; Blatner, Keith A.; Zamora, Benjamin. 1992. Pacific Northwest forest lands potential for floral greenery production. Northwest Science. 66(1): 44-55. 
182. Schoonmaker, Peter; McKee, Arthur. 1988. Species composition and diversity during secondary succession of coniferous forests in the western Cascade Mountains of Oregon. Forest Science. 34(4): 960-979. 
183. Scoggan, H. J. 1978. The flora of Canada. Part 2: Pteridophyta, Gymnospermae, Monocotyledoneae. National Museum of Natural Sciences: Publications in Botany, No. 7(2). Ottawa, ON: National Museums of Canada. 545 p. 
184. Sharrow, Steven H.; Leininger, Wayne C.; Osman, Khalid A. 1992. Sheep grazing effects on coastal Douglas-fir forest growth: a ten-year perspective. Forest Ecology and Management. 50(1-2): 75-84. 
185. Shatford, Jeff; Hibbs, David; Norris, Logan. 2003. Identifying plant communities resistant to conifer establishment along utility rights-of-way in Washington and Oregon, U.S. Journal of Arboriculture. 29(3): 172-176. 
186. Sheridan, Chris D.; Spies, Thomas A. 2005. Vegetation-environment relationships in zero-order basins in coastal Oregon. Canadian Journal of Forest Research. 35(2): 340-355. 
187. Smith, Jane Kapler; Fischer, William C. 1997. Fire ecology of the forest habitat types of northern Idaho. Gen. Tech. Rep. INT-GTR-363. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Research Station. 142 p. 
188. Smith, Winston Paul. 1985. Plant associations within the interior valleys of the Umpqua River Basin, Oregon. Journal of Range Management. 38(6): 526-530. 
189. Soltis, P. S.; Soltis, D. E. 1987. Population structure and estimates of gene flow in the homosporous fern Polystichum munitum. Evolution. 41(3): 620-629. 
190. Soltis, P. S.; Soltis, D. E.; Wolf, P. G.; Riley, J. M. 1989. Electrophoretic evidence for interspecific hybridization in Polystichum. American Fern Journal. 79(1): 7-13. 
191. Soltis, Pamela S.; Soltis, Douglas E.; Wolf, Paul G. 1990. Allozymic divergence in North American Polystichum (Dryopteridaceae). Systematic Botany. 15(2): 205-215. 
192. Sonnenfeld, Nancy L. 1987. A guide to the vegetative communities at the Valley of the Giants, Outstanding Natural Area, northwestern Oregon, USA. Arboricultural Journal. 11(3): 209-225. 
193. Stein, William A. 1980. Port Orford-cedar. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 108-109. 
194. Stein, William I. 1980. Oregon white oak. In: Eyre, F. H., ed. Forest cover types of the United States and Canada. Washington, DC: Society of American Foresters: 110-111. 
195. Stewart, R. E.. 1976. Herbicides for control of western swordfern and western bracken. PNW-284. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment Station. 11 p. 
196. Stickney, Peter F. 1989. Seral origin of species comprising secondary plant succession in northern Rocky Mountain forests. FEIS workshop: Postfire regeneration. Unpublished draft on file at: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT. 10 p. 
197. Sugihara, Neil G.; Reed, Lois J.; Lenihan, James M. 1987. Vegetation of the Bald Hills oak woodlands, Redwood National Park, California. Madrono. 34(3): 193-208. 
198. Sullivan, Thomas P. 1979. Virgin Douglas-fir forest on Saturna Island, British Columbia. Canadian Field-Naturalist. 93(2): 126-131. 
199. Swanson, Donald Oscar. 1970. Roosevelt elk-forest relationships in the Douglas-fir region of the southern Oregon Coast Range. Ann Arbor, MI: University of Michigan. 173 p. Dissertation. 
200. Talley, Steven N.; Griffin, James R. 1980. Fire ecology of a montane pine forest, Junipero Serra Peak, California. Madrono. 27: 49-60. 
201. Taylor, R. F. 1932. The successional trend and its relation to second-growth forests in southeastern Alaska. Ecology. 13(4): 381-391. 
202. Teraoka, Emily King. 2010. Structure and composition of old-growth and unmanaged second-growth riparian forests at Redwood National Park, USA. Humboldt, CA: Humboldt State University. 59 p. Thesis. 
203. Thilenius, John F. 1968. The Quercus garryana forests of the Willamette Valley, Oregon. Ecology. 49(6): 1124-1133. 
204. Thompson, Ralph L. 2001. Botanical survey of Myrtle Island Research Natural Area, Oregon. Gen. Tech. Rep. PNW-GTR-507. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 27 p. 
205. Thorne, Robert F. 1976. The vascular plant communities of California. In: Latting, June, ed. Symposium proceedings: plant communities of southern California; 1974 May 4; Fullerton, CA. Special Publication No. 2. Berkeley, CA: California Native Plant Society: 1-31. 
206. Titus, J. H.; Householder, E. 2007. Salvage logging and replanting reduce understory cover and richness compared to unsalvaged-unplanted sites at Mount St. Hellens, Washington. Western North American Naturalist. 67(2): 219-231. 
207. Titus, Jonathan H.; Moore, Scott; Arnot, Mildred; Titus, Priscilla J. 1998. Inventory of the vascular flora of the blast zone, Mount St. Helens, Washington. Madrono. 45(2): 146-161. 
208. Topik, Christopher; Halverson, Nancy M.; Brockway, Dale G. 1986. Plant association and management guide for the western hemlock zone: Gifford Pinchot National Forest. R6-ECOL-230A. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Region. 132 p. 
209. Traut, Bibit Halliday; Muir, Patricia S. 2000. Relationships of remnant trees to vascular undergrowth communities in the western Cascades: a retrospective approach. Northwest Science. 74(3): 212-223. 
210. Turner, Nancy Chapman; Bell, Marcus A. M. 1973. The ethnobotany of the southern Kwakiutl Indians of British Columbia. Economic Botany. 27(3): 257-310. 
211. Turner, Nancy J.; Cocksedge, Wendy. 2001. Aboriginal use of non-timber forest products in northwestern North America: applications and issues. Journal of Sustainable Forestry. 13(3-4): 31-57. 
212. Tyler, Marnie W.; Peterson, David L. 2006. Vascular plant species diversity in low elevation coniferous forests of the western Olympic Peninsula: a legacy of land use. Northwest Science. 80(3): 224-238. 
213. U.S. Department of Agriculture, Forest Service, Intermountain Region. 1977. Indicator species of forest habitat types in Idaho and western Wyoming. Ogden, UT: U.S. Department of Agriculture, Forest Service, Intermountain Region; Intermountain Forest and Range Experiment Station. 54 p. 
214. U.S. Department of Agriculture, Natural Resources Conservation Service. 2015. PLANTS Database, [Online]. Available: https://plants.usda.gov /. 
215. Van Pelt, Robert; O'Keefe, Thomas C.; Latterfell, Josh J.; Naiman, Robert J. 2006. Riparian forest stand development along the Queets River in Olympic National Park, Washington. Ecological Monographs. 76(2): 277-298. 
216. Wagner, David H. 1979. Systematics of Polystichum in western North America north of Mexico. Pteridologia. 1: 1-64. 
217. Waring, R. H.; Major, J. 1964. Some vegetation of the California coastal redwood region in relation to gradients of moisture, nutrients, light, and temperature. Ecological Monographs. 34(2): 167-215. 
218. Weinberg, Eric S.; Voeller, Bruce R. 1969. External factors inducing germination of fern spores. American Fern Journal. 59(4): 153-167. 
219. Whittaker, R. H. 1960. Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monographs. 30(3): 279-338. 
220. Wiens, John A.; Nussbaum, Ronald A. 1975. Model estimation of energy flow in northwestern coniferous forest bird communities. Ecology. 56(3): 547-561. 
221. Zobel, Donald B. 2002. Ecosystem use by indigenous people in an Oregon coastal landscape. Northwest Science. 76(4): 304-314. 
222. Zobel, Donald B.; McKee, Arthur; Hawk, Glenn M.; Dyrness, C. T. 1976. Relationships of environment to composition, structure, and diversity of forest communities of the central western Cascades of Oregon. Ecological Monographs. 46(2): 135-156.