More info for the terms: fern, frequency, mesic, vine
Light and water relations: Western sword fern is found growing in shade
or in small openings within moist coniferous forests, while the
morphologically similar imbricated sword fern is found in distinctly
drier habitats, including rock crevices and dry coniferous forests
[39,69]. Western sword fern can survive very little moisture stress,
and thus in places on Vancouver Island where summer moisture deficits
are common, it is found only where seepage aguments the soil moisture
[28]. It may indicate a high water table in northwestern Oregon [65].
Western sword fern is a minor species in Oregon riparian communities.
Its frequency is greatest in outer edges of riparian zones [11].
An ecological study of the coastal redwood (Sequoia sempervirens) region
grouped species along environmental gradients of moisture, nutrients,
light, and temperature. Western sword fern's distribution placed it in
the moderately moist to moist class. It had a low to moderate nutrient
requirement. Its ecological optimum light requirement was less than 3
percent, but it grew in areas having up to 40 percent of full sunlight
on a logarithmic light intensity scale [70].
Soils: In the Siskiyou Mountains of California, western sword fern is
an important mesic species found primarily on soils formed from quartz
diorite. Although a few plants are found in submesic conditions on
soils formed from olivine grabbro, imbricated sword fern is more common
on grabbro, and the only sword fern found on serpentine parent materials
[72]. In British Columbia western sword fern grows on a variety of
parent material but prefers deep, loamy soils derived from fluvial
parent materials. It also prefers nutrient-rich soils and can be an
indicator of such soils when it is abundant and vigorous [28]. Soils of
most sites in coastal Oregon where western sword fern is dominant are
deep and formed from sandstone and siltstone [6].
Elevation: Western sword fern grows from sea level to mid-elevations in
the mountains throughout its range [39]. Its elevational limit in
Montana is 3,000 feet (914 m). In California it is usually found below
2,500 feet (762 m) [54]. In coastal Oregon it is found below 1,700 feet
(518 m) [6].
Common associates: Associated understory species include salal
(Gaultheria shallon), salmonberry (Rubus spectabilis), thimbleberry (R.
parviflorus), vine maple (Acer circinatum), Oregon-grape (Mahonia
nervosa), twinflower (Linnaea borealis), oxalis, false
lily-of-the-valley (Maianthemum dilatatum), western springbeauty (Montia
sibirica), threeleaf foamflower (Tiarella trifoliata), evergreen violet
(Viola sempervirens), pioneer violet (V. glabella), red huckleberry
(Vaccinium parvifolium), evergreen huckleberry (V. ovatum), and rusty
menziesia (Menziesia ferruginea) [22].