Clearwater National Forest
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MAIDENHAIR SPLEENWORT Asplenium trichomanes L. STATUS USFS REGION 1: Sensitive USFWS: none ICDC: G5/S1 INPS: State Priority 1 TAXONOMY Family: Polypodiaceae Common name: maidenhair spleenwort Synonyms: Chamaefilix trichomanes Farw. Description A small evergreen fern with clustered spreading leaves, that are 0.7 - 3.5 dm long. Leaves are once-pinnate (single set of leaflets) with opposite or offset pairs of rounded leaflets that reduce in size towards the leaf tip. The leaf stem or rachis is reddish-brown and often remains several years after old leaflets have fallen, often creating a clump of old stems. Spore clusters (sori) are covered by a conspicuous flap-like cover (indusium) on the underside of the leaflet (Lorain 1989). Distinguishing Features and Similar Species No similar species to maidenhair spleenwort are known to occur within the same habitat and range. The only other spleenwort found in the Pacific Northwest is Asplenium viride (green spleenwort), which documented for a single site in far southeastern Idaho (Bear Lake County). Unlike maidenhair spleenwort, A. viride possesses a green rachis with glandular hairs, is weakly evergreen, and restricted to limestone or other basic rock. DISTRIBUTION Range Maidenhair spleenwort has an interruptedly circumboreal distribution with southern extensions in the United States. In the Pacific Northwest the species extends south into Oregon and northern Idaho. Two locations are documented for Idaho, one on the Idaho Panhandle National Forest near the Canadian border and one in the June Creek drainage, which is a small tributary of the North Fork Clearwater River of the Clearwater National Forest. This population was found in 1971, but efforts to relocated have failed. It is also known from the Wallowa Mountains of northeast Oregon and from a handful of locations in southern British Columbia. Habitat Maidenhair spleenwort occurs in moist, rocky, cliff crevices and talus slopes. Although the exact location of the Clearwater population is not known, the community surrounding the vicinity is relatively uniform. The likely habitat is along the boulder bed of a perennial creek in a Thuja plicata/Oplopanax horridum (western redcedar/devil's club) habitat type. The Boundary County population is found on a granitic outcrop/seep with wet mosses in an immature Thuja plicata/Clintonia uniflora (western redcedar/bead lily) habitat. Canopy coverage is 60%. The surrounding area is a drier Abies grandis/Clintonia uniflora (grand fir/bead lily) habitat with some Douglas fir and snowberry. A second site nearby is of the same habitat type but in a dry grand fir and Douglas fir cover type. The canopy coverage here is only 10%. The plants occupy flatter (horizontal) granite outcrops. The key seems to be subsurface water that seeps out of rocks. The landscape is heavily glaciated and granitic. The plants are greatly reduced during the mid summer but perk up well with fall rains (Mousseaux 1999). Throughout its range elevations range from mid to high mountain. REMARKS Depsite intensive searches of the population area, the Clearwater population has never been relocated. Substantial logging activity occurred between these surveys and the time of the original discovery and the population may have been extirpated as a result. With so few populations occurring in very different habitats, it is difficult to accurately assess the impacts of management activities on this species. Habitat altering activities are the main threat to this species, which could include harvest related activities, road or trail construction and rock quarrying. REFERENCES Lorain, C.C. 1989. Field Investigations of three Region 1 species on the Clearwater National Forest: Asplenium trichomanes, Thelypteris nevadensis and Dodecatheon hendersonii; plus new localities for additional sensitive species. Unpublished report on file at ID Dept. of Fish and Game, Conservation Data Center, Boise, ID. 19 pp. plus appendices. Mousseaux, M. 1999. Idaho Panhandle National Forest. Personal Communication.
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