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Management Recommendations
for
Large Round-leaved Orchid (Platanthera orbiculata [Pursh] Lindl.)
[syn. Habenaria orbiculata (Pursh) Torr.]

v. 2.0

by

R. D. Lesher and J. A. Henderson

December 1998


TABLE OF CONTENTS

EXECUTIVE SUMMARY 1
I. NATURAL HISTORY 4
A. Taxonomic/Nomenclatural History 4
B. Species Description 5
1. Morphology 5
2. Reproductive Biology 5
3. Ecology 7
C. Range, Known Sites 9
D. Habitat Characteristics and Species Abundance 11
II. CURRENT SPECIES SITUATION 14
A. Why Species is Listed under Survey and Manage Standards and Guidelines 14
B. Major Habitat and Viability Considerations 15
C. Threats to the Species 16
D. Distribution Relative to Land Allocations 16
III. MANAGEMENT GOALS AND OBJECTIVES 16
A. Management Goals for the Taxon 16
B. Specific Objectives 16
IV. HABITAT MANAGEMENT 17
A. Lessons from History 17
B. Identification of Habitat Areas for Management 18
C. Management Within Habitat Areas 18
D. Other Management Issues and Considerations 19
V. RESEARCH, INVENTORY, AND MONITORING NEEDS 19
A. Data Gaps and Information Needs 19
B. Research Questions 19
C. Monitoring Needs and Recommendations 20
VI. REFERENCES 21
FIGURES 25

EXECUTIVE SUMMARY

Species: Platanthera orbiculata (Pursh) Lindl. (Large Round-leaved Orchid)

Taxonomic Group: Vascular Plants

Rod Components: 1, 2

Other Management Status: Washington Natural Heritage Program Monitor List (WNHP 1997)

Range: Platanthera orbiculata (Habenaria orbiculata) is a rare species within the range of the northern spotted owl. Platanthera orbiculata is sporadic in its distribution in northern Washington and has been documented on federal lands of the Mt. Baker-Snoqualmie and Colville National Forests, North Cascades National Park, and Ross Lake National Recreation Area. On the Mt. Baker-Snoqualmie National Forest, this species is documented from the Baker Lake basin south to the Cedar River watershed. Platanthera orbiculata is not known to occur on the Olympic Peninsula, south of the Cedar River watershed, on the east slopes of the Cascades, or in Oregon.

Specific Habitat: Platanthera orbiculata is unusual among rare plants as it is not a species of rare or special habitats. It usually occurs on habitats considered mesic within its geographic range. What limits Platanthera orbiculata in this region, is probably related to its interactions with other organisms as much as environmental factors.

On the Mt. Baker-Snoqualmie National Forest, Platanthera orbiculata occurs primarily in mesic climatic areas, on moderate or mesic sites. It occurs on sites that average about 8oC (46oF) and about 254 cm (100 in) of precipitation. It is found at low to middle elevations, on moderate slopes, and on sites that are neither very dry nor very wet. The elevation of sample plots ranged from 229-994 m (750-3260 ft), with an average elevation of 765 m (2510 ft). This orchid occurs on all aspects, but its distribution shifts slightly with elevation and aspect.

Platanthera orbiculata is generally found in mature to old-growth stands. The majority of plots where this orchid was found were over 130 years old, although the ages of stands ranged from 54 to 837 years. The majority of known sites are in old-growth stands over 200 years old. Its habitat requirements appear to include shade and deep, moist, undisturbed litter.

Platanthera orbiculata was found most commonly in the mesic to drier plant associations in the Western Hemlock Zone; however, one-third of the known sites occurred in the lower Pacific Silver Fir Zone. The most frequent plant associations where Platanthera orbiculata occurred were the mesic Western Hemlock types characterized by salal and Oregongrape. Sites where it occurred in the Pacific Silver Fir Zone were often in the moist Alaska Huckleberry types. Stands usually had coarse woody debris, a deep litter layer, and abundant moss cover. Winter snow depth was usually less than 1.2 m (4 ft.).

Threats: While rare species of rare habitats are particularly vulnerable to the loss of the rare habitat, species such as Platanthera orbiculata are vulnerable to changes in the abundance of other species or subtle shifts in environmental conditions. This species is perceived to be at risk due to its specific and narrowly defined ecological niche, where it is dependent on other species to complete its life cycle. This includes basidiomycete fungi for germination and development, and unknown species of moth(s) for pollination. It is believed to be heavily browsed or grazed by a number of herbivores that may significantly limit its distribution. Suspected herbivores include mammals such as deer and elk, mollusks such as banana slugs, and various invertebrates.

This species may be sensitive to changes in a wide variety of ecological factors that may affect the abundance or distribution of the orchid itself, or any of the species upon which the orchid depends or interacts. Platanthera orbiculata also appears to be sensitive to forest clearing or litter disturbing events such as clear cutting, thinning, or wildfires. Forest management could limit the distribution of the orchid by limiting its habitat. Indiscriminate insecticide spraying could affect the moth pollinator. Introduction of new species or increases in slug or snail populations or other herbivores could severely limit this species. Climate change could affect the seasonal range of herbivores or change the timing or depth of winter snowpacks that may be limiting factors in Washington.

Management Recommendations:

  1. Ensure that indiscriminate insecticide spraying does not affect the populations of moths or other insects this species depends on for pollination or other aspects of its life cycle.
  2. Populations that occur on sites where management activities are scheduled or proposed need to be evaluated to determine their contribution to the viability of the species. Identify populations that are important in the geographic or ecological distribution of this species. These populations may contribute to the genetic diversity of this species. If populations are considered at risk or are important in maintaining the species viability, then maintain the population and its associated habitat. Some populations may be determined to be sufficiently secure that some disturbance can be tolerated. In this case, try to minimize disturbance to the litter layer and, if feasible, try to conduct disturbance activities in the dormant season.
  3. If a management decision is made that treatments will occur on sites where Platanthera orbiculata is present, then a monitoring plan should be developed and implemented to document the response of the orchid population. It is important that the monitoring program occur over a several-year period to document the response of individuals and the population over an extended period of time. The effects of a treatment may not be immediately apparent, and it is possible that a lag time of several years is necessary for an effect to be observed.
  4. Provide for a representation of all age classes of forests from young to old (and the accompanying structure and composition) for each landscape in which the species occurs. This condition allows some subpopulations to be disturbed by fire or timber harvesting, but only under the condition that parts of a watershed or landscape where the species occurs is in suitable old forest habitat at all times.

Information Needs:

  1. The current known locations of this species should be revisited to verify their existence and the condition of the population and habitat they occupy. Populations should be mapped to determine precise locations for developing a GIS layer.
  2. Identify and monitor the location and condition of populations of the species over time. Trends in population levels and condition can be used to help revise the management of this species in the landscape. Trends in populations or conditions may be due to changes in species population levels that the orchid is linked to, or changes in external conditions such as climate change that could precipitate a change in these population levels.
  3. Determine the extent of the distribution of Platanthera orbiculata in Washington for Federal lands covered under the Record of Decision. What is its southern extent, does it occur on the east side of the Cascades or in the Olympics?
  4. Study the biology of the orchid and the obligate or mutualistic species with which it is so closely linked. Some of the species involved in these relationships and the nature of these relationships in the Pacific Northwest are not known at this time.
  5. Monitor population levels of known or suspected herbivores or the introductions of potential new herbivores. A balance between herbivory, growth, and reproduction probably exists or has existed in the past. An imbalance in the future could have significant consequences on this species of orchid.

I. NATURAL HISTORY

A. Taxonomic/Nomenclatural History

The original description of what we now know as Platanthera orbiculata was published by Frederich Pursh in 1814. Pursh notes that this orchid was referred to as "heal-all" by the native mountaineers (Luer 1975). The type locality of this taxon was described as shady beech woods on the mountains of Pennsylvania and Virginia (Luer 1975).

The first record of Platanthera orbiculata in the Pacific Northwest was a specimen collected in 1890 by W. Suksdorf at "McCloud Lake" 1 in northwestern Washington (WNHP 1995). The earliest documentation of Platanthera orbiculata from the Mt. Baker-Snoqualmie National Forest was a collection by J. B. Flett (1898) from "dense forest, mossy places" in the North Fork of the Nooksack River.

Since 1814 the circumscription and rank of the taxon has changed as the species has been aligned with different groups and assigned to different genera and specific epithets. Table 1 is a summary of the chronological development of the nomenclature of Platanthera orbiculata (from Reddoch and Reddoch 1993).

Table 1. Nomenclatural History and Synonomy of Platanthera orbiculata.

Platanthera orbiculata (Pursh) Lindl., Gen. Sp. Orchid Pl 286. 1835
(as to name, not description or synonomy)
BASIONYM: Orchis orbiculata Pursh, Fl. Amer. Sept 2:588. 1814

SYNONYMS:

Habenaria orbiculata (Pursh) Torr. 1826
Platanthera menziesii Lindl. 1835
Habenaria menziesii (Lindl.) Macoun. 1888
Lysias orbiculata (Pursh) Rydb. 1900
Habenaria orbiculata (Pursh) Torr. var. longifolia Clute. 1904
Lysias menziesii (Lindl.) Rydb. 1917
Lysias orbiculata (Pursh) Rydb. var. pauciflora Jenn. 1920
Habenaria orbiculata (Pursh) Torr. f. trifolia Mousley. 1934
Habenaria orbiculata (Pursh) Torr. var. menziesi (Lindl.) Fernald. 1950
Habenaria orbiculata (Pursh) Torr. var. lehorsii Fernald. 1950
Platanthera orbiculata (Pursh) Lindl. var. lehorsii (Fernald) Catling. 1982

1 Probably McLeod Lake, now known as Green Lake (T39N, R3W, S10), 4 miles southeast of Lynden in Whatcom County, elevation 74 feet.

Several species' pairs occur within the genus Platanthera. One such pair includes Platanthera orbiculata and P. macrophylla (Reddoch and Reddoch 1993). These 2 species differ primarily in their adaptation to different pollinators (Reddoch and Reddoch 1993), and are distinguished primarily on the lengths of the spur and hemipollinaria. In the northeastern United States these species occur over a similar range and are even sympatric in some areas. These morphological traits appear to result in reproductive isolation (Reddoch and Reddoch 1993). Until 1988, P. macrophylla was considered a variety of P. orbiculata. Platanthera macrophylla does not occur in western North America.

B. Species Description

1. Morphology

Platanthera orbiculata is characterized by the pair of large, succulent, shiny deep green, nearly round, basal leaves that spread on the ground. Luer (1975) describes the emerging leaves as hugging the ground so closely that they often follow the contour of objects, which cannot be pushed aside as the leaves expand.

This orchid is perennial with a fleshy tuberous root and 2-7 cylindrical roots, a single glabrous flowering stem 20-60 cm tall, with 1-5 lance-shaped bracts. Leaves are usually 2, basal, round and opposite, clasping at the base, glabrous, glossy deep green with silvery underside, somewhat fleshy, 6-16 cm long and 3-14 cm broad. The flowers are pale to deep whitish-green; lip is straight, linear or strap-shaped; spur is long but less than 28 mm, cylindrical, tapering and curved upward at tip; hemipollinarium length is less than 4.6 mm; floral bracts are shorter than the flowers. Flowers are small, 5-25 in a loose, elongated terminal cluster. Fruit is an erect, curved capsule (MacKinnon et al. 1992, Hitchcock et al. 1955, Correll 1950, Williams and Williams 1983).

2. Reproductive Biology

In the genus Platanthera, the degree of pollinator specificity appears to be well correlated with spur length; the longer spurred species are more pollinator-specific, where the shorter spurred species are pollinated by a greater number of pollinator groups (Catling and Catling 1991). Many of the long-spurred Platanthera species are reported to be pollinated by lepidoptera ([Darwin 1877; Nilsson 1983; Inoue 1983] in Reddoch and Reddoch 1993, Catling and Catling 1991). Platanthera macrophylla is pollinated by larger lepidoptera and has a more restricted distribution than P. orbiculata. This trend is evident in several species pairs of Platanthera, where species pollinated by large lepidoptera have a more restricted distribution than similar species that are pollinated by smaller lepidoptera (Catling and Catling 1991).

There are few reports in the literature that specifically address the pollination of Platanthera orbiculata. It is reported to be pollinated by the large moth Sphinx drupiferanum (Pijl and Dodson 1966 in Catling and Catling 1991). The original citation of the night-flying hawk moth (Sphinx drupiferanum) by Sawyer in 1894 may have been in reference to Platanthera orbiculata var. macrophylla rather than var. orbiculata (Luer 1975). Stoutamire (Luer 1975) identified 2 small gray moths, Autographa ampla and Plusia balluca as pollinators of Platanthera orbiculata. There is some question as to which insects pollinate this species, as well as the probability of different species of pollinators over the large geographic range where P. orbiculata occurs.

Reddoch and Reddoch (1993) interpret various reports from the literature and conclude that it is likely that noctuid moths reported by Stoutamire (Autographa ampla and Diachrysia (Plusia) balluca) pollinate P. orbiculata, but outside of the Pacific Northwest. Diachrysia balluca occurs in most of the eastern half of the range of P. orbiculata and A. ampla covers almost of the entire range of the orchid, except for the Northwest. The question still remains then, what insects pollinate P. orbiculata in the Pacific Northwest?

The placement of the viscidia suggest that the hemipollinaria are attached to a visiting moths eyes, rather than the base of the proboscis (Reddoch and Reddoch 1993). Fewer species can act as pollinators when the hemipollinaria are attached to the eyes of the insect, because a specific proboscis length and distance across the eyes is necessary for proper placement of the hemipollinaria in order to achieve cross-pollination (Sheviak and Bowles 1986 in Catling and Catling 1991). North American species in the subfamily Orchidoideae (e.g., Platanthera) characteristically have nectar available in the spur (Catling and Catling 1991).

For effective cross pollination within a species, several criteria need to be met: the spur must be short enough for the tongue of the insect to reach the nectar at the end of the spur; the head of the insect must come into contact with the viscidia for placement of the hemipollinaria on the eyes or the base of the proboscis; and the spacing of the viscidia must be comparable to the separation of the eyes of the pollinating insect (Reddoch and Reddoch 1993). A characteristic that favors cross-pollination is the gradual bending of the pollen stalk, a feature that is characteristic of many North American Platanthera species. The bending of the pollen stalk to the correct orientation to contact the stigmatic surface appears to be dependent on the amount of time that an insect spends on a plant. The period of time for the pollen stalk to complete the bend is longer than the time an insect spends at a plant, and thus helps ensure cross-pollination (Catling and Catling 1991).

Pollinator-limited seed production has been reported for several species of Platanthera (Catling and Catling 1991). Species where seed production is pollinator-limited often have flowers that are relatively long-lived, and thus provide a more extended period for pollination (Catling and Catling 1991). It is possible in some cases that the rarity of an orchid may be due to the rarity of its pollinator (Catling and Catling 1991).

The flowering period for Platanthera orbiculata is from mid-June through mid-August on the Mt. Baker-Snoqualmie National Forest (MBS Ecology Program files 1995). There appears to be no relationship between date of flowering and elevation.

Orchid seeds have evolved into minute structures with limited food reserves, and rely on an association with a fungus for successful germination and establishment (Arditti et al. 1990). Numerous small seeds are produced and are dispersed primarily by wind. At the onset of germination, orchids go through a heterotrophic phase with their mycorrhizal fungus (Smreciu and Currah 1989). The developing plant relies on nutrition provided by the fungus, such as sugars, minerals, and other growth factors (Smreciu and Currah 1989).

Little is known about the germination requirements of Platanthera orbiculata. Results from germination experiments (Smreciu and Currah 1989) showed that few Platanthera seeds germinated in any of the treatments. Platanthera orbiculata seeds inoculated with Sistotrema sp. had swollen embryos and cracking testa, but no further development. Of the 3 species of Platanthera in the study, Platanthera orbiculata seeds had the poorest germination success and development, and germinated in association with only 1 species of fungus (Smreciu and Currah 1989).

3. Ecology

Orchids are highly evolved mutualistic species with specialized floral morphology and a high degree of dependence on certain species of fungi and insects. Epiphytic orchids may have evolved earlier than terrestrial orchids (Currah 1991). Evolution of terrestrial orchids appears to have included many examples of coevolution between orchids and their insect pollinators, and their mycorrhizal fungi. Terrestrial orchids require an association with a fungus for seed germination and plant establishment (Currah et al. 1990). These mycorrhizal associations consist of endophytic fungus that penetrates the cortical cells of the roots. This mycorrhizal association is essential for successful development and competition of orchids in their natural environments (Currah et al. 1990).

Orchid mycorrhizal relationships are similar within the orchid family, and unique among the angiosperms (Currah 1991). Most monocots and 90 percent of the dicots have vesicular arbuscular mycorrhizae (VAM), a type of endomycorrhizae; the fungal species belong to a primitive group of soil dependent fungi, the Zygomycota (Currah 1991). All orchids lack VAM. Instead they develop a type of endomycorrhizal association with fungi that belong to the subphylum Basidiomycotina. These are predominantly wood decomposing fungi (Currah 1991). Orchid mycorrhizae are thought to be different from other mycorrhizal associations as the flow of carbohydrates is primarily from the fungus to their orchid host (J. Ammirati, pers. comm.).

Orchids receive substantial benefits from their mycorrhizal fungi; carbohydrates are transferred from the fungus to the orchid, and mycorrhizae provide for an increased uptake of nutrients (Currah 1991). Other contributions to the orchid by the fungus include sugars, amino acids, vitamins, proteins and peptides, phosphates, and probably additional compounds (see citations in Arditti et al. 1990).

Fungi penetrate the cell walls and grow around and within the cortical cells of the orchid. Hyphae in orchid cells go through a deterioration process that is initiated by the orchid, where the fungus is digested by the orchid, and the plant gets the carbohydrates from the fungus (Currah 1991, J. Ammirati, pers. comm.).

Isolates of the endophytic fungi from mycorrhizae of Platanthera orbiculata collected in Alberta were cultured and identified (Currah et al. 1990). They found 2 fungal species, Leptodontidium orchidicola and Sebacina sp., associated with this orchid. Both species are wood decomposing fungi (Ammirati, pers. comm.). Leptodontidium orchidicola is the imperfect stage of the wood decomposing fungus Leptodontium sp. Leptodontidium orchidicola has been reported from mycorrhizae of Coeloglossum viride, Corallorhiza maculata, Platanthera hyperborea, and Calypso bulbosa (Currah et al. 1987), as well as Listera borealis and Corallorhiza trifida (Currah et al. 1990). Leptodontidium orchidicola appears to have a wide range of orchid hosts, and the nature of the relationship of this fungus with its terrestrial orchids is unknown (Currah et al. 1990). The fungus does not appear to be pathogenic to the orchids with which it associates (Currah et al. 1990). Sebacina sp. was isolated exclusively from the mycorrhizae of P. orbiculata; the identification of this fungus is still tentative. It is probable that specific fungi are not obligate mycorrhizal formers with orchids (Ammirati, pers. comm.).

Currah et al. (1990) describe the seasonal development of roots and mycorrhizae of Platanthera orbiculata. This species has a dimorphic root system, with 1 or 2 root-like tubers, and 2 or more fleshy roots, which are replaced annually. This root system is not uncommon among orchids. The dormant plant consists of a large shoot bud, a flattened, dichotomously branched tuber that subtends the shoot bud, and 5-6 fleshy roots that form at the union of the tuber and shoot. At anthesis, a bud originating from the crown of the current year's plant, gives rise to a shoot, 2 root primordia, and a tuber that elongates in late spring and early summer. The 2 root primordia have elongated by mid summer and 2 (or 3-4) more root primordia are formed from the crown of the developing shoot bud. The fleshy roots elongate prior to the onset of dormancy at the end of the growing season. At anthesis, the new tuber is partially elongated, and the root primordia of the first set of roots have formed at the base of next year's shoot bud. At the onset of dormancy, the tuber and roots formed during the previous growing season are withering, the new tuber and roots are fully elongated, and the new shoot bud is formed.

This yearly turnover of the root system utilizes considerable energy, which presumably is fueled by the carbohydrates produced by the single pair of leaves, and carbohydrates contributed by the fungus. If the leaves experience browsing, fungal infestation, or other loss of photosynthetic tissue, this may impact the development of the underground structures and may result in decreased viability or vigor of the individual. This aspect of the life history of the species could be one of the limiting factors in the distribution or successful competition of individuals, and perhaps contributes to the vulnerability of this species.

C. Range, Known sites

Platanthera orbiculata has a transcontinental distribution with a broad eastern range extending from northeastern Canada, south in the Appalachian Mountains to North Carolina and Tennessee; across the Prairie Provinces in Canada to western North America, where the distribution forms a narrower band (Reddoch and Reddoch 1993), and extends as far south as the central Washington Cascades (Figure 2). A distribution map is provided in Reddoch and Reddoch (1993); however, the western distribution of this species is under represented, as it was beyond the scope of their study.

There have been several recorded sightings of Platanthera orbiculata that, upon subsequent investigation, have proven to be erroneous, unsubstantiated, or not adequately documented. Reddoch and Reddoch (1993) and this document address some of these distribution questions. Reddoch and Reddoch contend that this species has not been recorded in Alaska except for the southern tip of the panhandle (Hulten 1968), and has not been located in the Yukon ([Boivin 1979 and W.J. Cody, pers. comm.] in Reddoch and Reddoch 1993). They have also been unable to document the sightings from far northeastern Canada, specifically the reference to Labrador and a site in Quebec just south of the Labrador border (Reddoch and Reddoch 1993).

The distribution of Platanthera orbiculata in northwestern North America has been compiled from several sources (Clark 1976; MacKinnon et al. 1992; Szczawinski 1959; Correll 1950; Hitchcock et al. 1955; Peck 1961; Gilkey and Dennis 1967; Hickman 1993; Washington Natural Heritage Program data files [WNHP]; Mt. Baker-Snoqualmie National Forest Ecology Program database and Botany Program database, University of Washington Herbarium; personal communication with Karl Urban, Jimmy Kagan, Sandy Musconi, Terry Lillybridge, and Helga Harm). Upon subsequent investigation of citations and the various sources available, some of the locality information for the Pacific Northwest has been concluded to be erroneous, and will be discussed later in this section.

Platanthera orbiculata occurs across the southern part of British Columbia, north to 56o latitude (MacKinnon et al. 1992). Szczawinski (1959) reported it as widely scattered in the central and southern interior of British Columbia with few collections made in the coastal region. He commented that this species is too scattered to give any idea of the distribution pattern except that it occurs quite commonly in the southern coastal region. It is very rare on Vancouver Island, known from only one collection by Toms in 1929 from Thetis Lake near Victoria (Szczawinski 1959). Clark (1976) described Platanthera orbiculata as being locally abundant over southern British Columbia and in Washington "on both sides of the Cascades", although scarce in north-central Washington and adjacent British Columbia. Hitchcock et al. (1955) describe the range as "Alaska and Yukon south on both sides of the Cascade mountains to Oregon".

Platanthera orbiculata has been documented in Washington (King, Snohomish, Stevens, Whatcom, Skagit, San Juan, and Pend Oreille Counties), northwestern Montana (Lincoln, Flathead, and Lake Counties), and northern Idaho (Bonner, Boundary, Kootenai, Idaho, and Latah counties) (Correll 1950, Washington Natural Heritage Program; Mt. Baker-Snoqualmie and Colville National Forests; University of Washington Herbarium).

No records have been found to document its occurrence on the east side of the Washington Cascades (as cited in Correll 1950 and Hitchcock et al. 1955; T. Lillybridge, pers. comm.). However, it does occur in the northeastern corner of Washington on the Colville National Forest and vicinity.

Known locations of Platanthera orbiculata within the region covered by the Record of Decision (USDA and USDI 1994b) occur only within the State of Washington. Sites under Federal ownership are restricted to the Mt. Baker-Snoqualmie National Forest and North Cascades National Park Complex, including Ross Lake National Recreation Area (WHNP, Mt. Baker-Snoqualmie National Forest Ecology Program and Botany Program files). Platanthera orbiculata is reported from about 70 sites on the Mt. Baker-Snoqualmie National Forest. Of these reports, it is documented on 47 ecology plots that range from Baker Lake south to the Cedar River watershed; 81 percent of these sites occur from Baker Lake south to the Skykomish River (MBS Ecology Program database 1998). There are a few historical records from herbaria, and the remainder are sites documented in Botany Program surveys (Figure 3) (MBS Botany Program files 1998). Platanthera orbiculata is not known to occur on the Olympic Peninsula.

The Washington Natural Heritage Program has additional records for Platanthera orbiculata in Washington State (WNHP 1995). Of these, 14 sites of Platanthera orbiculata that were documented prior to 1966 may no longer exist due to road building and timber harvest activities over the last several decades. Even more recent sites from the early 1980s may no longer exist. Four sites are documented for the North Cascades National Park Complex, including Ross Lake National Recreation Area. Ten sites are reported for northeastern Washington (WNHP, S. Musconi pers. comm.). Nine of these sites occur on the Colville National Forest and a historical site from 1902 on private land near Calispell Lake.

Platanthera orbiculata has been documented from 2 localities on the San Juan Islands, although both populations may no longer exist. A. S. Foster collected Platanthera orbiculata from Friday Harbor on San Juan Island in 1904; the specimen was identified by J. B. Flett. The voucher specimen was subsequently verified at the University of Washington Herbarium (R. Lesher, May 9, 1995). Drs. Helga and Walter Harm discovered a population 6 years ago in Moran State Park on Orcas Island near Summit Lake on Mt. Constitution. H. Harm visited this population of one plant (or possibly several closely spaced plants), and reported that it bloomed for several seasons; then in 1992 it was apparently dug by an unknown collector. The plant sprouted and flowered the next year. In 1994 it produced 2 leaves but did not flower. In 1995 no plant was observed at the site, and there is concern that the population has been extirpated. H. Harm has not observed evidence of slug browsing on Platanthera orbiculata at this Orcas Island population. The Harms have looked for this orchid elsewhere on Orcas Island, but to date this is the only known location in the San Juans.

The multiple locations of this taxon (at least historically) in the San Juan Islands, suggest that this is not merely a chance occurrence or a seed dissemination due to human interference. There are also implications for the somewhat "long distance" dispersal capabilities of the seeds, given that the San Juan Islands were covered by glacial ice 13,000 years ago. It appears that Platanthera orbiculata was established in the San Juan Islands following retreat of the glaciers. It is worth noting that the majority of known sites of Platanthera orbiculata in western Washington were covered with ice during the last glaciation.

Platanthera orbiculata is not documented south of the central Washington Cascades (King County), although Correll (1950) lists it as occurring in Oregon, and Reddoch and Reddoch (1993) state that it may be extinct in Oregon. Karl Urban (pers. comm.) confirmed that the historic siting of this species in Oregon near Wenaha Forks on the Umatilla National Forest was an error. Urban visited the historic site and found another species of Platanthera (Platanthera elegans) that had been previously mis-identified as Platanthera orbiculata. The identification of this specimen was verified by Dr. Ken Chambers at Oregon State University in 1988. Jimmy Kagan (WNHP, personal communication) does not have any records of this taxon occurring in the State of Oregon, and notes that the reference to extinction in Oregon by the Oregon Natural Heritage Program (ONHP 1985, as cited in Reddoch and Reddoch 1993), was in reference to what has since been determined to be a taxonomic error. The ONHP report listed species as extinct if the species had not been documented during the last 20 years before publication. Peck (1961) does not include P. orbiculata in "A Manual of the Higher Plants of Oregon". Gilkey and Dennis (1967) describe Habenaria orbiculata as rare in mountain woods of northern Washington, but do not mention it as occurring in Oregon. The Jepson Manual does not list Platanthera orbiculata as occurring in California (Hickman 1993).

D. Habitat Characteristics and Species Abundance

Platanthera orbiculata is rare throughout most of its range. Reddoch and Reddoch (1993) provide the following summary of its status in various regions. It is designated as rare in Saskatchewan (Maher et al. 1979 in Reddoch and Reddoch 1993), "of restricted range in the Northwest Territories" (Cody 1979 in Reddoch and Reddoch 1993), it is listed in rare plant studies for Connecticut, Rhode Island, Tennessee, Ohio, Indiana (Gade 1987 in Reddoch and Reddoch 1993), and may be extinct in Connecticut (Connecticut Geological & Natural History Survey 1985 in Reddoch and Reddoch 1993), Illinois (Sheviak 1974 in Reddoch and Reddoch 1993), and Oregon (Oregon Natural Heritage Data Base 1985 in Reddoch and Reddoch 1993). The reference to the extinction of this species in Oregon was apparently based on an erroneous report of Platanthera orbiculata from the Umatilla National Forest, as previously discussed.

General habitat descriptions throughout the range of Platanthera orbiculata are compiled from several references, as well as herbaria label data. Luer (1975) describes this species as not frequent, and most often occurring in damp rich humus in the deep shade of heavily forested areas. Platanthera orbiculata occurs in the boreal forest region of Canada, and in the temperate maritime and continental montane forests of the northwestern North America, mixed forests in the Great Lakes region, and deciduous forests of the Appalachians (Reddoch and Reddoch 1993). Herbaria records document occurrence with a variety of tree species, both conifers and angiosperms, and often describe the habitat as mesic or wet forests and swamp forests (Reddoch and Reddoch 1993).

Platanthera orbiculata occurs on sites with moisture regimes that vary from dry to mesic, or moist, or even swamps and bogs. Reference is often made to rich or humic forests, mossy sites, and acidic soils (MacKinnon et al. 1992; Hitchcock et al. 1955; Szczawinski 1959; Correll 1950). It occurs primarily at lower to mid elevations. The elevation may range up to 914 m (3000 ft.) in northwest coastal areas and northeastern North America, 1219 m (4000 ft.) in Montana and Idaho, and 1524 m (5000 ft.) in the southeastern United States (Correll 1950).

The specific habitat information available for western Washington comes from the 47 sightings on Area 1 Ecology plots on the Mt. Baker-Snoqualmie National Forest. More general descriptions available from WNHP data files and herbaria label data generally agree with habitat characteristics documented on ecology plots where Platanthera orbiculata occurs.

On the Mt. Baker-Snoqualmie National Forest, Platanthera orbiculata occurs primarily in mesic climatic areas (mostly ecozones 8-10, see Henderson et al. 1992), on moderate or mesic sites. It occurs on sites with a mean annual temperature about 8o C (46o F) and total annual precipitation about 254 cm (100 in.) (Figure 4) (Henderson 1995). It is found at low to mid elevations, on moderate slopes, and on sites that are neither very dry nor very wet. The populations generally spanned an elevation band of about 366 m (1200 ft.). However, the elevation of sample plots ranged from 229-994 m (750-3260 ft.), with an average elevation of 765 m (2510 ft.). This orchid occurs on all aspects, but its distribution shifts slightly with elevation and aspect. It is less common on cooler, northerly aspects where it occurs at lower elevations, up to about 853 m (2800 ft.); on warmer (south and westerly) aspects it is more frequent and occurs over a wider range of elevations, up to 1006 m (3300 ft.) (Figure 5).

Bedrock and parent material at Platanthera orbiculata sites is somewhat variable. Schist (36% of plots) was the most common bedrock, followed by gneiss (17%) and granite (15%). Over half the plots occurred on a regolith of neutral colluvium.

Platanthera orbiculata is generally found in mature to old-growth forests. The majority of plots where this orchid occurred were over 130 years old, although the ages of stands ranged from 54 to 837 years. Two-thirds of the plots were in old-growth stands over 200 years old (Figure 6).

Platanthera orbiculata was found most commonly in the mesic to drier plant associations in the Western Hemlock Zone; however 30 percent of the plots occurred in the lower Pacific Silver Fir Zone. The most frequent plant associations where Platanthera orbiculata occurred (Table 2) were the mesic types characterized by salal and Oregongrape, e.g., Western Hemlock/Salal-Oregongrape and Western Hemlock/Oregongrape; and the mesic swordfern types, e.g., Western Hemlock/Swordfern-Foamflower and Western Hemlock/Swordfern-Oregongrape plant associations (Henderson et al. 1992). Plots where it occurred in the Silver Fir Zone were often in the moist Alaska Huckleberry types, e.g., Silver Fir/Alaska Huckleberry-Swordfern and Silver Fir/Alaska Huckleberry-Queenscup plant associations (Henderson et al. 1992). Commonly associated species are listed in Table 3. Stands were often characterized by coarse woody debris and a deep litter layer. Moss cover was often high; the most common species present were Hylocomium splendens, Rhytidiadelphus loreus, and Rhytidiopsis robusta. Winter snow depth as indicated by the "lichen line" (Henderson et al. 1992) was usually less than 1.2 m (4 ft.).

Platanthera orbiculata is generally not abundant where it occurs. Records from Washington list very few sites where local populations of Platanthera orbiculata consist of more than a few individuals (WNHP, Mt. Baker-Snoqualmie and Colville National Forests). The largest documented population was reported by R. and D. Nass in 1982. It consisted of approximately 112 individuals at 5 sites within about a mile area in Ross Lake National Recreation Area (WNHP). The majority of plants in this population were in a vegetative state, only a few individuals were in bud or bloom. The other known large population was recorded in a timber sale area on the Colville National Forest, and consisted of 95 individuals (S. Musconi pers. comm.). This area has since been harvested and, although few individuals have been seen in the clear-cut area, this population has not been monitored to quantify effects of the harvest and site treatments. On the Mt. Baker-Snoqualmie National Forest, the largest known population consisted of 15 plants (MBS Ecology Progam database).

Table 2. Percent frequency of Platanthera orbiculata sightings by plant association
based on the Mt. Baker-Snoqualmie National Forest Ecology Program data.

PLANT ASSOCIATION

PERCENT
FREQUENCY

Western Hemlock/Salal-Oregongrape
Western Hemlock/Oregongrape
Western Hemlock/Swordfern-Foamflower
Western Hemlock/Swordfern-Oregongrape
Western Hemlock/Alaska Huckleberry
Silver Fir/Alaska Huckleberry-Swordfern
Silver Fir/Alaska Huckleberry-Queenscup
Western Hemlock/Oregongrape-Princes Pine
Western Hemlock/Salal
Western Hemlock/Alaska Huckleberry-Oregongrape
Western Hemlock/Swordfern-Salal
Silver Fir/Alaska Huckleberry-Salal
Silver Fir/Alaska Huckleberry-Foamflower
Western Hemlock/Vine Maple-Oregongrape
Western Hemlock/Alaska Huckleberry-Swordfern
Silver Fir/Alaska Huckleberry
Silver Fir/Alaska Huckleberry-Oregongrape
Silver Fir/Devils Club-Alaska Huckleberry
Silver Fir/Skunkcabbage

17.0
10.6
8.5
6.4
6.4
6.4
6.4
4.3
4.3
4.3
4.3
4.3
4.3
2.1
2.1
2.1
2.1
2.1
2.1

Table 3. Constancy of the common associated species with Platanthera orbiculata
based on Mt. Baker-Snoqualmie National Forest Ecology Program data.

SPECIES

CONSTANCY

Tsuga heterophylla
Thuja plicata
Pseudotsuga menziesiiVaccinium parvifolium
Berberis nervosa
Vaccinium alaskaenseAbies amabilis
Goodyera oblongifoliaLinnaea borealis
Chimaphila menziesii
Gaultheria shallon
Cornus canadensis
Polystichum munitum

100%
95%
89%
89%
78%
78%
65%
63%
61%
59%
59%
55%
51%

II. CURRENT SPECIES SITUATION

A. Why Species Is Listed under Survey and Manage Standards and Guidelines

Platanthera orbiculata is thought to be at low to moderate risk for maintaining species viability under the Northwest Forest Plan. Concern for this species was based on its rarity, low numbers of individuals in known populations, limited distribution throughout the region covered by the Northwest Forest Plan, susceptibility to herbivory, and its dependence on other species for its survival and fitness.

B. Major Habitat and Viability Considerations

The major viability considerations for Platanthera orbiculata are: shifts in populations or viability of other species that it depends on to complete its life cycle, increased herbivory, or direct impacts to its habitat and populations by natural disturbance or management actions. Platanthera orbiculata is unusual among rare plants in that it is not a species of rare or special habitats, rather it occurs in mesic habitats within its geographic range. While rare species of rare habitats are particularly vulnerable to habitat loss, species such as Platanthera orbiculata are vulnerable to subtle shifts in environmental conditions or changes in the abundance of associated species. These species may include herbivores that consume the plants, mycorrhizal fungi that Platanthera orbiculata is absolutely dependent for germination and nutrition, or insect pollinators necessary for reproduction. Suspected herbivores that may have a significant effect on the distribution of Platanthera orbiculata include mammals such as deer and elk, mollusks such as banana slugs, and various invertebrates. Platanthera orbiculata also appears to be sensitive to forest clearing or litter disturbing events such as clear cutting, thinning, or wildfires.

Platanthera orbiculata is believed to be rare due to biological factors, i.e., its interactions with other organisms, in addition to environmental factors. These factors include adequate litter and decomposing wood that provide a rooting medium and substrate for its mycorrhizal fungi; the presence and abundance of its moth pollinator(s) and the full complement of the pollinator's ecological requirements; the abundance of herbivores; and the abundance of pathogenic fungi that may infect this species. Factors that influence associated species may indirectly affect the viability of Platanthera orbiculata. Climate change, direct human intervention (such as spraying) or significant changes in forest composition or structure due to timber harvesting or wildfire may also affect these factors and potentially impact the viability or vigor of Platanthera orbiculata.

Platanthera orbiculata is limited in abundance in specific locales, but is widespread geographically. The risk of total extirpation of the species across its wide geographical range is unlikely under current conditions. However, each regional population or subpopulation is vulnerable to an imbalance in the biological factors on which it depends for reproduction, growth, and survival. Individual plants come and go, and sub-populations rise and fall as landscape disturbances reshape the pattern of forest structures. The species has survived, and like many other species may depend on a pattern of disturbances for rejuvenation of habitats and ecological conditions. It is, therefore, recognized that death of individual plants or even sub-populations is part of the natural ecological cycle.

C. Threats to the Species

Threats to Platanthera orbiculata are those actions or conditions that may limit or extirpate the species from an area, i.e., indiscriminant spraying to control pest Lepidoptera that could kill the moth pollinators; changes in environmental conditions caused by wildfire or timber harvesting activities that may result in heat or drought stress; reduction of organic matter by accelerated decomposition (by climate change or timber harvesting activities); introduction of nonnative invertebrates (including slugs or snails) that could increase herbivory; changes in site conditions that may preclude the occurrence of mycorrhizal fungi; or changes in climate that could affect the distribution of antagonistic fungi or herbivores.

D. Distribution Relative to Land Allocations

Preliminary analysis (1995) of the locations of Platanthera orbiculata on the Mt. Baker-Snoqualmie National Forest was conducted to determine the distribution of this taxon relative to the land allocations under the Northwest Forest Plan and the Mt. Baker-Snoqualmie National Forest Land Management Plan. The only locations that were specific enough for the analysis at that time were the 47 Ecology Program plots. WNHP and Botany Program surveys were not included, but should be addressed in future analyses once more precise location data can be obtained.

Land allocation analysis was based on about 70% of the reported populations. The majority of these populations of Platanthera orbiculata occur on lands designated as Late-Successional Reserves (64%), and 2 sites are in Wilderness areas. Seven locations occur on lands managed for timber production (15%). The other 8 sites of Platanthera orbiculata occur in areas managed for partial retention to achieve visual quality objectives (8%), wildlife areas (6%) and recommended scenic river designation (2%). Many sites occur near boundaries between land allocations or past treatments. Some locations should be checked or verified to determine their exact location.

III. MANAGEMENT GOALS AND OBJECTIVES

A. Management Goals for the Taxon

The management goal for Platanthera orbiculata is to assist in maintaining species viability within the range of the northern spotted owl.

B. Specific Objectives

The specific management objectives for Platanthera orbiculata are to provide the set of ecological conditions necessary for the continued survival of the species and all other species upon which it depends and any species that may depend on it. At the present time, the set of ecological conditions upon which the species depends is unknown. Based on what is known about this taxon, and on application of ecological principles and knowledge from other organisms, some generalized guidelines are proposed to guide the management of the landscape and the management of this species.

IV. HABITAT MANAGEMENT

A. Lessons From History

Platanthera orbiculata was listed as a Sensitive species by the Washington Natural Heritage Program until 1984 when its status was changed to Monitor Group 3. The Washington Natural Heritage Program was contacted to provide an account of the change in status for this taxon. John Gamon reviewed the WNHP files for this taxon, and noted that he could find no specific reason or documentation for the status change of this species. He suggested the following factors may have influenced the decision to change the status of this taxon to Monitor (J. Gamon, pers. comm. 5-2-95).

  1. "The distribution within Washington includes sites on the west side of the Cascades, in the San Juans, and in the northeastern corner of the State. Counties with either extant or historically known populations include King, Snohomish, Whatcom, San Juan, Pend Oreille, and Stevens.
  2. "The distribution suggests that the species has a greater ecological amplitude than previously thought.
  3. "Although the total number of populations (23) known at the time of the status change (1984) was not particularly high, at least some of those populations were located within areas with overall compatible management practices (e.g., North Cascades National Park, Stetattle Creek Research Natural Area, Ross Lake National Recreation Area)."

Platanthera orbiculata is considered to be a species closely associated with late-successional forests (Thomas et al. 1993; USDA and USDI 1994a). The majority of the location data for Washington supports this; however, there are occurrences of populations of this orchid in younger stands or mature forests. None of the populations on the Mt. Baker-Snoqualmie National Forest have been revisited to determine the status of the population or habitat factors, and, to our knowledge, no monitoring of this species has been conducted to see how it responds to various treatments.

There was a large population of this orchid on the Colville National Forest that occurred in a timber harvest area. Surveys conducted prior to harvest or treatment documented 95 plants in the timber sale area. The prescription for site preparation following harvest was modified to include no-burn areas where the orchid population occurred, and specifically restricted herbicide spraying after the orchid had leafed out. Most of the unit was subsequently harvested, although no follow-up monitoring has been conducted to determine the impact of the treatment on the orchid population. The area was revisited, and several orchids were observed in the harvest area. They appeared chlorotic and unhealthy; several individuals observed under a canopy of trees did appear healthy (S. Musconi, pers. comm.).

B. Identification of Habitat Areas for Management

All known sites are identified as habitat areas where these management recommendations should be applied.

C. Management Within Habitat Areas

  1. Ensure that indiscriminant insecticide spraying does not affect the populations of moths or other insects this species depends on for pollination or other aspects of its life cycle.
  2. Populations that occur on sites where management activities are scheduled or proposed need to be evaluated to determine their contribution to the viability of the species. Consider the landscape and ecological context of the population, e.g., factors such as the location of the population in relation to other known populations, relative isolation of the population, the ecological conditions of the site and how they compare to other known sites (typical or atypical), areal extent of the population and number of individuals present, and availability of potential suitable habitat in the area. Special consideration should be given to protect populations near the edge of the geographical range of Platanthera orbiculata, in watersheds where it is rare or of limited distribution, or in sites which represent the limits of its ecological amplitude. Identify subpopulations that are important in the geographic or ecological distribution of this species and maintain these populations and the habitats they occur in. These populations may contribute to the genetic diversity of this species. If populations are considered at risk or are important to maintaining the species viability, then maintain the population and its associated habitat. Some populations may be determined to be sufficiently secure that some disturbance can be tolerated. In this case, try to minimize disturbance to the litter layer and, if feasible, try to conduct disturbance activities in the dormant season.
  3. If a management decision is made that treatments will occur on sites where Platanthera orbiculata is present, then a monitoring plan should be developed and implemented to document the response of the orchid population. It is important that the monitoring program occur over a several-year period to document the response of individuals and the population over an extended period of time. The effects of a treatment may not be immediately apparent, and it is possible that a lag time of several years is necessary for an effect to be observed.
  4. Provide for a representation of all age classes of forests from young to old (and the accompanying structure and composition) for each landscape in which the species occurs. This condition allows some subpopulations to be disturbed by fire or timber harvesting, but only under the condition that parts of a watershed or landscape where the species occurs is in suitable old forest habitat at all times.

D. Other Management Issues and Considerations

Provide for a balance of age-classes of forests from very young to very old (and the accompanying structure and composition) for each landscape in which the species occurs. This condition allows some subpopulations to be disturbed by fire or timber harvesting, but only under the condition that parts of a watershed or landscape where the species occurs is in suitable old forest habitat at all times.

V. RESEARCH, INVENTORY, AND MONITORING NEEDS

The objective of this section is to identify opportunities for additional information which could contribute to more effective species management. The content of this section has not been prioritized or reviewed as to how important the particular items are for species management. While the inventory, research, and monitoring identified below are not required, these recommendations should be addressed by a regional coordinating body at the Northwest Forest Plan level.

A. Data Gaps and Information Needs

The current known populations of Platanthera orbiculata should be revisited to verify their existence and the condition of the population and the habitat it occupies. Populations should be mapped to determine their precise locations for developing a GIS layer.

Determine the specific ecological requirements of Platanthera orbiculata.

Determine the extent of the distribution of Platanthera orbiculata in Washington for Federal lands covered under the Record of Decision. What is its southern extent, and does it occur on the east side of the Cascades or on the Olympic Peninsula?

B. Research Questions

  • Study the biology of Platanthera orbiculata and the obligate or mutualistic species with which it is so closely linked, including fungal associates, pollinators and herbivores. Some of the species involved in these relationships and the nature of these relationships in the Pacific Northwest are not known at this time.
  • How does Platanthera orbiculata respond to treatments or disturbance?

C. Monitoring Needs and Recommendations

  • Identify and monitor the location and condition of subpopulations of the species over time. Trends in population levels and condition can be used to help revise the management of this species in the landscape. Trends in populations or conditions may be due to changes in species population levels that the orchid is linked to, or changes in external conditions such as climate change that could precipitate a change in these population levels.
  • Monitor population levels of known or suspected herbivores or the introductions of potential new herbivores. A balance between herbivory, growth, and reproduction probably exists or has existed in the past. An imbalance in the future could have significant consequences on this species of orchid.
  • Use information collected from monitoring of treatments to guide future management prescriptions.

VI. REFERENCES

Ammirati, J. F. 1995. Mycologist, Botany Department, University of Washington, Seattle, WA. Personal communication.

Arditti, J., R. Ernst, T. Wing Yam and C. Glabe. 1990. The contributions of orchid mycorrhizal fungi to seed germination: a speculative review. Lindleyana 5(4):249-255.

Catling, P. M. and V. R. Catling. 1991. A synopsis of breeding systems and pollination in North American orchids. Lindleyana 6(4):187-210.

Clark, L. J. 1976. Wild Flowers of the Pacific Northwest from Alaska to Northern California. Grays Publ. Ltd. Sidney, B.C. 604 p.

Cody, W. J. 1979. Vascular Plants of Restricted Range in the Continental Northwest Territories, Canada. Syllogeus No. 23. National Museum of Natural Sciences, Ottawa, Ontario. in Reddoch, A. H. and J. M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Connecticut Geological and Natural History Survey. 1985. Connecticuts Species of Special Concern Plant List. Hartford, Connecticut in Reddoch, A. H. and J. M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Correll, D. S. 1950. Native Orchids of North America North of Mexico. Chronica Botanica Co. Waltham, MA. 399 p.

Currah, R. S. 1991. Taxonomic and developmental aspects of the fungal endophytes of terrestrial orchid mycorrhizae. Lindleyana 6(4):211-213.

Currah, R. S., E. A. Smrecui, and S. Hambleton. 1990. Mycorrhizae and mycorrhizal fungi of boreal species of Platanthera and Coeloglossum (Orchidaceae). Can. J. Bot. 68:1171-1181.

Currah, R. S., L. Sigler and S. Hambleton. 1987. New records and taxa of fungi from the mycorrhizae of terrestrial orchids of Alberta. Can. J. Bot. 65:2473-2482.

Darwin, C. 1877. The Various Contrivances By Which Orchids are Fertilized by Insects. 2nd ed., revised, 1984 reprint. The University of Chicago Press, Chicago, Illinois. In: Reddoch, A. H. and J.M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Gade, S. 1987. State-by-state summary of protection afforded to native orchid species. Amer. Orchid Soc. Bull. 56:147-163. in Reddoch, A. H. and J. M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Gamon, John. 1995. Botanist, Washington Natural Heritage Program, Olympia, WA. Personal communication.

Gilkey, H. M. and L. J. Dennis. 1967. Handbook of Northwestern Plants. Oregon State University Bookstores, Inc., Corvallis. 505 p.

Harm, Helga. 1995. Orcas Island resident. Personal communication.

Henderson, J. A. 1995. Unpublished Potential Natural Vegetation Model. Mt. Baker-Snoqualmie National Forest. Mountlake Terrace, WA.

Henderson, J. A., R. D. Lesher, D. H. Peter and D. C. Shaw. 1992. Field Guide to the Forested Plant Associations of the Mt. Baker-Snoqualmie National Forest. USDA Forest Service, Pacific Northwest Region. R6-ECOL-TP-028-91. 196 p.

Hickman, J. C. (ed.). 1993. The Jepson Manual: Higher Plants of California. University of California Press, Berkeley. 1400 p.

Hitchcock, C. L., A. Cronquist and M. Ownbey. 1955. Vascular Plants of the Pacific Northwest. Part 1: Vascular Cryptogams, Gymnosperms, and Monocotyledons. University of Washington Press, Seattle. 914 p.

Hulten, E. 1968. Flora of Alaska and Neighboring Territories. A Manual of the Vascular Plants. Stanford University Press. Stanford, CA. 1008 p.

Inoue, K. 1983. Systematics of the genus Platanthera (Orchidaceae) in Japan and adjacent regions with special reference to pollination. J. Fac. Sci. Univ. Tokyo, Sect. 3, Bot. 13:285-374. in Reddoch, A. H. and J.M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Kagan, Jimmy. 1995. Botanist, Oregon Natural Heritage Program, Portland, OR. Personal communication.

Luer, C. A. 1975. The Native Orchids of the United States and Canada excluding Florida.  New York Botanical Garden.

MacKinnon, A., J. Pojar, R. Coupe (eds.). 1992. Plants of Northern British Columbia. Lone Pine Publishing, Vancouver, B.C. 351 p.

Maher, R. V., G. W. Argus, V. L. Harms and J. H. Hudson. 1979. The Rare Vascular Plants of Saskatchewan. Syllogeus No. 20. National Museum of Natural Sciences. Ottawa, Ontario. in Reddoch, A. H. and J.M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Mt. Baker-Snoqualmie National Forest Botany Program Database. 1995. Mountlake Terrace, WA

Mt. Baker-Snoqualmie National Forest Ecology Program Database. 1995. Mountlake Terrace, WA

Musconi, Sandy. 1995. Botanist, Colville Ranger District, Colville National Forest. Colville, WA. Personal communication.

Nilsson, L. A. 1983. Processes of isolation and introgressive interplay between Platanthera bifolia (L.) Rich. and P. chlorantha (Custer)Reichb. (Orchidaceae). J. Linn. Soc. Bot. 87:325-350. in Reddoch, A. H. and J.M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Oregon Natural Heritage Program Data Base. 1985. Rare, Threatened, and Endangered Plants and Animals of Oregon. in Reddoch, A. H. and J.M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Peck, M. E. 1961. A Manual of the Higher Plants of Oregon. 2nd edition. Binsford & Mort. 936 p.

Pijl, L. van der, and C. H. Dodson. 1966. Orchid Flowers, Their Pollination and Evolution. University of Miami Press, Coral Gables. in Catling, P.M. and V. R. Catling. 1991. A synopsis of breeding systems and pollination in North American orchids. Lindleyana 6(4):187-210.

Reddoch, A. H. and J. M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Szczawinski, A. F. 1959. The Orchids of British Columbia. British Columbia Provincial Museum Handbook No. 16.

Sheviak, C. J. 1974. An Introduction to the Ecology of the Illinois Orchidaceae. Scientific papers XIV, Illinois State Museum, Springfield, Illinois. in Reddoch, A. H. and J. M. Reddoch. 1993. The species pair Platanthera orbiculata and P. macrophylla (Orchidaceae): Taxonomy, morphology, distributions and habitats. Lindleyana 8(4):171-187.

Sheviak, C. J. 1990. Biological considerations in the management of temperate terrestrial orchid habitats. In Ecosystem Management: Rare species and significant habitats. New York State Museum Bulletin 471:194-196.

Sheviak, C. J. and M. L. Bowles. 1986. The Prairie Fringed Orchids: a pollinator-isolated pair. Rhodora 88:267-290. in Catling, P.M. and V. R. Catling. 1991. A synopsis of breeding systems and pollination in North American orchids. Lindleyana 6(4):187-210.

Smreciu, E. A. and R. S. Currah. 1989. Symbiotic germination of seeds of terrestrial orchids of North America and Europe. Lindleyana 4(1):6-15.

Thomas, J. W. and others. 1993. Forest Ecosystem Management: An Ecological, Economic and Social Assessment. 1993. Report of the Forest Ecosystem Management Assessment Team (FEMAT). Portland, Oregon. USDA Forest Service, USDI Bureau of Land Management, US Fish and Wildlife Service, National Park Service, US Dept. of Commerce National Oceanic and Atmospheric Administration, National Marine Fisheries Service, US Environmental Protection Agency.

Urban, Karl. 1995. Botanist, Umatilla National Forest, Pendleton, Oregon. Personal communication.

University of Washington Herbarium. Platanthera orbiculata specimens. Seattle, WA

USDA Forest Service and USDI Bureau of Land Management. 1994a. Final Supplemental Environmental Impact Statement on Management of Habitat for Late-successional and Old-growth Forest Related Species within the Range of the Northern Spotted Owl. Portland, Oregon. 2 vols.

USDA Forest Service and USDI Bureau of Land Management. 1994b. Record of Decision for Amendments to Forest Service and Bureau of Land Management Planning Documents within the Range of the Northern Spotted Owl, and Attachments. Washington D.C.

Washington Natural Heritage Program. 1995. Sighting reports for Platanthera orbiculata.

Washington Natural Heritage Program. 1997. Endangered, Threatened, and Sensitive Vascular Plants of Washington with Working Lists of Rare Non-vascular Species. Department of Natural Resources. Olympia. 62 p.

Williams, J. G. and A. E. Williams. 1983. Field Guide to Orchids of North America. Universe Books. New York, NY.

Figure 1. Platanthera orbiculata. (Line drawing from Hitchcock et al. 1955).
Reprinted by permission of University of Washington Press.

Figure 2. Distribution of Platanthera orbiculata across North America. From Reddoch and Reddoch 1993, Szczawinski 1959 and US Forest Service and WNHP data.

Figure 3. Distribution of Platanthera orbiculata on the Mt. Baker-Snoqualmie N.F.

Figure 4. Distribution of Platanthera orbiculata by estimated Total Annual
Precipitation and Mean Annual Temperature.
Estimates derived from
Mt. Baker-Snoqualmie National Forest Potential Vegetation Model (Henderson 1995).

Figure 5. Distribution of Platanthera orbiculata by aspect and elevation
on the Mt. Baker-Snoqualmie National Forest.

Figure 6. Frequency distribution of Platanthera orbiculata by stand age of Ecology Plots,
Mt. Baker-Snoqualmie National Forest.


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