The moss flora of the alpine - high subalpine Chowder Ridge area, western North Cascades Range, Washington State, U.S.A.

JOHN R. SPENCE Departrnerlt of Botany, UniversiQ of British Columbia, Vunco~iver, B. C. , Carlada V6T 2BI

Received October 18, 1984

SPENCE, J. R. 1986. The moss flora of the alpine - high subalpine Chowder Ridge area, western North Cascades Range, Washington State, U.S.A. Can. J . Bot 64: 146-150.

Chowder Ridge, a high elevation area near Mt. Baker, Washington State, possesses a moss flora of 77 species based on collections made during two visits. Three species, Dicranurn ~zuehlenbeckii B.S.G., Rhacomitrium microcarpon (Hedw.) Brid., and Mniurn arizonicurn Amann, are reported new to Washington State. Coscirlodon calyptratus (Hook.) C Jens. and Grirnmia ovulis (Hedw.) Lindb. are noted for the first time from the west slope of the North Cascades. Chowder Ridge harbors an unusually large number of disjunts of the Rocky Mountain interior compared with typical sites on the west slope of the North Cascades, while the Pacific North American element is underrepresented. The bulk of the flora consists of species widespread in western North America.

SPENCE, J. R. 1986. The moss flora of the alpine - high subalpine Chowder Ridge area, western North Cascades Range, Washington State, U.S.A. Can. J. Bot 64: 146-150.

D'aprks les rkcoltes effectukes au cours de deux visites, la flore bryologique de Chowder Ridge, une rkgion d'altitude klevke pres du mont Baker dans 1'Etat de Washington, comprend 77 espkces de mousses. Trois espkces sont des additions i la flore de 1'Etat de Washington: Dicranurn rnuehlenbeckii B.S.G., Rhacornitriurn rnicrocarpon (Hedw.) Brid. et Mniurn arizonicurn Amann. Deux espkces, Coscirzodon calyptratus (Hook.) C. Jens. et Grimrnia ovalis (Hedw.) Lindb., sont signalkes pour la premikre fois sur la pente ouest des Cascades septentrionales. Comparativement aux sites typiques de la pente occidentale des Cascades septentrionales, la flore de Chowder Ridge comprend un nombre exceptionnellement devk de taxons prksentant une disjonction d'aire avec les Rocheuses et l'intkrieur, tandis que I'klkment pacifique nord-amkricain y est sous-reprksente. La majeure partie de la flore est constituke d'espbces trks rkpandues dans l'ouest de I'Amerique du Nord.

[Traduit par le journal]

Introduction The diversity and distributions of mosses in alpine areas of

the Coast and Cascades ranges of British Columbia and Wash- ington are poorly documented. Much work has been done recently on plant communities in the area and has provided useful information concerning the more common and ecologi- cally important mosses (Archer 1963; Brooke et al. 1970; Fraser 1970; Eady 1971; Douglas 1972; Douglas and Bliss 1977; Selby 1980). Nevertheless, such studies rarely inten- sively sample the general flora of a region and many rare, but phytogeographically important species are often overlooked. The only studies on mosses which apply to the coastal regions of British Columbia and Washington are those of Lawton (197 1) and Schofield (1976).

Chowder Ridge, northeast of Mt. Baker, northwestern Washington State, supports one of the most extensive stretches of alpine tundra on the west slope of the North Cascades Range. The ridge is constructed primarily of sedimentary rocks with a west to southwest exposure, which fosters the develop- ment of dry alpine tundra that more closely resembles that of the east slopes of the North Cascades than that of the adjacent ridges of Mt. Baker. Many interesting and disjunctive species of vascular plants have been collected from the ridge (Taylor and Douglas 1978). This paper reports on collections of mosses made along the ridge and the adjacent subalpine Cougar Ridge during 1982 and 1983.

Area description Chowder Ridge is located in northwestern Washington State, just

south of the United States - Canada border (48'46' N, 121 "45' W). The ridge trends northwest from Mt. Baker, a large and heavily glaciated stratovolcano. The primary rock types are sedimentary and

basaltic (Misch 1966; Taylor and Douglas 1978). The upper portion of the ridge is a sharp arete-like crest reaching elevations of 2300 m, dropping southwest and northeast in steep slopes. The remnants of Hadley Glacier exist in a cirque on the sheltered northeast-facing slope. Just north of the cirque that harbors the glacier a large outcrop of basalt called Arch Point is located where Cougar Ridge merges with Chowder Ridge. This latter ridge runs from northeast to south- west, gradually merging into Chowder Ridge.

Forest line lies at about 1600 to 1700 m on Cougar Ridge, with its upper portion consisting of a complex of subalpine meadows domi- nated by broad-leaved herbs and dawrf shrubs and scattered clumps of trees. The northeast-facing slopes of Chowder Ridge are snow covered much of the summer, with the vegetation consisting of raw- mark, stripe, and snow-bed communities. The crest of Chowder Ridge is vegetated by a complex of alpine dry graminoid meadow and alpine fell-field communities, intempted by numerous sedimentary rock outcrops. Below Hadley Glacier are extensive flats of glacial till, which support a sparse pioneer community. More details on vegeta- tion in the area are found in Douglas and Bliss (1977) and Taylor and Douglas (1978).

Methods and materials

Collecting trips were made on October 2, 1982, and October 1, 1983. Species nomenclature follows Lawton (1971) and Corley et al. (1981) unless otherwise indicated. The list is arranged phylogeneti- cally by family, using the scheme of Vitt (1984), with the species arranged alphabetically within families. Distributions within western North America were analysed for all species, using information in Lawton (1971), Schofield (1976, 1980, 1984), and Tan (1980), as well as numerous floristic papers and the collections at UBC. The distribution categories (floristic elements) are basically an extension of the distribution categories in Schofield (1976). These are as fol- lows: widespread in western North America including the western Arctic (WAA element); widespread in western North America but not

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SPENCE 147

found in the western Arctic (WNA element); predominantly Rocky wide leaf cells, and are a bright yellow-green. The border ~ o u n t a i n and adjacent interior drylands (RMI element; these species also tends to be stronger, and the leaves are less decurrent than may or may not occur in the western Arctic); predominantly coastal in those of B. turbinatum. See Smith (1978) and Crum and western North America but reappearing in humid interior ranges (CHI Anderson (1981) for more comments on the differences be- element; these species may or may not occur in the western Arctic); restricted to coastal western North America (COS element; these species may or may not occur in the western Arctic); and anomalous (ANM element). This last category includes those species that are too rare in western North America for any recognizable pattern to be detected in their distributions. For comparative purposes the flora of Austin Pass. northeast of Mt. Baker and about 10 km east of Chowder Ridge, is included. Unless otherwise noted, collectors and col- lecting numbers are as follows: 1563-1629 are J. R. Spence, W. B. Schofield, and R. J. Taylor; 2397 -25 12 are J. R. Spence; and 78746-78823 are W. B. Schofield, J. R. Spence, and R. J Taylor. All voucher specimens are deposited at UBC. Localities are abbrevi- ated as CHR (Chowder Ridge), COR (Cougar Ridge), and ARP (Arch Point). Also listed are the acronyms for the floristic elements (see above). Cfr indicates that the species in question was collected with sporophytes.

List of species Andreaeaceae

Andreaea nivalis Hook. Damp rock face, NE slope of CHR, 2499. CHI.

A. rupestris Hedw. Damp rock outcrop, COR, 78763. WAA, cfr. Poly trichaceae

Oligotrichum hercynicum (Hedw .) Lam. & DC . Eroded edge of turf bank on soil, NE slope of CHR, 1582. WNA.

0. parallelum (Mitt.) Kindb. Overhanging turf bank on soil in shade, NE slope of CHR, 2487. CHI.

Polytrichastrum lyallii (Mitt.) G. L. Smith. Mesic soil bank in herb meadow, COR, 1572 WNA, cfr. (the treatment of this genus and the following one follows Smith 1971).)

P. sexangulare (Brid.) G. L. Smith. Gravel of raw-mark slope, NE slope of CHR, 1577. WNA.

Polytrichum juniperinum Hedw. Damp gravel flat below Hadley Glacier, 1570. WAA, cfr.

P. piliferum Hedw Dry gravel in fell-field, crest of CHR, 2406a. WAA, cfr. Orthotrichaceae

Orthotrichum laevigatum Zett. Dry rock outcrop, crest of CHR, Basabe s.n. WAA, cfr.

0. rupestre Scheich. ex. Schwaegr. Dry rock face, ARP, 1616. WNA, cfr. A common and widespread species in west- ern North America at low elevations, this is the first report from an alpine locality in the North Cascades. Bryaceae

Bryum amblyodon C. Muell. Dry soil over rock, ARP, 1622. WAA, cfr. This species has been treated previously under the name of B. stenotrichum C. Muell. in North Amer- ica; for the recent name change see Ochi (1980).

B. caespiticium Hedw. Damp hollow at base of rock in alpine fell-field, crest of CHR, 2472. WAA, cfr.

B. lisae De Not. Mesic soil in herb meadow, COR, 2417. WAA, cfr.

B. pseudotriquetrum (Hedw.) Gaertn., Meyer & Scherb. Dry soil over rock face, ARP, 1563. WAA, cfr.

B. schleicheri DC. Wet soil below seep, ARP, 1566. WAA, cfr. This species is generally included within the concept of B. turbinatum but is quite distinct from that species. The leaves are broader and not contorted when dry, have extremely

tween these species. B. weigelii Spreng. Wet soil in late snow hollow, COR,

1565. WAA. Pohlia bolanderi (Sull.) Broth. Shady thin soil over rock

above snowbank, crest of CHR, 2477. WNA. P. cruda (Hedw.) Lindb. Thin soil over rock in crevice,

ARP, 2478. WAA. P. drummondii (C. Muell.) Andr. Damp gravel on raw-mark

slope, NE slope of CHR, WAA. P. erecta Lindb. Reported by Taylor and Douglas (1978)

from an alpine fell-field on the crest of CHR, this species was not recollected. It is extremely rare in North America, with other reports from the Yukon and British Columbia (Shaw 1982). ANM, cfr.

P. filum (Schimp.) Mart. Damp soil over rock near snow- bed, NE slope of CHR, 78759. WAA, cfr.

P. ludwigii (Spreng. ex. Schwaegr.) Broth. Damp gravel in lee of boulder, raw-mark slope, NE slope of CHR, 2507. CHI.

P. nutans (Hedw.) Lindb. Edge of eroded turf bank, crest of CHR, 2425. WAA, cfr.

P. wahlenbergii (Web. & Mohr) Andr. Wet soil in seep, ARP, 1594. WNA, cfr.

Roellia roellii (Broth.) Andrews. Mesic soil in herb meadow, COR, 2421. WNA.

Mniaceae Mnium arizonicum Amann. Dry soil over rock, ARP,

1 6 2 5 ~ . RMI. This species is distributed across northern North America and Greenland as well as the Rocky Mountains of Alberta, Montana, Idaho, Wyoming, Colorado, and Arizona (Koponen 1972). The species is also found in the interior drylands of south central British Columbia. This is the first report from the west coast of North America, the North Cascades, and Washington.

M. thomsonii Schimp. Dry soil over rock, ARP, 1619a. WAA.

Bartramiaceae Bartramia ithyphylla Brid. Dry soil in rock crevice, ARP,

1619. WAA, cfr. Conostomum tetragonum (Hedw ) Lindb. Damp soil on raw-

mark slope, NE slope of CHR, 2468. WAA. Philonotis fontana (Hedw.) Brid. Damp gravel on raw-mark

slope, NE slope of CHR, 2423. WAA, cfr.

Amblystegiaceae Calliergon stramineum (Brid.) Kindb. Wet muck at edge of

pool, COR, 78771. WAA. Drepanocladus exannulatus (Br. Eur.) Warnst. Wet muck at

edge of pool, COR, 78755. WAA. D. uncinatus (Hedw.) Warnst. Damp soil over rock, ARP,

1627. WAA. Hygrohypnum molle (Hedw.) Loeske. Wet boulder in

stream, NE slope of CHR, 78787. CHI, cfr. H. ochraceum (Turn. ex Wils.) Loeske. Damp soil in stream

bed below Hadley Glacier, 2426. WAA. Brachytheciaceae

Brachythecium albicans (Hedw.) B.S.G. Mesic soil in herb meadow, COR, 2442. WAA.

B. collinum (C. Muell.) B.S.G. Dry shaded cliff crevice,

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ARP, 78799. RMI, cfr. B. starkei (Brid.) B.S.G. Damp shaded rock outcrop, NE

slope of CHR, 78792. WNA, cfr. B. velutinum (Hedw.) B.S.G. Dry soil over rock in shade,

ARP, 1600. WNA, cfr. Eurhynchium pulchellum (Hedw ) Jenn. Dry soil over rock,

ARP, 1626. RMI. Plagiotheciaceae

Plagiothecium laetum B. S . G. Dry soil under kmmmholz, ARP, 2504. WAA. Hy pnaceae

Hypnum revolutum (Mitt.) Lindb. Dry soil over rock, crest of CHR, 2407. RMI. Leskeaceae

Lescuraea incurvata (Hedw.) Lawt. Damp sedimentary rock above ARP, 1613 WNA.

L. patens (Lindb.) H. Am. & C. Jens. Damp soil over rock, ARP, 1599. WNA.

L. radicosa (Mitt.) Moenk Dry soil in vegetation patch, alpine fell-field, crest of CHR, 2456. WNA. Encalyptaceae

Encalypta rhaptocarpa Schwaegr. Thin soil over rock, crest of CHR, 2464. RMI, cfr. Pottiaceae

Bryoerythrophyllum recurvirostrum (Hedw.) Chen. Dry rock, ARP, 2476a. WAA, cfr.

Desmatodon latifolius (Hedw.) Brid. Dry soil in herb meadow, COR, 2441. WAA, cfr.

Tortella fragilis (Drumm.) Limpr. Dry cliff crevice, ARP, 78785. WAA.

T. tortuosa (Hedw.) Limpr. Dry cliff crevice, ARP, 78777. WAA, cfr.

Tortula norvegica (Web.) Wahlenb. ex Lindb. Mesic soil bank, COR, 2437. WAA.

T. ruralis (Hedw.) Gaertn., Meyer & Scherb. Dry rock, ARP, 1615. WAA.

Weissia controversa Hedw. Dry soil over rock, ARP, 2475. WAA, cfr. This species is common at low elevations along the coast of western North America, reappearing in humid interior regions (Schofield 1976). This is only the second locality from the alpine on the coast; the other is from Mt. Whistler north of Mt. Garibaldi in the British Columbia Coast Range.

Dicranaceae Dichodontium olyrnpicum Ren. & Card. Damp soil in herb

meadow, COR, 1570a. CHI. Dicranoweisia crispula (Hedw.) Milde. Dry rock outcrop,

crest of CHR, 2432. WAA, cfr. Dicranum muehlenbeckii B.S.G. Dry soil in graminoid

meadow, crest of CHR, 2402. RMI. This species is rare in coastal western North America, with collections from Vancouver Island, Mt. Garibaldi, the Fraser River Canyon in southwestern British Columbia, and Manning Provincial Park in south central British Columbia. Dicranum muehlenbeckii is widespread but never common in interior western North America, generally below timberline (Peterson 1979). This is the first report for Washington.

D pallidisetum (Bailey) Irel. On damp soil in herb meadow, COR, 1592. CHI.

Kiaeria blyttii (B.S.G.) Broth. Mesic soil under heath, COR, 78749. WNA, cfr.

K. falcata (Hedw.) I. Hag. Damp shady soil of turf bank,

VOL. 64, 1986

NE slope of CHR, 2490. CHI, cfr. Rhabdoweisiaceae

Amphidium lapponicum (Hedw.) Schimp. Damp rock cre- vice, ARP, 78813. WAA, cfr. Ditrichaceae

Ceratodon purpureus (Hedw.) Brid. Damp gravel below Hadley Glacier, 1570a. WAA, cfr.

Distichium capillaceum (Hedw.) B.S.G. Dry soil over rock face, ARP, 2474. WAA, cfr.

DitrichumJlexicaule (Schwaegr.) Hampe. Dry soil in alpine fell-field, crest of CHR, Taylor s.n. WAA. Grimmiaceae

Coscinodon calyptratus (Hook.) C. Jens. Dry rock, crest of CHR, 2397. RMI. This species is common in interior western North America from the Arctic to Mexico. This is the first report for the species from the west slope of the North Cascades Range.

Grimmia alpestris (Web. & Mohr) Schleich. & Hornsch. Loose shale outcrop, crest of CHR, 2482. WNA, cfr.

G. anodon B. & S. Dry rock outcrop, crest of CHR, 2414. RMI, cfr. This species has been mapped recently by Ireland and Miller (1982). Widespread in interior western North America, this is only the second report from west of the North Cascades crest, the other one being from the dry northeastern Olympic Mountains.

G. ovalis (Hedw .) Lindb. Dry rock outcrop, crest of CHR, 2399. RMI. Another species widespread in interior western North America, this is the first report from the west slope of the North Cascades Range.

Rhacomitrium canescens (Timm ex. Hedw.) Brid. Dry rock outcrop, crest of CHR, 2455. WAA. The treatment of this species as well as R. ericoides and R. muticum follows Frisvoll (1983).

R. ericoides ((Web.) ex. Brid.) Brid. Dry gravel in alpine fell-field, crest of CHR, 2406. WAA.

R. fasciculare (Hedw.) Brid. Dry soil over rock, NE slope of CHR, 2497. WNA.

R. lanuginosum (Hedw.) Brid. Dry rock outcrop, crest of CHR, 2415. WAA.

R. microcarpon (Hedw.) Brid. Damp rock face, COR, 1601. RMI. Generally considered part of the R. heterostichum complex, this species is distinct in leaf morphology and areola- tion, branching, and ecology, as shown by Dixon (1924) and Lawton (1972). Lawton reported the species from the Rocky Mountains of Idaho and Montana, as well as Alaska. The species has also been collected from alpine tundra in northern British Columbia and Wells Gray Provincial Park in east cen- tral British Columbia. This collection represents the first from the coast of western North America, the west slope of the North Cascades Range, and Washington.

R. muticum (Kindb.) Frisvoll. Dry sandy gravel below Hadley Glacier, 2465. CHI. This species has recently been segregated from R. canescens by Frisvoll (1983). It is very distinctive and cannot be easily confused with any other Rha- comitrium. The species is found in alpine and subalpine vege- tation in western North America and Japan.

R. sudeticum (Funck) B. & S. Dry rock face, NE slope of CHR, 2463. WNA, cfr.

Schistidium apocarpum (Hedw.) B. & S. Dry rock outcrop, crest of CHR, 2398. WAA, cfr.

S. rivulare (Brid.) Podp. Rock in dry stream bed, NE slope of CHR, 2459. WAA, cfr.

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TABLE 1. The distribution of moss species found at Chowder Ridge and Austin Pass, Mt. Baker,

among six phytogeographic elements

Phytogeographic Chowder Austin element Ridge Pass

WAA 41(53%)' 43(49%) WNA 16(2 1 %) 20(22 %) RMI 10(13%) -

CHI 9(11%) 19(22%) COS - 6(7 %)

ANM 1(1%) -

Total 77(100%) 88(100%)

umber of species (percent of the Flora at site in element).

Discussion Despite the rather dry nature of Chowder Ridge and adjacent

Cougar Ridge, the moss flora is quite diverse. The 77 species found in the area compare favorably with the 88 species re- corded from Austin Pass, a much wetter area (Table I). This richness is undoubtedly a result of the strong mesoclimatic differences among the dry southwest slopes, exposed ridge crest, and cooler and damper northeast slopes, as well as the varied rock types.

The dry nature of the ridge is reflected in the large percent- age of species (13%) disjunct from the interior (the RMI ele- ment). This value becomes more remarkable when compared with the flora of Austin Pass, a typical wet alpine-subalpine complex of the west slope of the North Cascades Range. No RMI disjuncts occur at Austin Pass, while 29 % of the flora has a predominantly coastal distribution (the CHI and COS ele- ments). Only 11 % of the flora on Chowder Ridge belongs to this group. Furthermore, none of the species on the ridge are restricted to the coast (the COS element). Despite its proximity to the Pacific Ocean (about 50 km), Chowder Ridge lacks many species which are characteristic of alpine and subalpine vegetation on the west slope of the North Cascades Range. These include (all are found at Austin Pass) Andreaea blyttii B.S.G., Grimmia olympica Britt., Arctoa fulvella (Dicks.) B.S.G., Dichodontium pellucidum (Hedw.) Schimp., Dicra- nella heteromalla (Hedw.) Schimp., Hypnum dieckii Ren. & Card., Anoectangium aestivum (Hedw .) Mitt., Rhizomnium nudum (Williams ex Britt. & Williams) Kop., Thamnobryum neckeroides (Hook.) Lawt., Lescuraea baileyi (Best & Grout) Lawt., and Sphagnum compactum DC ex Lam. & DC.

The above analyses show that the moss flora of Chowder Ridge is anomalous when compared with other sites on the west slope of the North Cascades, of which Austin Pass is typical. Several possible explanations can be posed concerning the presence of the RMI disjuncts on the ridge. Many of the species in this group commonly produce sporophytes (e.g., Encalypta rhaptocarpa, Grimmia anodon, Coscinodon calyp- tratus, and Hypnum revolutum) and their presence on Chowder Ridge could be the result of intermediate- or long-distance dispersal from populations to the east, following deglaciation. Alternatively, these species could be more widespread and common in the North Cascades than the data imply but have yet to be collected elsewhere in the region. Other species in this group, however, rarely produce sporophytes in western North America, although the possibility that their presence on the ridge is the result of long distance dispersal from undis-

TABLE 2. The distribution of the moss species on Chowder Ridge among three major types of habitats; soil in densely vegetated meadows; rock faces, outcrops, and ledges; and exposed gravel, fell-field, raw mark, turf banks, stream margins (i.e., unstable and often disturbed

habitats)

Phytogeographic Unstable element Soil Rock sites

WAA 10 18 16 WNA 4 10 4 RMI 1 9 -

CHI + COS 2 3 5

NOTE: The COS and CHI elements have been combined into a more general "coastal" element. Some overlap occurs, since several species are found in more than one habitat.

covered populations with sporophytes cannot be excluded. These include Dicranum muehlenbeckii, Grimmia ovalis, Rha- comitrium microcarpon, and Mnium arizonicum. Another pos- sibility is that these species might be relicts from a time in the past when conditions were more favorable for them. Similar disjuncts in both flowering plants and mosses exist in the dry northeastern Olympic Mountains. Kuramoto and Bliss (1970) have suggested that the presence of such disjuncts from the interior may be upward retreat and isolation of a dry graminoid vegetation in the Puget lowlands once more widespread during the Hypsithermal. There is clear evidence of such vegetation in the area from paleoecological studies (Baker 1983). Rather than being relicts from the Hypsithermal, these species might also be relicts from dry conditions that existed preceding the last major glaciation, the Fraser. Portions of Chowder Ridge are of sufficiently high elevations that, during the Fraser, they could have pierced the ice level as nunataks in the alpine glaciers on Mt. Baker. An analysis of habitat distributions of the 77 species (Table 2) shows that, of the 10 RMI disjuncts, 9 are found on exposed high elevation rock outcrops, which would have been the most probable habitat on a small nunatak. Examples of similar situations are known from elsewhere along the coast (Huesser 1954; Archer 1963). This possibility is highly tentative, and much more work on moss distributions and habitats as well as interpretations of glaciation levels in the North Cascades will be required to substantiate this idea.

Taylor and Douglas (1978) suggksted that Chowder Ridge would serve as an ideal alpine representative of the RNA (Research Natural Area) system in the Pacific Northwest. They suggested, among other reasons, that the presence of many interesting rare and potentially endangered species and the relatively undisturbed conditions on the ridge make the area important for research and other educational studies. The presence of the many disjunct and rare moss species on the ridge provides further support for Chowder Ridge being included in the RNA system.

Acknowledgements The manuscript benefited from criticisms by W. B.

Schofield and G. R. Brassard. Help in species determinations was provided by J. Shaw (Pohlia), T. McIntosh (Pottiaceae and Grimmiaceae), and W. B. Schofield (general). I especially thank R. J. Taylor for calling my attention to the uniqueness of Chowder Ridge and leading the first bryological trip to the ridge. Field expenses were covered by Natural Sciences and

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Engineering Research Council of Canada grant No. 67 - 1217 to W. B. Schofield.

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