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North American Terrestrial Vegetation Second Edition

North American Terrestrial Vegetation Second Edition

North American Terrestrial Second Edition

Edited by Michael G. Barbour William Dwight Billings PUBLISHED BY THE PRESS SYNDICATE OF THE UNIVERSITY OF CAMBRIDGE The Pitt Building, Trumpington Street, Cambridge,

CAMBRIDGE UNIVERSITY PRESS The Edinburgh Building, Cambridge CB2 2RU, United Kingdom www.cup.cam.ac.uk 40 West 20th Street, New York, NY 10011-4211, USA www.cup.org 10 Stamford Road, Oakleigh, Melbourne 3166, Ruiz de Alarco´n 13, 28014 Madrid, Spain

᭧ Cambridge University Press 1988, 1999

This book is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no of any part may take place without the written permission of Cambridge University Press.

First published 1988 Second edition 1999

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Library of Congress Cataloging-in-Publication Data North American terrestrial vegetation / edited by Michael G. Barbour, William Dwight Billings. – 2nd ed. p. cm. Includes bibliographical references (p. ) and index. ISBN 0-521-55027-0 (hardbound) 1. communities – . 2. Plant – North America. 3. Phytogeography – North America. I. Barbour, Michael G. II. Billings, W. D. (William Dwight), 1910–1997. QK110.N854 1999 581.7'22'097 – dc21 97-29061 CIP

ISBN 0 521 55027 0 hardback ISBN 0 521 55986 3 paperback Contents

Contributors page vii Preface to the First Edition ix Preface to the Second Edition xi

CHAPTER 1 and Polar 1 Lawrence C. Bliss CHAPTER 2 The Taiga and Boreal Forest 41 Deborah L. Elliott-Fisk CHAPTER 3 Forests and of the Rocky 75 Robert K. Peet CHAPTER 4 Pacific Northwest Forests 123 Jerry F. Franklin and Charles B. Halpern CHAPTER 5 Californian Upland Forests and Woodlands 161 Michael G. Barbour and Richard A. Minnich CHAPTER 6 203 Jon E. Keeley CHAPTER 7 Intermountain Valleys and Lower Slopes 255 Neil E. West and James A. Young CHAPTER 8 Warm 285 James A. MacMahon CHAPTER 9 323 Phillip L. Sims and Paul G. Risser CHAPTER 10 Eastern Deciduous Forests 357 Hazel R. Delcourt and Paul A. Delcourt CHAPTER 11 Vegetation of the Southeastern Coastal 397 Norman L. Christensen CHAPTER 12 Freshwater Wetlands 449 Curtis J. Richardson CHAPTER 13 Saltmarshes and Mangroves 501 Irving A. Mendelssohn and Karen L. McKee CHAPTER 14 Alpine Vegetation 537 William Dwight Billings CHAPTER 15 Mexican Temperate Vegetation 573 Alejandro Vela´zquez, Victor Manuel Toledo, and Isolda Luna CHAPTER 16 The 593 Ariel E. Lugo, Julio Figueroa Colo´n, and Frederick N. Scatena CHAPTER 17 Tropical and Subtropical Vegetation of 623 Gary S. Hartshorn

v vi Contents

CHAPTER 18 Vegetation of the Hawaiian Islands 661 Lloyd L. Loope

Subject Index 689 Species Index 695 Chapter 1 Arctic Tundra and Biome

L. C. BLISS 2 L. C. Bliss

Figure 1.1. Major subdivisions of the North American and arc- tic.

INTRODUCTION high) to dwarf shrub heath (5–20 cm high) and graminoid-. These have a total The Arctic is often viewed as a monotonous - plant cover of 80–100%, including an abundance of scape with a limited number of vascular and cryptogams in most sites. an abundance of cryptogams. In reality, the arctic tundra and polar desert biome is as diverse in its vegetation types and soils as are the bi- PHYSICAL ENVIRONMENT omes and the coniferous of the western mountains and the taiga. The Arctic constitutes about 20% of North America (Fig. 1.1, general map of biomes), about 2.5 M km2 in , 2.0 M km2 The macroclimate of the Arctic is characterized by in Greenland, and 0.3 M km2 in . Over this continuous darkness in midwinter, with a nearly large area there are considerable variations in cli- continuous cover of snow and ice for 8–10 mo and mate, ice cover, soils, sizes of the flora (cryptogam by continuous light in summer, with a short grow- and vascular), and plant communities. ing season of 1.5–4 mo. In winter a large semiper- As used here, ‘‘Arctic’’ refers to those areas be- manent high-pressure system of intensely cold dry yond the climatic limit of the boreal forest and tree- air occurs over the Territory and the west- line. There are often small pockets of trees, usually ern (N.W.T.). The average Picea glauca, in protected mesohabitats (south- southern position of these anticyclonic systems facing slopes, river terraces) beyond the treeline, parallels the southern boundary of the taiga in but the uplands are dominated by arctic tundra winter. However, outbreaks of cold arctic air pe- vegetation. Throughout these cold-dominated riodically extend into the midwestern and southern landscapes, soils are permanently frozen (perma- states during severe storms. In summer, the arctic frost) with only the upper portion (20–60 cm, ex- high-pressure system is weaker, with its southern cept 100–200 cm along rivers), the active layer, limit paralleling the arctic–boreal forest boundary thawing in summer. The Circumpolar Arctic is di- over 50% of the time (Bryson 1966). Low-pressure vided into the Low and High Arctic (Fig. 1.1) based systems in the and between Baffin on many ecological characteristics ( 1.1). Tun- Island and Greenland bring increased dras predominate in the Low Arctic, and polar to the Arctic in summer, when these storm systems semideserts and polar deserts dominate the High move across Alaska, into the Canadian Arctic Ar- Arctic. ‘‘Tundra’’ is a generic term that includes chipelago and Greenland. Winter penetration of vegetation types that range from tall shrub (2–5 m low-pressure systems into the Arctic seldom occurs Arctic Tundra and Polar Desert Biome 3

Table 1.1. Comparison of environmental and biotic characteristics of the Low and High Arctic in North America

Characteristics Low Arctic High Arctic

Environmental Length of growing season (months) 3–4 1.5–2.5 Mean July Temperature (؇C) 8–12 3–6 Mean July soil temperature at Ϫ 10 cm (؇C) 5–8 2–5 Annual degree days above 0؇C 600–1400 150–600 Active-layer depth (cm) fine-textured soils 30–50 30–50 coarse-textured soils 100–300 70–150 Botanical/vegetational Total plant cover (%) Tundra 80–100 80–100 Polar semidesert 20–80 20–80 Polar desert 1–5 1–5 flora (species) 700 350 Bryophytes Common Abundant Fruticose and foliose Frutcose growth form growth forms common minor, crustose and foliose common Growth-form types Woody and graminoid Graminoid, cushion, common and rosette common Plant height (cm) Shrubs 10–500 5–100 Forbs 5–30 2–10 Sedges 10–50 5–20 Shoot:root ratios (alive) Shrubs 1:1 1:1 Forbs 1:1–2 1:0.5–1 Sedges 1:3–5 1:2–3

except in southern Baffin Island and southern 1.2). These dramatic shifts in summer climate and Greenland, with much higher annual pre- length of the growing season explain much of the cipitation (Table 1.2). change in vegetation from the Low Arctic to the Whether the positioning of the Arctic Front High Arctic. Winter snow cover averages 20–50 cm (leading edge of polar air) in summer along the over many upland areas, whereas in the Low Arc- treeline results from changes in surface , tic, lee slopes and depressions may have snow- , and surface roughness of veg- banks 1–5ϩ m. In the High Arctic, with greatly re- etation, as suggested by Hare (1968), or from an duced winter precipitation, many uplands have assemblage of climatic variables, as suggested by only 10–20 cm snow and some areas even less. Bryson (1966), is not known. However, both the Deep snowbanks (1–3ϩ m) occur in protected vegetation limits of forest and tundra and the air- slopes and in depressions. With a lower angle mass systems are responding to the basic solar ra- and lower summer temperatures many of these diation controls of net radiation (Hare and Ritchie snowbanks do not melt until late July or August, 1972). Annual net radiation averages 1000–1200 MJ whereas in the Low Arctic nearly all snow is mϪ2 yrϪ1 in the northern boreal forest, 750–800 MJ melted by mid-June. The time of snowmelt greatly mϪ2 yrϪ1 across Canada, and about 670 MJ mϪ2 yrϪ1 influences the distribution of species, especially across Alaska at treeline. In the High Arctic it av- north of 74Њ latitude. There is also a very strong erages 200–400 MJ mϪ2 yrϪ1 over much of the land correlation between shrub height and average and drops to near zero in northern Ellesmere Is- snow depth, especially in the Low Arctic. This ex- land and northern Greenland. A similar pattern of why tall shrubs (2–5 m) are confined to river reduced summer temperature, mean annual tem- bottoms, steep banks, and drainages in uplands. perature, and precipitation occurs northward (Fig. Global is a major subject of cur- 4 L. C. Bliss

Table 1.2. Climatic data for selected stations in the Low and High Arctic

(Temperature (0؇ C) Precipitation (mm

Mean monthy Mean monthly Mean Degree-days Mean Station and latitude June July August annual (Ͼ0؇ C) June July August annual

Low Arctic Frobisher Bay, N.W.T., 64؇ 0.4 3.9 3.6 Ϫ12.7 610 38 53 58 425 Baker , N.W.T., 65؇ 3.2 10.8 9.8 Ϫ12.2 1251 16 36 34 213 Tuktoyaktuk, N.W.T., 70؇ 4.7 10.3 8.8 Ϫ10.4 903 13 22 29 130 Kotzebue, AK, 67؇ 8.2 12.4 8.5 Ϫ4.3 1462 22 44 37 246 Umiat, AK, 69 ؇ 9.1 11.7 7.3 Ϫ11.7 993 43 24 20 119 Angmagssalik, Greenland, 65؇ 5.8 7.4 6.6 Ϫ0.4 793 44 35 62 770 Godthaab, Greenland, 64؇ 5.7 7.6 6.9 Ϫ0.7 809 46 59 69 515 Umanak, Greenland, 71؇ 4.8 7.8 7.0 Ϫ4.0 682 12 12 12 201 High Arctic Barter Island, AK, 70؇ 1.8 4.6 3.7 Ϫ11.6 368 10 18 25 124 Barrow, AK, 71؇ 1.3 3.8 2.2 Ϫ12.1 288 8 22 20 100 Cambridge Bay, N.W.T., 69؇ 1.5 8.1 7.0 Ϫ14.8 579 13 22 26 137 Sacks Harbour, N.W.T., 72؇ 2.2 5.5 4.4 Ϫ13.6 458 8 18 22 102 Resolute, N.W.T., 75؇ Ϫ0.3 4.3 2.8 Ϫ16.4 222 13 26 30 136 Isachsen, N.W.T., 79؇ Ϫ0.9 3.3 1.1 Ϫ19.1 161 8 21 22 102 Eureka, N.W.T., 80؇ 2.2 5.5 3.6 Ϫ19.3 318 4 13 9 58 Alert, N.W.T., 83؇ Ϫ0.6 3.9 0.9 Ϫ18.1 167 13 18 27 156 Scoresbysund, Greenland, 70؇ 2.4 4.7 3.7 Ϫ6.7 333 26 38 33 248 Nord, Greenland, 81؇ Ϫ0.4 4.2 1.6 Ϫ11.1 202 5 12 19 204

Source: Data from various sources rent research, especially in relation to boreal and temperature of Toolik Lake has risen about 3Њ C arctic regions. Plant and animal communities and from 1975 through 1991 (Hobbie et al. 1994) and have changed greatly in the past and air temperatures at Barrow by AK Ӎ 1.5Њ C since no doubt will respond significantly to future cli- 1971 (Oechel, Vourlitis, Hastings, and Bochkarev mate changes (Warrick, Shugart, Antonovsky, Tar- 1995). However, on Devon Island N.W.T., where rant, and Tucker 1986). Arctic ecosystems are likely thawed completely in the early 1970s and to be the most altered with climate warming (Max- 1980s, only 30–50% of the ice has melted in 1991– and Barrie 1989; Maxwell 1992, 1995); there is 1996. The overall indications are that there is a a potential for a 2–5Њ C increase in summer tem- warming trend that is within the range of historic peratures. Variations in surface ocean tempera- variability yet that also appears to be a response to tures are believed to play a major role in governing increased levels of CO2. terrestrial climate (Lowe et al. 1994). Recent ice- core data from Greenland (Taylor et al. 1993) in- dicate that these climate changes have been abrupt in the past (as brief as one to two decades). ‘‘Permafrost’’ refers to those areas of soil, rock, and Data for 65 arctic stations from 1881–1981 (Kel- sea floor where the temperature remains below 0Њ C ley and Jones 1981) indicate that 1881–1920 was a for 2ϩ yr. In coarse gravels and frozen rock there is cool period, followed by warming until the early little ice; a dry permafrost predominates. Ice, how- 1950s. Climate warming has continued in Alaska ever, is generally an important component of per- and the western Canadian Arctic in the 1980s and mafrost, reaching 80–100% by volume in massive ice 1990s, whereas areas in the eastern Canadian Arc- wedges and ice lenses. Permafrost underlies all of tic are cooling (Chapman and Walsh 1993; Maxwell the Arctic and extends into the boreal forest,tapering 1995). Other indications of warming are the earlier off as discontinuous permafrost where mean annual melt of snow, especially at Barrow compared with temperature in the atmosphere ranges from Ϫ8.5Њ C the central Canadian Arctic (Foster 1989), the 2Њ C at the northern limit of discontinuous permafrost to rise in permafrost temperature in the past few de- about Ϫ1Њ C at its southern limit. The depth of the cades in northern Alaska (Lachenbruck and Mar- permafrost depends on mean annual temperature, shall 1986), and the more recent data from the Too- thermal conductivity of soil and rock, proximity to lik Lake, Alaska, site. The mean July–August water the sea, and topographic position. Permafrost is Arctic Tundra and Polar Desert Biome 5

Figure 1.2. Diagram of mean maximum and mean mini- Shaver 1985, Arctic, pp. 16–40 in B. F. Chabot and H. A. mum temperatures, snow depth, active-layer depth, and Mooney (ed.), Physiological ecology of North America solar radiation at Truelove Lowland (from NATV, 1st plant communities, Chapman & Hall, New York; with kind edition) and Barrow (From Chapin, F. S. III and G. R. permission of Kluwer Academic Publishers. about 320 m thick at Barrow, 500–600 m in the Mac- mounds (palsas) occur in the Low Arctic but are kenzie River Delta , and 400–650ϩ m through- more limited farther north. The most common fea- out the High Arctic. Mean annual temperature near tures, which are not restricted to the Arctic, are the top of the permafrost table has risen 2Њ C in parts sorted and nonsorted circles and stripes, polygons, of the Arctic in the past 30–100 yr, an indicationofcli- hummocks, and solifluction steps. The circles, mate warming. stripes, and polygons may be 10–25 cm across each Permafrost and the dynamic processes of the an- unit, but many polygons are 3–10 m, even 50–100 m nual freeze–thaw cycle result in many surface fea- in diameter. Raised and depressed-center polygons, tures. Ice-cored hills (pingos) (Fig. 1.3), and small ice sorted and nonsorted circles, soil hummocks, and 6 L. C. Bliss

Figure 1.3. Pingo (ice-cored hill) east of the Mackenzie River Delta. These form in old lake basins when perma- frost invades formerly unfrozen soils. terraces all influence the distribution of plants and nutrients, and synthesis of from weath- the development of soils (Fig. 1.4A–C). Large soil ering of clay all progress very slowly. polygons (Ͼ1 m) are common in lowlands, whereas The early concepts that arctic soils form under stone nets and stripes are typical of uplands. Polyg- processes quite different from those in temperate onal patterns occur on that are level or have regions have been replaced by the realization that gentle slopes (1–3Њ); elongated polygons, stripes,and the same soil-forming processes occur but at greatly solifluction steps are common on slopes Ͼ3–5Њ reduced rates. The process of podzolization is lim- (Washburn 1980). Cushion plants oftenpredominate ited in the Arctic to well-drained soils with a deep ac- on the step (tread), with taller herbs and shrubs pre- tive layer. Where dwarf shrub heath species and dominating on the riser where winter snow cover is dwarf birch predominate, weakly developed pod- deeper and continuous. zols (Spodosols) are found. Soils of uplands and dry Not all patterned ground features result from ice ridges that are less well developed are arctic brown formation. In the High Arctic, many small polygonal soils (Inceptisols). Cushion plant and heath shrub patterns (10–30 cm) result from desiccation cracks communities occur in these areas. The most common (Fig. 1.4D) that form as the silty to sandy soils dry group of soils in the Low Arctic includes the tundra each summer. Vegetated soil hummocks probably soil (Inceptisols) of cottongrass–dwarf shrub heath result from plant establishment, desiccation crack and some sedge communities of imperfectlydrained formation, and the slow accumulation of organic . These soils form under the process of glei- matter as plants grow on the hummocks and theybe- zation. Poorly drained lowlands, where soils remain come more defined (see Fig. 1.4C). Needle ice is an- saturated all summer, accumulate both sedge and other important feature in finer-textured soils. This moss peats. These bog and half-bog soils (Histosols) ice forms in many soils, especially in the fall, and the are dominated by sedge-moss or grass-moss plant resulting lifting of surface soils greatly inhibits seed- communities (Fig. 1.5). ling establishment in some sites. The arctic podzols (Spodosols) and arctic browns (Inceptisols) show some translocation of humus and , with iron-enriched B horizons and weakly elu- Soils 2 viated A2 horizons in the podzols. The surface layers Plant communities and soils are interrelated in the tend to be quite acidic (pH 6–4) and low in available Arctic, as they are in all biomes. Because of re- nutrients but quite well drained above the perma duced plant cover, a short growing season, and the frost layer. Inceptisols of imperfectly drained lands short time since ice retreat (Ͻ12,000 yr) or emer- (arctic tundra soils) are acidic (pH 6.5–4.5), contain B gence from the sea, the soils are less well devel- horizons that have subangular to angular structures, oped than in temperate regions. The presence of are grayish in color with iron oxide mottles, and are permafrost, which limits the vertical movement of low in available nutrients. Histosols of poorly water and the churning of some soils (cryoturba- drained lands are acidic (pH 6.5–5.0) and are similar tion), further restricts soil and plant development. to the arctic tundra soils in having limited transloca- Consequently, chemical decomposition, release of tion of minerals into the B horizon. and (D) desiccation cracks, with and the ‘‘safe development sites’’ of King for Christian vascular Island. plants to grow,

Banks Island; ,

on the top; noteon the Cornwallis pingo Island beyond; within (B) a(C) sorted soil polar polygons deserthummocks with ;

Figure 1.4. Patterned groundraised-center features polygons in in the the Arctic:with Mackenzie (A) sedges River in delta the area troughs and heath shrubs and lichens 8 L. C. Bliss

Figure 1.5. Generalized diagram of major soils in the Arctic (modified from Tedrow 1977).

Within the High Arctic, soil-forming processes warm temperate forests predominated in are further reduced. The very limited lowlands of time (Ӎ 55 M yr BP) (Wolfe 1977). In Miocene time sedge-moss or grass-moss communities have thin (Ӎ 22 M yr BP) there were mixed coniferous- peats, 2–20 cm thick overlying gleyed (arctic tundra) deciduous forests on Devon Island at what is now soils. Many slopes covered with cushion plant–cryp- 75 Њ N (Whitlock and Dawson 1990), and compa- togam communities overlie well-drained soils of the rable forests occupied uplands in central Alaska (Ӎ arctic brown group (Inceptisols). Within the barren 18–15 M yr BP) (Wolfe 1969). By time (Ӎ polar deserts, soils develop under the process of glei- 6–3 M yr BP), coniferous forests still predominated, zation or calcification. These soils are generally basic along with insects typical today of southern British (pH 7.5–8.5), contain very little organic matter, and and northern (Hopkins, are base saturated, but they are very deficient in ni- Matthews, Wolfe, and Silberman 1971). The Beau- trogen and phosphorus. There are some areas where fort Formation, extending from Banks Island (71Њ free carbonates are released from sedimentary rocks N) to Meighen Island (80Њ N) and estimated to be or from recently uplifted marine sediments along of middle Miocene to Pliocene age, contains fossils coastal areas. In these habitats, calcium and magne- of mixed coniferous-deciduous forests (Hills, Klo- sium effervesce on the soil surface during the van, and Sweet 1974). An amazing group of fossil brief warm and drier periods in summer. Halophytic seed plants, mosses, and invertebrates from species predominate in these sites, as they often doin Meighen Island indicates a forest-tundra vegeta- the extremely depauperate marshes in some tion in late Miocene to early Pliocene time on a coastal areas. For a detailed discussion of arctic soils, land surface that is now polar desert. Tundra prob- see Tedrow (1977). ably occurred farther north and at higher eleva- tions on Axel Heiberg and Ellesmere islands and in northern Greenland. Much of the arctic flora and PALEOBOTANY fauna is believed to have evolved in the highlands On a geological basis, arctic ecosystems are rela- of Central (Hoffman and Taber 1967; Yurtsev tively young. The fossil record from Cook Inlet, 1972) and to a more limited degree in the central Alaska, indicates that tropical, subtropical, and and northern (Billings 1974; Arctic Tundra and Polar Desert Biome 9

Packer 1974). From these centers of origin, plants along with the entrance of cottongrass and cotton- and animals spread north and across Beringia to wood pollen. The large fauna changed enrich the biota on both . with the loss of woolly mammoth at about 14,000 A circumpolar flora of perhaps 1500 species de- yr, bison at about 13,000 yr, and horse and wapiti veloped prior to the onset of Pleistocene glaciations at about 10,000 yr BP. Ritchie (1984) has presented (Lo¨ve and Lo¨ve 1974). Glacial advances and retreats, new data from the Bluefish Cave site in the north- with accompanying climatic changes, reduced both ern Yukon indicating that large changes occurred the flora and fauna of these northern lands. The re- in vegetation from herb tundra (15,000–12,000 yr sult is a truly Circumpolar Arctic vascular plantflora BP) to closed and open woodlands at low eleva- of 1000–1100 species, with about 700 of these species tions and to herb tundra in the uplands (9,000 BP occurring in the . to the present). The Late Pleistocene fauna of The evolution of arctic ecosystems in Beringia woolly mammoth, horse, Dall caribou, bison, (the land connection between Alaska and wapiti, and musk-ox shifted to caribou and moose during the Late Pleistocene) and the northern Yu- with major changes in vegetation. This is one of kon Territory has been discussed by Hopkins et al. the very few records in the north that conclusively (1982) and Ritchie (1984). The pollen record from documents simultaneous changes in mammal and the region from the Duvanny Yar In- vegetation patterns. The extinction and reduction terval (30,000–14,000 yr BP) was interpreted as a of large mammal species over a 4000 yr period fairly uniform herbaceous tundra in which upland probably resulted from a combination of climate sedges, grasses, and Artemisia predominated (Col- change that induced major changes in vegetation invaux 1964, 1967; Matthews 1974). It was assumed and from overhunting by (Martin 1974, that this vegetation was similar to that of the 1982). Grayson (1991) presents evidence that the tundra of eastern Siberia and that it occu- extinction of 35 genera of occurred pied much of northern Alaska and the Yukon Ter- over several thousand and that the overkill ritory. More recent studies by Ager (1982), Ander- hypothesis alone does not adequately explain the son and Brubaker (1986, 1994), Anderson, Reanier, large number of extinct mammals. and Brubaker (1988) in Alaska, and Cwynar and Studies indicate that a warmer period prevailed Ritchie (1980), Ritchie (1984, 1987), and Ritchie, across northern Alaska, the central Yukon, and the Cwynar, and Spear (1983) in the Yukon indicate adjacent N.W.T. from 10,000–6500 yr BP (Ritchie that more mesic graminoid communities typified 1984, 1987; Anderson et al. 1988; Cwynar and the western lowlands and that more xeric Spear 1991). Balsam poplar formed gallery forests herbaceous communities dominated eastern and localized groves. Open stands of white spruce Alaska and the Yukon Territory. Ericaceous heath dominated uplands from 9400–5000 yr when cli- shrubs probably have been underestimated be- mate cooled and shrub and tundra again cause of their low pollen production. Spruce be- became dominant. came extinct, and balsam poplar and aspen became more restricted during that period. Willow scrub VEGETATION was confined to river bottoms, as today. Although many fossils remains of large mam- Given the diversity of arctic landscapes (moun- mals have been found in central Alaska, most have tains, Precambrian Shield, low-elevation lands) and been reworked by rivers, so that accurate carbon their great latitudinal extent (55Њ along Hudson dates are difficult to determine. Earlier studies by Bay to 83Њ at northern Ellesmere Island and Green- Guthrie (1972) indicated that an arctic grassland land), with associated climatic changes, it is not must have predominated to support these mam- surprising that there are diverse patterns of plant mals. However, more recent studies and summa- communities. Although arctic vegetation has a gen- ries of various research indicate little basis for this eral structure and pattern of herbaceous species belief (Ritchie 1982, 1984; Ritchie and Cwynar 1982; and (often) low scattered shrubs, not all of it has Schweger 1982). Relict examples of this ‘‘mammoth the same appearance. steppe’’ exist in Alaska today on steep south-facing The major types include (1) tall shrub tundra river bluffs. Dominants include Artemisia frigida, (Salix, Alnus, Betula 2–5 m high) along river ter- Agropyron spicatum, and Calamagrostis purpurascens races, banks, steep slopes, and lake shores; (Wesser and Armbruster 1991). (2) low shrub tundra (Salix, Betula 40–60 cm high) The Birch Zone (14,000–12,000 yr BP) was a on slopes and uplands beyond the forest tundra; warmer period during which a rapid rise in the sea (3) dwarf shrub heath tundra (5–20 cm high) and level drowned the Bering land bridge. The increase cottongrass–dwarf shrub heath tundra (tussock in birch pollen indicates a rise in shrub tundra tundra) on rolling terrain with soils of intermediate 10 L. C. Bliss drainage; (4) graminoid-moss tundra (20–40 cm However, lichens and mosses are slow to return. high) on poorly drained soils; and (5) cushion In the Mackenzie River delta region, it takes about plant–herb–cryptogam polar semidesert (2–5 cm 200ϩ yr for an extensive cover to develop high) on wind-exposed slopes and ridges with lim- on the fine-textured soils (Black and Bliss 1978). On ited snow cover. This last vegetation is more sandy soils to the southeast, where shrubs are mi- typical of the High Arctic. nor, a lichen cover developed in 60–120ϩ yr in the There are general reductions in total plant Abitan Lake region (Maikawa and Kershaw 1976). cover, plant height, and woody and vascular plant Studies conducted near Inuvik, N.W.T., indicate species and increases in lichens and mosses from that there is a period of only 5–8 yr following fire the Low Arctic to the High Arctic. At the final limit during which seedlings of Picea mariana have a of plant growth in the polar desert barrens, the ul- chance to become established, because of a short timate restriction to plant growth appears to be period of seed viability, rapid seed release from soils which are saturated in the but of which surviving cones, and seed destruction by rodents the upper 1–2 cm bakes hard later in some sum- and insects (Black and Bliss 1980). Massive fires mers, preventing seedling establishment. These within the forest tundra could drive the treeline soils lack nitrogen and phosphorus and have few 50–100 km south should they occur during a cool safe sites in which vascular plants can become es- climatic period, for the seeds germinate only when tablished because of the lack of cryptogamic crusts temperatures are Ͼ15Њ C. Chapter 2 describes this that provide sites with more water and nutrients. vegetation and the role of fire in more detail. These bare soils also favor an abundance of needle ice in autumn. Plant limits are not caused by tem- Low Arctic Tundra perature alone, because vascular plants grow to within a few meters of and ice caps at el- The general appearance of most landscapes within evations of 650–720 m on Ellesmere and Devon is- the Low Arctic is that of a grassland in which low lands (Bliss et al. 1994). to dwarf shrubs are common, except in the wetter A vegetation classification system that follows habitats. The vascular flora in an area of 100–200 Russian concepts of the Arctic and an associated km2 may total 100–150 species, although any single circumpolar vegetation map are still under devel- plant community may have only 10–50 species of opment (Walker et al. 1995). vascular plants and 20–30 species of mosses and lichens. Forest Tundra Tall shrub tundra. The rivers that flow across the Throughout northern Alaska and Canada there is tundra have sandbars and gravel bars, islands, and a relatively narrow zone, 10–50 km wide, of forest terraces with well-drained soils that are relatively tundra. This vegetation consists of scattered warm, have a deep active layer (1–1.5 m), and con- clumps of trees in more protected sites where snow tain higher nutrient levels than do adjacent up- accumulates within a matrix of low shrub tundra. lands. These habitats and steeper slopes above An added factor in the role of climate (position of lakes and rivers that have a deep snow cover in the Arctic Front) is the role of soils. In Canada, winter (2–5 m) are generally covered with various where the forest tundra lies farther north, the tran- mixtures of Salix, Betula, and Alnus. In arctic sition zone is narrower and the soils tend to be Alaska, the Yukon, and the northwestern North- more nutrient-rich and of finer texture. Where the west Territories, Salix alaxensis predominates on transition zone lies south of the climatic poten- the coarser-textured alluvium, sands, and tial for forest, the zone is wider and the soils are slopes (Fig. 1.6). Associated shrubs, 1–2 m high, of nutrient-poor and more droughty (Timoney, lesser importance and of varying abundance from LaRoi, Zoltai, and Robinson 1992, 1993; Timoney site to site, include S. arbusculoides, S. glauca ssp. 1995). richardsonii, S. pulchra, and Alnus crispa (Table 1.3) In many places, the transition from forest tun- (Bliss and Cantlon 1957; Drew and Shanks 1965; dra to shrub tundra consists only in loss of stunted Johnson, Viereck, Johnson, and Melchior 1966; Gill trees. Because of this patterning, earlier Russian 1973; Komarkova and Webber 1980). There is often ecologists considered shrub tundra a part of the a rich understory of grasses and forbs in these rather than the Arctic (Aleksandrova shrub communities. 1980), for they believed that fire had eliminated the Depauperate outliers of the Salix alaxensis, S. trees in many places. Repeated fires within these lanata ssp. richardsonii, S. pulchra shrub community, Subarctic communities have little effect on the un- with sedges and forbs, occur along rivers and steep derstory vascular plants, for they easily resprout. slopes on southern Banks and Victoria islands (Kuc Arctic Tundra and Polar Desert Biome 11

Figure 1.6. Tall shrub tundra domi- nated by Salix alaxensis with lesser amounts of S. glauca ssp. desertorum, S. arbusculoides, and herbaceous plants including Lupinus arcticus, Hedysarum mackenzii, Deschampsia caespitosa, and Agropyron sericeum, on river gravels along the Colville River, Umiat, Alaska.

1974) within the southern High Arctic. Salix alax- In much of the northeastern mainland of Can- ensis is usually only 0.5–1.5 m tall, and the stands ada, low shrub tundra is minor, probably because look similar to those in the upper river drainages of limited winter snow and abrasive winter winds on the north slope of the Brooks Range. (Savile 1972). In the Chesterfield Inlet of , northern , and southern Baffin Island, Low shrub tundra. Plant communities dominated the dominant shrubs are Betula glanulosa, Salix by varying combinations of dwarf birch, low wil- glauca ssp. callicarpaea, and the aforementioned lows, heath species, scattered forbs, and grami- heath species, graminoids, and cryptogams (Po- noids are common on rolling uplands beyond the lunin 1948). forest tundra in Alaska and northwestern Canada In Greenland, low shrub occur in the (Hanson 1953; Corns 1974). Open forest and forest inner regions that are warmer in summer. tundra may have occupied these lands in north- These shrub communities, dominated by Salix in the past, but fires and changing glauca ssp. callicarpaea, Betula nana, and B. glandu- climate have forced the treeline south (Ritchie and losa predominate on steep slopes and along Hare 1971; Ritchie 1977). and rivers from Disko Island (69ЊN) and The open canopy of shrubs is 40–60 cm high Sønder Stromfjord (67Њ N) southward. The shrubs and is dominated by Betula nana ssp. exilis, Salix (Ͼ1 m in height) are associated with herbs and glauca ssp. acutifolia, S. planifolia ssp. pulchra, and S. dwarf heath shrubs (Bo¨cher 1954, 1959; Hansen lanata ssp. richardsonii, with the combinations of 1969). species varying from place to place (Fig. 1.7). Ground cover includes lugens and C. bigelovii Dwarf shrub heath tundra. As used here, ‘‘heath’’ in Alaska (C. bigelowii alone in the Northwest Ter- refers to species within the Ericaceae, Empetraceae, ritories), Eriophorum vaginatum, and numerous and Diapensiaceae. Some authors have broadened forbs, grasses, and heath shrubs (10–20 cm high). the concept to include Dryas and dwarf species of Varying combinations of Vaccinium uliginosum, V. Salix. A characteristic feature of these heath plants vitis-idaea ssp. minus, Empetrum nigrum ssp. herma- is the evergreen , although deciduous-leaved phroditum, Ledum palustre ssp. decumbens, Arctos species also occur (Vaccinium uliginosum, Arctosa- (Arctostaphylos) alpina, A. rubra, Rubus chamaemorus, taphylos alpina, A. rubra). Heath-dominated com- and dwarf species of Salix occur along with an munities occur on well-drained soils of river ter- abundant ground cover of lichens and mosses (Ta- races, slopes, and uplands where winter snows are ble 1.3). Where snow lies late into June, the heaths at least 20–30 cm deep. Heath tundra occupies rel- are often dominated by Cassiope tetragona. The most atively small areas, a few hundred meters square, common mosses include Aulacomnium turgidum, rather than the many hectares or square kilometers Hylocomium splendens, and Polytrichum juniperinum. of other tundra vegetation types. Important fruticose lichens are Cetraria nivalis, C. In western Alaska (Hanson 1953; Churchill cucullata, Cladonia gracilis, Cladina mitis, C. rangifer- 1955; Johnson et al. 1966), the northern Yukon ina, and Thamnolia vermicularis. (Hettinger et al. 1973), and the Mackenzie River 12 L. C. Bliss

Table 1.3. Prominence values (cover ϫ square root of frequency) for plant communities in the Low Arctic at Umiat, Alaska. Sampling area for each stand was 10 mϪ2.

Plant communities

Species Tall shrub Low shrub Cottongrass-heath Cushion plant Graminoid-moss

Eriophorum vaginatum —— 90— — Arctagrostis latifolia 29 27 19 — 27 Carex lugens —3027— — Carex glacialis —— — 27— confusa — — 19 — — Dryas integrifolia —— — 90— Ledum palustre ssp. decumbens 93030— — Vaccinium vitis-idaea 92970— — Vaccinium uliginosum 14 23 — — — Arctostaphylos alpina —212719— lapponicum —— — 9 — Cassiope tetragona —14299 — Empetrum nigrum ssp. hermaphroditum —2127— — Rubus chamaemorus —— 25— — Salix planifolia ssp. pulchra 80 14 9 — — Salix glauca ssp. acutifolia 9 29 — 25 — Betula nana ssp. exilis 93030— — Alnus crispa 375 23 — — — Pedicularis lanata —— — 25— Lupinus arcticus —— — 29— Saussurea angustifolia —14— — — Saxifraga punctuta —1419— — Saxifraga cernua 14 — — 9 29 Polemonium acutiflorum —14— — — Petasites frigidus 9— 19— — Polygonum bistorta —2316— — Pyrola grandiflora 21 25 — — Stellaria longipes —— — — 27 Caltha palustris —— — — 23 Carex aquatilis — — — — 375 —— — — 21 Cardamine pratensis —— — — 16 Hedysarum alpinum —— — 1929 Mosses 29 190 625 30 90 Lichens — 90 375 — — Total vascular species 13 20 17 17 9

Source: Churchill (1955)

Delta region (Corns 1974), communities of heath tragona dominating (Larsen 1965, 1972). Where species (10–20 cm high) are quite common. The snow is deep, Betula glandulosa and highly de- species occur in various combinations including formed Picea mariana (60–90 cm high) occur near Ledum palustre ssp. decumbens, Vaccinium uligi- the treeline at Ennadai. nosum, V. vitis-idaea, Empetrum nigrum ssp. herma- At Chesterfield Inlet along the west coast of phroditum, Loiseleuria procumbens, Rhododendron lap- Hudson Bay, at Wakeham Bay in northern Quebec, ponicum, R. kamschaticum, and Cassiope tetragona. and at Lake Harbour, Baffin Island, heath vegeta- Betula nana ssp. exilis and one or more species of tion is common. The dominant species include V. dwarf Salix are commonly associated, along with uliginosum, Ledum palustre ssp. decumbens, Empe- abundant lichens and mosses. trum nigrum ssp. hermaphroditum, Phyllodoce caeru- In the Keewatin District, N.W.T, west of Hud- lea, and the sedge Carex bigelovii. Where snow lies son Bay, dwarf shrub heath predominates on north into July, Cassiope tetragona dominates, with Salix exposures, fellfields, and gravel summits. Here, the reticulata, S. herbacea, Dryas integrifolia, Carex mis- heaths are less rich floristically, with Ledum palustre andra, , and numerous lichens and ssp. decumbens, V. uliginosum, V. vitis-idaea, Empe- mosses (Polunin 1948). trum nigrum ssp. hermaphroditum, and Cassiope te- In southeast and west Greenland, heath vege- Arctic Tundra and Polar Desert Biome 13

Figure 1.7. Low shrub tundra domi- nated by Salix planifolia ssp. pulchra, Salix glauca ssp. acutifolia, Betula nana ssp. exilis, Vaccinium uligi- nosum, V. vitis idaea, Empetrum ni- grum ssp. hermaphroditum, Ledum palustre ssp. decumbens, and Carex lugens in the Brooks Range.

Figure 1.8. Cottongrass–dwarf shrub heath tundra in the Caribou Hills, northeast of Inuvik, N.W.T. tation is found on steep, moist slopes, usually in and Salix arctica (Sørensen 1943), as they do on inland valleys, which have a warmer and drier Ellesmere in the High Arctic. as compared with the moist maritime climate along the coast and outer Cottongrass–Dwarf shrub heath tundra. Large areas (Bo¨cher 1954). Species dominating in various com- of rolling uplands between the mountains and the binations include Cassiope tetragona, Vaccinium uli- wet coastal plain in Alaska and the Yukon Terri- ginosum ssp. microphyllum, V. vitis-idaea ssp. minus, tory are dominated by tussocks of Eriophorum va- Ledum palustre ssp. decumbens, Rhododendron lappon- ginatum, dwarf shrubs, lichens, and mosses (Han- icum, Phyllodoce caerulea, Empetrum nigrum ssp. her- son 1953; Churchill 1955; Britton 1957; Johnson et maphroditum, and Loiseleuria procumbens (Sørensen al. 1966; Hettinger et al 1973; Wein and Bliss 1974; 1943; Bo¨cher 1954, 1959, 1963; Bo¨cher and Laegaard Komarkova and Webber 1980). This vegetation 1962; Hansen 1969; Daniels 1982). Betula nana is a type is of limited occurrence in the Northwest Ter- component of the more southern heaths. Ledum, ritories, except in the Mackenzie River Delta region Phyllodocae, and Loiseleuria drop out in the Melville (Corns 1974), where it is common (Fig. 1.8), and it Bugt region (72–75Њ N). At Thule (78Њ N) the dom- is absent from most of the eastern Canadian Arctic, inant species of the limited heaths include Cassiope with the exception of southern Baffin Island and tetragona, Vaccinium uliginosum ssp. microphyllum, northern Quebec (Polunin 1948). 14 L. C. Bliss

Historically, these landscapes have been called scheuchzeri are common (Fig. 1.9) in low-center cottongrass tussock tundra or tussock–heath tun- polygons and in the troughs of high-center poly- dra because of the conspicuousness of the cotton- gons (Britton 1957; Hettinger et al. 1973; Corns grass tussocks. However, the phytomass, net an- 1974). The nearly continuous cover of mosses in- nual production, and cover of heath and low shrub cludes species of Aulacomnium, Ditrichum, Callier- species often are greater than for cottongrass. The gon, Drepanocladus, Sphagnum, Hylocomium splen- Alaskan and western Canadian cottongrass is E. dens, and Tomenthypnum nitens (Britton 1957; vaginatum ssp. vaginatum, whereas the subspecies Johnson et al. 1966). spissum occurs in the eastern Arctic. Studies of plant succession in the thaw-lake cy- The predominant heath species are V. vitis-idaea cle of northern Alaska have shown that high-center ssp. minus, V. uliginosum ssp. alpinum, Ledum pal- polygons form in drained lake basins from the ustre ssp. decumbens, and Empetrum nigrum ssp. her- melting of ice wedges and postdrainage thermo- maphroditum. Scattered low shrubs of Betula nana karst . plants include the moss ssp. exilis and Salix pulchra are common, along with Psilopilum cavifolium on dry peaty sites and the Carex bigelovii, C. lugens, and several species of graminoids Arctophila fulva in wet sites, and Erio- forbs (Table 1.3). The cryptogam layer is well phorum scheuchzeri and Dupontia fisheri in the moist developed and includes the mosses Dicranum swales. Eriophorum angustifolium and Carex aquatilis elongatum, Aulacomnium turgidum, A. palustre, enter somewhat later, but in time they predomi- Rhacomitrium lanuginosum, Hylocomium splendens, nate (Britton 1957; Billings and Peterson 1980). Tomenthypnum nitens, and several species of Sphag- Sedge-dominated wet meadows are found in num. The most common lichens include Cetraria the Ennadai area (Larsen 1965), Chesterfield Inlet, cucullata, C. nivalis, Cladina rangiferina, C. mitis, Cla- northern Quebec, and Lake Harbour (Polunin donia arbuscula, Dactylina arctica, and Thamnolia ver- 1948). Common species include Eriophorum angus- micularis (Bliss 1956; Johnson et al. 1966). tifolium, E. scheuchzeri, Carex rariflora, C. membran- acea, and C. stans (Polunin 1948). Graminoid-moss tundra. The concept of arctic tun- In Greenland, graminoid-moss tundra is pres- dra is often associated with treeless wetlands in ent, but as with large areas of , the which species of Carex, Eriophorum, and sometimes marshes are less common. Important species in- the grasses Arctagrostis, Dupontia, Alopecurus, and clude Carex rariflora, C. vaginata, C. holostoma, Er- Arctophila predominate, along with an abundance iophorum angustifolium, and E. triste (Bo¨cher 1954, of bryophytes, but few lichens. In northern and 1959). western Alaska, arctic wetland meadows are of mi- nor extent in the mountain valleys, but they in- Other graminoid vegetation. With thousands of crease in importance in the Foothill Province and kilometers of arctic shoreline, one might assume dominate the Coastal Plain Province (Churchill that salt marshes, coastal dune complexes, and 1955; Britton 1957; Webber 1978; Komarkova and other coastal vegetation would be common. Such Webber 1980). Arctic wetlands are again minor in is not the case, for favorable habitats are limited. the Yukon mountains, but they increase in impor- Factors that restrict arctic salt marshes are the lim- tance on the coastal plain and eastward to the Mac- ited areas of fine sands and silts, the annual re- kenzie River region (Hettinger, Janz, and Wein working of shorelines by sea ice, a modest tidal 1973; Corns 1974). amplitude, the low salinity of coastal waters, a The dominant sedges are Carex aquatilis, C. rar- very short growing season, and low soil tempera- iflora, C. rotundata, C. membranacea, Eriophorum an- tures. Coastal salt marshes have been described gustifolium, E. scheuchzeri, and E. russeolum (Table from subarctic Alaska (Vince and Snow 1984), 1.3). The grasses Arctagrostis latifolia, Dupontia fish- northern Alaska (Jefferies 1977; Taylor 1981), eri, Alopercurus alpinus, and Arctophila fulva occur Tuktoyaktuk (Jeffries 1977) and Hudson Bay, along a gradient from drier sites to saturated soils N.W.T. (Kershaw 1976; Bazely and Jefferies 1986a), and standing water. In shallow waters of lakes and the west-central part of southern Greenland ponds (50–60 cm deep), Menyanthes trifoliata, Eq- (Søorensen 1943; Vestergaard 1978), and Devon, uisetum variegatum, and Arctophila fulva predomi- Ellesmere, and Baffin islands (Polunin 1948; Jeffer- nate, with Potentilla palustris and Hippuris vulgaris ies 1977; Muc, Freedman, and Svoboda 1989; Bliss in water 20–30 cm deep. The various species of and 1994). See also Chapter 13 of this volume. Carex and Eriophorum and Dupontia fisheri occur Many of these marshes have only a 5–20% plant with little (10–20 cm deep) or no standing water. cover, with plant heights of 1–5 cm. Floristically, Carex aquatilis, Eriophorum angustifolium, and E. most salt marshes have only three to five herba- Arctic Tundra and Polar Desert Biome 15

Figure 1.9. Graminoid-moss tundra in the High Arctic dominated by Dupon- tia fisheri on Melville Island. ceous species, none of which is woody or belongs Low Arctic Semidesert: to the Chenopodiaceae, a family of plants common Cushion Plant–Cryptogam in temperate and tropical latitudes. The most com- mon species are Puccinellia phryganodes on mud, From the Rocky Mountains of north to with scattered clumps of Carex ursina, C. ramenskii, the Yukon Territory and Alaska, windswept slopes C. subspathacea, Stellaria humifusa, and Cochlearia of- and ridges are often dominated by cushions or ficinalis. In many ways it is quite amazing that mats of Dryas integrifolia and D. octopetala. This there are any species at all adapted to living in vegetation type, often called Dryas fellfield or these harsh coastal environments, in contrast with Dryas tundra, is limited in areal extent within the the extensive and highly productive salt marshes western Low Arctic but increases in importance in of temperate regions. the large areas of barren rock and lag gravel sur- The Puccinellia marshes along Hudson Bay are faces in the eastern Arctic. In the Mackenzie Dis- heavily grazed by lesser snow geese. Grazing in trict and Keewatin District, N.W.T., where acidic summer increases the aboveground net primary soils derived from predominate, Dryas is production of these marshes by 40–100% because less prominent. Other cushion plants include Silene the geese produce so many droppings that accel- acaulis, Saxifraga oppositifolia, and S. tricuspidata. erate nitrogen cycling (Bazely and Jefferies 1986b; The lichens Alectoria nitidula, A. ochroleuca, Cetraria Jefferies 1988) in what are nitrogen-limited sys- cucullata, and C. nivalis, along with the moss Rha- tems. comitrium lanuginosum, are common in the Repulse Beach and dune grasslands are minor features Bay, Peely Lake, and Snow Bunting Lake areas in the Arctic. Elymus arenarius ssp. mollis often (Larsen 1971, 1972). dominates, with small amounts of the semisuccu- Within the ecotone between forest and tundra lents Honckenya peploides, Mertensia maritima, and in the Campbell–Dolomite uplands near Inuvik, Cochlearia officinalis ssp. groenlandica, along with N.W.T., mats of Dryas integrifolia and Cladonia stel- Festuca rubra and Matricaria ambigua (Barbour and laris cover the and dolomite rocks. Christensen 1993). Where small pockets of soil occur, open stands of Small areas of grassland are found in the inner Picea glauca predominate (Ritchie 1977). In the fjords of east-central Greenland, dominated by Cal- Brooks Range (Spetzman 1959) and northward amagrostis purpurascens, Arctagrostis latifolia, Poa arc- along exposed ridges within the Foothill Province, tica, and P. glauca (Seidenfaden and Sørensen 1937; Dryas-lichen vegetation is common. Dryas integri- Oosting 1948). In west Greenland, larger areas (1– folia or D. octopetala and their hybrids often com- 5 ha) of grassland occur that are dominated by Cal- prise 80–90% of the vascular plant cover. Associ- amagrostis neglecta, , and P. arctica ated species include Silene acaulis, Carex rupestris, (Bo¨cher 1959). Similar small grasslands are found C. capillaris, Kobresia myosuroides, Anemone parvi- in the eastern Canadian Arctic of Baffin Island (Po- flora, and Polygonum viviparum. Cushions of Dryas lunin 1948) and northern Keewatin (Larsen 1972). are often 0.5–1.0 m across, and they seldom reach 16 L. C. Bliss a height greater than 2–5 cm. The ground cover of lands, including northern Melville Island, the grass herbs, lichens, and mosses is generally sparse. As Dupontia fisheri dominates (Fig. 1.9), with lesser a result, there is often much bare rock and soil, amounts of Juncus biglumis and Eriophorum triste in although crustose lichens are often common. wetlands. Where there are shallow ponds, Pleuro- pogon sabinei occurs – the ecological equivalent of Arctophila fulva to the south (Savile 1961; Bliss and High Arctic Tundra Svoboda 1984). In contrast with the Low Arctic, the High Arctic is Bryophytes are abundant in the various wetland characterized by herbaceous rather than woody plant communities, including Orthothecium chry- species, and there is generally much less plant seum, Campylium arcticum, Tomenthypnum nitens, cover, especially of vascular plants. Lichens and Drepanocladus revolvens, Ditrichum flexicaule, and mosses contribute a much larger percentage of to- Cinclidium arcticum. are abundant, tal cover and than in the Low Arctic. Vast including species of Nostoc and Oscillatoria. Lichens areas are dominated by lichens and mosses, with are minor in these wetlands. only a 5–25% cover of flowering plants. Equally large areas of polar deserts have almost no cryp- Dwarf shrub heath tundra. Compared with the togams (0–3% cover) and only a 0.1–4% cover of Low Arctic, these heaths have few species, and vascular plants (Table 1.1). Vascular plants are they are almost always in snowbed sites that melt much smaller in size (3–10 cm) than those of the by early July. The heaths of central and northern same species (10–30 cm) in the Low Arctic, and Baffin Island are richer floristically than elsewhere. their root systems are also smaller. Cassiope tetragona is the dominant and characteristic Based on vegetation types, the High Arctic can species and is commonly associated with Vaccin- be divided into small areas of tundra (tall shrub, ium uliginosum ssp. microphyllum, Salix herbacea, S. dwarf shrub heath, cottongrass tussock, and arctica, Carex bigelovii, Luzula nivalis, and L. confusa. graminoid-moss), vast areas of cushion plant– Important lichens and mosses include Cladina mitis, cryptogam and cryptogam-herb polar semidesert, Dactylina arctica, Aulacomnium turgidum, Drepano- herb barrens, and very limited snowflush herb- cladus uncinatus, Hylocomium splendens, and Rha- moss vegetation of the polar deserts. With the ex- comitrium lanuginosum (Polunin 1948). ception of a few locations, woody species other Heath vegetation is sparse in western Green- than dwarf willows and semiwoody Dryas and land in terms of species and areal extent. Cassiope Cassiope are very minor components. dominates, with lesser amounts of Salix arctica, Dryas integrifolia, and (Sørensen Graminoid-moss tundra. Of the common vegeta- 1943). Small areas of heath with Cassiope, Dryas, tion types in the Low Arctic, only the graminoid- and Salix occur in northern Greenland at 81–83; dg moss tundra is ecologically important farther N (Holmen, 1957). north. It occupies 5–40% of the lands on the south- Farther north and west in the Queen Elizabeth ern islands, with the exception of Baffin Island, Islands, the depauperate heaths are dominated by which is mountainous. In the Queen Elizabeth Is- Cassiope, Dryas, and Luzula. Only in the warmer lands, Ͻ2% of the area contains this vegetation, yet eastern High Arctic is Vaccinium uliginosum ssp. mi- it provides the major grazing for musk-ox crophyllum present (Fig. 1.10) (Beschel 1970; Bras- and breeding grounds for waterfowl and shore sard and Longton 1970; Bliss, Kerik, and Peterson birds. 1977; Reznicek and Svoboda 1982; Muc et al. 1989). In the eastern and southern islands, Carex stans Lichens and mosses are also common in these (C. aquatilis) and C. membranacea are the dominants, heaths. with lesser amounts of , E. triste, Dupontia fisheri, and Alopecurus alpinus. Small Other tundra vegetation types. Cottongrass tus- clumps of Salix arctica and Dryas integrifolia are re- sock and tall shrub tundra occupy small areas on stricted to moss hummocks or rocky areas within Banks and Victoria islands, the northern limits for the wet meadows – the best-drained and best- these common vegetation types of the Low Arctic. aerated microsites. Plant communities of this veg- Tussock tundra is dominated by Eriophorum vagin- etation type occur where drainage is impeded atum ssp. vaginatum, with scattered plants of Vac- along river terraces, small valleys, and coastal low- cinium vitis-idaea ssp. minus, the only heath species, lands (Beschel 1970; Bird 1975; Muc 1977; Thomp- and a few other vascular species and cryptogams. son 1980; Sheard and Geale 1983; Freedman et al. Along some of the rivers and near the lakes of 1983; Bliss and Svoboda 1984; Muc et al. 1989; these same southern islands, there are small willow Schaefer and Messier 1994). In the northwestern is- thickets (0.5–1.5 m), with Salix alaxensis and S. pul- Arctic Tundra and Polar Desert Biome 17

Figure 1.10. Dwarf shrub heath tun- dra dominated by Cassiope tetragona with lesser amounts of Dryas integri- folia, Vaccinium uliginosum ssp. mi- crophyllum, and Luzula parviflora. Note the wet sedge-moss meadows beyond, Truelove Lowland, Devon Is- land. chra (Kuc 1974) and in southeastern Victoria Island 1994), Devon Island (Svoboda 1977), Ellesmere Is- S. lanata ssp. richardsonii (Schaefer and Messier land (Brassard and Longton 1970; Freedman et al. 1994). 1983; Muc et al. 1989), Bathurst Island (Sheard and Geale 1983; Bliss, Svoboda, and Bliss 1984), Corn- High Arctic Semidesert wallis and Somerset islands (Bliss et al. 1984), and South Hampton Island (Reznicek and Svoboda Arctic vegetation and plant communities included 1982). These landscapes are the major habitats for within this landscape unit have generally been Peary’s caribou, collared , ptarmigan, and considered polar desert (Aleksandrova 1980; several species of passerine birds. Andreyev and Aleksandrova 1981). However, in terms of plant cover, plant and animal biomass, Cryptogam–herb vegetation. This vegetation type species richness, and soil development, the High is common on the western Queen Elizabeth Is- Arctic semidesert is so different from barren polar lands, where the previous vegetation type is minor deserts that the two have been separated for North or totally lacking. Cryptogam–herb vegetation America (Bliss 1975, 1981). Areas of polar semides- covers low rolling uplands with sandy to silty and ert cover about 50–55% of the southern islands and clay loam soils. Vascular plants contribute 5–20% about 25% of the northern islands. The two major cover and cryptogams 50–80%. vegetation types include cushion plant–cryptogam Alopecurus alpinus, Luzula confusa, and L. nivalis and cryptogam–herb. are the common graminoids, along with three to five species of Saxifraga, Papaver radicatum, Draba Cushion plant–cryptogam vegetation. Large areas corymbosa, Cerastium alpinum, and Juncus albescens of the southern islands and the Boothia and Mel- (Table 1.4). Abundant bryophytes include the ville peninsulas are covered with large mats of mosses Rhacomitrium lanuginosum, R. sudeticum, Dryas integrifolia. Associated species include Salix Aulacomnium turgidum, Polytrichum juniperinum, arctica, Saxifraga oppositifolia, S. caespitosa, S. cernua, Pogonatum alpinum, Ditrichum flexicaule, Dicranow- Draba corymbosa, Papaver radicatum, and two to eisia crispa, Tomenthypnum nitens, and Schistidium three species each of Minuartia and Stellaria. Gra- holmenianum, and in wetter soils, the liverwort minoids are always present as scattered plants, in- Gymnomitrion corallioides. Common lichens include cluding Carex rupestris, C. nardina, Luzula confusa, crustose Lecanora epibryon, Lepraria neglecta, and and Alopecurus alpinus (Table 1.4). Lichens and Dermatocarpon hepaticum, and fruticose Cladonia mosses provide 30–60% of the total plant cover; gracilis, Parmelia omphalodes, Cetraria cucullata, C. de- vascular plants provide 5–25% of the cover (Fig. lisei, C. nivalis, and Dactylina ramulosa. There is of- 1.11). ten a black cryptogamic crust of lichens, mosses, This vegetation is common on rolling uplands, cyanobacteria, and fungi on soils (Bliss and Svo- gravelly raised beaches, and river terraces that are boda 1984). Seeds of vascular plants germinate at drier and warmer than surrounding lands in sum- random on a variety of microsite surfaces, but their mer. Plant communities of this type have been de- survival to adult plants is strongly favored by moss scribed from Victoria Island (Schaefer and Messier mats or desiccation cracks where mosses are also 18 L. C. Bliss

Table 1.4. Prominence values (cover ϫ square root of frequency) for plant communities in the High Arctic. Sampling area for each stand was 40 mϪ2.

Plant communities

Cushion plant Cryptogam-herb Graminoid-steppe Snowflush Herb barrens Species 31S 4M 27ER 12C 19C

Dryas integrifolia 28 — — — — Saxifraga oppositifolia 8——4— Saxifraga caespitosa —11—1— Saxifraga hieracifolia —9——— Saxifraga cernua —10—1— Saxifraga flagellaris —17—9— Phippsia algida ————— Papaver radicatum —14—62 Cerastium alpinum —4——— Oxyria digyna —7——— Ranunculus sulphureus —4——— Minuartia rubella —3——— Stellaria crassipes —6——— Draba corymbosa —2—59 Draba subcapitata —1——— Festuca brachyphylla —14——— Alopecurus alpinus —3720—— Puccinellia angustata ————6 Luzula confusa —681—— Luzula nivalis —52—— Mosses — 116 76 66 — Lichens 22 41 24 14 — Total vascular species 6 19 4 14 5

Note: Sampling area for each stand was 40 m2. Source: Data from Bliss and Svoboda (1984) and Bliss et al. (1984).

Figure 1.11. Cushion plant–crypto- gam vegetation of the polar semides- erts. Dryas-dominated community with lesser amounts of Saxifraga op- positifolia, and Salix arctica with Cas- siope tetragona in the small depres- sions, Thomson River, Banks Island. important (Sohlberg and Bliss 1984). Plant com- Large areas of fine sand to clay munities within this vegetation type have been de- Graminoid steppe. loam soils are dominated by Luzula confusa and Al- scribed from Axel Heiberg Island (Beschel 1970), opecurus alpinus on Ellef Ringnes and King Chris- Melville, Cameron, King Christian, and Ellef Ring- tian islands which is seen in Figure 1.12. Other nes islands (Bliss and Svoboda 1984), Laugheed Is- areas on Melville, Laugheed, King Christian, and land (Edlund 1980), and Prince Patrick Island (Bird Ellef Ringnes islands are dominated by A. alpinus 1975). Arctic Tundra and Polar Desert Biome 19

Figure 1.12. Luzula confusa and Alo- pecurus alpinus dominate this grami- noid steppe on Ellef Ringnes Island. on black soils derived from shales of the Lower within the polygonal patterns (sorted nets and Cretaceous age. There are very few herbs or cryp- stripes). Cryptogams were seldom present in close togams associated with Alopecurus (Bliss and Svo- association with vascular plants, in contrast to po- boda 1984). This great reduction in species richness lar semidesert and snowflush habitats within this may result from soil churning, which is so common barren landscape, where moss mats and crypto- in these dark soils, as well as low nutrient status. gamic crusts are preferred sites for vascular plants. Alopercurus is rhizomatous and can tolerate soil Of the vascular plants recorded, Draba corymbosa, movement. D. subcapitata, Papaver radicatum, Minuartia rubella, Saxifraga oppositifolia, and Puccinellia angustata were most commonly present (Table 1.4). The most im- High Arctic Polar Desert portant cryptogams were Hypnum bambergeri, Tor- Herb barrens. Landscapes that are almost totally tula ruralis, Thamnolia subuliformis, Dermatocarpon devoid of plants occupy thousands of square kil- hepaticum, and Lecanora epibryon (Bliss et al. 1984). ometers, especially in the Queen Elizabeth Islands The lack of lichens on rocks and the very depau- (Fig. 1.13A). These landscapes occur from near sea perate flora and plant cover suggest that these level (10–20 m) to upland at over 200–300 lands, especially uplands, may have become veg- m. The basic controls appear to be the geologic etated only since the Little (130–430 yr BP) substrate (which influences soil development), the (Svoboda 1982). very low amount of soil nutrients, formation of Not all uplands in the High Arctic constitute needle ice in autumn, surface soil drying (1–2 cm) true polar deserts. The uplands above Alexandra in many summers, and a very short growing sea- Fiord, Ellesmere Island, are much richer in vascu- son (1–1.5 mo). Soil texture ranges from medium- lar (37), bryophyte (22), and lichen (23) species than grained sands to silt loams. In many areas there is other comparable sites (Batten and Svoboda 1994). a thin veneer of rocks that covers much of the sur- Saxifraga oppositifolia, Luzula confusa, and L. nivalis face, reducing the area of safe sites for plant estab- dominated at 520–920 m elevation with three sites lishment. In other areas there is at least 30–70% having limited amounts of Salix arctica. Large mats open soil. of S. arctica were sampled at 525–530 m on the Woody or semiwoody species are very rare in western (Batten and Svoboda 1994; Bliss, these barren landscapes, where rosette (Draba), Henry, Svoboda, and Bliss 1994) as well as popu- cushion (Saxifraga), and mat-forming (Puccinellia) lations of Cassiope tetragona and Dryas integrifolia species predominate. In a study of 23 barren sites above 500 m. Cryptogamic crusts indicating higher on six islands, a total of 17 vascular species and 14 surface moisture levels in some sites and higher species of cryptogams were found, with a mean temperatures due to dark rock surfaces receiving species richness of 9 per site (60 m2). Vascular plant reflected radiation off the nearby glaciers (Labine cover averaged 1.8% and cryptogams 0.7%; the re- 1994) are important factors that account for the maining 97.5% was bare soil, frost-shattered rocks, presence of woody species and a richer flora than and (Fig. 1.13B). Most vascular plants were is typical of most polar deserts (Bliss et al. 1984; found in desiccation cracks or adjacent to stones Bliss et al. 1994). 20 L. C. Bliss

Figure 1.13. (A) Aerial view of a po- lar desert landscape on Prince Patrick Island. The darker areas are snowflush communities with an abundance of mosses and a few vascular plants. (B) Polar desert barrens on Ellef Ringnes Island, with 1–2% cover of Papaver radicatum and Puccinella angustata.

Snowflush community. Within the polar barrens, Draba corymbosa, Minuartia rubella, and Stellaria lon- the only habitats that have significant plant cover gipes) in others. The polygonal troughs and stripes are those below large snowbanks and snowfields. contain Orthothecium chryseum, Ditrichum flexicaule, The , present part of the summer, ena- and Drepanocladus revolvens, and nearly all vascular ble the development of cryptogamic crusts and plants are restricted to these moss mats or cryp- moss mats in which flowering plants become es- togamic crusts (Fig. 1.14). These microsites always tablished. Although snowflush communities oc- contain cyanobacteria and thus have the ability to cupy only 3–5% of the landscape, they are very fix nitrogen. Few species other than Phippsia algida, conspicuous features when present. Species rich- Alopecurus alpinus, Papaver radicatum, Cerastium al- ness was found to be much greater in these habi- pinum, and Stellaria longipes occur in the large areas tats (30 species of vascular plants and 27 species of of bare soil. cryptogams) at 12 sites (60 m2) on three islands (Bliss et al. 1984). Plant cover was also much PLANT COMMUNITY DYNAMICS greater in these habitats (vascular plants 9.5%, bry- ophytes 18.5%, and lichens 8.2%) than in the herb Succession–Low Arctic barrens (Table 1.4). Plant composition can be quite variable, with Primary succession. Plant succession has received graminoid-dominated meadows in some sites (Er- less attention in the arctic literature, for it is not a iophorum triste, Alopecurus alpinus) and herbs (Sax- conspicuous feature. Natural disturbances (fire, ifraga oppositifolia, S. cernua, Papaver radicatum, massive erosion, permafrost melt, retreat)

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