North American boreal and western temperate forest vegetation

Salvador Rivas-Martínez, Daniel Sánchez-Mata & Manuel Costa

Itinera Geobotanica 12:5-316 (1999)


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Description of Plant Communities: Betulo papyriferae-Populetalia tremuloidis

Ve. Betulo papyriferae-Populetalia tremuloidis ordo novus hoc loco

[Populetalia balsamiferae Knapp in Geobot Mitt. 4: 56. 1957 (art. 8), Populetalia balsamiferae Krajina in Ecol. West N. Amer. 2(1) 52. 1969 (art. 2b, 8), Populetalia balsamiferae Krajina ex Hoefs, Cowan & Krajina in Siesis 8 (Suppl. 1) 155. 1975 (art. 8, 10) [holotype: Junipero (communis et horizontalis)-Shepherdio (canadensis)-Populion tremuloidis Hoefs & Krajina in Hoefs, Cowan & Krajina in Siesis 8 (Suppl. 1) 157. 1975 (art. 8, 10), Populetalia tremuloidis Looman in Phytocoenologia 15(1) 60. 1987 (art. 5, 8)]

Typus nominis: Betulo neoalaskanae-Populion tremuloidis alliancia nova hoc loco.

Continental and Subcontinental Boreal and also Continental Temperate; thermo-, meso- and supraboreal, hemiboreal, supratemperate and orotemperate; from upper semiarid to hyperhumid; natural or deciduous secondary forests, distributed throughout the North American Boreal, North American Atlantic and Rocky Mountain Regions. These micro-, mesoforests and thickets have been originated from coniferous climactical forest belonging to class Linnaeo-Piceetea marianae by natural or human disturbances. Locally, they can also grow in upper oromediterranean wet habitats throughout the Sierra Nevada Sector territories (California), as degradation of the coniferous climactical forests of Abietetalia magnifico-lowianae order (Calocedro-Pinetea jeffreyi).

Bioclimatic diagnosis: Ic 21-46, Io 1.8-22.0, Tp 380-1200, Tps 280-700, Tmin < 0, m < -2.[Boco, Bosc, Booc, Teco-Tbo-Mbo, Sbo, Ste, Ote, Hebo-Uar, Dry, Shu, Hum, Hhu].

Within the order Betulo papyriferae-Populetalia tremuloidis we recognize three alliances with different ecological requirements and distribution: 11. Betulo neoalaskanae-Populion tremuloidis (Continental and Subcontinental Boreal, thermo-, meso- and supraboreal, upper semiarid to upper humid, in the Yukonian-Alaskan Province and the Western Canadian Boreal Sector territories, and also Continental Temperate, hemiboreal, upper supra- and orotemperate, upper dry to lower humid, in the Rocky Mountain Subregion). 12. Betulo cordifoliae-Populion tremuloidis (Continental and Subcontinental Boreal, thermo-, meso- and supraboreal, humid-hyperhumid in Newfoundandian and Eastern Canadian Boreal Sectors, and also Continental Temperate, hemiboreal, upper supra- and orotemperate, humid and hyperhumid in the Appalachian Sector). 13. Alnion rugosae (Continental, Subcontinental and Oceanic Boreal, thermo-, meso- and supraboreal, humid-hyperhumid, in the Newfoundlandian and Eastern Canadian Boreal Sectors and also Continental Temperate and Oceanic Temperate, hemiboreal and supratemperate, humid and hyperhumid in the Appalachian and Great Lakes Sectors growing on mucky gleysols) (figures 31, 32 and 33).

The characteristic deciduous trees of this order are: Populus tremuloides (quacking aspen), Populus balsamifera subsp. balsamifera (balsam poplar) and Betula papyrifera s. l (paper birch). Among the characteristic deciduous and small trees of the alliances it could be mentioned the following: 11. Betulo neoalaskanae-Populion tremuloidis: Betula neoalaskana (Alaskan paper birch), Betula kenaica (Kenai birch) and Alnus viridis subsp. sinuata (Sitka adler). 12. Betulo cordifoliae-Populion tremuloidis: Betula cordifolia (mountain white birch), Betula populifolia (gray birch), Sorbus americana (American mountain-ash) and Sorbus decora (showy mountain-ash), 13. Alnion rugosae: Alnus rugosa (swamp alder).

Syntaxa Ic Io Itc Tp Ts Tmin m Mb, Var
Ve. Betulo pap.-Populetalia trem. 18-46 1.8-22.0 - 380-1200 280-700 < 0 < -2 -
11. Betulo ne.-Populion tremul. 22-46 1.8-10.0 - 380-900 300-550 < -6 < -12 -
11a. Roso sa.-Populetum tremul. 28-46 1.8-6.0 - 380-650 300-450 < -12 < -16 Bo, Stp
11b. Piceo gl.-Betuletum neoalas. 28-46 3.6-10.0 - 380-630 300-450 < -10 < -15 Bo, Stp
11c. Piceo gl.-Betuletum kenaicae 22-30 4.6-10.0 - 380-640 300-470 < -9 < -14 B
11d. Spiraeo luc.-Populetum bals. 24-38 2.8-9.0 - 450-900 350-530 < -8 < -13 Te, Bo, Stp
11e. Symphoricarpo-Populetum t. 23-28 3.6-7.0 - 450-900 350-550 < -6 < -12 Te, Me, Sbm
12. Betulo c.-Populion tremuloid. 21-35 6.0-22.0 - 380-1000 280-600 < -3 < -8 -
12a. Sorbo-Betuletum cordifoliae 23-28 12.0-22.0 - 380-600 280-400 < -9 < -14 Te
12b. Populetum tremuloidis 23-32 6.0-15.0 - 600-1000 400-600 < -3 < -8 Te
12c. Aralio hisp.-Populetum trem. 21-35 6.0-18.0 - 380-800 280-500 < -5 < -9 Bo
13. Alnion rugosae 18-38 6.0-22.0 - 400-1200 280-700 < 0 < -2 Bo, Te
13a. Alnetum rugosae 21-38 6.0-18.0 - 400-800 280-500 < -4 < -7 Bo
13b. Carici-Alnetum rugosae 18-34 6.0-22.0 - 770-1200 400-700 < 0 < -2 Te

Figure 31. Synopsis of the bioclimatic diagnoses of syntaxa belonging to Betulo papyriferae-Populetalia tremuloidis order. Relationships between potential natural vegetation forests and the thresholds of the bioclimatic indexes and climactical parameter values [11. Betulo neoalaskanae-Populion tremuloidis (11a. Roso sayi-Populetum tremuloidis, 11b. Piceo glaucae-Betuletum neoalaskanae, 11c. Piceo glaucae-Betuletum kenaicae, 11d. Spiraeo lucidae-Populetum balsamiferae, 11e. Symphoricarpo utahensis-Populetum tremuloidis), 12. Betulo cordifoliae-Populion tremuloidis (12a. Sorbo americanae-Betuletum cordifoliae, 12b. Populetum tremuloidis, 12c. Aralio hispidae-Populetum tremuloidis), 13. Alnion rugosae (13a. Alnetum rugosae, 13b. Carici-Alnetum rugosae)]. Ic: Continentality Index, Io: Ombrothermic Index, Itc: Compensated Thermicity Index, Tp: Yearly Positive Temperature, Tps : Positive Summer Temperature, Tmin: Average temperature value of the coldest month of the year, m: Average minimum temperature of the coldest month of the year (Tmin and m in degrees Celsius), Mb: Macrobioclimate (Bo: Boreal, Te: Temperate), Var: Bioclimatic variants (Sbm: Submediterranean, Stp: Steppic).

Characteristic species: Antennaria umbrinella, Apocynum androsaemifolium var. androsaemifolium, Arnica chamissonis, Aster ciliolatus, Aster foliaceus var. foliaceus, Betula papyrifera var. papyrifera, Betula papyrifera var. commutata, Betula xsandbergii (B. pumila x papyrifera), Calamagrostis canadensis var. canadensis, Calamagrostis canadensis var. langsdorfii, Clematis columbiana var. columbiana, Clematis virginiana, Corydalis aurea subsp. occidentalis, Eleagnus commutata, Elymus glaucus var. glaucus, Equisetum pratense, Penstemon procerus, Petasites frigidus var. palmatus, Petasites frigidus var. sagittatus, Platanthera obtusata, Populus balsamifera subsp. balsamifera, Populus tremuloides, Prunus virginiana var. virginiana, Ribes glandulosum, Ribes hirtellum, Ribes hudsonianum, Ribes lacustre, Ribes triste, Rosa acicularis subsp. sayi, Rosa arkansana, Rosa woodsii var. ultramontana, Rubus idaeus subsp. strigosus, Salix petiolaris, Salix pseudomonticola, Sambucus racemosa subsp. pubens var. pubens, Solidago multiradiata var. multiradiata, Solidago canadensis var. salebrosa, Sorbus scopulina var. scopulina, Spiraea betulifolia var. lucida, Stachys palustris subsp. pilosa, Stenanthium occidentale, Thalictrum venulosum, Veratrum viride, Viburnum edule, Zigadenus elegans.

North American associations of
Betulo papyriferae-Populetalia tremuloidis

North American biogeographic sectors

2.2a 2.2b 3.3 4.3 4.4 2.1c 2.1a 2.1b 3.1 3.2
11. Betulo neoalaskan.-Populion tremuloidis + + + + + + . . . .
11a. Roso sayi-Populetum tremuloidis + + . . . . . . . .
11b. Piceo glaucae-Betuletum neoalaskanae + + . . . . . . . .
11c. Piceo glaucae-Betuletum kenaicae . + . . . . . . . .
11d. Spiraeo lucida-Populetum balsamiferae . . + + . + . . . .
11e. Symphoricarpo utahen.-Populetum trem. . . . . + . . . . .
12. Betulo cordifoliae-Populion tremuloidis . . . . . . + + + .
12a. Sorbo americanae-Betuletum cordifoliae . . . . . . . . + .
12b. Populetum tremuloidis . . . . . . . . + .
12c. Aralio hispidae-Populetum tremuloidis . . . . . . + + . .
13. Alnion rugosae . . . . . + + + + +
13a. Alnetum rugosae . . . . . + + + . .
13b. Carici-Alnetum rugosae . . . . .     . + +

Figure 32. Relationships between North American biogeographic sectors of the Rocky Mountain Subregion adjacent biogeographic territories and forest associations of Ve. Betulo papyriferae-Populetalia tremuloidis [11. Betulo neoalaskanae-Populion tremuloidis, 12. Betulo cordifoliae-Populion tremuloidis, 13. Alnion rugosae]. 2.2a. Cassiar and Mackenzie Mountains Sector, 2.2b. Continental Alaskan Sector. 3.3. Prairies Province. 4.3. Northern Rocky Mountain Province. 4.4. Central-Eastern Rocky Mountain Province. 2.1a. Newfoundlandian Sector, 2.1b. Eastern Canadian Boreal Sector, 2.1c. Western Canadian Boreal Sector. 3.1. Appalachian Province. 3.2. Great Lakes and Central Lowlands Province.

Within the alliance Betulo papyriferae-Populetalia tremuloidis we recognize three alliances and ten associations distributed throughout the North American Boreal, North American Atlantic and Rocky Mountain Regions. To classify the associations we present an easy floristic, structural, bioclimatic and biogeographic key.

1 Western North America (West of 100ºW) 2
Eastern North America (East of 100ºW) 6
2 With Betula kenaica (Subcontinental Alaska) 11c. Piceo glaucae-Betuletum kenaicae
Without Betula kenaica 3
3 With Betula neoalaskana but without Symphoricarpos utahensis in the territory (Continental Boreal and Continental Temperate in the Northern Rocky Mountain Province and Canadian Prairies Sector) 4
Without Betula neoalaskana but with Symphoricarpos utahensis in the territory (Continental Temperate in Central-Eastern Rocky Mountain Province) 11e. Symphoricarpo utahensis-Populetum tremuloidis
4 With Betula neoalaskana as dominant tree and Rubus chamaemorus or Arctagrostis arundinacea in the herb layer 11b. Piceo glaucae-Betuletum neoalaskanae
Without Betula neoalaskana as dominant tree but with Populus tremuloides or Populus balsamifera, but without Rubus chamaemorus or Arctagrostis arundinacea in the herb layer 5
5 With Spiraea lucida and Maianthemum canadense in the understory (Northern Rocky Mountain Province and Canadian Prairies Sector) 11d. Spiraeo lucidae-Populetum tremuloidis
Without Spiraea lucida or Maianthemum canadense but with Vaccinium minus or Empetrum hermaphroditum in the understory 11a. Roso sayi-Populetum tremuloidis
6 Forest of Populus tremuloides, Populus balsamifera, Betula papyrifera or Betula cordifolia 7
Tall thickets of Alnus rugosa 9
7 With Betula populifolia and somewhat Acer saccharum in the canopy (Temperate: Appalachian Sector, mostly hemiboreal) 12b. Populetum tremuloidis
Without Betula populifolia or Acer saccharum in the canopy 8
8 With Betula alleghaniensis in the canopy or in the territory, Picea rubens in regeneration in the undercanopy and Oxalis montana in the herb layer (Temperate, Appalachian Sector, mostly upper orotemperate) 12a. Sorbo americanae-Betuletum cordifoliae
Without Betula alleghaniensis, Picea rubens or Oxalis montana but with Picea glauca and Kalmia angustifolia in the understory. (Boreal, Eastern Canadian Boreal and Newfoundlandian Sectors) 12c. Aralio hispidae-Populetum tremuloidis
9 With Clematis virginiana, Onoclea sensibilis and Osmunda cinnamomea (Temperate, Appalachian and Great Lakes Sectors) 13b. Carici-Alnetum rugosae
Without Clematis virginiana, Onoclea sensibilis and Osmunda cinnamomea, but with Carex trisperma and Linnaea americana (Boreal, Newfoundlandian and Eastern Canadian Boreal Sectors) 13a. Alnetum rugosae