DISCUSSION AND RESULTS. DESCRIPTION OF PLANT COMMUNITIES

11. Betulo neoalaskanae-Populion tremuloidis alliancia nova hoc loco

[Junipero (communis et occidentalis)-Shepherdio (canadensis)-Populion tremuloidis Hoefs & Krajina in Hoefs, Cowan & Krajina in Syesis 8 (Suppl. 1) 157. 1973 [holotype: Roso (acicularis)-Shepherdio (canadensis)-Populetum balsamiferae Hoefs, Cowan & Krajina in Syesis 8 (Suppl. 1) 157. 1973, Populion tremuloidis Looman in Phytocoenologia 15(1) 61. 1987 (art. 5, 8), Betulion papyriferae Looman in Phytocoenologia 15(1) 70. 1987 (art. 5, 8)]

Typus nominis: Roso sayi-Populetum tremuloidis Lausi & Nimis ex Peinado, Aguirre & Cruz in Plant Ecology 137: 172. 1998.

Deciduous light-wood secondary forests in the northern North America, originated by natural or anthropic replacement of the climactical coniferous forest of the Linnaeo-Piceetea marianae class growing on dystric, gelic or gleyic podzols, throughout the Continental and Subcontinental Boreal areas: thermo-, meso- and supraboreal, upper semiarid to upper humid, spreading into Yukonian-Alaskan Province territories, as well as in Continental Temperate: hemiboreal, upper supra-, and orotemperate, upper dry to lower humid in the Rocky Mountain Subregion, and rare in Canadian Prairies Sector territories. It could be interpretated as relictic vegetation of oromediterranean wet soils in Sierra Nevada (California) as a seral deciduous microforests from the climactical red fir forests (Abietion magnificae, Calocedro-Pinetea jeffreyi).

Bioclimatic diagnosis: Ic 22-46, Io 1.8-10.0, Tp 380-900, Tps 300-550, Tmin < -6, m < -12. [Boco, Teco-Tbo, Mbo, Sbo, Ste, Ote, Hbo-Sar, Dry, Shu, Hum].

In a short synthesized synoptical table (table 53) we assemble twenty-three relevés from Alaska, Canada, Wyoming and Utah belonging to Betulo neoalaskanae-Populion tremuloidis alliance. Six different associations have been identified: Roso sayi-Populetum tremuloidis, Piceo glaucae-Betuletum neoalaskanae and Piceo glaucae-Betuletum kenaicae are Continental or Subcontinental Boreal in the Yukonian-Alaskan Province. Spiraeo lucidae-Populetum balsamiferae is a broad and may be somewhat heterogeneous association growing as seral deciduous woodland communities in Continental Temperate territories in the Northern Rocky Mountain Province and Canadian Prairies Sector, as well as in the Continental Boreal dry and subhumid areas in the Western Canadian Boreal Sector. Finally, on deep soils, in Central-Eastern Rocky Mountain Province could be accepted a broad association named Symphoricarpo utahensis-Populetum tremuloidis. Within the most significant deciduous trees of this alliance, common throughout the Yukonian-Alaskan Province territories, as well as Western Canadian Boreal Sector, and locally in Canadian Prairies Sector and Northern Rocky Mountains Province areas, it could be mentioned for Boreal terrirories: Betula kenaica, Betula neoalaskana and Betula xwinteri, and for both Boreal and Temperate: Betula xuthaensis, Populus balsamifera subsp. balsamifera and Populus tremuloides.

Figure 33. Distribution of the forest associations belonging to order Ve. Betulo papyriferae-Populetalia tremuloidis. 11. Betulo neoalaskanae-Populion tremuloidis (Western Canadian Boreal and Cassiar and Mackenzie Mountains Sectors, spreading in Prairies, Northern and Central-Eastern Rocky Mountain Provinces): 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 (Newfoundlandian and Eastern Boreal Continental Sectors, spreading in Appalachian Province): 12a. Sorbo americanae-Betuletum cordifoliae, 12b. Populetum tremuloidis, 12c. Aralio hispidae-Populetum tremuloidis. 13. Alnion rugosae (Continental Boreal, Appalachian and Great Lakes and Central Lowlands Province): 13a. Alnetum rugosae, 13b. Carici-Alnetum rugosae.

Table 53
11. Betulo neoalaskanae-Populion tremuloidis
(Short synthesized table syntaxa)

Associations: 1. [11a] Roso-Populetum tremuloidis (Betulo-Populion tremuloidis). 2. [11b] Piceo glaucae-Betuletum neoalaskanae (Betulo-Populion tremuloidis). 3. [11c] Piceo glaucae-Betuletum kenaicae (Betulo-Populion tremuloidis). 4. [11d] Spiraeo lucidae-Populetum balsamiferae (Betulo-Populion tremuloidis). 5. [11e] Symphoricarpo utahensis-Populetum tremuloidis (Betulo-Populion tremuloidis). 6. Synthesized table.

Characteristic species: Arnica mollis, Betula kenaica, Betula neoalaskana, Betula papyrifera var. subcordata (Betula xutahensis), Betula xwinteri (B. neoalaskana x papyrifera), Delphinium glaucum, Lupinus arcticus, Melampyrum lineare var. lineare, Saussurea angustifolia, Senecio indecorus, Senecio triangularis, Solidago canadensis var. subserrata, Solidago simplex var. nana, Spiraea splendens.

11a. Roso sayi- Populetum tremuloidis Lausi & Nimis ex Peinado, Aguirre & Cruz 1998

[Roso sayi-Populetum tremuloidis Lausi & Nimis ex Peinado, Aguirre & Cruz in Plant Ecology 137: 172. 1998, Shepherdia canadensis-Populus tremuloides community Lausi & Nimis in Nimis & Crovello, Quantitative App. Phytogeogr.: 74, tb. 9. 1991 et Lausi & Nimis in Peinado, Aguirre & Cruz in Plant Ecology 137: 175, tb. 10, relevés no. 33, 34, 38]

Continental and Xeric Boreal; meso- and supraboreal; steppic; upper semiarid, dry and subhumid; quacking aspen (Populus tremuloides) deciduous secondary mesoforests which replace the coniferous climactical forest vegetation in the Yukonian-Alaskan Province territories, mostly those belonging to Hypno-Piceetum glaucae association, but also to Piceetum glauco-marianae. This seral vegetation had been originated by fire and other anthropic or natural disturbances and grows on haplic, dystric or gelic podzols or regosols.

Bioclimatic diagnosis: Ic 28-46, Io 1.8-6.0, Tp 380-650, Tps 300-450, Tmin < -12, m < -16. [Boxe, Boco-Mbo, Sbo-USar, Dry, Shu-Stp].

Table 54 shows seven relevés from Yukon and Alaska, belonging to micro- and mesoforests dominated by Populus tremuloides, and showing an active regeneration of Picea glauca var. glauca and Picea mariana in the understory. The commonest shrubs and dwarf-scrubs are Arctostaphylos uva-ursi s. l., Rosa acicularis subsp. sayi, Empetrum nigrum subsp. hermaphroditum, Shepherdia canadensis, Salix glauca var. acutifolia, and Vaccinium vitis-idaea subsp. minus; between the herbs it could be mentioned Calamagrostis purpurascens, Geocaulon lividum and Lupinus arcticus. The floristic differentiation between these deciduous secondary forest-type and the related and wetter Alaska birch forests (Piceo glaucae-Betuletum neoalaskanae) are some species such as Shepherdia canadensis, Arctostaphylos uva-ursi s. l. and Empetrum nigrum subsp. hermaphroditum. Conversely, it could be mentioned: Alnus viridis subsp. sinuata, Arctagrostis arundinacea and Rubus chamaemorus.

Type relevé (holotypus): Peinado, Aguirre & Cruz 1998 in Plant Ecology 137: 175, tb. 10, relevé n. 324. Site: Yukon Territory: 30 miles West of Whitehorse. 60°51'12"N-135°40'24"W. 670 m, 200 m2. Estimated bioclimatic factors: Xeric Boreal (eucontinental) (Ic ~ 32), upper mesoboreal (Tp ~ 590), upper dry (Io ~ 3.0), Positive Summer Temperature Tps ~ 410, steppic.

Table 54
11a. Roso sayi-Populetum tremuloidis
(Betulo neoalaskanae-Populion tremuloidis, Betulo-Populetalia tremuloidis)

Other species. Characteristic species: Polemonium pulcherrimum 1, Salix scouleriana 1 in 2. Pyrola chlorantha 1, Gentianella propinqua 1 in 3. Zigadenus elegans 1 in 4. Amelanchier alnifolia 2, Solidago multiradiata 1, Penstemon procerus + in 5. Galium boreale 1 in 5 and 7. Ledum groenlandicum 1 in 6. Viburnum edule 3, Pyrola asarifolia 2, Moehringia lateriflora 2, Arctostaphylos adenotricha 1, Cornus canadensis 1, Actaea rubra 1, Delphinium glaucum 1, Lycopodium annotinum 1, Viola renifolia + in 7. Companion species: Achillea borealis 1 in 1, + in 4. Carex deflexa + in 2. Carex rossii 1 in 3. Peltigera scabrosa 2 in 4. Equisetum pratense 1 in 7.

Localities: 1. Yukon Territory: Champagne, Mendelhall. 60º48'N-136º25'W. 15 m, 30 cm, 100 m2 (reg. 1994a: 121). 2. Alaska: Robertson River-Bear Creek. 63º36'N-143º56'W. 20 m, 40 cm, 200 m2 (reg. 1994a: 183). 3. Alaska: Tok, Tetlin Junction. 63º19'N-142º43'W. 10 m, 25 cm, 200 m2, podzol on paleodunes (reg. 1994a: 62). 4. Yukon Territory: Dawson City, Dempster Hwy, 18 km N of crossing. 64º18'N-138º32'W. 10 m, 20 cm, 200 m2 (reg. 1994a: 82). 5. Yukon Territory: Carmacks. 62º01'N-136º15'W. 10 m, 20 cm, 200 m2 (reg. 1994a: 111). 6. Yukon Territory: Stewart Crossing-Pelly Crossing. 63º15'N-136º33'W. 20 m, 40 cm, 400 m2 (reg. 1994a: 106). 7. Alaska: Fairbanks, Ester, Alder Creek. 64º51'N-147º58'W. 25%, 22 m, 45 cm, 400 m2 (reg. 1994a: 193). 8. Synthesized table.

Biogeographic location: North American Boreal Region, Mackenzie-Yukonian Province, Yukonian Drainage Basin Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 4 Populus tremuloides, 1 Picea glauca var. glauca. Others: 1 Achillea millefolium var. borealis, 1 Anemone patens subsp. multifida [Pulsatilla patens subsp. multifida] 4 Arctostaphylos uva-ursi, 1 Fragaria virginiana, + Galium boreale, 2 Rosa acicularis subsp. sayi. Companion species: 1 Epilobium angustifolium, + Linum lewisii, 1 Salix brachycarpa, + Solidago spathulata.

11b. Piceo glaucae-Betuletum neoalaskanae Peinado, Aguirre & Cruz 1998

[Piceo glaucae-Betuletum neoalaskanae Peinado, Aguirre & Cruz in Plant Ecology 137: 172. 1998, Loiseleurio procumbentis-Betuletum neoalaskanae Peinado, Aguirre & Cruz in Plant Ecology 137: 178. 1998, Alno sinuatae-Betuletum neoalaskanane nobis ined.]

Continental Boreal; meso- and supraboreal, somewhat with steppic character in their eastern and dryer territories; subhumid and humid; Alaskan birch (Betula neoalaskana) deciduous, anthropic or natural secondary micro- and mesoforests (also primary permanent forest communities in mobile pergelic soils and avalanche habitats), mainly related with the climactic coniferous forest associations: Piceetum glauco-marianae and Rubo chamaemori-Piceetum marianae. They are broadly distributed throughout the Yukonian-Alaskan Biogeographic Province territories, but also grow throughout the xeric areas in the Cassiar and Mackenzie Mountains Sector or in the Boreal Xeric Alaskan Subsector. The Alaskan birch forests (Piceo-Betuletum neoalaskanae) spread on wet and protected stations on gleyic, histic, dytric and gelic podzols and somewhat in terric, fibric and gelic histosols.

Bioclimatic diagnosis: Ic 28-46, Io 3.6-10.0, Tp 380-630, Tps 300-450, Tmin < -10, m < -15. [BoCo-Mbo, Sbo-Shu, Hum].

Table 55 shows six relevés from Alaska and Yukon belonging to Alaskan birch micro- and mesoforests with an active regeneration of Picea mariana and Picea glauca var. glauca in the understory. The commonest dwarf-scrubs in the understory are Alnus viridis subsp. sinuata, Ledum groenlandicum, Rosa acicularis subsp. sayi, Salix glauca var. acutifolia, Spiraea stevenii and Vaccinium vitis-idaea subsp. minus; between the common plants growing in the herb layer it could be mentioned Arctagrostis arundinacea, Calamagrostis purpurascens, Cornus canadensis, Geocaulon lividum, Linnaea americana and Lycopodium annotinum.

Type relevé (holotypus): Peinado, Aguirre & Cruz 1998 in Plant Ecology 137: 172, tb. 9, relevé n. 408. Site: Alaska: Livengood. 65°30'08"N-148°04'22"W. E, 200 m, 200 m2. Estimated bioclimatic factors: Continental Boreal, eucontinental (Ic ~ 38), upper mesoboreal (Tp ~ 550), lower subhumid (Io ~ 4.0), Positive Summer Temperature Tps ~ 400. Biogeographic location: North American Boreal Region, Yukonian-Alaskan Province, Continental Alaskan Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 5 Betula neoalaskana, 2 Picea glauca var. glauca. Others: + Alnus viridis subsp. crispa, 1 Cornus canadensis, + Geocaulon lividum, + Juniperus communis var. depressa, 1 Ledum groenlandicum, 1 Linnaea borealis subsp. longiflora [L. americana], 1 Lycopodium complanatum [Diphasiastrumcomplanatum], + Ribes triste, 1 Rosa acicularis subsp. sayi, 1 Salix glauca, 1 Spiraea stevenii. Companion species: + Epilobium angustifolium.

Table 55
11b. Piceo glaucae-Betuletum neoalaskanae
(Betulo neoalaskanae-Populion tremuloidis, Betulo-Populetalia tremuloidis)

Other species. Trees: Populus tremuloides (S2) + in 6. Characteristic species: Vaccinium alpinum 2 in 4 and 6. Mertensia paniculata 1 in 5 and 6. Pedicularis labradorica 1, Viburnum edule 1, Orthilia secunda + in 3. Salix scouleriana 1, Arctostaphylos adenotricha 1 in 4. Lupinus arcticus 2, Delphinium glaucum +, Solidago nana +, Moneses uniflora + in 6. Companion species: Peltigera scabrosa 2 in 5. Equisetum boreale 4, Polytrichum commune 3 in 6.

Localities: 1. Alaska: Dot Lake. Bear Creek. 63º39'N-144º02'W. SW, 5%, 12 m, 20 cm, 200 m2 (reg. 1994a: 186). 2. Alaska: Tok, Robertson Lake. 63º30'N-143º49'W. E, 20%, 12 m, 20 cm, 200m2 (reg. 1994a: 178). 3. Alaska: Fairbanks, Alder Creek. 64º50'N-148º01'W. S, 15%, 25 m, 30 cm, 400 m 2 (reg. 1994a: 196). 4. Alaska: Dot Lake, Bear Creek. 63º40'N-144º04'W. W, 15 m, 30 cm, 400 m2 (reg. 1994a: 184). 5. Alaska: Richardson. 64º17'N-146º19'W. N, 25%, 18m, 30cm, 400 m2, mor. (reg. 1994a: 192). 6. Yukon Territory: Dawson City, Dempster Hwy, 46 km N of crossing. 64º18'N-138º34'W. N, 10%, 15 m, 25 cm, 200 m2 (reg. 1994a: 83). 7. Synthesized table.

11c. Piceo glaucae-Betuletum kenaicae Peinado, Aguirre & Cruz 1998 nom. invers.

[Betulo kenaicae-Piceetum glaucae Peinado, Aguirre & Cruz in Plant Ecology 137: 172. 1998 nom. inv. propos. (art. 10c, 42, 48), Spiraeo stevenii-Betuletum kenaicae nobis ined.]

Subcontinental Boreal, somewhat barely Continental Boreal; subhumid and humid; Kenai birch (Betula kenaica) deciduous anthropic or natural secundary micro- or mesoforests, mainly related with the climactic coniferous forest associations belonging to Piceetum glauco-marianae and Rubo chamaemori-Piceetum marianae associations. The Kenai birch forests are distributed throughout the subhumid and humid Boreal Subcontinental Alaskan Subsector territories (Continental Alaskan Sector) and grow on dystric, gleyic and histic podzols and also on terric and fibric histosols.

Bioclimatic diagnosis: Ic 22-30, Io 4.6-10.0, Tp 380-640, Tps 300-470, Tmin < -9, m < -4. [Bosc-Mbo, Sbo-Shu, Hum].

Table 56 gives two relevés from Boreal Subcontinental Alaska territories (Susitna and Chulitna River Valleys), where the most important deciduous tree is Betula kenaica and as subordinated trees it could be mentioned Populus balsamifera subsp. balsamifera and Populus tremuloidis. The regional coniferous climactical species Picea glauca var. glauca and Picea mariana are often present as young trees in the undercanopy. The commonest and characteristic species and the differential species (*) against the rest of Yukonian-Alaskan associations of the alliance Betulo neoalaskanae-Populion tremuloidis are: Alnus viridis subsp. sinuata, Athyrium filix-femina var. cyclosorum (*), Calamagrostis purpurascens, Cornus suecica (*), Equisetum sylvaticum (*), Menziesia ferruginea (*), Oplopanax horridus (*), Spiraea stevenii and Trientalis europaea subsp. arctica.

Table 56
11c. Piceo glaucae-Betuletum kenaicae
(Betulo neoalaskanae-Populion tremuloidis, Betulo-Populetalia tremuloidis)

Other species. Trees: Populus balsamifera 2, Picea mariana (S2) +, Populus tremuloides + in 1. Characteristic species: Salix alaxensis var. alaxensis + in 1. Oplopanax horridus 4, Cornus canadensis 2, Gymnocarpium dryopteris 2, Viburnum edule 2, Menziesia ferruginea 1, Rubus pedatus 1, Streptopus amplexifolius 1, Vaccinium ovalifolium 1, Veratrum viride 1 in 2. Companion species: Hylocomium splendens 2 Equisetum hyemale + in 1.

Localities: 1. Alaska: Between Montana and Casswell. 61º59'N-150º02'W. 18 m, 30 cm, 100 m2 (reg. 1994a: 207). 2. Alaska: Talkeetna, Trapper Creek. 62º17'N-150º14'W. 16 m, 40 cm, 400 m2, iron gleyic podzol on sandy sediments (reg. 1994a: 205). 3. Synthesized table.

Type relevé (holotypus): Peinado, Aguirre & Cruz 1998 in Plant Ecology 137: 173, tb. 8, relevé n. 374. Site: Alaska. Soapstone Road, Palmer Valley. 61°39'57"N-149°05'17"W. 220 m, 200 m2. Estimated bioclimatic factors: Subcontinental Boreal (Ic ~ 25), lower mesoboreal (Tp ~ 620), upper subhumid (Io ~ 5.2), Positive Summer Temperature Tps ~ 390. Biogeographic location: North American Boreal Region, Yukonian-Alaskan Province, Continental Alaskan Sector, Boreal Subcontinental Alaskan Subsector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 3 Betula papyrifera var. kenaica [B. kenaica], 1 Picea glauca, 3 Populus balsamifera var. balsamifera. Others: 1 Aconitum delphiniifolium subsp. delphiniifolium, 3 Alnus viridis subsp. sinuata, 1 Cornus canadensis, 1 Geranium erianthum, 2 Gymnocarpium dryopteris, 1 Mertensia paniculata var. paniculata, + Rosa acicularis subsp. sayi, 2 Salix glauca, 2 Streptopus amplexifolius, 3 Viburnum edule. Companion species: 3 Athyrium filix-femina var. cyclosorum, 1 Epilobium angustifolium, 2 Equisetum arvense.

11d. Spiraeo lucidae-Populetum balsamiferae associatio nova hoc loco

Continental Temperate (subcontinental and eucontinental), upper supra-, hemiboreal and orotemperate; and also Continental Boreal (eucontinental), thermo- and mesoboreal, upper dry, subhumid and lower humid, balsam poplar (Populus balsamifera subsp. balsamifera), quacking aspen (Populus tremuloides), and in few cases Alaskan birch (Betula neoalaskana), deciduous secondary mesoforests [seral from Mertensio paniculatae-Abietetum balsameae forest association (Gaultherio-Piceion glaucae) or Menziesio ferrugineae-Abietetum bifoliae and Piceetum engelmannii forest associations (Piceo engelmannii-Abietion bifoliae)], spreading into Northern Rocky Mountain Province, Western Canadian Boreal and Canadian Prairies Sectors and growing on deep soils mostly dystric, histic or gleyic podzols and regosols.

Bioclimatic diagnosis: Ic 24-38, Io 2.8-9.0, Tp 450-900, Tps 350-530, Tmin < -8, m < -13. [Boco, Teco-Tbo, Mbo, Hbo, Ste, Ote,-Dry, Shu, Hum-Stp].

Table 57 gives five relevés from Boreal and Temperate areas of Alberta in which balsam poplar (Populus balsamifera subsp. balsamifera) and quacking aspen (Populus tremuloides) are the most important and dominant deciduous light-wooded trees, and Alaskan birch (Betula neoalaskana) seldom being in evidence. As small coniferous trees growing in the undercanopy it could easily found according to the biogeographic territories white spruce (Picea glauca var. glauca), Alberta spruce (Picea glauca var. albertiana) or Engelmann spruce (Picea engelmannii var. engelmannii) as well as balsam fir (Abies balsamea) or subalpine fir (Abies bifolia). All these coniferous trees, in their natural conditions became dominants in the progressive succession after decades and they lead the climax. Besides the general characteristic species of these secondary deciduous forests we could remark Arctostaphilos uva-ursi var. adenotricha, Calamagrostis purpurascens, Linnaea americana, Pyrola asarifolia, Rosa acicularis subsp. sayi and Shepherdia canadensis, as well as some central-eastern characteristic species are frequent plants: Aralia nudicaulis, Aster ciliolatus, Maianthemum canadense, Spiraea betulifolia var. lucida and Symphoricarpos occidentalis.

Table 57
11d. Spiraeo lucidae-Populetum balsamiferae
(Betulo neoalaskanae-Populion tremuloidis, Betulo-Populetalia tremuloidis)

Other species. Characteristic species: Geranium viscosissimum 1 in 1. Cornus sericea 2, Alnus sinuata + in 4. Actaea rubra 2, Rubus strigosus 2, Prunus melanocarpa 1, Galium boreale 1 in 5.

Localities: 1. Alberta: Between Calgary and Banff, Bow Valley Provincial Park. 51º06'N-115º02'W. S, 10%, 20 m, 30 cm, 200 m2 (reg. 1992e: 33). 2. Alberta: Between Calgary and Banff, Kananaskis Country Provincial Area, Bow River. 50º58'N-115º09'W. E, 10%, 20 m, 30 cm, 200 m2 (reg. 1992e: 34). 3. Alberta: Between Calgary and Banff, Kananaskis Country Provincial Area. 51º02'N-115º05'W. SE, 20%, 22 m, 30 cm, 200 m2 (reg. 1992e: 35). 4. Alberta: Lesser Slave Lake Provincial Park, Steep Hill. 55º27'N-114º49'W. W, 5%, 20 m, 30 cm, 400 m2 (reg. 1995d: 154). 5. Alberta: Elkwater Cypress Hill. Cypress Hill Interprovincial Park. 49º38'N-110º13'W. N, 5%, 23 m, 40 cm, 400 m2, holotypus ass. (reg. 1995d: 158). 6. Synthesized table.

Type relevé (holotypus): Table 57, relevé n. 5. Rivas-Martínez reg. 1995d: 158. 08.09.95, made with Dr. Costa. Site: Alberta: Elkwater, Cypress Hill. Cypress Hill Interprovincial Park. 49º38'N-110º13'W. 1250 m, N, 5%, 25 m, 40 cm, 400 m2. Physiognomy and habitat: Balsam poplar (Populus balsamifera subsp. balsamifera) and aspen (Populus tremuloides) riparian mesoforest. Estimated bioclimatic factors: Continental Temperate, eucontinental (Ic ~ 31), lower orotemperate (Tp ~ 670), upper subhumid (Io ~ 5.6), Positive Summer Temperature Tps ~ 450. Biogeographic location: North American Atlantic Region, Prairies Province, Canadian Prairies Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 1 Picea glauca var. glauca (S2), 4 Populus balsamifera subsp. balsamifera, 3 Populus tremuloides. Others: + Alnus viridis subsp. sinuata, + Aralia nudicaulis, 3 Aster ciliolatus, + Galium triflorum, 1 Linnaea americana, 2 Maianthemum canadense, 1 Prunus virginiana var. melanocarpa, 1 Pyrola asarifolia, 2 Ribes oxyacanthoides, 2 Rosa acicularis subsp. sayi, 1 Spiraea betulifolia var. lucida, + Symphoricarpos occidentalis, 1 Thalictrum venulosum, + Viburnum edule, 2 Viola adunca. Companion species: 1 Bromus vulgaris, + Epilobium angustifolium, 1 Equisetum arvense var. boreale, 1 Galium boreale.

11e. Symphoricarpo utahensis-Populetum tremuloidis associatio nova hoc loco

Continental Temperate (subcontinental); upper supra- and orotemperate; subhumid and lower humid; quacking aspen (Populus tremuloides) deciduous secondary mesoforests [seral in mesic of hydric habitats from Piceetum pungentis and Vaccinio scoparii-Abietetum bifoliae associations (Piceo engelmannii-Abietion bifoliae) and in few cases from Shepherdio canadensis-Pseudotsugetum glaucae association (Pino scopulorum-Pseudotsugion glaucae)], spreading into Central-Eastern Rocky Mountain Province territories and growing on dystric, ferric, cambic or gleyic podzols]

Bioclimatic diagnosis: Ic 23-28, Io 3.6-7.0, Tp 450-900, Tps 350-550, Tmin < -6, m < -12. [Teco-Ste, Ote-Shu, Hum].

Table 58 shows three relevés from Utah Rocky Mountains in which quackin aspen (Populus tremuloides) is the dominant deciduous tree in the community. A lot of northern forest species are missing: Alnus viridis subsp. sinuata, Betula neoalaskana, Geocaulon lividum, Mertensia paniculata var. paniculata, Populus balsamifera subsp. balsamifera, Rubus chamaemorus, Viburnum edule, etc.; conversely, some more southern plants take place in this secondary deciduous micro- or mesoforests: Paxistima myrsinites, Rudbeckia occidentalis s. l., Symphoricarpos oreophilus var. utahensis, Valeriana acutiloba, Verastrum californicum var. californicum, etc. These relevant floristic and biogeographic differences probably will allow to recognize a new Central-Eastern Rocky Mountain alliance in the future.

Type relevé (holotypus): Table 58, relevé n. 1. Rivas-Martínez reg. 1996b: 35. 28.08.96, made with Drs. Llorens and Sánchez-Mata. Site: Utah: Salt Lake Co. Wasatch-Cache National Forest. Guardsman Pass Road, between Redman Campground and Brighton. 40º37'N-111º33'W. 2500 m, S, 10%, 20 m, 30 cm, 200 m2. Physiognomy and habitat: Aspen (Populus tremuloides) mesoforest. Estimated bioclimatic factors: Continental Temperate, subcontinental (Ic ~ 25), lower orotemperate (Tp ~ 620), upper subhumid (Io ~ 5.0), Positive Summer Temperature Tps ~ 480. Biogeographic location: Rocky Mountain Region, Rocky Mountain Subregion, Central-Eastern Rocky Mountain Province, Utah Rockies Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 5 Populus tremuloides. Others: 2 Amelanchier alnifolia var. alnifolia, 3 Symphoricarpos oreophilus var. utahensis, 3 Geranium viscosissimum, 3 Lonicera involucrata, 1 Paxistima myrsinites, 1 Prunus virginiana var. melanocarpa, + Pyrola asarifolia, 2 Rudbeckia occidentalis var. montana, 1 Sambucus racemosa subsp. pubens var. microbotrys, 2 Thalictrum sparsiflorum, 1 Valeriana acutiloba, 1 Veratrum californicum. Companion species: + Brachypodium sylvaticum, 3 Epilobium angustifolium, 2 Potentilla pensylvanica.

Table 58
11e. Symphoricarpo utahensis-Populetum tremuloidis
(Betulo-Populion tremuloidis, Betulo-Populetalia tremuloidis)

Other species. Trees: Pinus flexilis + in 2. Abies concolor (S2) + in 3. Characteristic species: Juniperus depressa + in 2. Companion species: Lupinus sericeus 1 in 2. Schizachyrium scoparium 2, Achillea alpicola 1 in 3.

Localities: 1. Utah: Salt Lake Co. Wasatch-Cache National Forest, Guardsman Pass Road, between Redman Campground and Brighton. 40º37'N-111º33'W. S, 10%, 20 m, 30 cm, 200 m2, holotypus ass. (reg. 1996b: 35). 2. Wyoming: Teton Co. Bridger-Teton National Forest, Grand Teton National Park, Gros Ventre Road, between Kelly and Lower Slide Lake. 43º38'N-110º34'W. N, 10%, 20 m, 30 cm, 200 m2 (reg. 1994b: 23). 3. Utah: Wasatch Co. Wasatch-Cache National Forest, between Brighton and Midway. Guardsman Pass. 40º35'N-111º29'W. SE, 20%, 23m, 40 cm, 200 m2 (reg. 1996b: 40). 4. Synthesized table.