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: Alno rubrae-Populion trichocarpae/h1>

8. Alno rubrae-Populion trichocarpae alliancia nova hoc loco

Typus nominis: Aceri macrophylli-Alnetum rubrae associatio nova hoc loco.

The only alliance of the Alno rubrae-Populetalia trichocarpae order includes the riparian and secondary meso- and macroforests associations of black cottonwood (Populus balsamifera subsp. trichocarpa) and red alder (Alnus rubra), as well as permanent or secondary Sitka alder (Alnus viridis subsp. sinuata) thickets. Each of these communities are broadly distributed throughout the Cascade and Boreal Oceanic Alaskan territories, and they are less common in Northern Rocky Mountain Province territories. They spread north to Alaska Peninsula Subsector and south to Northern Californian Coastal Sector. Forests and thickets of Populus balsamifera subsp. trichocarpa and Alnus viridis subsp. sinuata have their eastern boundaries in the subcontinental territories of the Northern Rocky Mountain Province.

Bioclimatic diagnosis: Ic 5-25, Io 4.8-40.0, Itc < 280, Tp 400-1400, Tps 250-550, Tmin < 8, m < 5. [Booc, Boco, Teoc, Teco, Mepo-Tbo, Mbo, Sbo,Hbo, Mte, Ste, Ote, Mme-Ushu, Hum, Hhu, Uhh].

Within the alliance Alno rubrae-Populion trichocarpae we recognize six deciduous forest and shrubby associations, distributed throughout the Cascade, Boreal Oceanic Alaskan and Northern Rocky Mountain Provinces (figures 26, 27). To identify the different recognized associations we propose an easily floristic, structural, bioclimatic and biogeographic key as follows:

1 Deciduous meso- or macroforests with Alnus rubra (red alder) or Populus trichocarpa (black cottonwood) as dominant trees in the canopy 2
Deciduous thickets with Alnus sinuata (Sitka alder) as dominant shrub or small tree in the overstory 5
2 Riparian or secondary meso- and macroforests with Alnus rubra as dominant tree in the canopy 3
Riparian or secondary meso- and macroforests without Alnus rubra but with Populus trichocarpa as dominant tree in the canopy 4
3 Mesotemperate, lower supratemperate and mesomediterranean (Tp > 1050), hyperoceanic or euoceanic (Ic 5-18) territories, with Acer macrophyllum and Frangula purshiana (Oregonian-Vancouverian Coastal, Northern Californian Coastal Sectors and bottomlands in the Cascade Ranges Sector) 8a. Aceri macropyhylly-Alnetum rubrae
Upper supratemperate, hemiboreal and thermoboreal (Tp 700-1050), euoceanic and semicontinental (Ic 11-20) territories without Acer macrophyllum or Frangula purshiana (Canadian Coastal Mountains Sector, locally in Columbia Mountains and Boreal Oceanic Eastern Alaskan -Haines-Juneau Subsector- Sectors)  8b. Oplopanaco horridi-Alnetum rubrae
4 Thermo-, mesoboreal, lower supraboreal, hemiboreal and barely upper supratemperate (Tp 450-1000), oceanic, semicontinental or barely subcontinental (Ic 11-25) territories with Alnus sinuata, Amelanchier semiintegrifolia and Equisetum boreale in the understory (Boreal Oceanic Alaskan Province and North Canadian Coastal Mountain Subsector) 8c. Alno sinuatae-Populetum trichocarpae
Upper supratemperate and lower orotemperate (Tp 600-1100), semicontinental or barely subcontinental (Ic 18-25) territories with Alnus tenuifolia, Betula xutahensis and Symphoricarpos laevigatus in the understory (Northern Rocky Mountain Province)  8d. Alno tenuifoliae-Populetum trichocarpae
5 Thermo-, mesoboreal and lower supraboreal (Tp 450-740), semicontinental or barely subcontinental (Io 16-25) territories with Salix longistylis, Salix acutifolia and Oplopanax horridus (Boreal Oceanic Alaskan Province) 8f. Salici longistylis-Alnetum sinuatae
Orotemperate and sligthly upper supratemperate (Tp 400-900), semicontinental and subcontinental (Ic 18-24) territories with Vaccinium membranaceum, Rubus lasiococcus, Chimaphila occidentalis and Paxistima myrsinites (Northern Rocky Mountain Province) 8e. Vaccinio membranacei-Alnetum sinuatae

8a. Aceri macrophylli-Alnetum rubrae associatio nova hoc loco

Hyperoceanic and Oceanic Temperate (euhyperoceanic, barely hyperoceanic and euoceanic), upper mesotemperate to lower supratemperate; subhumid to lower ultrahyperhumid (often with submediterranean pattern of rainfall and sometimes mesomediterranean spreading into Northern California coastal areas), deciduous secondary or riparian macroforests of red alder (Alnus rubra) and big-leaved maple (Acer macrophyllum) growing on humic, umbric, gleyic or stagnic, cambisols, andosols, podzols and fluvisols in Oregonian-Vancouverian Coastal Sector and at the bottomlands windward in the Cascade Ranges Sector territories.

Bioclimatic diagnosis: Ic 5-18, Io 9.0-18.0, Itc 120-250, Tp 1050-1400, Tps 450-550, Tmin <8, m <5. [Teoc, Mepo-Mte, Ste, Mme-Uhu, Hhu-Sbm].

Table 33 shows 11 relevés sampled throughout the coastal territories of Oregon, California, Washington and British Columbia, and someones in the west side of Cascade Ranges Sector areas.

Alnus rubra is the dominant tree in the canopy with Acer macrophyllum, and vine maple (Acer circinatum) is also an important tree in the undercanopy species against the rest of the associations belonging to the Alno rubrae-Populion trichocarpae alliance. Polystichum munitum, Rubus parviflorus and Rubus spectabilis usually are some dominant species in the understory.

Table 33
8a. Aceri macrophylli-Alnetum rubrae

(Alno-Populion trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 10 24 5 9 20 61 9 16 2 12 59 21
Number of species 17 17 17 17 18 19 21 22 23 25 26 20
Ordinal number 1 2 3 4 5 6 7 8* 9 10 11 12
Trees:
Alnus rubra 4 4 5 4 5 3 4 5 3 3 5 V
Acer macrophyllum 2 2 + 2 2 3 3 2 2 2 1 V
Acer circinatum . 1 . + . 2 4 . 2 . 2 III
Populus trichocarpa . . . 1 . 1 + . . . . II
Thuja plicata (S2) . + . 1 + . . . . . . II
Picea sitchensis (S2) . . + . . . . + + . . II
Pseudotsuga menziesii (S2) . . . + 1 . . . . . + II
Characteristic species:
Polystichum munitum 2 3 + . + 2 4 3 1 2 2 V
Rubus parviflorus 1 2 . 1 1 3 + 4 1 2 2 V
Galium trifidum 2 1 1 1 2 1 . . + 1 2 IV
Rubus spectabilis 2 . 4 1 4 . 2 3 . 4 1 IV
Frangula purshiana . 1 1 . 2 . 2 1 2 + . IV
Sambucus arborescens 2 . 2 . . 2 . 2 2 1 . III
Adenocaulon bicolor 1 . + . . 1 . . + + . III
Holodiscus discolor . 1 . 2 . 1 . 1 . . + III
Stachys mexicana . . 1 . . . 2 2 2 2 . III
Tolmiea menziesii 2 . . . . . . 2 1 1 . III
Athyrium cyclosorum . 2 . 1 . + 2 . . 2 . III
Marah oreganus . . 2 . . . + . 3 2 . III
Dicentra formosa 2 . . . 2 . . 1 . . . II
Maianthemum dilatatum . 1 . . . . 1 . 1 . . II
Rubus leucodermis . 1 . . . 2 . . . . 2 II
Maianthemum stellatum . . . + . . . + . . 1 II
Oxalis oregana . . . . + . . 1 . 2 . II
Rubus macropetalus . . . . . . . 1 2 . 2 II
Asarum caudatum . . . . . . . 1 . 1 2 II
Companion species:
Pteridium pubescens 1 1 1 1 2 3 . . . 1 3 III
Claytonia sibirica 1 . 1 . 1 + . 2 1 2 3 IV
Urtica gracilis 3 . . . . . + . 2 . . II
Carex leptopoda . . 2 . . . . . 1 1 . II
Corylus californica . . . . . . 2 . . 1 1 II

Other species. Trees: Tsuga heterophylla (S2) + in 4 and 8. Betula papyrifera 2 in 4. Sequoia sempervirens (S2) + in 9. Characteristic species: Mahonia nervosa 1 in 1 and 11. Circaea pacifica 1 in 5 and 8. Disporum smithii + in 5, 1 in 10. Cornus sericea + in 5 and 11. Stellaria crispa 1 in 8 and 11. Mitella caulescens 2 in 9, 1 in 10. Disporum oreganum 1, Osmorhiza purpurea 1 in 1. Stachys ciliata + in 2. Spiraea douglasii 3, Lonicera ciliosa 1 in 4. Viola glabella + in 5. Ribes sanguineum 1 in 6. Oxalis trilliifolia 2, Dryopteris expansa 1, Streptopus amplexifolius 1 in 7. Maianthemum amplexicaule 2, Oemleria cerasiformis 2 in 9. Symphoricarpos laevigatus 2, Tiarella unifoliata 2, Achlys triphylla 1, Amelanchier alnifolia +, Cornus canadensis + in 11. Companion species: Geranium robertianum 3 in 1, + in 7. Adiantum aleuticum 2 in 2, 1 in 7. Equisetum braunii 1 in 3, + in 6. Digitalis purpurea + in 2, 1 in 8. Baccharis pilularis + in 3 and 9. Whipplea modesta + in 5, 1 in 6. Epilobium angustifolium 2 in 6, 1 in 10. Carex obnupta 1 in 10 and 11. Lampsana communis 1 in 2. Heracleum maximum 2 in 3. Bromus vulgaris 2 in 6. Brachypodium sylvaticum 1, Mimulus dentatus + in 7. Mimulus guttatus 1 in 8. Blechnum spicant 1, Mimulus moschatus 2 in 10. Mycelis muralis 2 in 11.

Localities: 1. Washington: Clallam Co. Port Angeles. Olympic National Park. Creek close to Visitor Center. 48º02'N-123º25'W. N, 15%, 30 m, 40 cm, 400 m2 (reg. 1998a: 69). 2. Oregon: Douglas Co. Between Elkton and Scottsburg. Umpqua Hwy. close to Weatherly Creek. 43º39'N-123º44'W. 25 m, 30 cm, 200 m2 (reg. 1997: 4). 3. Oregon: Curry Co. Samuel H. Boardman State Park. Arch Rock Point. Miller Creek. 42º11'N-124º22'W. W, 20%, 30 m, 40 cm, 600 m2 (reg. 1998a: 17). 4. British Columbia: Vancouver (North Vancouver), Capilano Lake. 49º14'N-123º04'W. NW, 20%, 25 m, 40 cm, 200 m2 (reg. 1995d: 115). 5. Oregon: Coos Co. Remote. Sandy Creek Road. Sandy Creek. 43º01'N-123º53'W. NE, 25%, 30 m, 40 cm, 400 m2 (reg. 1998a: 29). 6. Oregon: Lane Co. Between Odell Lake and Heather. Western side of Willamette Pass near Salt Creek. 43º37'N-122º04'W. S, 25%, 30 m, 40 cm, 200 m2 (reg. 1998:b 43). 7. Oregon: Lane Co. Between Penn and Flagg close to Wildcat Creek. 44º01'N-123º31'W. 30 m, 50 cm, 400 m2 (reg. 1996b: 109). 8. Oregon: Tillamook Co. Siuslaw National Forest between Happy Hollow and Hebo. Three River. 45º10'N-123º49'W. NW, 10%, 30 m, 40 cm, 400 m2, holotypus ass. (reg. 1998a: 46). 9. California: Del Norte Co. Crescent City-Smith River. Morrison River. 41º55'N-124º07'W. S, 15%, 20 m, 40 cm, 400 m2 (reg. 1998a: 15). 10. California: Del Norte Co. Del Norte Coast Redwood State Park. 41º43'N-124º05'W. SW, 10%, 25 m, 40 cm, 400 m2 (reg. 1998a: 12). 11. Oregon: Marion Co. Detroit-Niagara. Detroit Lake State Park Tumble Creek. 44º44'N-122º11'W. W, 10%, 20 m, 30 cm, 200 m2 (reg. 1998a: 45). 12. Synthesized table.

Type relevé (holotypus): Table 33, relevé n. 9. Rivas-Martínez reg. 1998a: 46. 12.06.98, made with Drs- Costa, Ladero & Sánchez-Mata. Site: Oregon: Tillamook Co. Siuslaw National Forest, between Happy Hollow and Hebo. Three River. 45º10'N-123º-49'W. 160 m, NW, 10%, 30 m, 40 cm, 400 m2. Physiognomy and habitat: Red alder (Alnus rubra) and Big-leaf maple (Acer macrophyllum) secondary macroforest. Estimated bioclimatic factors: Hyperoceanic Temperate (Ic ~ 9), upper mesotemperate (Itc ~ 200), lower hyperhumid (Io ~ 14), Positive Summer Temperature Tps ~ 440, submediterranean (Ios2 ~ 1.8). Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Oregonian-Vancouverian Coastal Sector, Oregonian Coastal Subsector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 2 Acer macrophyllum, 5 Alnus rubra. Others: 1 Asarum caudatum, 1 Circaea alpina var. pacifica, 1 Dicentra formosa, 1 Frangula purshiana, 1 Holodiscus discolor, + Maianthemum stellatum, 1 Oxalis oregana, + Picea sitchensis (S2), 3 Polystichum munitum, 1 Rubus ursinus subsp. macropetalus, 4 Rubus parviflorus, 3 Rubus spectabilis, 2 Sambucus racemosa subsp. pubens var. arborescens, 2 Stachys mexicana, 1 Stellaria crispa, 2 Tolmiea menziesii, + Tsuga heterophylla (S2). Companion species: 2 Claytonia sibirica, 1 Digitalis purpurea, 1 Mimulus guttatus.

North American associations of
Alno rubrae-Populion trichocarpae
North-Western Pacific biogeographic subsectors
4.1a 4.1b 4.2a 4.2b 4.2c 4.2d 4.3
8. Alno rubrae-Populion trichocarpae + + + + + + +
8a. Aceri macrophylli-Alnetum rubrae . . + + . . .
8b. Oplopanaco horridi-Alnetum rubrae . + . . + . .
8c Alno sinuatae-Populetum trichocarpae + + . . + . .
8d. Alno tenuifoliae-Populetum trichocarpae . . . . . + +
8e. Vaccinio membranacei-Alnetum sinuatae . . . + + + .
8f. Salici longistylis-Alnetum sinuatae + + . . . . .

Figure 27. Relationships between North American biogeographic Sectors of North-Western Pacific Subregion and adjacent biogeographic territories and the associations of Alno rubrae-Populion trichocarpae alliance. 4.1a. Boreal Oceanic Western Alaskan Sector, 4.1b. Boreal Oceanic Eastern Alaskan Sector, 4.2a. Oregonian Vancouverian Coastal Sector, 4.2b. Cascade Ranges Sector, 4.2c. Canadian Coastal Mountains Sector, 4.2d. Columbia Mountains Sector, 4.3. Northern Rocky Mountain Province.

8b. Oplopanaco horridi-Alnetum rubrae associatio nova hoc loco

Oceanic Temperate (euoceanic and semicontinental); upper supratemperate, hemiboreal and thermoboreal; hyperhumid to ultrahyperhumid; deciduous secondary or primary riparian meso- and macroforests usually with red alder (Alnus rubra) as dominant tree in the canopy growing on dystric, gleyic or stagnic podzols, cambic podzols and fluvisols throughout the Canadian Coastal Mountains and Boreal Oceanic Eastern Alaskan Sectors.

Bioclimatic diagnosis: Ic 11-20, Io 12.0-30.0, Itc < 120, Tp 600-1050, Tps 380-430, Tmin < 4, m < 2. [Teoc, Booc-Ste, Ote, Hbo, Tbo, Hhu, Uhh].

Table 34 shows two relevés sampled near Prince Rupert in British Columbia into the vegetation series territory of Abieti amabilis-Piceo sitchensis sigmetum in an ultrahyperhumid area characterized by Lysichiton americanus and Circaea alpina subsp. pacifica. Alnus rubra is the dominant tree in the canopy and Populus balsamifera subsp. trichocarpa usually grows as a non significant tree in this forest association. More thermic trees or small trees such as Acer macrophyllum, Acer circinalis or Frangula purshiana cannot grow in optimum in Oplopanaco-Alnetum rubrae forest association.

Table 34
8b. Oplopanaco horridi-Alnetum rubrae

(Alno-Populion trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 4 3 3
Number of species 24 25 24
Ordinal number 1 2* 3
Trees:
Alnus rubra 5 5 2
Tsuga heterophylla (S2) 2 1 2
Picea sitchensis (S2) 1 2 2
Thuja plicata (S2) 1 + 2
Populus trichocarpa (S2) 1 . 1
Characteristic species:
Rubus spectabilis 3 3 2
Oplopanax horridus 3 2 2
Sambucus arborescens 3 2 2
Ribes bracteosum 2 3 2
Athyrium cyclosorum 2 2 2
Geum macrophyllum 2 2 2
Vaccinium parvifolium 2 2 2
Polystichum munitum 1 2 2
Cornus canadensis 1 + 2
Circaea pacifica . 2 1
Tiarella trifoliata . 2 1
Companion species:
Lysichiton americanus 2 2 2
Equisetum boreale 1 2 2

Other species. Characteristic species: Streptopus americanus 2, Maianthemum dilatatum 1, Menziesia ferruginea 1, Vaccinium membranaceum 1, Alnus sinuata +, Gymnocarpium dryopteris + in 1. Cinna latifolia 2, Dryopteris expansa 1, Osmorhiza purpurea 1, Trientalis latifolia 1, Aruncus pubescens + in 2. Companion species: Blechnum spicant 2, Polypodium glycyrrhiza + in 1. Equisetum braunii 1, Hylocomium splendens 1, Rhytidiadelphus loreus 1 in 2.

Localities: 1. British Columbia: Prince Rupert, Diana Lake. 54º14'N-130º15'W. NW, 30%, 20 m, 30 cm, 400 m2 (reg. 1997: 28). 2. British Columbia: Between Prince Rupert and Diana Lake. 54º14'N-130º10'W. 25 m, 40 cm, N, 5%, 400 m2, holotypus ass. (reg. 1997: 21). 3. Synthesized table.

Type relevé (holotypus): Table 34, relevé n. 2. Rivas-Martínez reg. 1997: 21. 27.08.97, made with Dr. Sánchez-Mata and P. Rodríguez-Rojo. Site: British Columbia: Prince Rupert, between Prince Rupert and Diana Lake. 54º14'N-130º10'W. 30 m, N, 5%, 20 m, 30 cm, 400 m2. Physiognomy and habitat: Red alder (Alnus rubra) secondary mesoforest. Estimated bioclimatic factors: Oceanic Temperate (Ic ~ 13), hemiboreal (Tp ~ 880), ultrahyperhumid (Io ~ 25), Positive Summer Temperature Tps ~ 400. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Canadian Coastal Mountains Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 5 Alnus rubra. Others: 2 Cinna latifolia, 2 Circaea alpina subsp. pacifica, + Cornus canadensis, 1 Dryopteris expansa, 2 Geum macrophyllum, + Oplopanaxhorridus, 1 Osmorhiza purpurea, Picea sitchensis (S2), 2 Polystichum munitum, 3 Ribes bracteosum, 3 Rubus spectabilis, 2 Sambucus racemosa subsp. pubens var. arborescens, 2 Tiarella trifoliata var. trifoliata, + Thuja plicata (S2), 1 Trientalis borealis subsp. latifolia, 1 Tsuga heterophylla (S2), 2 Vaccinium parvifolium. Companion species: + Aruncus dioicus var. pubescens, 2 Athyrium filix-femina var. cyclosorum, 2 Equisetum arvense var. boreale, 1 Equisetum telmateia subsp. braunii, 1 Hylocomium splendens, 2 Lysichiton americanus, 1 Rhytidiadelphus loreus.

8c. Alno sinuatae-Populetum trichocarpae associatio nova hoc loco

Oceanic Temperate (euoceanic and semicontinental) and Continental Temperate (barely subcontinental); thermo-, meso-, and lower supraboreal, hemiboreal and upper supratemperate; upper subhumid to ultrahyperhumid; deciduous primary riparian or secondary meso- and macroforests with black cottonwood (Populus balsamifera subsp. trichocarpa) as dominant tree in the canopy growing on dystric, gleyic or stagnic podzols, cambic-podzols or fluvisols throughout the Boreal Oceanic Alaskan Province territories and in the less severe subcontinental mesoboreal lowlands in the Boreal Subcontinental Alaskan Subsector (Continental Alaskan Sector) areas.

Bioclimatic diagnosis: Ic 11-25, Io 4.8-30.0, Tp 450-1000, Tps 380-430, Tmin < -2, m < 0. [Teoc, Teco, Booc, Bosc-Ste, Hbo, Tbo, Mbo, Sbo-Ushu, Hum, Hhu, Uhh].

Table 35 gives three relevés sampled throughout the semicontinental Alaska coastal territories into the vegetation series territory of Rubo stellati-Piceo sitchensis sigmetum.

Populus balsamifera subsp. trichocarpa is the dominant tree in the canopy and in warmer territories, Acer glabrum var. douglasii becomes a frequent tree. In the understory of the primary macroforest, Sitka alder (Alnus viridis subsp. sinuata) is the dominant small tree with other species such as Viburnum edule and Cornus sericea subsp. sericea.

Table 35
8c. Alno sinuatae-Populetum trichocarpae

(Alno-Populion-trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 3 3 1 2
Number of species 16 17 19 17
Ordinal number 1* 2 3 4
Trees:
Populus trichocarpa 5 5 5 3
Acer douglasii . 1 . 1
Characteristic species:
Alnus sinuata 4 4 3 3
Pyrola asarifolia 2 1 3 3
Osmorhiza depauperata 1 2 2 3
Athyrium cyclosorum 1 1 2 3
Rosa sayi 1 3 + 3
Galium boreale 1 + 2 3
Oplopanax horridus + . 2 2
Viburnum edule 4 3 . 2
Cornus sericea 3 3 . 2
Salix scouleriana 1 1 . 2
Actaea arguta 1 1 . 2
Streptopus brevipes . + 2 2
Companion species:
Equisetum boreale 3 3 2 3
Heracleum maximum + . 1 2

Other species. Characteristic species: Aster modestus 1 in 1. Salix barclayi 1, Sorbus scopulina 1, Amelanchier semiintegrifolia + in 2. Circaea alpina 3, Aruncus pubescens 2, Sambucus pubens 2, Orobanche fasciculata 1, Orthilia secunda 1, Ribes laxiflorum +, Veratrum viride + in 3. Companion species: Ligusticum hultenii 2 in 1. Epilobium angustifolium 1 in 3.

Localities: 1. Alaska: Haines Wells, Chilkat River. 59º25'N-135º56ºW. 35 m, 100 cm, 200 m2, holotypus ass. (reg. 1994a: 158). 2. Alaska: Valdez close to Robe Lake. 61º05'N-146º09'W. 25 m, 45 cm, 200 m2 (reg. 1994a: 16). 3. Alaska: Haines, Klukwan, Chilkat River. 59º25'N-135º59'W. 40 m, 100 cm, 200 m2 (reg. 1994a: 159). 4. Synthesized table.

Type relevé (holotypus): Table 35, relevé n. 1. Rivas-Martínez reg. 1994a: 158. 25.08.94, made with Drs. Asensi. Costa, Fernández-González & Molero. Site: Alaska: Haines. Wells, Chilkat River. 59º25'N-135º56'W. 30 m, 35 m, 100 cm, 200 m2. Physiognomy and habitat: Black cottonwood (Populus balsamifera subsp. trichocarpa) riparian macroforest. Estimated bioclimatic factors: Oceanic Boreal, semicontinental (Ic ~ 19), upper thermoboreal (Tp ~ 710), upper humid (Io ~ 11), Positive Summer Temperature Tps ~ 400. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Boreal Pacific Province, Boreal South-Eastern Pacific Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 5 Populus balsamifera subsp. trichocarpa. Others: 1 Actaea rubra subsp. arguta, 4 Alnus viridis subsp. sinuata, 1 Aster modestus, 1 Athyrium filix-femina var. cyclosorum, 3 Cornus sericea subsp. sericea, + Oplopanax horridum, 1 Osmorhiza depauperata, + Pyrola asarifolia, 1 Rosa acicularis subsp. sayi, 1 Salix scouleriana, 4 Viburnum edule. Companion species: 3 Equisetum arvense var. boreale, 1 Galium boreale, + Heracleum maximum, 2 Ligusticum hultenii.

8d. Alno tenuifoliae-Populetum trichocarpae associatio nova hoc loco

Oceanic Temperate (semicontinental) and Continental Temperate (barely subcontinental); upper supratemperate, hemiboreal, and orotemperate, upper subhumid to humid, submediterranean; deciduous secondary or primary riparian meso- and macroforests with black-cottonwood (Populus balsamifera subsp. trichocarpa) as dominant tree in the canopy often with Acer glabrum var. douglasii growing on dystric, gleyic or stagnic podzols, cambisols or fluvisols throughout the Columbia Mountains Sector and Northern Rocky Mountain Province territories mainlyin Flathead and Salmon Mountain Sector.

Bioclimatic diagnosis: Ic 18-25, Io 4.8-12.0, Tp 600-1100, Tps 450-550, Tmin <-3, m < -5. [Teoc, Teco-Uste, Hbo, Ote-Ushu, Hum-Sbm].

Table 36 gives four relevés sampled throughout the Montana and British Columbia territories (Flathead and Upper Kootenay River, and Thompson Plateau Subsectors) where the transitions between the forests of Tsugion heterophyllae, Piceo engelmannii-Abietion bifoliae and Pino scopulorum-Pseudotsugion glaucae alliances are common. Alno tenuifoliae-Populetum trichocarpae represents the boundary between the riparian forests of Alno-Populetalia trichocarpae and the more continental cottonwood forests of Populetalia angustifolio-deltoidis order (Betulo occidentalis-Populion angustifoliae).

Within the more common species in this black cottonwood forest association we could remark in the understory some small trees and shrubs such as Alnus incana subsp. tenuifolia, Cornus sericea subsp. occidentalis, Betula xutahensis (=Betula papyrifera x occidentalis), and Symphoricarpos albus var. laevigatus.

Table 36
8d. Alno tenuifoliae-Populetum trichocarpae

(Alno-Populion trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 98 98 100 75 93
Number of species 15 15 16 19 14
Ordinal number 1* 2 3 4 5
Trees:
Populus trichocarpa 4 3 5 4 4
Acer douglasii 1 2 + . 3
Characteristic species:
Cornus occidentalis 1 2 3 3 4
Alnus tenuifolia 1 2 2 3 4
Betula utahensis 2 2 1 1 4
Symphoricarpos laevigatus 1 + 2 + 4
Amelanchier alnifolia 1 1 1 + 4
Rubus parviflorus 1 3 . 1 3
Sambucus pubens 1 + + . 3
Prunus melanocarpa . . 2 + 2
Salix amygdaloides 1 . . 1 2
Crataegus douglasii 1 1 . . 2
Holodiscus discolor 1 + . . 2
Companion species:
Brachypodium sylvaticum 1 2 2 1 4
Urtica dioica . 1 1 + 3
Epilobium angustifolium 1 1 + . 3

Other species. Trees: Populus tremuloides +, Picea engelmannii (S2) + in 1. Larix occidentalis (S2) + in 2. Thuja plicata (S2) 1 in 4. Characteristic species: Cornus canadensis 2, Maianthemum amplexicaule 2, Rosa ultramontana 1, Prunus pensylvanica + in 1. Crataegus columbiana 3, Rosa nutkana 3 in 2. Companion species: Equisetum arvense 2, Equisetum hyemale 1 in 1. Tanacetum vulgare + in 2. Pteridium pubescens + in 3.

Localities: 1. Montana: Flathead Co. Fisher River, Little Bitterroot Lake close to Bitterroot Lane. 48º06'N-114º44'W. SW, 30 m, 100 cm, 200 m2 (reg. 1996b: 76). 2. Montana: Flathead Co. West Glacier, Glacier National Park, Lake McDonald. 48º31'N-113º59'W. NW, 30 m, 100 cm, 200 m2 (reg. 1992e: 20). 3. Montana: Flathead Co. West Glacier, Glacier National Park, Lake McDonald. 48º32'N-113º59'W. N, 25 m, 80 cm, 200 m2, holotypus ass. (reg. 1992e: 19). 4. British Columbia: Tête Juane Cache, Fraser River. 52º55'N-119º25'W. S, 25 m, 80 cm, 200 m2, holotypus ass. (reg. 1995d: 136). 5. Synthesized table.

Type relevé (holotypus): Table 36, relevé n. 1. Rivas-Martínez 1996b: 76. made with Drs. Llorens & Sánchez-Mata. Site: Montana: Flathead Co. Fisher River, Little Bitterroot Lake close to Bitterroot Lane. 48º06'N-114º44'W. 980 m, SW, 30 m, 200 m2. Physiognomy and habitat: Black cottonwood (populus trichocarpa) riparian macroforest. Estimated bioclimatic factors: Continental Temperate, subcontinental (Ic ~ 24), upper supratemperate (~ 900), upper subhumid (Io ~ 5), Positive Summer Temperature Tps ~ 500, submediterranean (Ios2 ~ 2.2). Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Cascade Ranges Sector, Washingtonian Cascade Subsector. Floristic combination: Linnaeo-Piceetea characteristic species: 4 Alnus viridis subsp. sinuata, + Chimaphila umbellata subsp. occidentalis, 1 Clintonia uniflora, 1 Cornus canadensis, + Gaultheria ovatifolia, 1 Goodyera oblongifolia, 1 Gymnocarpium dryopteris, 1 Linnaea americana, 1 Orthilia secunda, + Pyrola asarifolia, 2 Ribes laxiflorum, 3 Rubus lasiococcus, 2 Rubus spectabilis, 1 Salix sitchensis, 1 Sorbus sitchensis var. sitchensis, 3 Vaccinium membranaceum. Companion species: 1 Epilobium angustifolium.

8e. Vaccinio membranacei-Alnetum sinuatae associatio nova hoc loco

Oceanic Temperate (semicontinental) and Temperate Continental (barely subcontinental); orotemperate and upper supratemperate; upper subhumid to lower hyperhumid; deciduous secondary or snow-pack permanent thickets of Sitka alder (Alnus viridis subsp. sinuata) as dominant small tree. Broadly distributed throughout the Cascade Ranges, Canadian Coastal Mountains and Columbia Mountains Sectors these forest communities grow on gleyic, dystric or stagnic podzols or gleysols. Within the most common shrubs or dwarf-shrubs living in these thicket communities of Alnus viridis subsp. sinuata could be mentioned Vaccinium membranaceum, Ribes laxiflorum, Rubus lasiococcus, Sorbus scopulina, Chimaphila umbellata subsp. occidentalis and Menziesia ferruginea.

Bioclimatic diagnosis: Ic 18-23, Io 4.8-15.0, Tp 400-900, Tps 300-500, Tmin <-4, m < -6. [Teoc, Teco-Ste, Ote-Ushu, Hum, Lhhu].

Table 37 shows seven relevés sampled throughout the British Columbia, Washington and Oregon areas, which represent the seral vegetation of the Tsugo mertensianae sigmion and sometimes the permanent potential natural vegetation of deep snowy avalanche small valleys and reduced bottomlands.

Type relevé (holotypus): Table 37, relevé n. 3. Rivas-Martínez 1998a: 74. 26.08.98, made with Drs. Costa, Ladero & Sánchez-Mata. Site: Washington: Chelan Co. Mount Baker-Snoqualmie National Forest, between Skykomish and Berne, Steven Pass. 47º45'N-121º05'W. 1370 m, N, 20%, 4 m, 100 m2. Physiognomy and habitat: Sitka alder (Alnus viridis subsp. sinuata) dense woodland thicket. Estimated bioclimatic factors: Oceanic Temperate, semicontinental (Ic ~ 19), upper orotemperate (Tp ~ 500), lower hyperhumid (Io ~ 15), Positive Summer Temperature Tps ~ 350. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Cascade Ranges Sector, Washingtonian Cascade Subsector. Floristic combination: Linnaeo-Piceetea characteristic species: 4 Alnus viridis subsp. sinuata, + Chimaphila umbellata subsp. occidentalis, 1 Clintonia uniflora, 1 Cornus canadensis, + Gaultheria ovatifolia, 1 Goodyera oblongifolia, 1 Gymnocarpium dryopteris, 1 Linnaea americana, 1 Orthilia secunda, + Pyrola asarifolia, 2 Ribes laxiflorum, 3 Rubus lasiococcus, 2 Rubus spectabilis, 1 Salix sitchensis, 1 Sorbus sitchensis var. sitchensis, 3 Vaccinium membranaceum. Companion species: 1 Epilobium angustifolium.

Table 37
8e. Vaccinio membranecei-Alnetum sinuatae

(Alno-Populion trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 135 134 137 82 130 135 133 10
Number of species 18 19 20 21 23 24 25 24
Ordinal number 1 2 3* 4 5 6 7 8
Trees:
Populus trichocarpa (S2) 1 . . 1 . + . III
Characteristic species:
Alnus sinuata 5 5 4 4 4 5 3 V
Linnaea americana 2 3 1 1 + + 1 V
Clintonia uniflora 1 3 1 1 1 + + V
Vaccinium membranaceum 1 2 3 + 1 1 3 V
Pyrola asarifolia 1 2 + + . 1 + V
Goodyera oblongifolia + 1 1 . + 1 1 V
Tiarella unifoliata 2 1 . 1 1 1 1 V
Ribes laxiflorum 1 1 2 . 1 . 1 IV
Rubus lasiococcus + 1 3 . 1 . + IV
Cornus canadensis 1 + 1 . . + 1 III
Orthilia secunda 1 . 1 . 1 1 1 IV
Gymnocarpium dryopteris 1 . 1 . + 2 + IV
Sorbus scopulina 1 2 . + + . . III
Chimaphila occidentalis . 2 + . + . . III
Gaultheria ovatifolia . 2 + . + . . III
Viola orbiculata . + . . . 1 1 III
Rubus spectabilis . . 2 . 3 . + III
Menziesia ferruginea . . . . 1 + 2 III
Rubus parviflorus + . . 3 . . . II
Amelanchier alnifolia . 2 . . . + . II
Paxistima myrsinites . 2 . . . . + II
Ribes lacustre . . . . 1 . + II
Companion species:
Epilobium angustifolium 2 . 1 3 + 2 1 V
Pteridium pubescens 1 1 . 2 + . + IV
Equisetum boreale . . . 2 . + + III

Other species. Trees: Pinus latifolia (S2) + in 2 and 4. Abies amabilis (S2) 1, Tsuga mertensiana (S2) + in 3. Pseudotsuga glauca (S2) 1, Acer douglasii +, Picea albertiana (S2) + in 4. Acer circinatum 1 in 5. Characteristic species: Veratrum caudatum + in 1 and 3. Salix sitchensis 1 in 3 and 6. Sorbus sitchensis 1 in 3, + in 7. Spiraea lucida + in 4 and 5. Holodiscus discolor + in 5 and 7. Hieracium albiflorum 1 in 6 and 7. Adenocaulon bicolor + in 6, 1 in 7. Osmorhiza purpurea + in 6 and 7. Rosa ultramontana + in 2. Aruncus pubescens 2, Corylus cornuta 2, Lonicera involucrata 2 in 4. Arnica cordifolia 1, Vancouveria hexandra 1 in 5. Calamagrostis purpurascens 1, Valeriana sitchensis 1 in 6. Companion species: Anaphalis margaritacea 2 in 4, 1 in 6. Bromus vulgaris 1 in 6.

Localities: 1. British Columbia: Glacier National Park, Roger Pass. 51º23'N-117º28'W. SE, 10%, 5 m, 100 m2 (reg. 1992e: 105). 2. Washington: Okanogan Co. Okanogan National Forest, between Klipchuck and Washington Pass, Cutthroat Creek. 48º34'N-120º38'W. S, 20%, 6 m, 200 m2 (reg. 1994: 91). 3. Washington: Chelan Co. Mount Baker-Snoqualmie National Forest between Skykomish and Berne, Steven Pass. 47º45'N-121º05'W. N, 20%, 4 m, 100 m2, holotypus ass. (reg. 1998a: 74). 4. British Columbia: Between Avola and Blue River, Thompson River, Monashee Mountains. 51º49'N-119º18'W. SW, 10%, 6 m, 200 m2 (reg. 1995d: 132). 5. Oregon: Clackamas Co. Mt. Hood National Forest, Mt. Hood, between Government Camp and Barlow Pass. 45º17'N-121º41'W. N, 15%, 6 m, 100 m2 (reg. 1998b: 60). 6. British Columbia: Revelstoke, Mt. Revelstoke National Park. 51º06'N-118º05'W. S, 10%, 6 m, 200 m2 (reg. 1998b: 103). 7. British Columbia: Glacier National Park, Rogers Pass between Rogers Pass City and Donald. 51º22'N-117º28'W. E, 15%, 6 m, 200 m2 (reg. 1998b: 113). 8. Synthesized table.

8f. Salici longistylis-Alnetum sinuatae associatio nova hoc loco

Oceanic Boreal (euoceanic and semicontinental) and Subcontinental Boreal (barely subcontinental); mesoboreal and lower supraboreal; upper subhumid to ultrahyperhumid; deciduous secondary or snow-pack permanent thickets of Sitka alder (Alnus viridis subsp. sinuata) growing on gleyic, stagnic podzols or gleysols in the Boreal Oceanic Alaskan Province. Within the most common shrubs could be mentioned Salix alaxensis var. longistylis, Ribes laxiflorum and Salix glauca var. acutifolia.

Bioclimatic diagnosis: Ic 16-25, Io 4.8-40.0, Tp 450-740, Tps 280-420, Tmin < -2, m < -6. [Booc, Bosc-Tbo, Mbo, Sbo-Ushu, Hum, Hhu, Uhh].

Table 38 gives three relevés sampled throughout the Alaska territories, which represent the initial or the seral vegetation of Piceo sitchensis-Tsugo mertensianae sigmetum, and also the potential natural vegetation of deep snow-beds or very snowy slopes.

Table 38
8f. Salici longistylis-Alnetum sinuatae

(Alno-Populion trichocarpae, Alno-Populetalia trichocarpae)

Altitude (1=10m) 3 4 3 3
Number of species 13 13 15 14
Ordinal number 1 2* 3 4
Characteristic species:
Alnus sinuata 4 5 5 3
Salix longistylis 2 1 + 3
Athyrium cyclosorum 1 2 4 3
Oplopanax horridus 1 2 3 3
Aruncus acuminatus 1 2 1 3
Gymnocarpium dryopteris + 1 3 3
Ribes laxiflorum + 1 1 3
Salix acutifolia 1 . + 2
Sambucus arborescens . 2 2 2
Heuchera glabra . + 1 2
Dryopteris expansa . + 1 2
Companion species:
Equisetum boreale 2 + 1 3
Athyrium americanum 1 2 3 3
Epilobium latifolium 1 . + 2

Other species. Trees: Populus trichocarpa (S2) + in 2, 1 in 3. Companion species: Epilobium angustifolium 1, Angelica lucida + in 1.

Localities: 1. Alaska: Portage Lake. 60º47'N-148º48'W. N, 15%, 3 m, 200 m2. (reg. 1994a: 9). 2. Alaska: Between Portage and Glacier Byron moraine. 60º45'N-148º47'W. N, 15%, 20 m, 30 cm, 200 m2, holotypus ass. (reg. 1994a: 7). 3. Alaska: Between Portage and Glacier Byron moraine. 60º45'N-148º47'W. N, 15%, 30 m, 40 cm, 200 m2. (reg. 1994a: 8). 4. Synthesized table.

Type relevé (holotypus): Table 38, relevé n. 2. Rivas-Martínez 1994a: 7. 21.08.94, made with Drs. Asensi, Costa, Fernández-González & Molero. Site: Alaska. Between Portage and Glacier Byron Moraine. 60º45'N-148º47'W. 1370 m, N, 20%, 4 m, 100 m2. Physiognomy and habitat: Sitka alder (Alnus viridis subsp. sinuata) dense woodland thicket. Estimated bioclimatic factors: Oceanic Boreal (Ic ~ 20), upper mesoboreal (Tp ~ 590), lower hyperhumid (Io ~ 15), Positive Summer Temperature Tps ~ 340. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Boreal Pacific Province, Boreal Western Pacific Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: + Populus trichocarpa (S2). Others: 5 Alnus viridis subsp. sinuata, 2 Aruncus dioicus var. acuminatus, 2 Athyrium filix-femina var. cyclosorum, 2 Athyrium alpestre var. americanum, + Dryopteris expansa, 1 Gymnocarpium dryopteris, + Heuchera glabra, 2 Oplopanax horridus, 1 Ribes laxiflorum, 1 Salix alaxensis var. longistylis, 2 Sambucus racemosa subsp. pubens var. arborescens. Companion species: 1 Epilobium angustifolium, + Equisetum arvense var. boreale.