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: Pino scopulorum-Pseudotsugion glaucae

10. Pino scopulorum-Pseudotsugion glaucae alliancia nova hoc loco

Typus nominis: Larici occidentalis-Pseudotsugetum glaucae associatio nova hoc loco.

Climactical and permanent edapho-xerophilous coniferous meso- and macroforests spreading into Continental and Xeric Temperate and Continental Pluviseasonal Mediterranean (subcontinental and eucontinental) bioclimate territories; supratemperate and lower orotemperate, supra- and oromediterranean; dry and subhumid; submediterranean and occasionally steppic. The most characteristic trees are Pseudotsuga menziesii var. glauca (Rocky Mountain Douglas fir), Pinus ponderosa var. scopulorum (Rocky Mountain ponderosa pine) and Larix occidentalis (western larch). These coniferous forests are distributed throughout the Rocky Mountain Subregion territories and very locally reach some dry valleys in the Cascade Province areas (mainly in Columbia Mountain Sector) and in high ranges of the Great Basin Region. Pino scopulorum-Pseudotsugion glaucae alliance forests grow on cambisols, andosols, luvisols, leptosols and podzols.

Bioclimatic diagnosis: Ic 21-34, Io 2.0-6.0, T 700-1300, Tps 400-650, Tmin < -3, m < -7. [Teco, Texe, mepc-Ste, Ote, Ome, Sme-Dry, shu-Sbm, Stp].

Characteristic species: Abies concolor, Amelanchier alnifolia var. humptulipensis, Amelanchier pumila, Aster glaucodes, Chimaphila menziesii, Clematis columbiana var. tenuiloba, Holodiscus dumosus, Juniperus scopulorum, Larix occidentalis, Mahonia repens, Physocarpus malvaceus, Picea engelmannii var. glabra, Picea pungens, Pinus ponderosa var. scopulorum, Pinus ponderosa var. scopulorum x P. ponderosa var. ponderosa, Pseudotsuga menziesii var. glauca, Rhus trilobata, Symphoricarpos oreophilus var. oreophilus, Valeriana acutiloba.

Within the alliance Pino scopulorum-Pseudotsugion glaucae (coniferous forests with Rocky Mountain Douglas fir and ponderosa pine) we distinguish four forest associations. Regarding their geographical distribution and their floristic and phyto-topographical features, the involved forest communities could be easily recognized using the following diagnostic key. [A general key for all the coniferous forests associations of the Linnaeo americanae-Piceetea marianae class has been proposed at the begining of the syntaxonomical chapter, see pg. 39]

1 Forests distributed throughout the Rocky Mountain Subregion areas: Northern Rocky Mountain and Central-Eastern Rocky Mountain Provinces [climactical or permanent edapho-xerophilous communities with Pinus flexilis, but without Larix occidentalis, Rhus trilobata or Chimaphila occidentalis] 2
Forests not distributed in the Rocky Mountain Sugbregion territories [climactical or permanent edapho-xerophilous communities with Larix occidentalis, Rhus trilobata or Chimaphila occidentalis but without Pinus flexilis] 3
2 Edapho-xerophilous micro- or mesoforests with Pinus flexilis and Pseudotsuga glauca, spreading into Rocky Mountain Subregion territories with the exception of Fraser Interior Plateau Sector [in the understory Elymus glaucus, but without Amelanchier alnifolia s.l., Juniperus scopulorum or Shepherdia canadens] 10d. Pseudotsugo glaucae-Pinetum flexilis
Climactical Pseudotsuga glauca mesoforests but without Pinus flexilis, spreading into Rocky Mountain Subregion territories [in the understory with Amelanchier alnifolia s.l., Juniperus scopulorum or Shepherdia canadensis 10b. Shepherdio canadensis-Pseudotsugetum glaucae
3 Climactical meso-macroforests with Larix occidentalis, spreading into Canadian Rockies Sector territories, as well as Flathead and Salmon Mountains, and Columbia Mountains Sectors [in the understory with Orthilia secunda, Maianthemum stellatum or Chimaphila occidentalis, but without Juniperus scopulorum, Rhus trilobata or Symphoricarpos oreophilus] 10a. Larici occidentalis-Pseudotsugetum glaucae
Climactical mesoforests without Larix occidentalis but with Pinus ponderosa var. scopulorum as main tree, spreading into High Plains Sector and High Missouri Subsector [in the understory with Juniperus occidentalis, Rhus trilobata or Symphoricarpos oreophilus but without Orthilia secunda, Maianthemum stellatum or Chimaphila occidentalis] 10c. Rhoo trilobatae-Pinetum scopulorum

10a. Larici occidentalis-Pseudotsugetum glaucae associatio nova hoc loco

Climactical meso- and macroforests spreading into the Continental Temperate (subcontinental) bioclimate territories; supratemperate and lower orotemperate; subhumid; often submediterranean. The main forest trees are Pseudotsuga menziesii var. glauca (Rocky Mountain Douglas fir) and Larix occidentalis (western larch). These forests spreading into Canadian Rockies Sector territories, as well as Flathead and Salmon Mountains Sector (Northern Rocky Mountain Province) and Columbia Mountain Sector (Cascade Province) and grow on haplic and ferric podzols, podzo-luvisols and dystric cambisols. In the coldest territories of the association area, in the lower orotemperate thermotype belt, it could be distinguished a particular variant with Engelmann spruce (Picea engelmannii var. engelmannii) which represents the natural ecotone with the Northern Rocky Mountain orotemperate forest association Menziesio ferrugineae-Abietetum bifoliae (Piceo-Abietion bifoliae alliance).

Bioclimatic diagnosis: Ic 21-26, Io 3.6-6.0, Tp 700-1000, Tps 420-550, Tmin < -3, m < -7. [Teco, Mepc-Ste, Ote, Sme, Ome-Shu-Sbm].

Table 49 shows ten relevés from Montana and Washington, in the Canadian Rockies Sector, as well as Flathead and Salmon Mountain Sector territories. Pseudotsuga menziesii var. glauca (Rocky Mountain Douglas fir) and Larix occidentalis (western larch), are the commonest trees; Picea engelmannii var. engelmannii (Engelmann spruce) is also noticeable in lower orotemperate thermotype territories and in burned or disturbed forests by fires, Pinus contorta var. latifolia (lodgepole pine) exists mainly as isolated trees. Within the most important plants in the understory it could be mentioned Linnaea americana, Paxistima myrsinites, Spiraea betulifolia var. lucida, Maianthemum stellatum, Symphoricarpos albus var. laevigatus and Chimaphila umbellata subsp. occidentalis, which give a westerly and oceanic aspect to the association.

Table 49
10a. Larici occidentalis-Pseudotsugetum glaucae

(Pino-Pseudotsugion glaucae, Pseudotsugo-Abietetalia bifoliae)

Altitude (1=10m) 130 133 75 120 114 48 140 102 140 119 112
Number of species 21 22 23 26 27 29 29 31 31 33 27
Ordinal number 1 2 3 4 5* 6 7 8 9 10 11
Trees:
Pseudotsuga glauca 5 4 3 5 3 3 3 3 3 3 V
Larix occidentalis 3 1 2 2 4 3 2 2 2 3 V
Pinus latifolia 1 1 . 1 . + . 1 1 + III
Picea engelmannii . . . . . . 2 2 2 2 III
Characteristic species:
Linnaea americana 4 2 1 3 1 2 1 3 2 2 V
Paxistima myrsinites 1 3 1 + 3 2 3 . 3 3 V
Orthilia secunda + 1 1 . 2 + 2 1 2 1 V
Spiraea lucida 2 2 + 3 2 . 1 1 . 2 IV
Maianthemum stellatum + + 3 2 1 . 2 2 . 1 IV
Symphoricarpos albus 1 . 2 3 1 3 . 3 2 + IV
Amelanchier alnifolia 1 + + 2 . 2 . . 1 2 IV
Arctostaphylos uva-ursi 2 3 . 2 1 1 . 1 . 2 IV
Chimaphila occidentalis 1 1 1 1 . . . 2 2 1 IV
Goodyera oblongifolia + 1 1 . . . 2 . 2 1 III
Galium trifidum . . 1 1 2 . 2 1 + . III
Mahonia repens . . 1 2 + 3 . 2 + . III
Hieracium albiflorum 2 1 + . . . . . 1 1 III
Ribes montigenum 1 + 1 . . . + . 1 1 III
Osmorhiza purpurea . 1 + . . . . 1 + 2 III
Clintonia uniflora . . + . 1 . 2 1 2 . III
Rubus parviflorus . . . . 1 . 1 + + + III
Antennaria racemosa 1 1 + 2 . . . . . . II
Vaccinium scoparium . 2 . . . . + . 3 1 II
Cornus canadensis . + . . . . . 3 1 + II
Aralia nudicaulis . . 2 . 2 2 . 2 . . II
Companion species:
Fragaria bracteata 1 1 . 2 1 2 . . 1 1 IV

Other species. Trees: Pinus scopulorum 1 in 1 and 4, 2 in 6. Thuja plicata 2 in 3, + in 9. Populus tremuloides 1 in 6, + in 8. Taxus brevifolia 1 in 5. Acer douglasii 2 in 6. Picea glabra + in 10. Characteristic species: Viola renifolia + in 2 and 10, 1 in 6 and 8. Betula occidentalis 1in 5. Pyrola asarifolia + in 6, 2 in 7, 1 in 8 and 10. Alnus sinuata 1 in 7 and 9, + in 8 and 10. Clematis columbiana 1 in 4, 5 and 7. Ribes lacustre 2 in 5, 1 in 7 and 10. Tiarella unifoliata 2 in 5 and 7, 1 in 9. Calamagrostis rubescens 2 in 1, 1 in 2. Rosa nutkana 1 in 3, 2 in 5. Rosa ultramontana 2 in 4, 1 in 5. Elymus glaucus 2 in 4, + in 6. Arnica cordifolia 2 in 4, 1 in 7. Thalictrum venulosum + in 4, 1 in 8. Disporum trachycarpum 2 in 5, 1 in 7. Cornus sericea 1 in 5, + in 7. Lonicera utahensis + in 5 and 7. Trillium ovatum + in 5 and 7. Rosa arkansana 2 in 6, 1 in 8. Shepherdia canadensis 1 in 6 and 8. Juniperus montana + in 6 and 8. Vaccinium caespitosum 3 in 6, 2 in 10. Disporum smithii 1 in 6, + in 10. Viola glabella + in 6, 1 in 10. Antennaria rosea + in 6 and 10. Rosa gymnocarpa + in 6 and 10. Arnica latifolia 1 in 9 and 10. Vaccinium membranaceum 2 in 1. Holodiscus dumosus + in 3. Mitella breweri 1, Physocarpus malvaceus 1, Prunus virginiana 1, Crataegus piperi + in 4. Campanula scouleri 1 in 6. Gymnocarpium dryopteris 2, Stenanthium occidentale 2, Streptopus chalazatus 2, Thalictrum occidentale 2 in 7. Disporum oreganum 2, Corallorhiza trifida +, Maianthemum amplexicaule +, Platanthera orbiculata + in 8. Lonicera ciliosa 1 in 8, 2 in 9. Adenocaulon bicolor 1, Lonicera involucrata 1, Viola orbiculata 1 in 9. Companion species: Brachypodium sylvaticum 1 in 1, 3 and 7, + in 6. Epilobium angustifolium 1 in 4, + in 10. Polytrichum juniperinum 3 in 5, 1 in 9. Antennaria microphylla 1 in 2. Corylus californica 1 in 6. Bromus vulgaris + in 9.

Localities: 1. Washington: Okanogan Co. Loup-Loup Summit. 48º25'N-119º50'W. S, 20%, 30 m, 40 cm, 400 m2. (reg. 1994b: 87). 2. Washington: Okanogan Co. Loup-Loup Summit. 48º25'N-119º55'W. NE, 10%, 30 m, 50 cm, 500 m2, sandy soils. (reg. 1994b: 86). 3. Montana: Lincoln Co. Kootenai National Forest, Libby. 48º22'N-115º33'W. N, 100%, 40 m, 170 cm, 500 m2 (reg. 1996b: 77). 4. Montana: Missoula Co. Lolo National Forest, Lewis and Clark Camp, Between Lolo and Lolo Hot Springs. 46º46'N-114º21'W. NE, 35%, 35 m, 60 cm, 400 m2. (reg. 1994b: 73). 5. Montana: Flathead Co. West Glacier, Glacier National Park. 48º30'N-113º58'W. N, 20%, 25 m, 50 cm, 1000 m2, holotypus ass. (reg. 1996b: 74). 6. Washington: Stevens Co. Between Marble and Hudson, Onion Creek. 48º53'N-117º51'W. NW, 25%, 25 m, 40 cm, 1000 m2, glacier alluvial deposits. (reg. 1998b: 94). 7. Montana: Glacier Co. Lewis and Clark National Forest, Between Marias Pass and East Glacier Park. 48º19`N-113º20'W. N, 45%, 25 m, 50 cm, 500 m2 (reg. 1996b: 73). 8. Montana: Lincoln Co. Kootenai National Forest, Between Stryker and Kickey Lake. 48º42'N-114º47'W. N, 20%, 35 m, 80 cm, 1000 m2 (reg. 1998b: 120). 9. Washington: Ferry Co. Colville National Forest, Deer Creek-Boulder Creek Road, Boulder-Deer Creek Summit. 48º52'N-118º23'W. N, 15%, 35 m, 80 cm, 2000 m2. (reg. 1998b: 93). 10. Washington: Okanogan Co. Loup-Loup Summit, Frazer Creek. 48º23'N-119º54'W. SW, 15%, 35 m, 80 cm, 2000 m2, glacier sands (reg. 1998b: 92). 11. Synthesized table.

Type relevé (holotypus): Table 49, relevé n. 5. Rivas-Martínez reg. 1996b: 74. 01.09.96, made with Drs. Llorens and Sánchez-Mata. Site: Montana: Flathead Co. West Glacier, Glacier National Park. 48º30'N-113º58'W. 1140 m, N, 20%, 25 m, 50 cm, 1000 m2. Physiognomy and habitat: Mature Western larch (Larix occidentalis) and Rocky Mountain Douglas fir (Pseudotsuga menziesii var. glauca) mesoforest. Estimated bioclimatic factors: Pluviseasonal Continental Mediterranean, subcontinental (Ic ~ 24), upper supramediterranean (Tp ~ 950), lower subhumid (Io ~ 4), Positive Summer Temperature Tps ~ 450. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Salmon and Flathead Mountain Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 4 Larix occidentalis, 3 Pseudotsuga menziesii var. glauca, 1 Taxus brevifolia. Others: 2 Aralia nudicaulis, 1 Arctostaphylos uva-ursi var. uva-ursi, 1 Clematis columbiana var. columbiana, 1 Clintonia uniflora, 1 Cornus sericea subsp. sericea, 2 Disporum trachycarpum, 2 Galium trifidum, 1 Linnaea americana, + Lonicera utahensis, + Mahonia repens, 1 Maianthemum stellatum, 2 Orthilia secunda, 3 Paxistima myrsinites, 2 Ribes lacustre, 1 Rosa nutkana, 1 Rosa woodsii var. ultramontana, 1 Rubus parviflorus, 2 Spiraea betulifolia var. lucida, 1 Symphoricarpos albus var. albus, 2 Tiarella trifoliata var. unifoliata, + Trillium ovatum. Companion species: 1 Fragaria vesca subsp. bracteata.

10b. Shepherdio canadensis-Pseudotsugetum glaucae associatio nova hoc loco

Climactical meso and macroforests spreading into Continental and Xeric Temperate, Continental Pluviseasonal Mediterranean (subcontinental) bioclimate areas; supratemperate and lower orotemperate, upper supra-and lower oromediterranean, upper dry and lower subhumid; often Steppic or submediterranean. The dominant tree is Pseudotsuga menziesii var. glauca (Rocky Mountain Douglas fir), and in drier habitats Pinus ponderosa var. scopulorum (Rocky Mountain ponderosa pine) becomes frequent. These forests are distributed throughout the Rocky Mountain Subregion territories and Columbia Mountains Sector and grow on cambisols, andosols, podzo-luvisols and podzols. Usually, these Rocky Mountain Douglas fir forests has a dense shrubby understory where the most important plants are Shepherdia canadensis, Juniperus communis var. depressa, Amelanchier alnifolia s. l., Juniperus scopulorum and Rosa woodsii var. ultramontana. East of Northern Rocky Mountain Province areas, in the upper Missouri Basin territories (High Missouri Subsector and the High Plains Sector) the climate becomes drier and more continental, and consequently the forests of Pinus ponderosa var. scopulorum, usually without Pseudotsuga menziesii var. glauca, become fragile forest communities and easily transformed in grasslands (Rhoo trilobatae-Pinetum scopulorum).

Bioclimatic diagnosis: Ic 23-28, Io 2.8-4.8, Tp 700-1000, Tps 420-600, Tmin < -6, m < -12. [Teco, Texe, Mpco-Ste, Ote, Sme, Ome-Udry, Lshu-Stp].

Table 50
10b. Shepherdio canadensis-Pseudotsugetum glaucae

(Pino-Pseudotsugion glaucae, Pseudotsugo-Abietetalia bifoliae)

Altitude (1=10m) 74 93 86 170 157 77 109
Number of species 13 13 14 18 19 19 16
Ordinal number 1 2 3* 4 5 6 7
Trees:
Pseudotsuga glauca 4 3 4 2 5 4 V
Pinus scopulorum . 2 . 4 + 3 III
Characteristic species:
Shepherdia canadensis 3 2 2 2 1 1 V
Juniperus depressa 3 2 1 2 1 2 V
Amelanchier alnifolia 3 + 1 + 3 3 V
Calamagrostis rubescens 1 1 2 1 2 1 V
Juniperus scopulorum 2 2 2 1 . 1 IV
Rosa ultramontana 2 1 2 . 2 1 IV
Symphoricarpos oreophilus . . 1 2 3 2 III
Elymus glaucus . . 1 + 1 . II
Mahonia repens . . + 2 1 . II
Poa stenantha 2 . . . 1 . II
Arctostaphylos adenotricha . . . . 2 3 II
Spiraea lucida . . . . 2 2 II
Prunus melanocarpa . . . . 2 1 II
Companion species:
Verbascum thapsus + 1 1 + 1 . IV
Festuca campestris 2 1 1 . . + III
Elymus trachycaulus . . 1 . 1 1 II

Other species. Trees: Acer glabrum 1, Populus tremuloides + in 5. Pinus latifolia + in 6. Characteristic species: Linnaea americana 1 in 1. Galium triflorum 2, Pulsatilla occidentalis 2, Antennaria rosea 1, Disporum trachycarpum 1, Goodyera oblongifolia 1 in 4. Apocynum androsaemifolium 1 in 6. Companion species: Artemisia tridentata 1 in 1 and 2. Chrysothamnus nauseosus + in 2, 1 in 3. Dicranum pallidisetum 1 in 1. Artemisia frigida 1 in 2. Bupleurum americanum 1, Ribes aureum 3 in 4. Epilobium angustifolium 1, Campanula parryi + in 5. Purshia tridentata 2, Solidago spathulata 1 in 6.

Localities: 1. British Columbia: Williams Lake. 52º08'N-122º09'W. W, 15%, 25 m, 70 cm, 400 m2 (reg. 1992e: 86). 2. British Columbia: Clinton. 51º04'N-121º40'W. E, 10%, 20 m, 60 cm, 200 m2 (reg. 1992e: 88). 3. British Columbia: Radium Hot Springs. 50º38'N-116º04'W. W, 20%, 20 m, 60 cm, 200 m2, holotypus ass. (reg. 1992e: 107). 4. Wyoming: Sheridan Co. Between Granite Pass and Burgess Junction, Bighorn Mountains. 44º41'N-107º29'W. N, 20%, 12 m, 30 cm, 200 m2 (reg. 1996b: 62). 5. British Columbia: Skookumchuck. 49º56'N-115º53'W. E, 5%, 25 m, 80 cm, 400 m2 (reg. 1992e: 109). 6. Montana: Lewis & Clark Co. Helena National Forest, Priest Pass Road. 46º36'N-112º15'W. S, 15%, 30 m, 80 cm, 400 m2 (reg. 1994b: 72). 7. Synthesized table.

Type relevé (holotypus): Table 50, relevé n. 3. Rivas-Martínez reg. 1992e: 107. 24.08.92. Site: British Columbia: Radium Hot Springs. 50º38'N-116º04'W. 860 m, W, 20%, 20 m, 60 cm, 200 m2. Physiognomy and habitat: Rocky Mountain Douglas fir (Pseudotsuga menziesii var. glauca) mesoforest. Estimated bioclimatic factors: Continental Temperate, subcontinental (Ic ~ 24), upper supratemperate (Tp ~ 950), upper dry (Io ~ 3.5), Positive Summer Temperature Tps ~ 480, steppic. Biogeographic location: Rocky Mountain Region, North-Western Pacific Subregion, Cascade Province, Columbia Mountains Sector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 4 Pseudotsuga menziesii var. glauca. Others: 1 Amelanchier alnifolia, 2 Calamagrostis rubescens, 1 Elymus glaucus, 1 Juniperus communis var. depressa, 2 Juniperus scopulorum, + Mahonia repens, 2 Rosa woodsii var. ultramontana, 2 Shepherdia canadensis, 1 Symphoricarpos oreophilus var. oreophilus. Companion species: 1 Chrysothamnus nauseosus, 1 Elymus trachycaulus, 1 Festuca campestris, 1 Verbascum thapsus.

10c. Rhoo trilobatae-Pinetum scopulorum associatio nova hoc loco

Climactical mesoforests spreading into Xeric Temperate (subcontinental and eucontinental) and Continental Pluviseasonal Mediterranean; supratemperate, supramediterranean and lower oromediterranean; dry, steppic and submediterranean. In these pine forests Pinus ponderosa var. scopulourm (Rocky Mountain ponderosa pine) is the dominant, and frequently the unique tree; only in the more mesic habitats occasionally coexists with Pseudotsuga menziesii var. glauca (Rocky Mountain Douglas fir). Their distribution range includes the High Plains Rockies Sector territories mainly in the Flat High Plains Subsector and grow on haplic cambisols, andosols, regosols and podzo-luvisols. The Rocky Mountain ponderosa pine forest association (Rhoo-Pinetum scopulorum), is replaced by the also ubiquitous association Shepherdio canadensis-Pseudotsugetum glaucae at higher altitudes and weter areas in the High Plains Rockies Sector territories (Central Montana and Bighorn Mountains Subsector), as well as Flathead and Salmon Mountains and High Missouri-Yellowstone Sector. Within the most significant territorial characteristic and differential species it could be mentioned Rhus trilobata, Clematis hirsutissima and Stipa nelsonii.

Bioclimatic diagnosis: Ic 26-34, Io 2.0-3.6, Tp 800-1300, Tps 500-650, Tmin < -8, m < -15. [Texe, Mepc-Ste, Ote, Sme, Ome-Stp].

Table 51 shows five relevés from Montana and South Dakota, in the Flat High Plains Subsector, as well as Central Montana and Bighorn Mountains Subsector (High Plains Rockies Sector). Pinus ponderosa var. scopulorum is the only abundant tree, and in the sunny understory are frequents some shrubs such as Rhus trilobata, Symphoricarpos oreophilus var.oreophilus, Prunus virginiana var. melanocarpa, Juniperus scopulorum and Juniperus communis var. depressa.

Table 51
10c. Rhoo trilobatae-Pinetum scopulorum

(Pino-Pseudotsugion glaucae, Pseudotsugo-Abietetalia bifoliae)

Altitude (1=10m) 115 109 136 111 163 135
Number of species 11 11 12 13 15 12
Ordinal number 1 2 3 4* 5 6
Trees:
Pinus scopulorum 4 5 4 5 5 V
Pseudotsuga glauca 1 . . . . I
Populus tremuloides . . . . 1 I
Characteristic species:
Symphoricarpos oreophilus 2 1 1 1 2 V
Prunus melanocarpa + 2 1 + 1 V
Rhus trilobata 2 3 3 2 . IV
Juniperus depressa 2 1 . 2 3 IV
Juniperus scopulorum . 2 1 3 + IV
Amelanchier alnifolia + . + . 1 III
Elymus glaucus 1 2 . 1 . III
Clematis hirsutissima . 2 . 1 . II
Companion:
Stipa nelsonii 3 2 3 2 1 V
Agropyron pectinatum + . 2 1 . III
Artemisia pedatifolia . 1 . + . II
Ribes aureum . + 1 . . II
Artemisia wyomingensis . . 1 + . II

Other species. Characteristic species: Juniperus horizontalis 2 in 1. Rosa arkansana 2 in 3. Physocarpus malvaceus 2 in 4. Arctostaphylos uva-ursi 3, Betula occidentalis 1, Calamagrostis rubescens 2, Pterospora andromedea 1, Ribes glandulosum 1, Rubus strigosus + in 5. Companion species: Poa cusickii 1 in 3. Penstemon angustifolius + in 5.

Localities: 1. Montana: Musselshell Co. Between Roundup and Klein. 46º25'N-108º33'W. W, 25%, 15 m, 35 cm, 300 m2 (reg. 1994b: 67). 2. Montana Stillwater Co. Between Greycliff and Columbus. Reedpoint. 45º13'N-109º32'W. SE, 15%, 18 m, 50 cm, 400 m2 (reg. 1994b: 66). 3. Montana: Big Horn Co. Kirby, Rosebud Battlefield State Park. 45º13'N-107º00'W. W, 20%, 14 m, 40 cm, 200 m2 (reg. 1996b: 64). 4. Montana: Hill Co., Havre, Oscar Ranch. 48º27'N-109º37'W. W, 25%, 15 m, 40 cm, 200 m2, holotypus ass. (reg. 1996b: 70). 5. South Dakota: Custer Co. Custer, Custer State Park. Needela Hwy. 43º48'N-103º36'W. E, 30%, 15 m, 30 cm, 200 m2 (reg. 1995d: 177). 6. Synthesized table.

Type relevé (holotypus):Table 51, relevé n. 4. Rivas-Martínez reg. 1996b: 70. 31.08.96, made with Drs. Llorens and Sánchez-Mata. Site: Montana: Hill Co. Havre, Oscar Ranch. 48º27'N.109º37'W. 1110 m, W. 25%, 15 m, 40 cm, 200 m2. Physiognomy and habitat: Rocky Mountain ponderosa pine (Pinus ponderosa var. scopulorum) open mesoforest. Estimated bioclimatic factors: Pluviseasonal Continental Mediterranean, eucontinental (Ic ~ 30), upper supramediterranean (Tp ~ 1200), upper dry (Io ~ 3.0), Positive Summer Temperature Tps ~ 400, steppic. Biogeographic location: Rocky Mountain Region, Rocky Mountain Subregion, Central-Eastern Rocky Mountain Province, Transrockies High Plains Sector, Northern Transrockies High Plains Subsector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: 5 Pinus ponderosa var. scopulorum. Others: 1 Clematis hirsutissima, 1 Elymus glaucus, 2 Juniperus communis var. depressa, 3 Juniperus scopulorum, 2 Physocarpus malvaceus, + Prunus virginiana var. melanocarpa, 2 Rhus trilobata, 1 Symphoricarpos oreophilus var. oreophilus. Companion species: 1 Agropyron pectinatum, + Artemisia pedatifida, + Artemisia tridentata subsp. wyomingensis, 2 Stipa nelsonii.

10d. Pseudotsugo glaucae-Pinetum flexilis associatio nova hoco loco

Coniferous edapho-xerophilous micro- or mesoforests, spreading into Xeric Temperate, Continental Pluviseasonal Mediterranean (subcontinental and barely eucontinental) bioclimate territories; upper supra- and orotemperate, upper supra- and oromediterranean; dry; steppic and submediterranean. The dominant and characteristic tree in these forests is the limber pine (Pinus flexilis) usually with Pseudotsuga menziesii var. glauca, Pinus ponderosa var. scopulorum and Populus tremuloides. They are widespread throughout the Rocky Mountain Subregion territories and reach the higher ranges of Great Basin Region (mainly in the Intermountain Province), growing on leptosols or shallow haplic cambisols, andosols and podzo-luvisols with tangel humus. At lower altitudes, on deep soils, the Rocky Mountain limber pine rupestrian forests (Pseudotsugo glaucae-Pinetum flexilis) are contiguous with the climactical Rocky Mountain Douglas fir forests (Shepherdio canadensis-Pseudotsugetum glaucae), whereas at higher altitudes, in orotemperate or locally oromediterranean dry bioclimatic belts, are close with the subalpine fir-Engelmann spruce climactical forests (Vaccinio scoparii-Abietetum bifoliae).

Bioclimatic diagnosis: Ic 26-30, Io 2.0-3.6, Tp 500-1000, Tps 400-550, Tmin < -5, m < -11. [Texe, Mepc-Ste, Ote, Sme, Ome-Dry-Stp, Sbm].

Table 52 shows four relevés from Utah, Colorado and Wyoming in the Utah and Colorado Rockies Sectors. Pinus flexilis (limber pine) is the commonest tree in the forest community, and Pseudotsuga menziesii var. glauca and Pinus ponderosa var. scopulorum are near always present. In the barely shaded understory some small shrubs and herbs are frequent such as Arctostaphylos uva-ursi var. adenotricha, Mahonia repens, Ribes aureum, Paxistima myrsinites, Pulsatilla patens subsp. multifida, Elymus glaucus and Carex rossii.

Table 52
10d. Pseudotsugo glaucae-Pinetum flexilis

(Pino-Pseudotsugion glaucae, Pseudotsugo-Abietetalia bifoliae)

Altitude (1=10m) 290 255 230 270 261
Number of species 15 17 21 22 19
Ordinal number 1 2 3* 4 5
Trees:
Pinus flexilis 4 4 4 5 4
Pseudotsuga glauca 1 2 1 + 4
Populus tremuloides 1 + + 1 4
Pinus scopulorum . . + + 2
Characteristic species:
Elymus glaucus 2 1 1 + 4
Mahonia repens 1 2 + 1 4
Arctostaphylos adenotricha 1 1 2 1 4
Osmorhiza depauperata + 1 1 1 4
Pulsatilla multifida + 1 + 2 4
Thalictrum sparsiflorum + 1 . 1 3
Symphoricarpos oreophilus 2 3 . . 2
Paxistima myrsinites 2 2 . . 2
Juniperus depressa . . 2 2 2
Thermopsis montana . . + 2 2
Companion species:
Artemisia vaseyana 1 1 1 . 3
Carex rossii 2 1 . 1 3
Ribes aureum . 1 2 1 3
Ribes inerme . 1 + 2 3
Geranium caespitosum . . 2 + 2

Other species. Trees: Picea pungens + in 1. Acer glabrum 1, Abies concolor + in 3. Pinus latifolia + in 4. Characteristic species: Rosa ultramontana 1 in 1. Prunus melanocarpa 1 in 2. Apocynum pumilum 1 in 3, Calamagrostis rubescens 1 in 4. Companion species: Penstemon sp. 1 in 2. Potentilla hippiana 2, Purshia tridentata 2, Artemisia frigida + in 3. Jamesia americana 2, Frasera speciosa 1, Cercocarpus montanus 2, Sedum lanceolatum 1 in 4.

Localities: 1. Utah: Wasatch Co. Wasatch-Cache National Forest, Guardsman Pass Road, Wasatch Mountain. 40º35'N-111º29'W. N, 10 m, 35 cm, 200 m2. (reg. 1996b: 39). 2. Utah: Cache Co. Wasatch-Cache National Forest, Montecristo Range, Montecristo Pass. 41º29'N-111º30'W. E, 10 m, 35 cm, 20%, 400 m2 (reg. 1996b: 42). 3. Wyoming: Albany Co. Medicine Bow National Forest, between Granite and Laramie, Ames Monument. 41º08'N-105º23'W. S, 10 m, 30 cm, 20%, 200 m2, holotypus ass. (reg. 1995d: 187). 4. Colorado: Boulder Co. Roosevelt National Forest. 40º05'N-105º32'W. NW, 20%, 15 m, 35 cm, 400 m2 (reg. 1995d: 9). 5. Synthesized table.

Revealing relevé: Table 52, relevé n. 3 Rivas-Martínez reg. 1995d: 187. 13.09.95, made with Dr. Costa. Site: Wyoming: Albany Co. Medicine Bow National Forest, between Granite and Laramie, Ames Monument. 41º08'N-105º23'W. 2300 m, S, 10 m, 30 cm, 20%, 200 m2. Physiognomy and habitat: Limber pine (Pinus flexilis) open mesoforest with Rocky Mountain Douglas fir (Pseudotsuga menziesii var. glauca). Estimated bioclimatic factors: Pluviseasonal Continental Mediterranean, subcontinental (Ic ~ 26), lower oromediterranean (Tp ~ 800), upper dry (Io ~ 3.0), Positive Summer Temperature Tps ~ 450, steppic. Biogeographic location: Rocky Mountain Region, Rocky Mountain Subregion, Central-Eastern Rocky Mountain Province, Colorado Rockies Sector, Colorado-Wyoming Rockies Subsector. Floristic combination: Linnaeo-Piceetea characteristic species, trees: + Abies concolor, 1 Acer glabrum, 4 Pinusflexilis, + Pinus ponderosa var. scopulorum, + Populus tremuloides, 1 Pseudotsuga menziesii var. glauca. Others: 2 Arctostaphylos uva-ursi var. adenotricha, 1 Elymus glaucus, 2 Juniperus communis var. depressa, + Mahonia repens, 1 Osmorhiza depauperata, + Pulsatilla patens subsp. multifida, + Thermopsis rhombifolia var. montana. Companion species: + Artemisia frigida, 1 Artemisia tridentata subsp. vaseyana, 2 Geranium caespitosum, 2 Potentilla hippiana, 2 Purshia tridentata, 2 Ribes aureum, + Ribes inerme.