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-Populetalia trichocarpae/h1>

Vc. Alno rubrae-Populetalia trichocarpae ordo novus hoc loco

[Aceretalia macrophylli Knapp in Geobot Mitt. 4: 28. 1957 (art. 8), Alnetalia rubrae Knapp in Geoobt. mitt. 4: 28. 1957 (art. 8)]

Typus nominis: Alno rubrae-Populion trichocarpae alliancia nova hoc loco.

North-Western Pacific Subregion riparian and deciduous secondary meso- and macroforests with red alder (Alnus rubra) or black cottonwood (Populus balsamifera subsp. trichocarpa) as dominant trees. This order also includes Sitka alder (Alnus viridis subsp. sinuata) thickets. Their complete distribution includes the Hyperoceanic Temperate, Oceanic Temperate, Continental Temperate and Oceanic Boreal territories and, occasionally some Pluviseasonal Oceanic Mediterranean areas (frequently with submediterranean character) spreading into meso-, supra-, and orotemperate, hemiboreal, and thermo-, meso-, and lower supraboreal, subhumid to ultrahyperhumid bioclimatic belt territories. These forests and shrublands are broadly distributed throughout the Cascade and Boreal Oceanic Alaskan Provinces, and only locally in Northern Rocky Mountain Province, mainly as adjacent riparian or as secondary deciduous forests of the climactical coniferous associations of Tsugetalia mertensiano-heterophyllae order. As riverine permanent communities, they are also present in hyperoceanic territories of theNorthern Californian Coastal Sector territories with Pluviseasonal Oceanic Mediterranean bioclimate. These forests and thickets grow on all kind of soils, particularly on their precedent and related climactical coniferous association communities (cambisols, luvisols, vertisols, podzols, etc.), and when they represent the riparian primary forests are usually growing in eutric, dystric, mollic and umbric fluvisols.

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

Map Figure 25. Distribution of the deciduous forests of black cottonwood (Populus balsamifera subsp. trichocarpa), red alder (Alnus rubra) and the deciduous Sitka alder (Alnus viridis subsp. sinuata) thickets belonging to the order and alliance Alno rubrae-Populetalia trichocarpae and 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].

Within the order Alno rubrae-Populetalia trichocarpae we recognize only one alliance: Alno rubrae-Populion trichocarpae (figure 25). In this alliance it could be possible to identify four groups of plant communities: 1. Oceanic Temperate and Boreal riparian macroforests of black cottonwood (Populus balsamifera subsp. trichocarpa), 2. Oceanic and Continental Temperate (semicontinental and occasionally subcontinental) riparian macroforests of black cottonwood (Populus balsamifera subsp. trichocarpa), 3. Pluviseasonal Oceanic Mediterranean, Hyperoceanic and Oceanic Temperate and Boreal (thermoboreal), meso- and macroforests, secondary and sometimes riparian woodlands of red alder (Alnus rubra), 4. Oceanic Temperate, Continental Temperate (subcontinental) and Oceanic Boreal secondary thickets, and snow-pack permanent shrubby communities of Sitka alder (Alnus viridis subsp. sinuata).

In a short synthesized synoptical table (table 32) we assemble thirty relevés from North-Western Pacific Subregion and Northern Rocky Mountain Province belonging to Alno rubrae-Populetalia trichocarpae and Alno rubrae-Populion trichocarpae.

Within the most significant deciduous trees which could be used as differential species between the riparian and secondary forests of the order Alno rubrae-Populetalia trichocarpae and the rest of the riparian and deciduous secondary forests and woodlands in the Holarctic North America (Betulo papyriferae-Populetalia tremuloidis, Populetalia angustifolio-deltoidis, Populetalia fremontii) we can mentione Alnus rubra (red alder), Acer glabrum var. douglasii (Douglas western mountain maple), Acer macrophyllum (big-leaved maple), Acer circinatum (vine maple), and Populus balsamifera subsp. trichocarpa (black cottonwood). 

Table 32
8. Alno rubrae-Populion trichocarpae
(Short synthesized table syntaxa)

Number of species (average) 20 23 17 16 24 13 20
Number of relevés 11 2 3 4 9 3 30
Association number 8a 8b 8c 8d 8e 8f .
Ordinal number 1 2 3 4 5 6 7
Trees:
Acer macrophyllum V . . . . . I
Picea sitchensis (S2) II 2 . . . . II
Alnus rubra V 2 . . . . II
Acer circinatum III . . . I . II
Populus trichocarpa I 1 3 4 III 2 IV
Characteristic species:
Frangula purshiana IV . . . . . I
Tolmiea menziesii III . . . . . I
Stachys mexicana III . . . . . I
Ribes bracteosum . 2 . . . . I
Geum macrophyllum . 2 . . . . I
Alnus tenuifolia . . . 4 . . I
Cornus occidentalis . . . 4 . . I
Symphoricarpos laevigatus . . . 4 . . I
Vaccinium membranaceum . . . . V . I
Linnaea americana . . . . V . I
Rubus lasiococcus . . . . IV . I
Salix longistylis . . . . . 3 I
Aruncus acuminatus . . . . . 3 I
Athyrium cyclosorum III 2 3   . 3 IV
Alnus sinuata . 1 3 . V 3 IV
Cornus canadensis I 2 . 1 IV . III
Sambucus arborescens III 2 . . . 2 III
Rubus spectabilis IV 2 . . II . III
Rubus parviflorus V . . 3 III . II
Oplopanax horridus . 2 2 . . 3 III
Ribes laxiflorum . . 1 . IV 3 III
Polystichum munitum V 2 . . . . II
Maianthemum dilatatum II 1 . . . . II
Pyrola asarifolia . . 3 . V . II
Gymnocarpium dryopteris . . . . IV 3 II

 Associations: 1. [8a] Aceri macrophylli-Alnetum rubrae. 2. [8b] Oplopanaco horridi-Alnetum rubrae. 3. [8c] Alno sinuatae-Populetum trichocarpae. 4. [8d] Alno tenuifoliae-Populetum trichocarpae. 5. [8e] Vaccinio membranacei-Alnetum sinuatae. 6. [8f] Salici longistylis-Alnetum sinuatae. 7. Synthesized table.

Characteristic species: Acer glabrum var. douglasii, Acer macrophyllum, Alnus rubra, Alnus viridis subsp. sinuata (A. sitchensis), Arnica diversifolia, Aruncus dioicus var. pubescens, Boykinia occidentalis, Cardamine angulata, Cornus sericea subsp. occidentale, Holodiscus discolor, Populus balsamifera subsp. trichocarpa, Prunus virginiana var. demissa, Ribes bracteosum, Ribes laxiflorum, Ribes sanguineum, Rubus leucodermis, Rubus spectabilis, Salix alaxensis var. longistylis, Salix athabascensis Sambucus racemosa subsp. pubens var. arborescens, Spiraea douglasii var. douglasii, Spiraea douglasii var. menziesii, Stachys ciliata, Stachys mexicana, Stellaria crispa, Tolmiea menziesii, Veratrum californicum var. caudatum.

Syntaxa Ic Io Itc Tp Ts Tmin m Mb
Vc. Alno rubr.-Populetalia trichoc. 5-25 4.8-40.0 < 250 400-1400 280-550 < 8 < 5 -
8. Alno rubr.-Populion trichocarpae 5-25 4.8-40.0 < 250 400-1400 280-550 < 8 < 5 -
8a. Aceri macrophylli-Alnetum rubrae 5-18 9.0-18.0 120-250 1050-1400 450-550 < 8 < 5 Te, Me
8b. Oplopanaco horr.-Alnetum rubrae 11-20 12.0-30.0 < 120 700-1050 380-430 < 4 < 2 Bo, Te
8c. Alno sinu.-Populetum trichocarpae 11-25 4.8-30.0 < 120 450-1000 380-430 < 2 < 0 Bo, Te
8d. Alno ten.-Populetum trichocarpae 18-25 4.8-12.0 - 500-1100 400-550 < -3 < -5 Te, Me
8e. Vaccinio membr.-Alnetum sinuatae 18-23 4.8-15.0 - 400-900 300-500 < -4 < -6 Te
8f. Salici longistylis-Alnetum sinuatae 16-25 4.8-40.0 - 450-740 280-420 < -2 < -6 Bo

Figure 26. Synopsis of the bioclimatic diagnoses of syntaxa belonging to Alno rubrae-Populetalia trichocarpae order. Relationships between the potential natural vegetation forest and shrubland territories and the thresholds of the bioclimatic indexes and climatic parameter values [8. Alno rubrae-Populetalia 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-Alntetum sinuatae)]. 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).