Vegetation Zones and Bioclimatic Domains in Québec
1. The committee responsible for mapping ecological regions (Comité sur la carte des régions écologiques) was composed of Jean-Pierre Saucier, f.eng., D.Sc. (committee leader),Pierre Grondin, f.eng., M.Sc., André Robitaille, geomorphologist, M.Sc., and Jean-François Bergeron, biologist, M.Sc.
VEGETATION ZONES AND SUBZONES
Québec is divided into three vegetation zones,namely the northern temperate zone, dominatedby hardwood and mixed stands, the boreal zone,characterized by softwood stands, and the Arcticzone, where the vegetation is mostly made ofshrubs and herbaceous plants. These three zones,which reflect Québec’s major climatological divi-sions, harbor their own distinct plant communi-ties. They correspond to world biomes categories.
The vegetation zones are divided into subzonesaccording to the type of vegetation dominatingthe landscape at the final stage of succession. Forexample, the northern temperate zone covers twosubzones, namely the hardwood forest (northernhardwood stands dominated by sugar maple) andthe mixed forest (a mixture of boreal species,such as balsam fir or black spruce, and southernspecies, such as yellow birch). The mixed forestsubzone is slightly less rich in terms of vegeta-tion diversity than the hardwood forest.
The boreal zone includes three subzones: the con-tinuous boreal forest subzone, where relativelydense stands are composed mainly of boreal soft-wood species and intolerant hardwoods, the taiga,dominated by open softwood forests on a lichenmat, and the forest tundra, a combination ofstands of variable density, and tundra, charac-terized mainly by shrubs and lichens. The tree line(black spruce, white spruce and tamarack) sepa-rates the boreal zone from the Arctic zone.Québec’s Arctic zone covers only one subzone, theSouthern arctic, characterized by the absence oftrees, continuous permafrost and tundra-specificvegetation, which mainly consists of shrubs,herbaceous plants (mostly gramineous likespecies), mosses and lichens.
BIOCLIMATIC DOMAINS AND SUBDOMAINS
A bioclimatic domain is an area characterized bya particular type of vegetation that, at the finalstage of succession, grows on sites with averagesoil conditions, drainage and exposure (mesicsites). The balance between vegetation and cli-mate is the main factor that distinguishes onedomain from another. The bioclimatic domainboundaries were revised in 1998 by a committeeresponsible for the map of ecological regions 1,which established a new ecological land classifi-cation system for Québec.
Québec has ten bioclimatic domains. Six of these,namely the sugar maple-bitternut hickory, sugarmaple-basswood, sugar maple-yellow birch, bal-sam fir-yellow birch, balsam fir-white birch andspruce-moss domains, are located in the southernQuébec. The four others, namely the spruce-lichen, forest tundra, shrub arctic tundra andherbaceous arctic tundra domains, are located innorthern Québec.
Some of the bioclimatic domains found in south-ern Québec are divided into subdomains becauseof their distinct vegetation patterns reflectingdifferences in the precipitation pattern.
Confined to southwestern Québec, with its moreclement climate, the sugar maple-bitternut hick-ory domain contains Québec’s most southerlyspecies, some of which are thermophiles. Itsforests are highly diversified. Some of the speciesfound here are at the northernmost limit of theirrange. This is the case of the bitternut hickory,after which the forest is named, as well as theshagbark hickory, hackberry, black maple,swamp white oak, cork elm, pitch pine and sev-eral shrubs and herbaceous plants. The forest alsocontains other species that extend further north,such as the sugar maple, fir and spruce. It is notdivided into subdomains.
2. Sugar maple-basswood domain (31 000 km2)
The sugar maple-basswood domain stretches fur-ther to the north and east than the sugar maple-bitternut hickory domain. Its plant life is alsovery diversified, although several species are atthe northernmost limit of their range. In areasthat are favourable, the basswood, American ash,hop-hornbeam and butternut grow alongside thesugar maple, but they are less common furthernorth. There are two subdomains, distinguishedby the aboundance of red oak stands and theirdistinct precipitation systems: one in the west,which is drier, and the other in the east, whereprecipitation is more abundant.
3. Sugar maple-yellow birch domain (65 600 km2)
The sugar maple-yellow birch domain covers thehills bordering the southern Laurentian plateauand the Appalachians, in the northernmost por-tion of the hardwood forest subzone. Its plantlife, less diversified on all but the best sites,includes many boreal species found throughoutQuébec. On its mesic sites, the yellow birch isone of the most predominant companion speciesto the sugar maple. The American beech, red oakand Eastern hemlock also grow here, but arerarely found past the forest’s northern boundary.This domain also signals the end of the basswoodand hop-hornbeam ranges. As for the entirehardwood forest subzone, forest dynamics areattributable mainly to windfall. The sugarmaple-yellow birch forest has two subdomains, adrier one in the west and the other in the east,distinguished by their precipitation levels andthe aboundance of white and red pine stands.
B. Mixed forest subzone
4. Balsam fir-yellow birch domain (98 600 km2)
The balsam fir-yellow birch domain is an eco-tone, i.e. a transition zone between the northerntemperate zone to which it belongs, and theboreal zone. It stretches westward as far as centralQuébec, between latitudes 47o and 48o, and
encompasses the Gaspé peninsula, theAppalachian hills east of Québec City, theLaurentian foothills north of the St. LawrenceRiver and the lowlands of Lake Saint-Jean. Itsmesic sites feature mixed stands of yellow birchand softwoods, such as the balsam fir, white spruceand white cedar. The sugar maple is at the north-ernmost limit of its range here. Spruce budwormepidemics and forest fires are the two main ele-ments of forest dynamics. The presence of yellowbirch and pine stands, which diminish towards theeast, is the main defining factor for two separatesubzones, one in the west, characterized by theomnipresence of yellow birch-balsam fir forests onmesic sites, and one in the east, characterized bybalsam fir-yellow birch forests.
II. BOREAL ZONE
A. Continuous boreal forest subzone
5. Balsam fir-white birch domain (139 000 km2)
The balsam fir-white birch domain occupies thesouthern portion of the boreal zone. The forestlandscape is dominated by balsam fir and whitespruce stands mixed with white birch on mesicsites. On less favourable sites, black spruce, jackpine and larch often grow alongside white birchor trembling aspen. The yellow birch and redmaple grow only in the southern portion of thedomain. Forest dynamics are controlled prima-rily by the spruce budworm, since the balsam firis abundant here. However, fire is also an impor-tant factor. There are two subdomains. The west-ern one has a relatively even topography, withminimal changes in altitude. The fire cycle isalso shorter, which explains the abundance ofhardwood or mixed stands with intolerant hard-woods (trembling aspen, white birch and jackpine). Precipitation is generally more copious inthe eastern subdomain due to the influence of themaritime climate; consequently, the fire cycle islonger here.
6. Spruce-moss domain (412 400 km2)
Moving northward, the spruce-moss domainreplaces the balsam fir-white birch domain. Itstretches approximately to the 52nd parallel, andits northern boundary coincides with the bound-ary of the continuous boreal forest subzone.Forest landscapes are fairly uniform here, sincethe forest canopy is dominated extensively by theblack spruce, often growing in pure stands butalso accompanied on occasion by other species,such as the balsam fir. Balsam fir stands are foundonly on some of the slopes of the domain’s hills.Some hardwoods, such as the white birch, trem-bling aspen and, to a lesser extent, the balsampoplar, also grow here. The undergrowth is com-posed of hypnaceous mosses and ericaceousshrubs. Herbaceous species are rare. The spruce-moss domain is divided into two precipitation-based subdomains. The fire cycle, which is themain factor in forest dynamics, is much longer inthe east, where balsam fir stands are more abun-dant and the percentage of firs in spruce stands ishigher.
B. Taiga subzone
7. Spruce-lichen domain (299 900 km2)
The spruce-lichen domain extends over the entiretaiga subzone, which stretches from the 52nd par-allel to the 55th parallel. Its main difference withthe spruce-moss forest is its low-density forestcover. The lichen mat is dotted with black sprucetrees, whose propagation is favoured by the harshclimate and low precipitation level. The balsam firand jack pine are at the northernmost limit of theirrange here. Fire has destroyed vast areas of thespruce-lichen forest.
C. Forest tundra subzone
8. Forest tundra domain (217 000 km2)
The forest tundra bioclimatic domain is the eco-tone, or transitional area, between the borealzone to which it belongs, and the Arctic zone. Itextends approximately from the 55th parallel tothe 58th parallel. The landscape resembles amosaic dominated by shrubby heathland punctu-ated by forests on sheltered sites. The mosaic isthe result of fire and the harsh northern climatewith its discontinuous permafrost. The northernboundary of the domain coincides with the treeline. It contains mainly stands of stunted blackspruce measuring less than three metres inheight.
III. ARCTIC ZONE
A. Southern arctic subzone
9. Shrub arctic tundra domain (197 800 km2)
The shrub arctic tundra bioclimatic domainextends approximately from the 58th parallel tothe 61st parallel. Here, willows and dwarf birchgrow alongside herbaceous species, mostly grass-like plants, as well as mosses and lichens. Thedomain is characterized by continuous per-mafrost and a topography resulting from iceactivity. The vegetation canopy rarely growsbeyond two metres high, and even then, onlysome species of arctic willow are capable of reach-ing this height. Pockets of vegetation resemblingthe shrub arctic tundra can be found on some ofsouthern Québec’s highest summits, includingthe Chic-Chocs and Groulx mountains.
10. Herbaceous arctic tundra domain (38 200 km2)
The herbaceous arctic tundra domain is Québec’snorthernmost bioclimatic domain. The regionalclimate is so harsh that even shrubs are scarce andvery small. Cyperaceous and gramineous species(sedges and grasses) mix with mosses and lichensto dominate landscapes where the bedrock andmineral soil are often bare. The entire area is cov-ered with continuous permafrost.
Thedis tr i -bution of veg-etation in Québec isdetermined mainly by climaticfactors, which are generallyless favourable the furthernorth one goes. In the St.Lawrence Plain, the climatechanges gradually from thesouthwest to the northest. Insouthern Québec, variations inaltitude, if significant, cancause changes in vegetationcomparable to those occa-sioned by latitude. Soil type,topography and disturbancessuch as forest fires, insect epi-demics and logging also affectvegetation distribution. Thesefactors determine how plantcommunities are distributedover the various physicalfeatures (hilltops, mid- andlower slopes, etc.) within agiven bioclimatic zone.
Vegetation Zones and Bioclimatic Domains in Québec
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