56

TABLE 4. Climatic characteristics for the biogeoclimatic zones of British Columbia

ZoneRange and

Lat. Long. ElevationMean annual Mean summer Mean precip. Mean precip.

Driest Wettestreference( ° ′ ) ( ° ′ ) (m)

precip.precip. of driest of wettest

month monthstation (mm)(May-Sept) month month

(mm) (mm) (mm)

AT Old Glory Mtn. 49 09 117 55 2347 755.5 287.0 40.0 84.1 Jul Dec

BG Max 588 335.7 174.5 17.3 55.4Min 297 205.6 98.0 8.0 27.3Kamloops 50 40 120 20 379 241.7 111.4 8.0 36.1 Mar Jan

BWBS Max 840 503.7 305.3 24.3 879.0Min 382 327.1 144.7 8.3 41.1Fort Nelson A 58 50 122 35 382 451.8 297.9 16.7 84.3 Apr Jul

CDF Max 223 1262.6 238.3 38.6 232.9Min 8 647.2 107.3 13.4 119.2Victoria Int’l A 48 39 123 26 19 872.9 141.9 18.1 157.3 Jul Dec

CWH Max 671 4386.8 1162.0 151.0 625.4Min 0 990.2 159.3 16.8 145.7Haney UBC 49 16 122 34 143 2140.1 467.8 65.5 331.7 Jul Dec

RF Admin

ESSF Max 1862 1995.4 424.5 64.8 297.4Min 863 514.1 204.6 26.6 57.4Boss Mountain 52 06 120 53 1532 1177.1 401.6 63.5 140.6 May Dec

ICH Max 1085 1419.0 439.3 57.2 224.3Min 314 497.7 199.9 21.4 57.8Revelstoke 51 00 118 12 456 1063.7 325.0 51.4 177.0 Apr Jan

IDF Max 1128 1198.9 290.7 37.6 208.8Min 122 295.1 107.5 13.5 34.8150 Mile House 52 07 121 56 738 414.2 214.0 15.8 60.7 Apr Jun

MH Hollyburn Ridge 49 23 123 12 930 2954.3 694.4 106.9 434.8 Jul Dec

MS Max 1554 663.8 252.1 38.5 108.1Min 1128 380.8 158.2 17.9 45.2Peachland 49 52 120 00 1520 638.3 197.0 29.3 89.1 Apr Dec

Brenda Mines

PP Max 939 604.5 270.3 30.7 77.6Min 244 319.5 86.3 11.0 34.5Kelowna 49 54 119 28 354 332.2 136.3 15.3 45.1 Apr Dec

SBPS Max 1219 517.8 299.8 21.1 86.5Min 914 464.1 242.6 20.8 36.4Alexis Creek 52 33 123 11 1219 464.1 242.6 20.8 57.6 Apr Jun

Tautri Creek

SBS Max 1245 1588.2 352.6 36.8 278.7Min 488 438.9 188.9 15.2 49.8Prince George A 53 63 122 40 676 628.3 300.8 27.4 68.2 Apr Aug

SWB Cassiar 59 17 129 50 1078 699.5 275.1 25.7 84.2 Apr Oct

Zone key

AT Alpine TundraBG BunchgrassBWBS Boreal White and Black SpruceCDF Coastal Douglas-firCWH Coastal Western HemlockESSF Engelmann Spruce — Subalpine FirICH Interior Cedar — Hemlock

IDF Interior Douglas-firMH Mountain HemlockMS Montane SprucePP Ponderosa PineSBPS Sub-Boreal Pine — SpruceSBS Sub-Boreal SpruceSWB Spruce — Willow — Birch

59

TABLE 5. Occurrencea of trees in the biogeoclimatic zones of British Columbia

Gymnosperms BG PP IDF ICH MS SBPS SBS BWBS SWB MH CDF CWH ESSF ATb

Abies amabilis - - - + - - - - - +++ - +++ (+) -(amabilis fir)

A. grandis- - ++ ++ + - - - - - ++ + - -(grand fir)

A. lasiocarpa- - - ++ +++ (+) +++ ++ +++ ++ - + +++ -(subalpine fir)

Chamaecyparisnootkatensis - - - - - - - - - +++ - ++ (+) -

(yellow-cedar)

Juniperus scopulorum+ + ++ - - - + (+) - - ++ (+) - -(Rocky Mountain juniper)

Larix laricina- - - - - - (+) ++ - - - - - -(tamarack)

L. lyallii- - - - - - - - - - - - ++ -(alpine larch)

L. occidentalis- + +++ ++ +++ - - - - - - - + -(western larch)

Picea engelmannii- - + ++ +++ - - - - + - - +++ -(Engelmann spruce)

P. engelmanniix glauca - (+) ++ ++ +++ + +++ - - - - - ++ -

(hybrid white spruce)

P. glauca- (+) + - + +++ ++ +++ +++ - - - + -(white spruce)

P. glaucax sitchensis - - - ++ - - - - - (+) - ++ - -

(Roche spruce)

P. mariana- - - + - - ++ +++ + - - - - -(black spruce)

P. sitchensis- - - - - - - - - + + +++ - -(Sitka spruce)

Pinus albicaulis- - - - - - - - - + - - ++ -(whitebark pine)

P. banksiana- - - - - - - (+) - - - - - -(jack pine)

P. contorta(+) - +++ ++ +++ +++ +++ +++ ++ + ++ ++ +++ -(lodgepole pine)

P. flexilis- - (+) - - - - - - - - - (+) -(limber pine)

P. monticola- - + ++ + - - - - + + ++ + -(western white pine)

P. ponderosa+ +++ +++ + - - - - - - - - - -(ponderosa pine)

Pseudotsuga menziesii+ ++ +++ ++ +++ + ++ - - (+) +++ +++ + -(Douglas-fir)

Taxus brevifolia- - + ++ - - - - - - ++ ++ - -(western yew)

Thuja plicata- (+) ++ +++ + - + - - + ++ +++ + -(western redcedar)

Tsuga heterophylla- - + +++ + - (+) - - ++ + +++ + -(western hemlock)

T. mertensiana- - - + - - - - - +++ - + ++ -(mountain hemlock)

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TABLE 5. Continued

Angiosperms BG PP IDF ICH MS SBPS SBS BWBS SWB MH CDF CWH ESSF ATb

Acer macrophyllum- - + - - - - - - - ++ ++ - -(bigleaf maple)

Alnus rubra- - - - - - - - - - +++ +++ - -(red alder)

Arbutus menziesii- - - - - - - - - - ++ + - -(arbutus)

Betula neoalaskana- - - - - - - ++ - - - - - -(Alaska paper birch)

B. occidentalis+ + + (+) - - (+) + - - - - - -(water birch)

B. papyrifera+ + ++ ++ + - ++ ++ - - + + - -(paper birch)

Cornus nuttallii- - + - - - - - - - ++ ++ - -

(western floweringdogwood)

Populus balsamiferassp. balsamifera - - - - - - + ++ + - - - - -

(balsam poplar)

P. balsamiferassp. trichocarpa + + + ++ + + ++ + - - ++ ++ + -

(black cottonwood)

P. tremuloides+ ++ +++ ++ ++ + +++ +++ + - + + +(trembling aspen)

Prunus emarginata- - +c ++c - - +c - - - ++ + - -(bitter cherry)

Quercus garryana- - - - - - - - - - ++ (+) - -

(Garry oak)

Rhamnus purshiana- - - ++d - - - - - - ++ + - -(cascara)

a Occurrence classes: +++(abundant); ++(common); +(present but uncommon); (+)(very rare); -(absent).b Tree species occur only in krummholz form in the Alpine Tundra zone.c P. emarginata occurs in these zones, but only rarely as a (small) tree.d Rarely as a small tree.

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Chapter 13: Sub-Boreal Pine — Spruce Zone

by

O. Steen and D.A. Demarchi

LOCATION AND DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

ECOLOGICAL CONDITIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

NOTES ON CLASSIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

SUBZONES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199

SOME REPRESENTATIVE SITE ASSOCIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

Lodgepole pine — Juniper — Feathermoss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

Lodgepole pine — Kinnikinnick — Cladonia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

White spruce — Scrub birch — Feathermoss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

White spruce — Horsetail — Glow moss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

WILDLIFE HABITATS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204

RESOURCE VALUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

196

LOCATION AND DISTRIBUTION

The Sub-Boreal Pine — Spruce zone (SBPS) is a montane zone that occurs on thehigh plateau in the west central interior of British Columbia (Figure 46). It lies southand west of the Sub-Boreal Spruce zone (SBS) in the rainshadow of the CoastMountains. It is mostly within the area known as the Chilcotin.

The SBPS occupies the gently rolling landscape of the Fraser Plateau and thesouthern-most portions of the Nechako Plateau. These are high elevation plateaus.Elevations in the northern part of the zone are mostly 850-1300 m, while in thesouthern and western parts, near the Coast Mountains, elevations range from 1100 to1500 m. The SBPS generally occurs at elevations above the Interior Douglas-fir zone(IDF) and below the Montane Spruce, Sub-Boreal Spruce, and Engelmann Spruce —Subalpine Fir zones on the Fraser Plateau. The Sub-Boreal Pine — Spruce zone isdrained primarily by the Chilcotin, West Road (Blackwater), Dean, and Entiako rivers.

ECOLOGICAL CONDITIONS

Climate of the SBPS is continental and characterized by cold, dry winters and cool,dry summers (Figure 47). Compared to the SBS, the SBPS is drier and has similarmean daily temperatures in winter, but cooler mean daily temperatures in summer.The number of growing degree days above 5°C in the SBPS is significantly less than ineither the SBS or the Boreal White and Black Spruce zones (Table 4). The cool, drygrowing seasons of the SBPS result in large part from its position in the strongrainshadow of the Coast Mountains and its relatively high elevations. The lowprecipitation, dry air, and clear skies created by the rainshadow effect result insignificant night-time radiation cooling and low overnight temperatures. Night-timefrosts are common in all months. Mean annual temperatures in the SBPS range from0.3 to 2.7°C with a mean of 1.9°C. As in the SBS, mean monthly temperatures arebelow 0°C for 4-5 months of the year but, unlike in the SBS, are above 10°C for only1-3 months of the year. Mean annual precipitation ranges from 335 to 580 mm, ofwhich 30-50% falls as snow. Peak snowpack is only 50-60 cm.

Upland coniferous forests dominate the SBPS landscape. Lodgepole pine is by farthe most common tree species and, in fact, large areas of the forest contain no treespecies other than lodgepole pine. Owing to an extensive fire history, the pine trees aregenerally young, even-aged, and often dense. Productivity of the forest is severelylimited by the harsh climate.

In addition to lodgepole pine, the only common tree species of the SBPS are whitespruce and trembling aspen. White spruce is common in the understory and isoccasionally present in the canopy of mature pine stands on zonal sites, especially inthe wetter northern and eastern parts of the zone. In the very dry, southwestern partof the zone, spruce is uncommon even in the understory of pine stands. White spruce-dominated forests occur on many of the moist sites throughout the SBPS, but these

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FIGURE 46. Sub-Boreal Pine — Spruce zone.

FIGURE 47. Representative climatic diagram for the Sub-Boreal Pine — Spruce zone.

198

spruce stands are usually small and they often ring the perimeter of non-forestedwetlands. Trembling aspen is a common seral species throughout the zone but thestands it dominates are usually small.

Other tree species that occur occasionally in the SBPS are Douglas-fir, subalpinefir, black spruce, and black cottonwood. Douglas-fir occurs on some warm south-facingslopes, especially in the eastern part of the zone and near the boundary with the IDF.Subalpine fir is absent west of the Fraser River but occurs infrequently in theunderstory of stands east of the river. Black spruce occurs in some cold valley bottomsand in wetlands in the northern part of the zone. Black cottonwood occurs locally onthe floodplains of the principal rivers, but is not common.

White spruce is the theoretical climatic climax tree species over most of the SBPS.In the very dry southwestern part of the zone, however, the abundance of pineregeneration and the virtual absence of spruce regeneration on zonal sites suggest thatlodgepole pine is the climatic climax tree species. In the remainder of the zone, thedominance of pine on zonal sites has been maintained by recurrent wildfires, and pineis considered a persistent fire-climax species. In the absence of fire, succession to sprucedominance would be very slow.

Undergrowth vegetation of pine forests on zonal sites is generally low-growingand dominated by dwarf shrubs, grasses, lichens, and mosses. Lichens dominate themoss layer in the very dry southwestern part of the zone, while mosses dominateelsewhere.

Soil development in the SBPS is relatively weak and soils on zonal sites aremembers primarily of the Brunisol and Luvisol orders. Brunisolic Gray Luvisols andOrthic Dystric Brunisols are the most common soils on the dominant morainal deposits.The surface organic layer (humus form) is typically very thin (less than 4 cm) and hasvery slow rates of decomposition. On imperfectly and poorly drained sites, common soilsare gleyed subgroups of Brunisolic and Luvisolic soils or Gleysols. Zonal humus formsare thin Xeromors and Hemimors.

Non-forested wetlands are abundant on the SBPS landscape as a result of thepoorly developed drainage patterns on the plateau surface. Many of these wetlands aremanaged for hay production or grazing. Common wetland community types includeshrub-carrs dominated by Betula glandulosa (scrub birch) and Salix (willow) spp.,shrub fens with various Salix and Carex (sedge) species, and several types of sedgefens. Grass or sedge-dominated meadows, which are only seasonally wet, are commonaround the periphery of wetter types and in some better-drained but cold depressions.Acidic bogs are uncommon.

Small natural grasslands occur occasionally in the SBPS, especially on dry, south-facing slopes of glaciofluvial landforms.

The Sub-Boreal Pine — Spruce zone has a history of frequent wildfires. Effectsof these fires are evident in the patchwork of different aged stands and the smallnumber of stands more than 120 years old. A recent mountain pine beetle epidemichas resulted in extensive mortality of pine trees in the SBPS, especially in thesouthwest.

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NOTES ON CLASSIFICATION

The area of the Sub-Boreal Pine — Spruce zone was originally (Krajina 1965)included in the northwestern portion of the Cariboo Aspen — Lodgepole Pine zone.More recently (Annas and Coupe 1979), it was reclassified as part of the Sub-BorealSpruce zone. However, it is now considered a zone distinct from the SBS because of itscolder, drier climate; its distinctive forest undergrowth with relatively abundantlichens, Calamagrostis rubescens (pinegrass), and Arctostaphylos uva-ursi(kinnikinnick); and the climax or persistent-seral status of lodgepole pine on zonalsites.

SUBZONES

Four subzones are included within the SBPS (Table 27). The driest subzone, theSBPSxc, occurs in the southwest part of the zone in an arc along the inside of theCoast Mountains as far north as the Rainbow Range. On zonal sites in this subzone(Figure 48), white spruce is poorly represented, Arctostaphylos uva-ursi andCalamagrostis rubescens dominate the herb layer, and lichens dominate the moss layer.A slightly more moist subzone, the SBPSdc, occurs in the northeast quarter of thezone. Compared to the very dry subzone, white spruce is more common, a greaternumber of species are well represented in the herb layer, and mosses (especiallyPleurozium schreberi [red-stemmed feathermoss]) dominate the moss layer. An evenmore moist but cold subzone, the SBPSmc, occurs in the northwest corner of the zone,generally north and west of the Ilgachuz Range. Spruce is relatively well representedand mosses dominate the forest undergrowth on zonal sites. Unlike other areas of theSBPS, Calamagrostis rubescens is uncommon on zonal sites. This subzone istransitional to cold, dry subzones of the SBS zone. The fourth subzone, the SBPSmk,occurs in the eastern-most part of the zone, largely east of the Fraser River. It is thewarmest subzone of the SBPS and includes the greatest amount of Douglas-fir.Calamagrostis rubescens and mosses dominate the undergrowth on zonal sites.

TABLE 27. Synopsis of subzones in the Sub-Boreal Pine — Spruce zone (SBPS)

Subzone Code Old code

Very Dry Cold SBPS SBPSxc (SBSa1)Dry Cold SBPS SBPSdc (SBSa3)Moist Cool SBPS SBPSmk (SBSb)Moist Cold SBPS SBPSmc (SBSa2)

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FIGURE 48. Zonal vegetation subzones of the Sub-Boreal Pine — Spruce zone.

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SOME REPRESENTATIVE SITE ASSOCIATIONS

The following four site associations are common on the SBPS landscape and forma sequence of ecosystems from dry to wet in the SBPSdc (see Figure 49).

Lodgepole pine — Juniper — Feathermoss

This is the zonal and most common association of the SBPSdc. It is extensive onwell and moderately well-drained morainal deposits and also occurs on finer-textured glaciofluvial deposits. Soils are mostly Brunisolic Gray Luvisols or, lessoften, Orthic Gray Luvisols and have a thin (3-4 cm) Hemimor humus form.

Even-aged stands of lodgepole pine with a moderately closed canopy dominatethe vegetation. White spruce is seldom present in the canopy, although it occurs inthe understory of most stands. Trembling aspen is sometimes present in the treecanopy, especially in young seral stands.

The shrub layer in most stands has low to moderate cover and is usuallydominated by Juniperus communis (common juniper), Shepherdia canadensis(soopolallie), and Rosa acicularis (prickly rose). A very well-developed cover ofJuniperus communis is present in some relatively old stands. Lodgepole pineregeneration is consistently present but usually patchy.

The herb layer is moderately well developed and dominated by Calamagrostisrubescens and Arctostaphylos uva-ursi. Other common species are Vacciniumcaespitosum (dwarf blueberry), Cornus canadensis (bunchberry), Linnaea borealis(twinflower), Epilobium angustifolium (fireweed), and Fragaria virginiana (wildstrawberry).

A well-developed cover of mosses, primarily Pleurozium schreberi (red-stemmedfeathermoss), is present on most sites. Lichens are also consistently present but lessabundant than on drier sites. Lichen species are mainly Cladonia spp., Cladinaspp., Peltigera spp., and Stereocaulon spp.

Lodgepole pine — Kinnikinnick — Cladonia

This site association is very common in the two driest SBPS subzones, theSBPSxc and SBPSdc. In the SBPSdc, it includes all forested sites drier than thezonal site; in the very dry SBPSxc, it includes the zonal as well as drier sites. In thewetter climate of the SBPSmc, it includes only the driest forested sites. Thus, thisassociation occurs on the driest sites of the SBPS zone, encompassing a broad rangeof site features.

Such sites are most common on well and rapidly drained morainal deposits, butare also present on sandy glaciofluvial deposits and on thin soils over bedrock. Soilsare predominantly Dystric Brunisols or weakly developed Brunisolic Gray Luvisols.The humus form is most often a very thin (less than 3 cm) Xeromor or Hemimor.

The vegetation is characterized by open stands of lodgepole pine with onlyoccasional scattered white spruce. Lodgepole pine, sometimes with a few tremblingaspen, dominates the young seral stands.

202

203

In the undergrowth, low shrubs 0.5-1 m tall cover 5-30% of the surface.Juniperus communis and Shepherdia canadensis are most abundant, but Spiraeabetulifolia (birch-leaved spirea) and Rosa acicularis are also common. Lodgepole pineregeneration, 0.5 and 2.0 m tall, is often well represented but clumped. A fewwhite spruce seedlings can be present.

The herb layer is dominated by dwarf shrubs, especially Arctostaphylos uva-ursi(kinnikinnick), and by a relatively small number of low herbaceous species. Commonspecies are Linnaea borealis, Solidago spathulata (spike-like goldenrod), Carexrichardsonii (Richardson’s sedge), Oryzopsis pungens (short-awned ricegrass), andCalamagrostis rubescens.

The moss layer is dominated by lichens; species are similar to those in theLodgepole pine — Juniper — Feathermoss association. Principal mosses arePleurozium schreberi, Dicranum polysetum (wavy-leaved moss), and Polytrichumjuniperinum (juniper haircap moss). A large proportion of the soil surface can lackvegetation cover over the pine needle litter.

White spruce — Scrub birch — Feathermoss

This is a common site association of moist lower slopes in the SBPSxc, SBPSdc,and SBPSmc. It occurs primarily on moderately well to imperfectly drained morainaldeposits and less commonly on fluvial or lacustrine deposits. Soils are mostlyBrunisolic Gray Luvisols and gleyed subgroups of Dystric Brunisols and GrayLuvisols. Humus forms are thicker (mostly 4-10 cm) than on the drier sites and aremostly Humimors, Hemimors, and Mormoders. As a result of the greater supply ofmoisture and nutrients, these are relatively productive sites for trees and othervegetation in the western SBPS.

Stands are dominated by white spruce with some lodepole pine.

The shrub layer is generally better developed and contains a larger number ofspecies than in the drier site associations. Common species are Rosa acicularis,Shepherdia canadensis, Lonicera involucrata (black twinberry), Juniperus communis,Salix glauca (grey-leaved willow), and Betula glandulosa (scrub birch). Treeregeneration is predominantly white spruce.

The herb layer is relatively sparse but contains several low-growing species.Common species include Petasites frigidus var. palmatus (palmate coltsfoot), Linnaeaborealis, Epilobium angustifolium, Fragaria virginiana, Cornus canadensis, andAchillea millefolium (yarrow).

The moss layer is moderately well developed and dominated by feathermosses,especially Pleurozium schreberi (red-stemmed feathermoss) and Hylocomiumsplendens (step moss). Aulacomnium palustre (glow moss), a moist-site moss, isusually present. Lichens are consistently present and include Peltigera aphthosa,Cladonia spp., and Cladina spp.

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White spruce — Horsetail — Glow moss

The White Spruce — Horsetail — Glow moss association includes the wettest siteswith a closed forest canopy in the SBPS. It is common in all SBPS subzones onimperfectly and poorly drained morainal or fluvial deposits, primarily at the toe ofslopes and in small depressions. A water table is commonly present near the soilsurface for a significant part of the growing season. Soils are primarily Gleysols butalso include gleyed subgroups of Brunisols and Luvisols on the imperfectly drainedsites. Humus forms include Hydromors, Histomors, and Hydromoders.

The forest canopy of mature stands is dominated by white spruce or hybrid white(Engelmann x white) spruce and only occasionally includes other species such aslodgepole pine or trembling aspen. The canopy tends to be relatively open and the treesclumped.

The shrub layer is moderately to well developed and often dominated by Lonicerainvolucrata. Other common species include Salix spp., Ribes spp. (gooseberries andcurrants), Rosa acicularis, Cornus stolonifera (red-osier dogwood), Alnus tenuifolia(mountain alder), and Viburnum edule (highbush-cranberry). White spruce, hybridspruce, or occasionally black spruce are the principal species of tree regeneration. Onpoorly drained sites, tree seedlings establish primarily on raised microsites.

The herb layer includes many species, most of which are low-growing forbs.Equisetum arvense (common horsetail) is consistently present and often dominant.Other common species include Rubus pubescens (trailing raspberry), Linnaea borealis,Petasites frigidus var. palmatus, Cornus canadensis, Calamagrostis canadensis(bluejoint), and Carex disperma (soft-leaved sedge).

Hylocomium splendens and Mniaceae mosses (mostly leafy mosses) commonlydominate the moderately well-developed moss layer. Other common species areAulacomnium palustre, Pleurozium schreberi, Ptilium crista-castrensis (knight’s plume),and Tomenthypnum nitens (golden fuzzy fen moss).

WILDLIFE HABITATS

The factors that most influence the assemblage of wildlife species in this zone(Table 28) are its cold, dry winters and cool, dry summers; its occurrence on highelevation plateaus; and its position, in the centre of the province, leeward of the Pacific,Chilcotin, and Kitimat ranges. Wildlife that inhabit this zone are those that areadapted to either survive or avoid the long, cold winters. Moose can survive on theriparian shrubs, Caribou seek out terrestrial lichen patches in open pine forests, BlackBear spend the winter in hibernation, and most insect-eating birds migrate to warmerclimates.

Wetlands are common and provide excellent habitat for the production ofwaterbirds, including Sandhill Cranes, sandpipers, dabbling and diving ducks, CanadaGeese, and loons. The only nesting colony of White Pelican in the province occurs onStum Lake within this zone. The wetland vegetation provides year-round forage for

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TABLE 28. Selected wildlife habitats and species in the Sub-Boreal Pine — Sprucezone (adapted from Wildlife Branch 1989)

Habitat Habitat Representative wildlife species Wildlife species at riska

distribution

Lodgepole Extensive Moose, Black Bear, Cougar, ♦ Cariboupine forests Lynx, Marten, Gray Wolf, Snowshoe Hare,

Porcupine, Red Squirrel, Yellow-pine Chipmunk,Deer Mouse, Masked Shrew

Northern Goshawk, Great Horned Owl, NorthernHawk-Owl, Barred Owl, Ruffed Grouse, SpruceGrouse, Pileated Woodpecker, HairyWoodpecker, Gray Jay, Red Crossbill, MountainChickadee, Red-breasted Nuthatch, BrownCreeper

Riparian Common Moose, Mule Deer, Black Bear, ∇ American White Pelicanareas, Red Fox, Beaver, Muskrat,wetlands, Meadow Jumping Mouse, Pygmy Shrew ♦ Caribou, Grizzly Bear,meadows, Western Grebefloodplains, Bald Eagle, Ruffed Grouse,

lakes, and Trumpeter Swan, Canada Goose,

streams Sandhill Crane, Herring Gull, Ring-billed Gull,Spotted Sandpiper, Black Tern, Eared Grebe,Common Loon, Barrow’s Goldeneye, HarlequinDuck, Rusty Blackbird, Eastern Kingbird, DuskyFlycatcher, Marsh Wren, Catbird

Common Garter Snake, Western Toad, WoodFrog, Spotted Frog, Long-toed Salamander

Spruce Limited Moose, Black Bear, Gray Wolf, ♦ Caribouforests areal extent Lynx, Fisher, Marten, Little Brown Myotis,

Northern Flying Squirrel, SouthernRed-backed Vole

Great Gray Owl, Boreal Owl, Three-toedWoodpecker, Gray Jay, Magnolia Warbler, Yellow-rumped Warbler, Red-breasted Nuthatch

Open Limited Moose, Mule Deer, Black Bear, ♦ Grizzly Bearaspen forests areal extent Coyote, Red Fox, Badger, Woodchuck,and grasslands Yellow Pine Chipmunk, Deer Mouse,

Pygmy Shrew

American Kestrel, Pygmy Owl, Sharp-tailedGrouse, Northern Flicker, Yellow-belliedSapsucker, Downy Woodpecker, Steller’s Jay,Mountain Bluebird, Vaux’s Swift, BorealChickadee

Common Garter Snake, Western Toad

a Wildlife species and subspecies at risk are those on the preliminary Red and Blue Lists proposed in the Provincial WildlifeStrategy, B.C. Ministry of Environment (October 1989 draft).

∇ Red-listed wildlife species. These are being considered by the Wildlife Branch for designation as endangered orthreatened in British Columbia.

♦ Blue-listed wildlife species. The Wildlife Branch considers these species ‘‘sensitive’’ and/or deserving of managementattention. Population viability is a concern for these species because of (a) major declines in population numbers; or (b)major changes in habitat that will further reduce existing distribution. Species that are generally suspected of beingvulnerable, but for which information is too limited to allow designation in another category, are included in this category.

206

Moose, Beaver, and Muskrat. Black Bear and the occasional Grizzly Bear also forage onvegetation here during the summer months, and some of the larger streams supportspawning salmon, another food source for bears. Many birds, such as the EasternKingbird, Dusky Flycatcher, Marsh Wren, and Catbird, are attracted by the myriadinsects that swarm over these wetlands.

The extensive pine forests provide habitat for seed-eating animals such as RedSquirrel; bark insect-eating birds such as Pileated Woodpecker, Hairy Woodpecker,Mountain Chickadee, Red-breasted Nuthatch, Brown Creeper, Hermit Thrush; andpredatory animals such as Marten, Fisher, Goshawk, Great Horned Owl, and BarredOwl that feed on the insect and seed-eating animals. A few animals, such as the SpruceGrouse and Porcupine, thrive on the needles, buds, and bark of the pine trees. Withthe exception of terrestrial lichens for Caribou, these upland forests provide very poorforage for ungulates.

While not common, mature spruce forests provide cover for Moose, Mule Deer, andBlack Bear, and the arboreal lichens provide winter forage for Caribou. Many of theseed and insect-eating birds are the same ones that occur in the pine forests, althoughhere the snags are larger and last longer, providing better habitat opportunities forcavity-nesting birds and mammals.

Open grassland and aspen habitats are used by a variety of birds feeding oninsects or succulent herbs. Birds include Sharp-tailed Grouse, Northern Pygmy-Owl,Vaux’s Swift, Northern Flicker, Yellow-bellied Sapsucker, Downy Woodpecker, Steller’sJay, and Boreal Chickadee. Moose, Mule Deer, Black Bear, Grizzly Bear, and SnowshoeHare also forage in these herbaceous-rich habitats. Large predatory mammals inthese habitats include the Gray Wolf, Coyote, Red Fox, and Lynx.

RESOURCE VALUES

Timber productivity in the SBPS is low. However, the gentle terrain and small,relatively uniform size of trees allows for efficient mechanized harvesting. In recentyears, timber harvesting has greatly increased in the SBPS, stimulated primarily byattempts to reduce losses of merchantable timber killed by epidemics of mountain pinebeetle.

The SBPS has very low capability for agriculture. However, the numerousnonforested wetlands in the zone are extensively used for hay production and, to alesser extent, cattle grazing. Water levels in many of the wetlands are manipulated forhay production. The abundance of Calamagrostis rubescens in the understory of uplandforests of the eastern parts of the zone contributes to the range value of the SBPS.

Fur harvest from this zone is among the highest in the province.

207

LITERATURE CITED

Annas, R.M. and R. Coupe (editors). 1979. Biogeoclimatic zones and subzones of theCariboo Forest Region. B.C. Min. For., Williams Lake, B.C.

Krajina, V.J. 1965. Biogeoclimatic zones and biogeocoenoses of British Columbia. Ecol.West. N. Amer. 1:1-17.

Wildlife Branch. 1989. Regional wildlife habitat maps. B.C. Min. Environ., Victoria,B.C. 15 maps, 1:500000.

SBPS ESSF MH AT

54 928 ha 1 040 925 ha 1442 068 ha 1 788 468 ha0.5% 17.5% 13.0% 16.1%850 - 1400 m 900 - 1800 m 400 - 1650 m 1100 - 1800 m

Nechako Plateau: East slopes of Coast West slopes of Coast All, mainly Coast,mainly Entiako River Mtns. to Nechako Mtns. to Hecate Hazelton, and Skeenadrainage Plateau Lowland mtns.

Rolling plateau dotted Mid to upper mountain Steep, rocky mountain Rugged, rocky mountainwith wetlands and slopes and high slopes topslakes plateaus; usually not

very steep

Continental; cool, dry Interior subalpine; Coastal subalpine; wet Severe alpine; cold,summers and cold, dry short, fairly dry and very snowy with a windy, and snowy withwinters summers and long short, cool summer very short growing

snowy winters season

Gray Luvisols; Humo-Ferric and Ferro-Humic and Orthic and HumicDystric Brunisols Ferro-Humic Podzols; Humo-Ferric Podzols; Regosols; Brunisols

Podzolic Gray FolisolsLuvisols

Hemimors; < 10 cm Hemimors and Snow-compacted Rhizomulls, Hernimors,thick Hemihumimors; Hemimors and and Mormoders

2 - 15 cm thick Humimors; 5 - 40 cmthick

Pl, Sw, Sb Bl, Hm, Sxw, Pl Hm, Hw, Ba, Yc, (Bl) Bl, Hm krummholz-- -- -- --

All Zones — South

4 • 7

SBPS ESSF IM

0/0/2 0/0/8 1/0/0Alexis Cr.bd Equity Silver Minecd Tahtsa Lake West1219 m 1270 m 863 m

-- -- --464 579 1995

156 – 236 197 – 431 --243 269 399

-- -- --195 249 1041

-- -- --10 10 9

0.7 – 0.8 - 0.7 to - 0.6 --0.4 1.6 1.8

- 12.9 to - 12.2 - 13.5 to - 11.5 --- 13.8 - 8.3 - 9.1

-- -- --- 51.1 - 44.0 - 35.6

10.6 – 11.1 8.0 – 11.6 --11.6 11.7 11.3

-- -- --32.2 30.0 31.7

-- -- --697 147 629

-- -- --12 -- 56

All Zones — South

4 • 9

4.2.6 SBPS Sub-Boreal Pine – Spruce Zone

Location and Distribution: (Figure 4.11; Table 4.2) Only a small area ofSBPS occurs in the PRFR, making up 0.5% of the south half. It is locatedwithin the Lakes Forest District and just barely extends into the adjacentportion of Tweedsmuir Provincial Park. The SBPS in the PRFR occursentirely within a portion of the Nechako Plateau bounded in the north byTetachuck Lake, in the east by the Entiako River, and in the south by theDean River. It represents the northwestern extent of the region known as“the Chilcotin”.

The SBPS ranges from 850 to 1300 - 1400 m in the PRFR. To the north andwest it grades into the SBS zone; at its upper elevations it gives way to theESSF zone.

Climate: (Table 4.3) The SBPS has a severe, cold continental climate thatis reflected in low forest productivity. Its cool, dry climate is caused by thestrong rainshadow effect of the solid mass of Coast Mountains to the west,and the relatively high elevation. The low precipitation, dry air, and clearskies result in cold night-time temperatures and frequent summer froststhat inhibit tree growth. There are no long-term climatic stations locatedwithin the SBPS in the PRFR, but it is known to be somewhat moister andmilder than the Alexis Creek - Anahim Lake country to the south.

Vegetation: (Figure 4.12) Extensive even-aged stands of lodgepole pinedominate the rolling plateau landscape of the SBPS, interrupted only by thedepressional wetlands or “wet meadows” so typical of the Chilcotin. Withinthe PRFR, white spruce (or, if hybrid, predominantly white spruce)commonly occurs in the understory of these pine stands. Mixtures of maturepine and spruce are found in moist depressions, frequently ringingwetlands. Trembling aspen is the major deciduous tree, but it is much lessabundant than in the SBS zone. Black spruce may be found both in bogsand on upland sites. Subalpine fir occurs rarely and Douglas-fir is absent.

Zonal ecosystems of the SBPS characteristically have sparse shrub andherb layers and a moderately developed moss layer (red-stemmedfeathermoss) with abundant lichens (mostly Cladonia and Cladina spp.).Typical species in the shrub layer include common juniper, soopolallie,prickly rose, and birch-leaved spirea. The herb layer includes twinflower,dwarf blueberry, kinnikinnick, bunchberry, bastard toad-flax, fireweed,yarrow, wild strawberry, ricegrasses, bluejoint, and pinegrass.

Soils: (Table 4.2) Zonal soils are Brunisolic Gray Luvisols with relativelythin Hemimor humus forms. The soils are most often formed in compactedglacial till parent materials. Orthic and Gleyed Gray Luvisols, DystricBrunisols, and Organic soils are also common in the SBPS landscape.

Differentiating Features: The SBPS can be distinguished from adjacentsubzones of the SBS and the ESSF by the dominance of poor stands oflodgepole pine, the relative lack of hybrid spruce, and the virtual absence ofsubalpine fir. Features of zonal ecosystems that distinguish the SBPS are:the ability of lodgepole pine to regenerate under its own canopy; the sparse

SBPS

4 • 47

FIGURE 4.11. Distribution of SBPS and SBS subzones and variants in the PRFR, south half.

BG

C U

nits

4 • 48

understory with its strong lichen component; and the presence of speciessuch as common juniper and kinnikinnick that elsewhere indicatedrier-than-mesic site conditions.

Subzones: (Figures 4.11 and 4.12; Table 4.7) There is only one subzone ofthe SBPS in the PRFR:

SBPSmc - Moist Cold subzone.

SBPS

4 • 49

TABLE 4.7. Environmental characteristics of SBPS and SBS subzones andvariants in the PRFR, south half

Subzone or varianta SBSdk SBSmc2

ExtentArea 849 383 ha 1 550 314 ha

% of PRFR, south half 7.6% 14.0%Elevation range 500 - 750 m in the north 500 - 1050 m in the north

700 - 1100 m in the south 700 - 1100 m in the south

DistributionPhysiographic regions Nechako Plateau, Skeena Mtns., Skeena Mtns., Nechako Plateau,

Hazelton Mtns. Hazelton Mtns.

Major drainages Bulkley and Endako river valleys; Most of Babine and NilkitkwaS. Babine Lk. shoreline, Sutherland drainages; upper elev. BulkleyR.; Francois, Ootsa, Cheslatta, and Valley, Morice R., Nadina R.;Netalkuz lakes upper Nass, Damdochax, Bell

Irving rivers; Tahtsa, Whitesail,Eutsuk and Sigutlat lakes

ClimateContinental; relatively dry, warm Wetter, snowier climate thansummers with longer growing SBSdk or SBPS (snowpacks up toseason than SBSmc2 or SBPSmc; 1 m); summers cool, often cloudy,winters cold, relatively dry; relatively moist; growing seasonsnowpack usually < 50 cm intermediate length between

SBSdk and SBPS

SoilsZonal soils Brunisolic Gray Luvisols; Dystric Gray Luvisols; Dystric Brunisols;

Brunisols Humo-Ferric Podzols

Humus forms Hemimors; Mormoders; < 10 cm Hemimors; 8 - 10 cm thickthick

Vegetationb

Major tree species Sxw, Pl, At, Ep, Act Sxw, Bl, Pl, At

Seral stands Abundant throughout; both PI and Widespread; mainly PI-dominated;deciduous; minor native grassland At mainly on south-facing slopesand scrub-steppe

Zonal site association Sxw - Spires - Purple peavine Sxw - Huckleberry

a For a description of the SBSwk3 refer to MacKinnon et al. (1990). b Tree species codes are found in Appendix 3.

BGC Units

4 • 50

SBPSmc

54 928 ha0.5%900 - 1300 m in the north850 - 1400 m in the south

Nechako Plateau

Entiako drainage; south of Ootsa andNetalkuz lakes

Drier, colder, more severe than SBS;short growing season marked by frost;long cold winter with low snowpack

Brunisolic Gray Luvisols; DystricBrunisols

Hemimors; ±8 cm thick

Pl, Sw, Sb

Dominant throughout; almost allPl-dominated; At uncommon

Pl - Feathermoss - Cladina

SBPS/SBS

4 • 51

FIGURE 4.12. Vegetation table for SBPS and SBS subzones and variants in the PRFR, south half.

BG

C U

nits

4 • 52

FIGURE 4.12. (Continued)

SB

PS

4 • 53

4 • 54

5�10 - 1

SBPS

SBPSSub-Boreal Pine�Spruce Zone

Overview

Location and Distinguishing Features The Sub-Boreal Pine�SpruceZone is distinguished from other zones in British Columbia by havingthe following set of characteristics:1) lodgepole pine is the climax or long-persistent seral tree species on zonal sites;2) lodgepole pine is the most common species of tree regeneration beneath the forest canopy;3) the only other coniferous tree species common on zonal sites is hybrid white spruce (or white spruce);4) the undergrowth vegetation on zonal sites is dominated primarily by pinegrass, kinnikinnick, lichens, and (except in the SBPSxc) mosses.

The Sub-Boreal Pine�Spruce Zone is the most extensive zone (21 948km2) on the level to gently rolling landscapes of the Fraser Plateau westof the Fraser River. It also occurs on the southernmost portions of theNechako Plateau, north of the Blackwater River (Steen and Demarchi1991) and along the eastern edge of the Fraser Plateau from the McIn-tosh Lakes to Bonaparte Lake areas. Elevations in the northern andeastern parts of the zone are mostly 900�1250 m, while in southern andwestern areas, elevations range from approximately 1100 to 1500 m.The SBPS occurs above the IDF Zone and below the MS Zone in theChilcotin River drainage. In the Nazko River area, the SBPS occursabove the SBSdw and below the SBSmc. East of the Fraser River, itoccurs primarily on an area of low-relief terrain east of the IDFdk andwest of the SBSdw subzones.

The SBPS Zone occurs primarily in the Cariboo Forest Region. Smallerportions occur in the Prince Rupert, Prince George, and Kamloops forestregions, although the extent of the zone in the latter two forest regions isvery small.

5�10 - 2

BGC UNITS

Climate The SBPS Zone has cold, dry winters and cool, dry summers.Mean annual precipitation ranges from 335 to 580 mm with an averageof about 440 mm (Table 12). Peak precipitation periods are earlysummer (June) and early winter (January). About half of the annualprecipitation falls during the May through September period, while 30�50% falls as snow during the remainder of the year. Peak snowpack inmost years is generally 40�60 cm. Substantial moisture deficits arenormal during the middle and latter parts of the growing season. Meanannual temperatures range from 0.3 to 3.2 °C with an average of 1.9 °C.Subfreezing temperatures can occur at any time of the year, especially inlow-lying areas (Steen et al. 1990).

The cool summers and cold winters of the SBPS Zone result largely fromits position in the strong rainshadow of the Coast Mountains and itsmoderately high elevations. The low precipitation, dry air, and clearskies in the rainshadow result in significant night-time radiation coolingand low overnight temperatures. Based on annual climatic means, theSBPS Zone is colder than all other zones in the Cariboo Forest Regionwith the exception of the MS, ESSF, and AT zones and is drier than allother zones except the BG and IDF zones. It is one of the leastproductive areas for tree growth in the Region outside of the BG and ATzones.

5�10 - 3

SBPS

TABLE 12 Environmental characteristics of SBPS subzones in the

Cariboo Forest Region

SBPSxc SBPSdc SBPSmc SBPSmk

Area (km2) 10898 4227 1165 5658Elevation range (m) 1100� 900� 900� 950�

1500 (S) 1280 1250 1350 (S) 850� 900� 1300 (N) 1250 (N)

ClimatePrecipitation (mm)

Mean annual 389 508 no data 506Mean summer 177 275 196 232Mean winter 212 233 no data 283Mean annual snowfall (cm) 179 178 no data no data

Temperature(°C) Mean annual 1.7 1.9 0.8 3.2 Mean - warmest month 12.3 13.9 10.9 13.7 Mean - coldest month -11.8 -13.5 -12.5 -10.3Frost-free days 93 152 no data no data

SoilsZonal soilsa O.DYB O.DYB O.DYB O.GL

(O.GL) (O.GL)Zonal humus formb HR HR HR HR

aO.DYB = Orthic Dystric Brunisol; O.GL = Orthic Gray LuvisolbHR = HemiMor

5�10 - 4

BGC UNITS

Vegetation The SBPS landscape is dominated by extensive lodgepolepine forests and abundant wetlands. Smaller areas of spruce andtrembling aspen forests are present and small grasslands and meadowsoccur locally. The abundance of wetlands is due to poorly developeddrainage patterns. Late seral or climax vegetation on zonal sites is alodgepole pine or lodgepole pine � spruce forest. The spruce isprimarily hybrid white spruce except in the driest parts of the zone(SBPSxc) where the spruce is typically white spruce. Due to extensivefire history, most stands are young (<140 years), even-aged, and oftendense. The lodgepole pine trees are generally of uniform size. Whitespruce seldom dominates stands on zonal sites but, where it is present,it typically has a wider range in size and age than pine. Lodgepole pineis the most common species of regeneration on most zonal sites. Itsdistribution is typically patchy in response to canopy gaps and pastdisturbances that have created a mineral soil seedbed. The undergrowthof forests on zonal sites is most often dominated by pinegrass,kinnikinnick, and a variety of lichens (especially Cladonia spp.). Othershrubs, especially prickly rose and common juniper, are often scatteredthrough the stand. Lichens dominate the bryophyte/lichen layer in thevery dry southwestern parts of the zone, but mosses are dominantelsewhere.

Trembling aspen stems are common and frequently dominate smallstands, especially on moist sites. Small spruce stands are common at thefringe of wetlands and along stream courses. Douglas-fir forests occurlocally in the SBPS, primarily on upper slopes that are freely drained ofcold air. They are most common east of the Fraser River in the SBPSmk.Other tree species that occur locally are subalpine fir (moist sites ineastern parts of zone), black spruce (cold air accumulation sites innorthern parts of zone), and black cottonwood (floodplains of somerivers).

Non-forested wetlands, meadows, and shrublands are very common andoften extensive on the SBPS landscape due to poorly developed drainagepatterns. The most common types are fens, shrub-carrs, swamps, andmeadows (Roberts 1984). Bogs are uncommon but occur more fre-quently than in the IDF Zone. They are most common in northern partsof the zone. Tree establishment in meadows and shrub-carrs is limitedby frequent summer frosts, cold soils, and occasionally soil salinity.

5�10 - 5

SBPS

Soils Soils of the SBPS Zone are developed primarily on base-rich,sandy loam morainal deposits derived from weathering of basalt and avariety of other bedrock types. In western parts of the zone, especiallysouth of Anahim Lake, morainal deposits are derived from granitic andmetasedimentary rocks and are coarse textured. Sandy glaciofluvialoutwash deposits are also common. Soil development in the SBPS Zoneis weak, and soils on zonal sites are predominantly Orthic DystricBrunisols and Brunisolic Gray Luvisols. The clay-enriched horizon ofthe Luvisols is weakly developed and typically within 15�20 cm of thesoil surface. Soil textures are predominantly sandy loam and oftengravelly. The surface organic layer is typically very thin (<4 cm) andhas very slow rates of decomposition. Humus forms are predominantlyhemimors.

Seepage volumes in the SBPS are small, and permanent seepage isinfrequent in forested ecosystems. Sustained seepage occurs in broad,sloping, diffuse drainage tracks vegetated by wetland species. Forestedseepage sites occur primarily as narrow bands at the base of long north-facing slopes and adjacent to drainage channels.

Subzones of the SBPS Zone in the Cariboo Forest Region

The SBPS Zone includes four subzones. From driest to wettest theyare:SBPSxc - Very Dry Cold SBPS SubzoneSBPSdc - Dry Cold SBPS SubzoneSBPSmc - Moist Cold SBPS SubzoneSBPSmk - Moist Cool SBPS Subzone

No biogeoclimatic variants have been identified. Mature forest vegeta-tion on zonal sites in the four subzones is compared in Table 13.

SBPSxc Subzone The SBPSxc occurs in the southern and western partsof the zone, in an arc along the inside of the Coast Mountains as farnorth as the Rainbow Range. This area is strongly affected by the CoastMountains rainshadow, and the SBPSxc has the least annual precipita-tion of the SBPS subzones (Table 12). Vegetation production and soildevelopment are severely limited by the cold, very dry climate.

5�10 - 6

BG

C U

NIT

S

Biogeoclimatic Unit Pinus contorta

Picea glauca

Juniperus communis Shepherdia canadensis

Rosa acicularis Spiraea betulifolia

Amelanchier alnifolia Vaccinium membranaceum

Oryzopsis pungens Carex richardsonii

Solidago spathulata Arctostaphylos uva-ursi

Geocaulon lividum Linnaea borealis

Epilobium angustifolium Vaccinium caespitosum

Fragaria virginiana Calamagrostis rubescens

Orthilia secunda Aster conspicuus Arnica cordifolia

Cornus canadensis Goodyera oblongifolia

Aster ciliolatus Lilium columbianum

Pyrola chlorantha

Cladonia spp. Cladina spp.

Peltigera spp. Peltigera aphthosa

Dicranum polysetum Pleurozium schreberi

Hylocomium splendens Ptilium crista-castrensis

TABLE 13 SBPS vegetation table - zonal sitesa

TreeLayer

ShrubLayer

HerbLayer

MossLayer

SBPSxc5

3

3

3

1

2

3

2

5

3

2

1

2

4

4

3

3

1

1

3

SBPSmk5

3

1

3

3

2

3

1

1

3

2

3

2

5

2

2

3

4

2

2

2

2

1

2

3

5

1

4

SBPSmcb

5

4

3

3

1

3

3

2

3

1

3

3

3

3

1

5

1

SBPSdc5

3

3

3

2

1

1

3

2

3

2

3

2

4

1

1

2

3

1

1

3

3

3

5

aData are for zonal sites only. bData are from Prince Rupert Forest Region portion of this subzone. Species abundance: 1 present in 40�60% of plots surveyed; 2 >60% of plots, mean cover <1%; 3 >60% of plots, mean cover 1�7%;

4 >60% of plots, mean cover >7�15%; 5 >60% of plots, mean cover >15%

lodgepole pinewhite spruce

common junipersoopolallieprickly rosebirch-leaved spireasaskatoonblack huckleberryshort-awned ricegrassRichardson�s sedgespike-like goldenrodkinnikinnickbastard toad-flaxtwinflowerfireweeddwarf blueberrywild strawberrypinegrassone-sided wintergreenshowy asterheart-leaved arnicabunchberryrattlesnake-plantainfringed astertiger lilygreen wintergreen

cladonia lichensreindeer lichenspelt lichensfreckle peltwavy-leaved mossred-stemmed feathermossstep mossknight�s plume

5�10 - 7

SBPS

Soil organic accumulations are small due to low vegetation productionand a history of frequent wildfires. These fires have left a mosaic ofstand ages, with a high proportion of young stands. Mature lodgepolepine trees are typically short (<18 m) and open-grown.

Lodgepole pine is the only common species of tree regeneration on zonalsites in the SBPSxc. White spruce occurs on moist sites, principally atthe perimeter of wetlands, but is uncommon on the uplands. Tremblingaspen is the only other common tree species in the SBPSxc and isscattered throughout the forest. The forest undergrowth on zonal sitesis dominated by kinnikinnick, pinegrass, and lichens (Table 13). Incontrast to other SBPS subzones, lichens are much more abundant thanmosses. Within the Cariboo Forest Region, the proportion of whitespruce compared to hybrid white spruce is apparently greatest in theSBPSxc.

SBPSdc Subzone The SBPSdc occurs on the Fraser Plateau north andeast of the SBPSxc in an area less strongly affected by the CoastMountains rainshadow. Although nearly all stands on zonal sites aredominated by lodgepole pine, hybrid white spruce is often present in theunderstory and occasionally present as scattered stems in the canopy.The forest canopy is typically more closed than in the SBPSxc.Lodgepole pine is the predominant species of tree regeneration. Theundergrowth vegetation on zonal sites is dominated by pinegrass,kinnikinnick, mosses, and lichens (Table 13). Pinegrass is more abundantand more vigorous and the moss layer is better developed than in theSBPSxc. This subzone is transitional in climate and vegetation betweenthe SBPSxc and the SBPSmk.

SBPSmc Subzone The SBPSmc occurs only in the northwest part ofthe Cariboo Forest Region, north of the Itcha and Ilgachuz mountains. Itis more extensive in the Prince Rupert Forest Region. As in the SBPSdc,hybrid white spruce is common in this subzone but unlike all otherSBPS subzones, pinegrass is uncommon (Table 13). The undergrowth isdominated by feathermosses, lichens, and kinnikinnick. This subzone isclimatically and ecologically transitional to cold, dry portions of the SBSzone, particularly the SBSmc3.

5�10 - 8

BGC UNITS

SBPSmk Subzone The SBPSmk occurs in the eastern portions of theFraser Plateau where the Coast Mountain rainshadow effect is weakerthan in other parts of the zone. It includes the warmest and wettestportions of the SBPS Zone and is the only subzone of the SBPS inwhich Douglas-fir is occasionally present on zonal sites. Within the areaof its distribution, the SBPSmk occurs on two types of terrain. South ofthe Blackwater River in the north-central part of the Cariboo ForestRegion and near Bonaparte Lake, it occurs on hilly terrain at midelevations. In the McIntosh Lakes to Sheridan Lake area, it occurs onlevel to gently rolling terrain where elevations are often lower but frost iscommon due to poor cold air drainage.

Although nearly all forests on zonal sites are dominated by lodgepolepine, hybrid white spruce is usually present in the canopy and regenera-tion layers. Lodgepole pine regeneration is generally less abundant inmature forests than in the SBPSxc or SBPSdc due to the more closedcanopy. Small trembling aspen stands are common, and aspen is oftenscattered through the pine canopy. Douglas-fir is more common than inany other SBPS subzone. It occurs primarily at lower elevations and onsites freely drained of cold air. The undergrowth on zonal sites isdominated by pinegrass and feathermosses. Shrubs, including blackhuckleberry, are more common than in other SBPS subzones.

Trembling aspenPopulus tremuloides