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Home , Cassiar Mountains, Klastline Plateau, Skeena Mountains, Spectrum Range, Stikine Plateau, Tahltan Highland

23

IV THE ENVIRONMENT

The traditional territories of the contribute to the nature, abundance, and people, as outlined above, are located distribution of resources available for within two natural physiographic regions, human exploitation. This section the and the Skeena summarizes the environmental factors which Mountains (as shown in Figure 4). The have influenced human occupation of the complex interaction of geologic processes, area. topography, climate, soils, and vegetation

Physiographic Areas

The Stikine Plateau is generally B.P, with even younger material overlying it characterized by flat and gently sloping (Souther 1970:63). Edziza derives its name upland surfaces which represent remnants of from the Tahltan term 'edziOa' meaning late Tertiary erosional surfaces, uplifted ' ash and sand mountain,' and oral during the Pliocene. It also includes areas traditions describe eruptions which have modified by extensive Pleistocene volcanic forced people to move their camps quickly. activity and glaciation. The Stikine Plateau The base of the dome provides sources of is differentially dissected by several major good quality obsidian for stone tool river valleys, and is subdivided into several technologies. Most of the obsidian is black units each with its own distinct whose thinned edges sometimes show black geographical and geological characteristics lines and specks. Opaque green, grey, and (Holland 1976:49-55). blue varieties are less common while The , running from mottled, striped or speckled varieties are northwest to southeast, is a transitional rare. These good quality obsidians were zone between the Boundary Range of the formed about 0.9 to 1.1 million years ago, Coastal Mountains and the plateau areas to according to fission track and potassium the east. The Complex and argon dating, and have an abnormally high the dominate the eastern uranium content (Souther 1970:63). edge of the highlands. Mt. Edziza is a The blocky alkali olivine basalt flows composite volcano rising to a height of from the younger cone do not 2700 metres (9000 feet) with an ice covered produce a workable glass suitable for peak. The first Edziza flow, dated to six making stone tools. However, the scattered million years ago by radiometric assay eruptions of these cones have caused sudden (Souther 1973:16), was followed by many changes in drainage patterns. Well defined similar flows forming a basal lacustrine terraces on Mess Creek and with a radial system of canyons. During Klastline River mark the former extent of the late Pleistocene, until about 10,000 now dry dammed lakes that persisted years ago, activity in the central conduit for hundreds of years and may have built up the central dome and influenced the location of early campsites. crater with lava flowing down the radial The effect of lava dams on salmon valleys. migrations may also have had important Since 10,000 years ago, 30 to 40 repercussions on early human populations. eruptions from small pyroclastic cones have The absence of salmon in upper River produced mobile flows of blocky olivine may be attributed to an impassable barrier basalt. One of these on the north slope of recent lava from a near the of Edziza has been dated to 1340 + 130 mouth of Forest Kerr Creek (Souther 1970:55). 24 TAHLTAN ETHNOARCHAEOLOGY

The plateau areas, including Nahlin, such as marmots. Kawdy, Tanzilla, Spatsizi, and Klastline The extend south from Plateaus, have gently rolling upland the Spatsizi and areas. surfaces of low relief, lying mainly above The transition between the plateau areas timberline at 15 00 metres (5 000 feet). and the mountains is represented by gently These areas support a wide range of sloping upland areas which are remnants of subalpine and alpine vegetation including dissected late Tertiary erosional surfaces. grassland communities, low lying shrubs, Drained by the Stikine, Nass, and Skeena mosses, and lichens. Within the Spatsizi Rivers, the Skeena Mountains consist of a Plateau, Pojar (1976) has identified more series of ranges divided by prominent than 370 species of vascular plants and northwesterly trending valleys. The valley over 200 species of mosses and lichens. bottoms lie at 2,500 to 4,000 feet (750 to These rich habitats support large 1200 m) in elevation and are wide and drift populations of larger game such as caribou, filled (Holland 1976:55). sheep, and goats as well as small animals

Climate

Most of the study area has a climate Table 2 Hours of Direct Sunlight which is in direct contrast to that of the Coastal Mountains. Situated within the Latitude December 21______Tune 21 rainshadow of the , the Stikine Plateau has low precipitation, 56° 6 hr 57 min 17 hr 37 min averaging 12 to 23 inches (3 0-5 8 cm) 5 7° 6 hr 41 min 17 hr 56 min annually. Precipitation is particularly low 58° 6 hr 24 min 18 hr 15 min in the Tahltan highlands adjacent to the 59° 6 hr 08 min 18 hr 34 min mountains and increases eastward towards 60° 5 hr 52 min 18 hr 53 min the . The area also experiences extremes in temperature, (Kendrew and Kerr 1956:156) although it is characterized by long cold winters and short cool summers, due to the combined factors of high northern latitude The major rivers freeze over by the end and high elevation of most of the area. of November and are closed to navigation by The amount of direct sunlight received boat until late April. At higher elevations, within the study area varies greatly from lakes start to freeze over in October and do summer to winter as shown in Table 2. not open again until late May or June. The long hours of daylight during summer Within the study area marked differences contribute to high plant productivity of in topography, climate, soils, and vegetation more hardy frost resistant species. Low are related to elevational zonation in local rainfall, combined with short frost free land forms. These differences are presented summers in the Stikine Plateau, prohibits according to the biogeoclimatic classification extensive horticulture or agricultural system developed by Dr. V.J. Krajina (196 5, activities except in a very restricted portion 1969). of the Middle Stikine Valley in the vicinity of . THE ENVIRONMENT 25

Biogeoclimatic Zones

Alpine Tundra Zone between 900 and 1800 metres (3,000 to 6,000 feet). It is characterized by a cold The Alpine Tundra zone consists of continental climate (Dfc after Koppen) with treeless meadows, slopes, rocky ridges, short cool summers, and severe winters. snowfields, and icefields at high elevations Only tress which tolerate extended periods in mountainous as well as plateau areas. of frozen ground grow successfully in this Within the study area alpine tundra occurs zone. These include subalpine fir (Abies above 1500 to 1800 metres (5,000 to 6,000 lasiocarpa). white and black spruce (Picea feet) (Valentine et. aL 1978:154). The harsh glauca and mariana). Sitka alder (Alnus climate of the alpine environment is the sinuata). willows (Salix spp.), and shrub result of both increasing elevation and birch (Betula occidental is}*. latitude. The climate is described as Within the subalpine zone, Hutno-Ferric subarctic (Dfc after K op pen) with less than Podzols are the most common soils 25 frost free days. Frost may occur, throughout. On moderate to well drained however, any day of the year at higher sites on colluvial and morainal parent elevations. Absolute temperatures range materials white spruce and subalpine fir from 28° C to -45° C (83° to -49° F) while often grow in colonies or pure stands with the average temperature of the warmest a resulting thin acidic litter mat. On the month is less than 10° C (50° F). Average dry exposed plateau areas, such as the annual precipitation is 72 cm (29 in.) with Spatsizi, shrub willows and birch approximately 75% as snowfall (Krajina predominate, along with grassland 1965, 1969). communities. In some valleys subject to Factors such as high elevation, very cold cold air drainage from adjacent mountains, subarctic climate, lack of moisture, and shrub willows and birch, along with alpine rugged or often rocky terrain, all tend to species, occupy the valley floor as well as restrict soil formation processes in the upper elevations (Valentine e t.il. 1979: Alpine Tundra zone. Periglacial activity 154:55). Turbic Cryosol soils occur at such as cryoturbation is very active in this higher elevations where solifluction and zone resulting in churning of soil materials, nivation become active in moist areas patterned ground features, and poor horizon between clumps of krummholz, or dwarf, differentiation. Regosol landscapes are most tree forms. Although the Stikine Plateau common under these conditions (Valentine et_ lies south of the limit of discontinuous aL 1978:155). permafrost, permafrost occurs sporadically Alpine meadows occur under moist at higher elevations in the subalpine and conditions on flat or gently sloping alpine tundra zones, particularly in the topography where snow cover lasts longer. mountainous areas of the region. They have a short but colourful vegetative season and produce such species as grasses, Boreal White and Black Spruce Zone sedges, lupines, anemones, Indian paintbrush, and arnicas. A wide variety of mosses, This boreal forest zone occurs at lower lichens, and mountain heathers grow in the elevations in the major river valleys of the alpine tundra zone. Subalpine fir and Stikine Plateau from 150 to 900 metres scrub birch may occur in Krummholz, or (5 0 0 to 3 0 0 0 feet). This zone is dwarf, form in especially protected habitats characterized by a humid continental climate with moderate snow cover (Valentine et. al. (Dfc - Dsb after Koppen), with cool 1978:38). summers and fairly evenly distributed precipitation over the year. Mean annual Spruce - Willow - Birch Zone temperatures range from -3° to 3° C (27° to 37° F). The number of frost free days The subalpine Spruce - Willow - Birch varies from 20 to 150 (Krajina 1965, 1969). zone occurs in the Stikine Plateau area The major tree species in this zone are 26 TAHLTAN ETHNOARCHAEOLOGY

white and black spruce (Picea glauca and Mean Daily Temperature - Line Graph mariana), lodgepole pine (Pinus contorta)T Total Monthly Precipitation - Bar Graph subalpine fir (Abies lasiocarpa)r trembling aspen (Pop ulus tremuloides)T cottonwood (Populus trichocarpa), alders (Alnus sinuata and tenuifolia)r and paper birch (Betula papyfera). Within the broad valleys of this zone, extensive fluvioglacial deposits are common. These coarse textured soils of the Dystric and Eutric Brunisolic type are characterized by rapid percolation and iron accumulation, especially on acidic parent materials. Dystric Brunisols occur on dry acidic sites, where forest fires are common and lodgepole pine dominates the forest growth which is kept in a constant early successional stage. Black spruce, which is the most shade tolerant tree growing in this zone, often grows with moss communities on imperfectly drained habitats with acid soils (Valentine eL aL. 1979:153). The penetration of warm westerly winds up the valley produces a small warmer and drier microclimate in the middle section of the Stikine valley. Annual total precipitation in this area is 12 ---- - Telegraph Creek (165m) to 15 inches (30 to 37 cm). Absolute - Cold Fish Lake (1200m) temperatures range from 3 5° to -50° C (95° to -60° F). Eutric Brunisol soils occur on Figure 5. Comparisons of temperatures and precipi­ the dry, south facing terraces in this area tation at Telegraph Creek and Cold Fish where grassland communities dominate. The Lake (data from , Department of surface soil horizons (Bm) are reddish Transport 1967 and Pojar 1976) yellow or yellowish brown, with an average depth of 2 0 cm having occasional leached (Ae) surfaces. Soil pH ranges from 6 to 7 block out cold arctic air from the north in value with surface soil horizons slightly moderating winter temperatures in this more acidic than underlying deposits (Epp region. and Fenger 1978:8). The soils in this area Due to warmer temperatures and are closer to neutral than most areas of the increased precipitation, the Boreal White and Stikine Plateau and thus more likely to Black Spruce Zone of the Stikine Plateau yield preserved faunal remains. is replaced by the Sub-Boreal Spruce zone Figure 5 compares the yearly at elevations of 300 to 900 metres (1000 to d i s t r i b u t i o n of p re c ip ita tio n and 3 0 0 0 ft.) in the Skeena Mountains. temperatures at Telegraph Creek at 165m Although the major tree species are the within the Boreal Forest Zone and at Cold same in both zones their productivity is Fish Lake at 1200 m in the Subalpine greatly increased within the Sub-Boreal Zone. Zone. Within the subalpine zone climatic The large valley of the modifications are also felt, so that the allows westerly winds to penetrate the Spruce - Willow - Birch Zone north of 57° Coast Mountain barrier, resulting in latitude is replaced by the Subalpine Fir increased precipitation locally in the Zone at 900 to 1500 metres (3000 to 5000 Skeena Mountains and deep snow ft.) in the Skeena Mountains (Krajina 1965, accum ulations. The higher peaks also 1969, Valentine et al. 1978:159). THE ENVIRONMENT 27

Palcoclimate

Post glacial paleoclimatic data for of the region was two to three degrees northern are only Centigrade cooler and somewhat drier than available from the Atlin region where at present. By 8,000 years ago the climate palynological profiles have been dated was similar to that of today. A postglacial (Anderson 1970). Since the Atlin region, maximum has been proposed for the region located within the Plateau area, has between 8,000 and 2,500 years ago with a very similar climate at present, in terms mean July temperatures up to one degree of temperatures and precipitation, to that higher than present and precipitation at the of the Stikine Plateau, it would seem same level as today or somewhat higher. logical to assume that the paleoclimates of Climatic fluctuations in the Atlin region the two neighbouring areas were also appear to have differed from other areas of similar. the province in terms of moisture regime, Within the northwestern corner of being moister when other areas were drier British Columbia, deglaciation proceeded in during the postglacial thermal maximum an irregular fashion. The palynological (Clague 1981:23). profile from Atlin indicates that tundra While in southern British Columbia the shrubs were established by 11,000 years late postglacial climate became cooler and ago. The existence of a late glacial lake in wetter than earlier periods, late postglacial the area of the middle Stikine and its three cooling in the Atlin region was marked by northern tributaries, the Tahltan, Tuya, and reduced precipitation. A cool dry period Tanzilla Rivers (Valentine £t_ jil_. 1978: occurred between 2,500 and 750 years ago Figure 1.3.2) and the presence of while alpine glaciers in the nearby drumlin-like features in the topography of of the Coastal Mountains the plateau areas marking the northward were expanding. Within the last 750 years retreat of glacial ice (Holland 1976:48-54) precipitation and temperatures have increased suggest that the middle Stikine area was ice to values comparable to those prior to free earlier than the Atlin region. The 2,500 years ago (Clague 19 81:25). The geothermal potential of volcanic activity in latest advance of alpine glaciers in the Mt. the area during the late Pleistocene may Edziza complex in the Tahltan Highland, possibly have stimulated early deglaciation occurring prior to 1340 + 130 radiocarbon in the Stikine area. years ago, extended no more than one to two The Atlin pollen profile indicates that kilometres (J. Souther: personal during early post glacial times the climate communication) from their present position.