Background Research (cont.)

Geology

The “Soils of the Taseko Lakes area, British Columbia” soil survey, prepared by Agriculture Canada, reports that:

"[The Fraser Plateau] is a rolling drumlinized till plain dissected by deep valleys and containing some isolated hills. It slopes from the southwest to the northeast starting at about 1500 m above sea level (asl) and gradually falling to 1000 m asl. Most of the plateau is covered with moraine depositions that reflect the mineralogy and surface configuration of the basalt flows underneath. There are many enclosed depressions with wet soils and organic deposits as well as glaciofluvial gravels in shallow valleys” (Valentine et al, 1987).

The Fraser Plateau is underlain by base rich and fine grained basalt and andestie lava flows (Valentine et al, 1987). Major rivers such as the Chilcotin and Fraser flow in deep valleys within the plateau and the rivers have eroded into the glacial and outwash materials including till, silts, sands, gravels and lacustrine deposits which fill the older valleys (Foweraker). The “Geology and mineral occurrences of the Taseko-Bridge River area” geological survey, prepared by Ministry of Employment and Investment: Geological Survey Branch: Energy and Minerals Division, provides a more detailed study (Schiarizza et al., 1997). ^ top

Climatology

Most of the area has a moderate continental climate with cold winters and warm summers. The “Soils of the Taseko Lakes area, British Columbia” soil survey report states that:

“[The] local climatic conditions are governed largely by elevation, aspect, and physiographic setting, especially proximity to mountain ranges. In the lee of the Coast Mountains there is a rain shadow, giving less total precipitation and clearer skies, particularly in the Fraser Plateau West. In addition, being higher the Fraser Plateau West has a short frost-free period and consequently a short growing season. The mountains adjacent to it have even lower temperatures, a shorter growing season, and comparatively more precipitation. Aspect affects the local, or micro, climate on sloping lands. South- and southwest-facing slopes are considerably drier and warmer than adjacent north- or northeast-facing slopes. The warmest and driest lands are in and adjacent to the Major River Valleys” (Valentine et al, 1987). ^ top

Vegetation

Annas and Coupe (1979) defined a Biogeoclimatic Zone as "a definite geographical area having basically similar patterns of energy flow, biochemical cycling, vegetation, and soils as a result of a broadly homogeneous macroclimate” (Valentine et al, 1987). They also described the following four main vegetation (or Biogeoclimatic) zones in the Fraser Platuea/Taseko Lakes survey area:

The Engelman Spruce-Subapline Fir (ESSF) subzone has low biological productivity due to the cold dry climate. Typical overstory vegetation consists of lodgepole pine with sparse whitebark pine, subalpine fir, and Engelmann spruce. It is noted that south-facing slopes often have much less vegetation than north-facing slopes due to greater moisture stress. .
The Montane Spruce subzone (MS) consists of mostly lodgepole pine and hybrid white spruce overstories. Wet sites have an overstory of hybrid white spruce and occasionally subalpine fir.
The Interior Douglas Fir zone (IDF) consists of lower elevation forest centered along some of the major drainages. In the other subzone of the IDF, Douglas fir and lodgepole pine are the most common trees. White spruce, aspen, and black cottonwood occur on moist to wet sites.
Subboreal Spruce, Chilcotin Pine subzone (SBSa) occurs below the MS and receives less precipitation because of the rainshadow region to the lee of the Coast Mountains. The most common vegetation is an overstory of lodgepole pine and moister forested sites often have an overstory of white spruce and trembling aspen (Valentine et al, 1987).

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Soil

The “Soils of the Taseko Lakes area, British Columbia” soil survey report, describes the characteristics of the soils and map units, and specifies their location and extent (Valentine et al., 1987). 34 predominant soil associations are found in the study area. Valentine et al. (1987) describes soil associations as:

"a group of related soils developed on similar parent materials, which differ due to different soi1 water regimes or other characteristics such as depth to bedrock. The soils occur under similar climatic conditions and usually within one physiographic area or vegetation zone.”