The High Subarctic Forest-Tundra of Northwestern Canada: Position, Width, and Vegetation Gradients in Relation to Climate

A phytogeoclimatic study of the high subarctic region of Canada between Hudson Bay and the Cordillera at the northern Yukon-Mackenzie border was undertaken to provide a verifiable and quantitative synthesis of forest-tundra vegetation ecology. Three field seasons of vegetation and terrain studies provided ground truth for a grid of 1314 black-and-white air photos that cover ca. 24% of the forest-tundra and adjacent low Subarctic and low Arctic. Air photos were analyzed for percentage cover of nine vegetation-terrain types, bedrock and parent materials, landforms, and elevations. The forest-tundra, as bounded by the 1000:1 and 1:1000 tree:upland tundra cover isolines, spans an average 145 ± 72 km (median 131 km) and increases in width from northwest to southeast. The transition from 10:1 to 1:10 tree:upland tundra cover occupies one-fourth to one-half the area of the forest-tundra. Regional slope of the land probably accounts for much of the variation in width of the forest-tundra. Southern outliers of forest-tundra in the northwest are found mainly in areas of high elevation. Across much of the northwest, steep vegetation gradients occur near the northern limit of trees. North of Great Slave Lake, steep vegetation gradients shift from the northern to the southern half of the forest-tundra and maintain this position eastward to Hudson Bay. The forest-tundra of the northwest receives roughly three-fourths the mean annual net radiation available to the southeast and central districts. Key words: air photos, boreal, climate, ecology, forest-tundra, high Subarctic, Northwest Territories, plant geography, tree line, vegetation

[1]  J. A. Larsen.  The Vegetation of the Ennadai Lake Area, N.W.T.: Studies in Subarctic and Arctic Bioclimatology , 1965 .

[2]  B. Rizzo,et al.  Assessing the sensitivity of Canada's ecosystems to climatic change , 1992 .

[3]  H. Bostock.  Physiographic subdivisions of Canada , 1970 .

[4]  C. Brooks,et al.  The climates of North America , 1938 .

[5]  W. Cody,et al.  Vascular Plants of Continental Northwest Territories, Canada , 1981 .

[6]  F. Kenneth Hare,et al.  Climate and Zonal Divisions of the Boreal Forest Formation in Eastern Canada , 1950 .

[7]  J. C. Ritchie.  The Vegetation of Northern Manitoba V. Establishing the Major Zonation , 1960 .

[8]  A. Leahey,et al.  The Canadian System of Soil Classification and the Seventh Approximation1 , 1963 .

[9]  W. Kellogg,et al.  Sensitivity of Soil Moisture to Doubling of Carbon Dioxide in Climate Model Experiments. Part I: North America , 1988 .

[10]  J. Tedrow.  Soils of the polar landscapes , 1978 .

[11]  D. Elliott-Fisk.  The Stability of the Northern Canadian Tree Limit , 1983 .

[12]  V. K. Prest,et al.  Glacial map of Canada , 1968 .

[13]  W. Rouse,et al.  Impact of Hudson Bay on the energy balance in the Hudson Bay Lowlands and the potential for climatic modification , 1985 .

[14]  Peter A. Scott,et al.  CROWN FORMS AND SHOOT ELONGATION OF WHIlE SPRUCE AT IHE TREELINE, CHURCHILL, MANITOBA, CANADA , 1987 .

[15]  R. Bryson.  Air Masses, Streamlines and the Boreal Forest , 1966 .

[16]  K. Timoney.  A geobotanical investigation of the subarctic forest-tundra of the Northwest Territories , 1988 .

[17]  J. C. Ritchie,et al.  Past and Present Vegetation of the Far Northwest of Canada. , 1985 .

[18]  F. Hare,et al.  Climates of North America , 1974 .

[19]  D. C. Thomas.  Population estimates and distribution of barren-ground caribou in Mackenzie District, NWT, Saskatchewan, and Alberta - march to may, 1967 , 1969 .

[20]  R. A. Black.  Reproductive biology of Picea mariana (Mill.) BSP. at treeline , 1977 .

[21]  J. A. Larsen.  The Northern Forest Border in Canada and Alaska , 1988, Ecological Studies.

[22]  Doris Love,et al.  SUBARCTIC AND SUBALPINE: WHERE AND WHAT? , 1970 .

[23]  J. Cayford,et al.  Forest Regions of Canada , 1974 .

[24]  W. Kellogg,et al.  Sensitivity of Soil Moisture to Doubling of Carbon Dioxide in Climate Model Experiments. Part II: The Asian Monsoon Region , 1988 .

[25]  H. Nichols.  Historical Aspects of the Northern Canadian Treeline , 1976 .

[26]  K. Everett.  Soils of Canada , 1979 .

[27]  Arctic and Alpine Environments , 1976 .

[28]  L. Evans.  Soils of Canada , 1978 .

[29]  J. C. Ritchie.  THE VEGETATION OF NORTHERN MANITOBA: IV. THE CARIBOU LAKE REGION , 1960 .

[30]  J. C. Ritchie,et al.  The Boreal Bioclimates , 1972 .

[31]  W. Rouse.  Microclimate at Arctic Tree Line 1. Radiation Balance of Tundra and Forest , 1984 .