Environment of the Yukon

The Yukon Territory, situated in the northwest corner of Canada adjacent to Alaska, and north of 60 °, has a rugged and complex physiography and geology, dominated by mountainous terrain. There are five major watersheds, several large rivers, and many smaller, rich river valleys. The area has innumerable small ponds and damp depressions, but few large lakes. Yukon climate is typified by long, cold winters and short, warm summers. The Yukon has the most variable climate in North America, and across the Territory nine distinct climatic regions can be recognized. Most of the Yukon has either permanent, discontinuous or scattered permafrost. Cryosolic soils dominate in the northern permanent permafrost areas, whereas Brunisolic soils occur in the south where there is discontinuous or scattered permafrost. The dominant vegetation types in the Yukon are arctic tundra, alpine tundra, taiga or subarctic forest, boreal forest and subalpine-shrub forest. Arctic tundra and taiga prevail in the northern part of the Territory, whereas the boreal forest and subalpine-shrub forest characterize the southern part. Alpine tundra occurs at higher elevations throughout the Territory. Five distinct ecozones and 23 ecoregions are now recognized in the Yukon. In addition, scattered throughout the Territory are a number of habitats of special interest to entomologists. These include springs, peatlands, saline flats, sand dunes, and distinctive xeric sites with Artemisia frigida-grass communities. During the Pleistocene much of the Yukon remained ice-free and was part of Beringia, the largest refugial area in the north during the last ice age. As such, the Yukon is a central focus of biogeography in the Nearctic region. Resume. L'environnement au Yukon . Le territoire du Yukon, situe dans la partie nord-ouest du Canada, juste a cote de l'Alaska, au nord du 60 e parallele, a une geologie et une physiographie accidentees et complexes et est domine par les systemes de montagnes. On y trouve cinq bassins hydrographiques principaux, plusieurs grandes rivieres et de nombreuses petites vallees de cours d'eau plus petits. Le terrain est parseme d'innombrables petits etangs et depressions humides mais compte peu de grands lacs. Les hivers sont longs et froids, les etes, courts et chauds. Le Yukon est soumis aux conditions climatiques les plus variables en Amerique du Nord et neuf regions climatiques distinctes peuvent etre reconnues. Presque toute la surface du Yukon est recouverte de pergelisol permanent, discontinu ou clairseme. Les cryosols sont dominants dans les zones de pergelisol permanent du nord, alors que les brunisols dominent dans le sud ou le pergelisol est discontinu ou clairseme.