Biome: Tundra

The word tundra originates from the Finnish tunturi, which means “completely treeless heights.” This is how the word is applied broadly all over the world to areas of higher altitude than the tree line. However, the geographically largest [Page 247]and most significant tundra areas are those north of the latitudinal tree line in Eurasia and North America. These tundra areas are mainly situated in lowlands.

The tundra as a biome is relatively young, having developed in the early Pleistocene. However, the characteristic floras of tundras developed earlier, probably during the Miocene-Pliocene, in the highlands of Central Asia and in the Rocky Mountains of North America. In the same period (late Tertiary), present tundra areas were covered by various types of mixed and coniferous forests, now associated with the boreal forest region. Circumpolar regions of tundra-steppe environments developed during the Pleistocene. Rapid expansion of these areas during this period may have been associated with the success of such now-extinct macrograzers as mammoths.

A relative mild climate with spruce forests north of their present limit occurred in the last interglacial (Eem). During the last glaciation (Wisconsin), major parts of the Northern Eurasian and American continents were covered by the Eurasian and Laurentide ice sheets, respectively. There were, however, nonglaciated pockets extending far north, as in parts of Beringia and Northern Yukon Territory. In such nonglaciated areas, the diversity of animal and plant species and the general development of the soil and plant communities have been shown to be no more complex than comparable glaciated land masses nearby. This has lent support for the theory that at present arctic tundra ecosystems, including soils, are in equilibrium with the prevailing climate. Thus, they have been considered quite stable, although many areas have been deglaciated for only 3,000 to 8,000 years. Whether this apparent stability now is threatened with a warming climate is the subject of considerable current research. The following two sections review briefly the basic biogeographical and soil formation characteristics of the tundra region.