ABSTRACT
The largest permafrost areas in the northern hemisphere stretch across both the northern part of North America and from southwestern Europe to Eastern Siberia. In the latter area, the associated vegetation ranges from alpine and meadow tundra in Scandinavia, south and east into the Taiga , which is the most extensive forest in the world (Figure 18.1). In eastern Siberia, it even reaches northeast China and northern Mongolia. It also underlies the northern parts of the Boreal Forest (as the taiga is referred to in North America) in northern Canada, extending polewards into tundra and the northern polar barrens. Both forests have a small number of tree species and a characteristic understory. When traced in the same direction, the trees become smaller and more widely spaced northwards, and are replaced by shrub tundra, with decreasing size and fewer shrub species. These give way to scattered herbs and lichens, but there are also cold, Arctic deserts where there is low precipitation.
