THE TUNDRA–TAIGA INTERFACE

Will climatic warming allow the boreal forest to advance onto the treeless tundra? This is one of the most tantalizing questions that can be asked in any discussion in relation to vegetation margins. The zone between the northern limit of the boreal forest (taiga) and the southern extent of the arctic tundra is the world's only circumpolar vegetation boundary and stretches for 13,400 km around the northern hemisphere and across three continents (Figs. 5.1–5.3). It is probably more exact to refer to this boundary as a zone, for in many places, and particularly in Russia, there is a well-developed interface region. This variable interface ecotone is best developed in Siberia where it is referred to by Russian ecologists as lesotundra (Russian les, forest). The term forest–tundra has also been adopted in describing similar ecotones or zones in eastern Canada created over the last 3000 years by deforestation as a result of the combined action of forest fires and climatic cooling (Asselin & Payette, 2005).

Such is the length of this boundary that it cannot be expected to have the same appearance or behave uniformly throughout its entire length. In some places it can be seen as a relatively abrupt change from forest to open tundra while in others, and particularly in Siberia, there is a lesotundra transition zone that can be several hundred kilometres deep.