Extensive areas of the Arctic in North America and northern Asia are formed by the low-lying treeless plains of the tundra which range from wet meadow to dry heath and rocky fellfields. The proportion of wet ground is small, however, in the fiord terrain of the eastern Canadian Arctic and Greenland and in the mountains of Alaska, Anadyr, and Kamchatka, and very large in the other areas. The alpine areas of the world are of course markedly non-contiguous and are exposed to a wide variety of regional climatic controls. Nevertheless, the broad comparability of the physiognomy of alpine and arctic vegetation is readily apparent, although xeric and mesic alpine communities usually form a more complex small-scale mosaic due to the nature of the terrain, and the extensive wet tundras are largely lacking.
It is commonly argued that cool summers are the basic cause of the treeless character of both tundra environments, and that mean annual temperature likewise provides an indication of the occurrence of permafrost throughout the Arctic and, as is being increasingly recognized, in many alpine areas also. However, quantitative comparisons and evaluations are almost wholly lacking and we cannot assume that the apparent similarities derive from the same environmental controls. The climatic environments of the arctic and alpine regions are similar in terms of mean annual temperature and snow cover duration, but little else. For up to six months of the year the Arctic receives virtually no solar radiation, whereas alpine areas experience regular diurnal and seasonal regimes appropriate to their latitude. The Arctic is no more windy than most mid-latitude areas, while many alpine sites experience extreme maximum and high mean wind speeds. Much of the Arctic receives little snowfall whereas certain alpine areas have among the highest totals of the world.
In spite of the need for quantitative comparative studies of environmental characteristics and processes in these environments, a serious difficulty is posed by the problem of scale. The heterogeneity in the alpine environment resulting from slope, orientation, and superficial mantle is displayed in microclimate, geomorphic activity, hydrology, fauna and flora, so that proper sampling encounters conceptual problems which may have no real solution.
On the gross scale, arctic and alpine environments can be treated as a continuum from high latitude/low altitude to low latitude/high altitude conditions, as suggested by world timberline and snowline elevations. Eventually, it should be possible to formulate this relationship more precisely in terms of an energy exchange model. Evaluation of the energy transfers between organisms and their environment, on the one hand, and amongst the organisms themselves, on the other, is the basis of modern ecosystems analysis.
Productivity studies at arctic and alpine tundra sites indicate that temperature is the primary limiting factor and that net primary production is in the same range as that of deserts. However, the importance of below ground production necessitates care in interpreting the available data. Webber’s data indicate greater primary production in the Colorado alpine (200–250 g m−2 yr−1) than at Point Barrow (100 g m−2 yr−1) but net photosynthetic efficiency is apparently about 1 per cent in each case. Although a detailed evaluation in these terms is not yet possible for tundra environments, the groundwork for this is being laid as several of the following chapters show.
Finally, we should point to certain features which are unique to one or other of the tundra environments. The principal ones result from geographical location and altitude as they affect seasonal regime and atmospheric density, respectively. Thus, the ‘polar night’ has important consequences for the fauna of the Arctic, while at altitudes above 4–5 km hypoxia is a severe hindrance to man’s activities, at least. Nevertheless, this constraint is mitigated by the fact that man and animals can move into and out of the alpine environment much more readily than in the case of the Arcti