In this article we will discuss about:- 1. Location of Tundra Climate 2. Temperature of Tundra Climate 3. Precipitation of Tundra Climate 4. Natural Vegetation.
Location of Tundra Climate:
Tundra is a Finnish word which means barren land. Thus, the tundra region having least vegetation and polar or arctic climate is found in North America and Eurasia between the southern limit of the permanent ice caps in the north and the northern limit of the taiga or subarcitc climate in the south.
Thus, tundra climate has developed over parts of Alaska (USA), extreme northern parts of Canada, the coastal strips of Greenland and the arctic seas-board regions of European Russia and northern Siberia. Besides, tundra climate has also developed over arctic islands (fig. 39.8). Vegetations rapidly change to the north of treeline because of increasing severity of climate.
Tundra climate is further divided into two subtypes e.g.:
(i) Arctic tundra climte, and
(ii) Alpine tundra climate (which is found over high mountains of tropical to temperate areas).
Based on variations in general vegetation characteristics arctic tundra is divided in 3 zones from south to north viz.:
(i) Low arctic tundra,
(ii) Middle arctic tundra, and
(iii) High arctic tundra. It may be pointed out that high, middle, and low are not indicative of altitudes rather these indicate latitudes.
The poleward boundary of tundra climate is demarcated by 0°C isotherm of the warmest month of the year while 10°C isotherm of the warmest month makes the equator-ward boundary.
Temperature of Tundra Climate:
The tundra climate is characterized by general absence of insolation and sunlight and very low temperature throughout the year. The average annual temperature is -12°C. Winters are long, bitterly cold and very severe while summers are very short but cool. The warmest month of the year records average temperature between 0°C and 10°C.
It is interesting to note that diurnal range of temperature is very low because of very little difference in day and night temperatures but the annual range is quite large. The severe climate does not favour much vegetation growth and hence most of the areas under tundra climate remain barren land.
The ground surface is covered with snow at least for 7 to 8 months each year. The region is swept by speedy cold powdery storms known as blizzards. Growing season is less than 50 days in a year. The ground is permanently frozen (permafrost). Even soil is also perennially frozen.
Precipitation of Tundra Climate:
Mean annual precipitation, mostly in the form of snowfall, is below 40 cm. The absolute humidity is very low because of very low rate of evaporation due to very low temperature throughout the year. The divergent system of air circulation and anticyclonic conditions do not favour much precipitation. Most of the annual precipitation is received during summer and autumn because of relatively higher temperature.
Natural Vegetation of Tundra Climate:
There is prefect relationship between vegetation and the condition of moisture in the soils. The characteristic lithosols of tundra biome support only lichens and mosses. Only 3 per cent species of the total world species of plant could develop in tundra climate because of the severity of cold and the absence of minimum amount of insolation and sunlight.
The vegetations of tundra climate are cryophytes i.e., such vegetations are well adapted to severe cold conditions as they have developed such unique features which enable them to withstand extreme cold conditions. Most of the plants are tufted in form and range in height between 5 cm and 8 cm.
These plants have the tendency of sticking to the ground surface because the temperature of the ground surface is relatively higher than the temperature of the overlying air. The herbs have developed only in those areas where heaps of ice and snow protect the plants from gusty icy winds.
Such herbaceous plants include willow the stems of which are very close to the ground surface (hardly a few centimetres above the ground). Though the growth rate of these herbaceous plants is exceedingly slow but their survival period is unbelievably very long (between 150 to 300 years). The evergreen flowering plants develop on the ground like cushions mostly during short cool summers.