- Cool temperate continental (Siberian) climate is only experienced in northern hemisphere, where the continents within the high latitudes have a broad east west spread.
- On its poleward side, it merges into Arctic tundra of Canada & Eurasia at around Arctic Circle;
- Southwards, the climate becomes less severe & fades into the temperate Steppe climate
- Predominant vegetation of this Siberian or sub-arctic type of climate is evergreen coniferous forests that stretch in a great, continuous belt across North America, Europe & Asia.
- The greatest single band of the coniferous forest is Taiga (a Russian word for coniferous forest) in Siberia.
- In Europe, this climate & forests are mainly confined to Northern Europe, Sweden & Finland;
- However there are small amount of coniferous forests at high altitudes in Germany, Poland, Austria, Switzerland & other parts of the Europe.
- In North America, the sub-arctic belt stretches across from Alaska across Canada into Labrador & is found in the high Rocky Mountains further south.
The Siberian climate is conspicuously absent in the southern hemisphere because of the narrowness of the southern continents in the high latitudes. The strong oceanic influence reduces the severity of the winters & coniferous forests are found only on the mountainous uplands of southern Chile, New Zealand, Tasmania & South East Australia.
Siberian Climate
- Siberian type climate is typified by bitterly cold winters of long duration & cool brief summer; lies across 60* N of equator.
- Spring & autumn are merely brief transitional periods
- Annual range of temperature is quite high due to extremes of temperature observed in this type of climate, as temp. well below freezing point in winters & approx. 15* in summers.
- With low temperatures in cold season, heavy snowfall can be expected, with frost occurring as early as August
- By September, most of the lakes & ponds are icebound; with the number of days in which the rivers are frozen, increases from south to north.
- The interiors of Eurasian continent are so remote from maritime influence that annual precipitation cannot be high.
- Generally, a total of 40 – 60 cm of rainfall is typified in this sub-arctic type of climate.
- Rainfall is quite well distributed throughout the year, with a summer maximum from the convectional rain, when the continental interiors are greatly heated approx. 20* C.
The total precipitation of Siberian climate is marked by many factors viz. altitude, latitude, proximity to the poles, amount of exposure to influences by westerlies (on western part of the continent), temperate monsoon (on eastern part of the continent) & penetration of cyclones.
- Snow falls nearly everywhere in USSR in long, cold winter, but the amount varies from place to place; with heaviest in northern tundra & Siberian taiga.
- Permanent snowfields like of Alps or the Himalayas are absent, because any accumulation of snow is melted with the return of spring & the warm summer.
- Frozen rivers are thawed, causing a rise in the water level, sometimes resulting in extensive floods.
- Being a poor conductor of heat, the presence of thick mantle of snow protects the soil of ground from severe cold above, which may be approx. 5* – 10* C colder.
- It also provides moisture for the vegetation when the snow melts in spring.
Natural Vegetation
- No other trees are as well adapted as the conifers, to withstand such a severe inhospitable environment as Siberian type of climate.
- Coniferous belts of Eurasia & North America are the richest sources of softwood; Used in construction, furniture, matches, paper & pulp, rayon & other chemical products.
- The world’s greatest softwood producers are USSR, USA, Canada & Fenoscandian countries (Finland, Sweden & Norway).
- USA is the leading producer in the production of wood pulp & Canada in newsprint, accounting for almost half of the world’s production.
Coniferous Evergreen forests
- Coniferous forests are more uniform in height, & grow straight & tall upto a height of 100 feet approx.
- There are four major groups of conifers viz. Fir, Pine, Spruces & Larch.
- Coniferous trees grow up instead of out and are of a triangular shape to prevent snow accumulation & also offers little grip to the winds.
- There is no annual replacement of new leaves as in deciduous trees.
- The same leaf remains on the tree for as long as 5 years.
- By keeping their leaves, conifers can quickly begin food production when the warm weather returns in the spring.
- The needles have a waxy coating that helps reduce moisture loss in cold weather.
- The narrow needles offer less surface area to the drying winds of winter. Food is stored in trunks, & bark is thick to protect the trees from excessive cold.
- Soils of coniferous forests are poor, podzolized, excessively leached & very acidic.
- Evergreen leaves provide little leaf fall for humus formation & the rate of decomposition of the leathery needles in a region of such a low temperature is slow.
- All above mentioned factors along with absence of direct sunlight & short duration of summers are deterrent to the growth of much undergrowth.
Agricultural Developments
- Conifers are limited in species with pine, spruce & fir predominant in northern forests, while larch predominant in warmer south.
- They occur in homogeneous groups, not mixed as tropical forests, which saves cost & time, and enhances the commercial value of felled timber.
- Coniferous forests are felled & transported to the saw mills for the extraction of temperate soft woods & forms the basis of lumbering industry; & is used for varieties of purposes viz.
- Paper & Pulp industry in which USA & Canada are leading exporters
- Industrial raw materials used for various industrial products such as matches, which form a major export item in Sweden;
- For making plywood, hardboards, furniture, toys, planks & packing cases
- For making many chemical processed articles such as rayon turpentine, paints, dyes, wood alcohol, disinfectants & cosmetics.
- Trapping of fur bearing animals is practised on large scale for extracting fur, which fetches high price.
- Only in more sheltered valleys & land bordering the steppes are some cereals (barley, oats, rye) & root crops (potatoes) are raised for local needs.
No comments:
Post a Comment