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In this article we will discuss about:- 1. Location of Temperate Grassland Biome 2. Climate of Temperate Grassland Biome 3. Vegetation Community 4. Animal Community 5. Man and Temperate Grassland Biome.
Location of Temperate Grassland Biome:
Temperate grasslands are located in the interiors of the continents which come in the westerly wind belt but because of their more interior locations they do not get sufficient rainfall and hence the grasslands are practically treeless.
The temperate grasslands of the southern hemisphere are located along the south-eastern margins of the continents and therefore have more moderate climate than their counterparts of the northern hemisphere because of more marine influences as they are closer to the marine environments.
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The temperate grasslands of Eurasia, known as steppes, are most extensive as they extend for a distance of more than 3200 km from the shores of the Black Sea across the Great Russian Plain to the foothills of the Altai Mountains. Their continuity is broken at few places by the highlands. There are also some isolated patches of steppes e.g., in Hungary (known as pustaz) and in the plains of Manchuria (Munchurian Grassland).
The temperate grasslands of North America (extending in the U.S.A. and Canada both) are locally known as prairies which extend from the foot-hills of the Rockies in the west to the temperate deciduous forest biome in the east.
The temperate grasslands of the southern hemisphere include the pampas of Argentina and Uruguay of South America; bush veld and the high veld of south Africa; and downs of the Murray—Darling basins of South-Eastern Australia and Canterbury grassland of New Zealand.
Climate of Temperate Grassland Biome:
The temperate grasslands of the northern hemisphere are characterized by continental climate wherein extremes of summer and winter temperatures are well marked but the temperate grasslands of the southern hemisphere are characterized by more moderate climate. Summers are warm with over 20°C temperature during July (Winnipeg, Canada) and 22°C during January (Pretoria, South Africa, January is summer month in the southern hemisphere).
Winter season becomes very cold in the northern hemisphere because of enormous distances of the temperate grasslands from the nearest sea as Winnipeg records- 20°C temperature during January. On the other hand, the steppe climate of the temperate grasslands of the southern hemisphere is never severe rather it is moderate because of the nearness of these areas to the sea. The average winter temperature ranges between 1°C and 12°C.
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The steppe climate is characterized by high annual range of temperature. For example, Winnipeg (Canada) records mean annual range of temperature of 40°C. Due to marine influences, the mean annual range of temperature in the southern hemisphere is much lower than the northern hemisphere as it is around 10°C to 12°C.
The mean annual precipitation ranges between 250mm and 750mm in different locations of the temperate grasslands. The winter precipitation in the northern hemisphere is usually received in the form of snowfall and most parts of the Eurasian Steppe are snow-covered for several months during northern winters. Most of the annual rainfall is received during summer season.
Vegetation Community of Temperate Grassland Biome:
Grasses are most dominant members of the, different regions of the temperate grasslands of both the hemispheres. The perennial grasses, mostly belonging to the family of gramineae of this biome are considered to be the climax community. Besides, some herbaceous plants are also found in this biome but trees and shrubs are conspicuous by their general absence.
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There are two concepts of the evolution of temperate grasslands biome viz.:
(i) The temperate grasslands are the result of climatic conditions and pedogenic properties of these areas. The extreme continental climate and limited supply of water to the plants because of low rainfall are the main factors for the dominance of grasses and general absence of trees and bushes.
(ii) The climatic origin of the temperate grasslands is not always acceptable because many scientists believe that these grasslands are the result of human activities mainly burning of vegetation.
This biome exhibits close relationships among vegetation types, soil types and climatic conditions and between plant and animal communities. The temperate grassland biome is unique in the sense that it has single-layered structure of vegetation community where the upper canopy of the grasses is formed by their leaves but for a short period the flowering stalks also join the canopy and add grandeur to the top-layer.
The flowers do not have petals. The pollination of flowers and the dispersal of seeds are facilitated by wind. It may be pointed out that most of the areas of the temperate grasslands have been now cleared and are used for cereal crops. Thus, the temperate grasslands have become now the grainaries of the world and the heartland of the world dairy industry.
Since there are some spatial variations in the general characteristics of the vegetations of the different parts of the temperate grasslands of the northern and the southern hemispheres, a brief separate description of vegetation characteristics of each region is necessary to understand the overall nature of the vegetation community of this biome.
(1) Eurasian Steppes:
The steppe biome has the largest areal extent in the former Soviet Union wherein it extends from Eastern Europe to western Siberia and between temperate coniferous forest in the north and arid regions in the south-west.
The Russian Steppes are divided into two sub-types on the basis of vegetation’s e.g.:
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(i) Forest steppe, and
(ii) Grass steppe.
These two combined together represent 12 percent of the total geographical area of the former Soviet Union. The forest-steppe consists of alternate bands of woodland and open steppe. The European forest-steppe is represented by oak, limes, elms and maple while the Siberian part of forest-steppe consists of birch, aspen and willow.
The intervening bands of open steppes in the forest steppes are called meadow steppes which are characterized by the common genera of grasses of fescues (Festuca) and feather grasses (Stipa). The forest steppes receive mean annual precipitation between 500mm-600mm whereas the grass-steppes receive mean annual precipitation of 400mm-500mm.
The combinations of climate, vegetation and soil change from north to south in the Russian Steppes. In the extreme northern part of the Russian Steppes are found forest-steppes. The soils of the woodland-steppe or the forest steppe are degraded chernozem because the chernozem has been extensively leached out and transformed into grey forest soils.
The grass-steppes, further south of the forest-steppe, is characterized by true chernozem soil. Further southward, the increasing aridity has been responsible for the transformation of true grass steppe into semi-arid steppe which is associated with chestnut soil. Further southward, the climate becomes arid and steppe grasslands cease to exist.
The following sequences of vegetation are found from north to south in the Russian Steppe:
(i) Forest Steppe:
Forest steppe consists of trees mainly oak, elms, limes, mapple, a few arboreal vegetation of Siberian steppe such as birch with mixture of aspen and willow. The soils have degraded chernozem. There are alternate bands of open steppes between the woodland bands.
(ii) Meadow Steppes:
Meadow steppes are open steppes between the woodland zones of the forest steppes as described above. The meadow steppes have developed in the areas of well-developed deep chernozem soils. These are characterized by the species of turf-grasses (such as the species of Stipa and Fescue) and numerous flowering herbaceous plants (such as Trifolium and several types of daisy).
(iii) Grass Steppes:
Grass steppes are found over well-developed deep chernozem soils and are dominated by grasses, wherein the tussock forming species of stipa are the most important members of the vegetation community. Besides, a few flowering xerophytic shrubby species of Artemisia are also found in the southern marginal belt of the main grass-steppes.
(iv) Semi-arid Xerophytic Steppe:
Semi-arid xerophytic steppe is found in the extreme southern and south-western parts of the Russian Steppes where the xerophytic grasses (such as fescue and feather grass species) are also associated with chestnut soil and semi-arid climatic conditions (mean annual precipitation ranging between 300mm and 350mm). A few species of xerophytic herbs (such as Artemisia) and some ephemeral herbs are also found in this semi-arid tract.
(2) North American Prairie:
North American Prairie has developed in the U.S.A. and Canada between the foothills of the Rockies in the west and the temperate deciduous forest biome in the east.
On the basis of decreasing trend of mean annual precipitation from east (1050 mm) to west (400mm) and a gradient of falling Net Primary Productivity (NPP) the North American Prairies are divided into 3 sub-regions viz.:
(i) Tall grass prairie,
(ii) Mixed grass prairie, and
(iii) Short grass prairie.
It may be pointed out that there is a complete sequence of taller to shorter grasses from east to west:
(i) Tall Grass Prairie:
Tall grass prairie is found in the eastern part of the North American Temperate Grasslands (Prairies) wherein the most dominant species of the tallest grass are bluestem and switch grasses which attain the height of 1.5 to 2.5m. There are a few patches of oak and hickory trees within the vast areas of tall grasses.
(ii) Mixed Prairie:
Mixed prairie has most extensive cover in the Great Plains of the U.S.A. This belt extends between the U.S.—Canada border in the north and Texas in the south. This prairie is characterized by the mixture of medium (0.6-1.2m in height) and short grasses such as little bluestem, needlegrass (Stipa spartea), june grass (Koeleria cristata) and the short and bunch grasses such as buffalo grass (Buchloe dactyloider) and blue gramma (Bouteloua gracilis).
(iii) Short Grass Prairie:
Short grass prairie is developed in the western part of the Great Plains and is dominated by the species of short grasses which seldom exceed the height of 60cm.
(3) South American Pampas:
South American Pampas have their most extensive cover in Argentina where these account for about 15 percent of its total geographical area. The South American Pampas are comparatively more humid than the Eurasian Steppes and North American Prairies. The mean annual precipitation decreases from the east (coastal land, 900mm) to the west (450mm).
Thus, the Pampas are divided into two sub-types e.g.:
(i) Humid pampas, and
(ii) Sub-humid pampas.
The humid Pampa, developed in the eastern part of Argentina, is characterized by tall grasses whereas the increasing aridity westward results in the growth of short grasses in the western sub-humid Pampa. The important grasses of the pampa include Briza, Bromus, Panicum, Paspalum, Lolium etc.
It may be pointed out that the grasses of the Pampas have multi-layered structure which is the result of the availability of moisture, soil and effects of grazing by the animals. Man has introduced lucerne plant of legume species which forms good forage for the animals. Major part of the Pampas has been cleared of their original grasses and has been converted into agricultural farms mainly wheat fields.
(4) African Veld:
African Veld has developed on the high plateau land of vaying heights (1500m to 2000m) in the south-eastern part of South Africa. The African Velds include the temperate grasslands of southern Transwaal and Orange Free State of South Africa and some parts of Lisotho.
It may be pointed out that the South American Pampas are developed on flat lowland terrain whereas the South African Velds have developed over 1500-2000m high plateau surface where the growth of plants is not possible because of uncertainty of rainfall, increasing aridity, severity of frosts during nights and high daily range of temperature during winter season.
Thus, the true climax grass lands of African Velds have developed. There are much variations in the composition and structure of grasses because of variations in the topographic characteristics, soils, altitudes and climatic conditions.
Based on aforesaid considerations the South African Veld biome is further divided into 3 sub-types viz.:
(i) Themeda Veld,
(ii) Alpine Veld, and
(iii) Sour Veld.
(i) Themeda Veld:
Themeda veld has developed at the altitude ranging between 1500m and 1700m where mean annual precipitation of 650mm to 750mm is recorded. The most dominant grass species is red grass (Themeda triandra) which has developed on black turf soils. It may be pointed out that the original dominant red grasses of this biome have been transformed to less useful xerophytic forms because of continued pressure of overgrazing by man.
(ii) Sour Veld:
Sour Veld represents those areas of Themeda Veld which are dominated by relatively less important grasses such as Aristida, Eragrostis and Hyparrhenia.
(iii) Alpine Veld:
Alpine Veld is found over relatively higher altitudes (2000-2500m) of the Darkersberg Mountain where Themeda grasses are found mixed with Festuca and Bromus which are developed on black soils.
(5) Australian Downs:
Australian Downs have developed in the south-eastern parts of Australia and northern part of Tasmania.
This region is characterized by:
(i) Relatively warmer winter season than the temperate grasslands of the northern hemisphere (Eurasian Steppes and North American Prairies), and
(ii) Mixture of grasses with eucalyptus trees.
The grasslands gradually change from south (Australian coast) to north (interior land) in accordance with the decreasing trend of mean annual precipitation from south (1524 mm) to north (635 mm).
Thus, 3 distinct and different grasslands are found in the Australian Downs (temperate grasslands) e.g.:
(i) Temperate tall grasslands,
(ii) Temperate short grasslands, and
(iii) Xerophytic grasslands.
(i) Temperate Tall Grasslands:
Temperate tall grasslands have developed in a region which extends from the eastern coastal lands of New South Wales to Victoria and eastern Tasmania. The dominant grasses are Poa tussock and Themeda Australia. The Themeda Australia is also called as kangaroo grass because it is very much palatable to kangaroos. Danthonia pallida dominates the areas with drier environmental condition.
(ii) Temperate Short Grasslands:
Temperate short grasslands have developed parallel to but north of the Temperate Tall Grasslands as discussed above. The important grasses developed in this biome include short species of grasses such as Danthonia and Stipa gegera of grasses.
(iii) Xerophytic Grasslands:
Xerophytic grasslands are developed further northward such as the interior lands of New South Wales and Queensland which are characterized by semi-arid climatic conditions and the grasses, which have developed in this biome, are adapted to dry conditions. The important species of this biome are Aristida and Mulga (a shrub species).
(6) Canterbury Grasslands of New Zealand:
The original temperate grasslands were developed in the eastern part of the southern island and the central part of the northern island of New Zealand wherein the tussock or bunch grasses were the dominant species but man has changed and transformed the original structure of the temperate grasslands within the last 100 years or so through his economic activities.
At present there are two main types of grasses in the temperate grassland biome of New Zealand e.g.:
(i) Short tussock grasses having the main species of Festuca and Poa, are 50cm tall and yellow-brown in colour, and
(ii) Tall tussock grasses (main species being Chinomechloa) are found relatively over higher grounds.
The average Net Primary Productivity of the Temperate Grassland Biome is 600 dry grams per square metre per year whereas the total Net Primary Production of all the regions of this biome spread in the northern and the southern hemispheres is 5.4 x 109 tons per year. The average biomass of these grasslands is about 1600 grams per spuare metre. It may be pointed out that the temperate grasses have well developed network of root systems.
The roots may penetrate upto 2m in the ground whereas the shoots of the grasses are only 0.6 to 1.2m above the ground. It is thus obvious that the root systems of the temperate grasslands have more biomass (2000 grams per square metre) than the biomass of grass standing above the ground (1600 grams per square metre). The long and dense mesh of root systems of short and bunch grasses such as blue grama and buffalo grasses account for 50-55 percent of their total biomass.
Animal Community of Temperate Grassland Biome:
The animal community of the temperate grassland biome is characterized by unique property in that every grassland region of the southern and the northern hemispheres is dominated by a few species of large mammals. For example, buffalo and pronghorn antelope in the North American Prairies; wild horse and saiga antelope in the Eurasian Steppes; antelopes in the South African Velds and guanaco in the South American Pampas.
Secondly, the large herbivorous animals of the temperate grasslands are endowed with sturdy bodies so that they are able to protect themselves to some extent from their predator enemies like wolf and coyote. Thirdly, the grazing mammals have developed migratory habits so that they may avoid overuse of their forage and thus can conserve their food resources.
Inspite of the aforesaid and even more similarities in the animal communities of different regions of the temperate grassland biome there are some regional variations as well:
(1) The most important animals of the Eurasian steppes are saiga antelopes of the western steppes and Mongolian gazelles of the eastern steppes and the rare species of wild horses of the ungulate category (animals having hoofs). Among the burrowing animals rodents are important species. These rodents and mole rats dig out long and circuitous tunnels in the soft-dry soils to store food and to protect them from the severe cold.
They remain indoor throughout the day (inside their tunnels) but come out of their tunnels during nights to get food. Predator animals include wolves, eagles, large hawks etc. which depend on rodents for their food. Polecat is also an important species of smaller predator animals.
(2) The bisons and pronghorns dominated the animal community of the North American Prairies before the arrival of the European settlers, explorers and fur traders in this continent but now these animals are on the verge of extinction because of their indiscriminate mass hunting by the European immigrants.
Similarly, there were numerous species of rodents in the American Prairies such as gophers and prairie dogs which used to live in long and narrow tunnels dug-out in the loose and dry soils to protect them from the predators during day-time but most of these rodents have been either eliminated or markedly reduced in number because of removal of grasses on a large-scale for agricultural development.
A large number of predator species depending primarily on rodents such as hawks, eagles, rattle-snakes, foxes, wolves etc., have also been adversely affected by ever-expanding agriculture in the prairies. Thus, the agricultural development of the North American Prairies has provided food to large number of human population on the one hand but this practice has disturbed the original natural ecosystem of the Prairie grassland and has created ecological imbalance on the other hand.
(3) The South American Pampas have now become major wheat fields and the remaining grasslands are so open that herbivorous animals are provided little natural refuge and protection from predator animals. The pampa deer is important among many species of herbivorous grazing animals whereas rodents mainly viscacha and mara are important burrowing species of mammals which like the rodents of the North American Prairies live in long and circuitous tunnels in the loose and dry soils.
Rhea is very important flightless species of birds which resembles emu of the Australian Downs and ostrich of African Savanna. Inspite of its giant body size the Rhea becomes successful to some extent in protecting him from his predators because his colour helps him to become invisible in the surroundings of the local vegetation and his height enables him to see and detect the enemies (predators).
The predator animals include manned wolf which depends on rodents, birds and even small reptiles. The pampas are enriched by many migratory seasonal birds such as herons, geese, ducks, etc.
(4) The animal life of the South African Velds has been largely affected and modified by human activities. The region was earlier enriched by large herds of game, antelopes, hyaenas, jackals, lions, leopards etc. (all belonging to carnivorous category) and zebra but now these animals are not seen in the Veldean grassland because large-scale hunting has either eliminated them or has forced them to seek refuge in other areas.
Since most of the natural habitats of these animals have been converted into farmlands, the original animals have also been replaced by domesticated animals such as farm animals, cattle (for dairy purposes), sheep and goats. Some of the birds and most of rodents are still found in this biome because the birds having high degree of mobility easily escape from their most dangerous enemy (man) while the rodents hide them in the long and circuitous earthen tunnels.
The important species of rodents are springhare and gerbil whereas important species of carnivorous group of burrowing animals include yellow mongoose.
(5) The Australian Downs are dominated by kangaroos which are of three types e.g.:
(i) red kangaroos,
(ii) grey kangaroos and
(iii) wallaroos.
The European rabbits introduced in this biome have so greatly multiplied within the last 100 years or so that they have now outnumbered other animals and have become dominant animal species of the Australian temperate grasslands. The introduction of sheep for commercial purposes has also altered the composition of animal community in this grassland biome. Emu is the typical flightless bird species of this region.
(6) The New Zealandean Grassland Biome is characterized by almost general absence of herbaceous mammals because of the fact that this island probably has always been isolated from the other landmases and therefore no migration of animals from other areas into New Zeland could be possible. Previously this biome was inhabited by giant flightless birds, the moas, but now these have disappeared because of their large- scale hunting by man.
Man and Temperate Grassland Biome:
The climatic conditions, resultant soils, native and transformed regional vegetations, animal communities and of course man produced a unique interactive temperate grassland biome ecosystem but the dominant activities of man and their widespread impacts on the total transformation of this biome/ecosystem have altogether changed the very nature of this biome/ ecosystem.
‘So virgin grasslands are rare since most of them have been altered by pastoralism of domesticated animals, replaced by agricultural ecosystems, or converted into a different species composition through the use of biocides (weed and/or pest killers) or mechanical processes such as brush removal, seeding with leguminous species or simply through the invasion of new (including exotic) species following utilization by man’.
No other natural ecosystem or biome tells the story of the impact of human activities better than the temperate grassland biomes of the world. Majority of the original grasslands have now been converted into agricultural farmlands which have now become famous ‘grainaries of the world’.
Wheat, corn and dairy farming now occupy most of the areas of the North American Prairies (of the U.S.A and Canada); wheat fields have replaced most of the Steppes of Kazakhastan and of northern China; South American Pampas are now extensively fanned for wheat and the semi-arid temperate grasslands have been converted into great sheep and cattle ranches of the world.
The wide-spread agricultural development in the temperate grassland biomes at the cost of natural and original stands of rich grasses of numerous varieties have led to the emergence of several ecological and environmental problems:
(i) The conversion of natural grasslands of this biome resulted into the obliteration of natural habitats of the animals of numerous species. Thus, the disappearance of natural habitats or their overall transformation has caused disappearance and extinction of several animal species.
For example, bisons and prong- horns, once the dominant animal species of the North American Prairies, are now facing imminent extinction many rodents of the temperate grasslands have now become endangered species because of the destruction of their natural hideouts of tunnels dug-out in the loose and dry soils through large-scale ploughing by tractors; many of the animal species such as game, antelopes, zebras, lions, leopards and hyaenas have disappeared from several temperate grasslands etc.
(ii) Large-scale hunting of animals has resulted into phenomenal decrease of the populations of some animals, migration of some animals to other areas and disappearance and extinction of some animals. For example, many species of animals such as game, antelope, zebra, lions, leopards, hyenas etc. have disappeared from the African Velds because of mass hunting of animals by the European immigrants.
(iii) The introduction of new species of exotic animals has altogether changed the composition of native vegetation. For example, the introduction of sheep by the European settlers in Australia has changed the composition of vegetation community which was originally suited to the native marsupial animals.
The introduction of European rabbits into Australia by the European immigrants has resulted into such a phenomenal growth in their populations that they have become menace to both the natural vegetation community and man. Predator foxes have been introduced in this region to control the ever-increasing population of rabbits but this has not produced any fruitful result.
(iv) The introduction of new species of exotic plants into many parts of the temperate grasslands has either suppressed the native natural vegetation or has eliminated many plant species. For example, the introduction of a few species of leguminous plants such as clover and grasses such as Bromus hardeum and perennial ryegrass by European immigrants into Australian temperate grasslands has suppressed several species of native perennial grasses.
(v) Extensive cultivation of the semi-arid prairie regions of the Great Plains of the U.S.A. has resulted into enormous deflation of dry, loose and friable soils by wind which (deflation of soil particles) generates dust storms during the periods of drought which cause great damage to crops and human property in the Mississippi plains. Due to greater frequency of intense dust storms the areas of the semi-arid parts of the western Kanasas, Texas and Oklahoma are called as Dust Bowl.
(vi) The large-scale removal of vegetation for agricultural purposes has resulted in the loosening of the soil cover because of the destruction of dense network of root systems of grasses. This change in the soil cover has resulted into accelerated rate of soil erosion and therefore loss of otherwise rich and fertile soils.