Grasslands


A Grassland is a is a type of Habitat or Biome which is dominated by Grasses and other Herbaceous (non-woody) Flowering Plants and a variety of scattered Trees and Bushes. Grasslands occur in areas where there is not enough regular rainfall to support the growth of a Forest, but not so little as to form a Desert.  About one quarter of the Earth's land is covered with Grasslands. Grasslands may occur naturally or as the result of human activity. Grasslands created and maintained by human activity are called 'Anthropogenic Grasslands'. Those formed naturally are called 'Natural Grasslands'.

In many areas, Grasslands separate Forests from Deserts. In fact, most Grasslands are located between Forests and Deserts. Natural Grasslands primarily occur in regions that receive between 500 and 900 mm (20 and 35 in) of rain per year. Grasslands can exist naturally in areas with higher rainfall when other factors prevent the growth of Forests, such as in serpentine barrens, where minerals in the soil inhibit most Plants from growing. Some of the World's largest expanses of Grassland are found in African Savannah, and these are maintained by wild herbivores as well as by nomadic pastoralists and their Cattle, Sheep or Goats. Grasslands are known by different names in different parts of the World: - ‘Steppes’ in Asia; ‘Prairies’ in North America; ‘Pampas’, ‘Llanos’ and ‘Cerrados’ in South America; ‘Savannahs’ and ‘Velds’ in Africa; and ‘Rangelands’ in Australia.

Classification / Types of Grasslands

 

Basic Types of Grasslands based on Climatic Dryness

1.  Tropical Grasslands - Tropical Grasslands are located near the equator, between the Tropic of Cancer and the Tropic of Capricorn. Most of the Tropical Grasslands are found in the interior part of continents between the Tropical Rain Forests and Tropical Deserts. Tropical Grasslands are also known as 'Savannahs'. Tropical Grasslands have a tropical continental climate wherein wet and dry seasons come alternately.

There are 3 Types of Savannahs

  1. Climatic Savannahs - Savannahs which result from climatic conditions are called Climatic Savannahs.
  2. Edaphic Savannahs - Savannahs that are caused by soil conditions and that are not entirely maintained by fire are called Edaphic Savannahs. These can occur on hills or ridges where the soil is shallow, or in valleys where clay soils become waterlogged in wet weather.
  3. Derived Savannah - Svanna which is formed as result of people clearing Forest land for cultivation is known as Derived Savannah. These originate when farmers clear a tract of Forest, burn the dead trees, and Plant crops in the ashes for as long as the soil remains fertile. Then, the field is abandoned and, although Forest trees may recolonize, Grass takes over on the bare ground (succession), becoming luxuriant enough to burn within a year or so.

Tropical Grasslands are warm year round with mean monthly temperatures occurring at or above 64° F.

The annual precipitation averages between 30 and 50 inches. For at least five months of the year, during the dry season, less than 4 inches of rain, a month is received. The dry season is associated with the low sun period.

Soils vary according to bedrock and edaphic conditions. In general, however, Laterization is the dominant soil-forming process and low fertility oxisols can be expected.

Savannahs are covered with Perennial Grasses which often are 3 to 6 feet tall at maturity. There is a wide range of Grasses but an area is usually dominated by one to two types of Grasses. They may or may not also have an open canopy of drought-resistant, fire-resistant, or browse-resistant trees, or they may have an open shrub layer. Trees are only found along rivers in the Savannah because only drought-resistant Plants can grow well under the long dry season with thin soils. The appearances of Savannahs change seasonally, in which they are green in colour in wet seasons and turn golden-brown in dry seasons.

There is a high diversity of Animals in the Tropical Grasslands especially in Africa. Over 40 different Species of Animals are found in African Savannahs, some of which are Eland, Impala, Wildebeest, Plains Zebra, Rhinoceros, Elephant, Warthog, Lion, Leopard and Cheetah. However in South America's Tropical Grassland the Fauna is not as diverse. It includes Animals like Capybara, Anaconda, Armadillo, Caiman and Termites.

Areas of Tropical Grasslands

  • Llanos of the Orinoco basin of Venezuela and Colombia.
  • Cerrado of Brazil.
  • Pine Savannahs of Belize and Honduras.

2.  Temperate Grasslands - Temperate Grasslands are located in the mid-latitudes, north of the Tropic of Cancer and south of the Tropic of Capricorn. They generally lie between Deserts and Temperate Forests. Temperate Grasslands have a temperate continental climate, which is cooler than Savannahs.

Temperate Grasslands have warm, humid summers with an average temperature of 18° C and cool, dry winters with an average temperature of 10° C.

These typically receive between 10 and 20 inches of precipitation a year. Much of this falls as snow, serving as reservoir of moisture for the beginning of the growing season. The evaporation rate is high, so little rain makes it into the soil.

Trees are rare in the Temperate Grasslands because there is not enough moisture for them to grow as they have longer life cycles and need longer growing season than Grasses. The appearances of Grasslands in winter are generally brown in colour because Grasses turn dry in winter.

Calcification is the dominant soil-forming process these areas. Mild leaching, high organic content, and concentration of calcium carbonate in the B horizon typifies the dark brown mollisols developed under the Temperate Grasslands. When this process works on a loess (silt deposit) that itself is rich in calcium, the World's most fertile soils are created, the Chernozems (black soil).

Perennial Grasses and Perennial Forbs and Leguminosae, the Sunflower and Pea families are dominant growth forms.

The Temperate Grassland is very low in diversity in terms of Animals, especially in comparison with the Tropical Grasslands. Some of the Animals include North American Bison, Pronghorn Antelope, Pocket Gopher, Ground Squirrels, Prairie Dog, Coyote, Badger and Black-Footed Ferret. Some of the Animals of Russia include European Bison (wisent), Wild Horse, Saiga Antelope, Mole Rats and Polecats.

6 Areas of Temperate Grasslands

  • Pampas in South America.
  • Veld in Africa.
  • Canterbury Plains in New Zealand.
  • Murray-Darling Basin in Australia.
  • Prairies in North America.
  • Steppes in Central Asia.

Types of Grasslands according to WWF (World Wide Fund for Nature)

1.  Tropical & Subtropical Grasslands, Savannahs & Shrubland - Thess type of Biomes are located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes. These are characterized by rainfall levels between 90-150 centimetres per year. There may be great variability in soil moisture throughout the year. Grasslands  are dominated by Grass and other Herbaceous Plants. Savannahs are Grasslands with scattered Trees, most of which are Acacia and Baobab. Shrublands are dominated by Woody or Herbaceous Shrubs. These are in habited by large Mammals that have evolved to take advantage of the ample forage found in these Habitats. The fauna is richest in African Savannahs and Grasslands. Restoration potential in these systems is high but ploughing, overgrazing by domestic livestock, and excessive burning can quickly degrade and alter natural communities.

Grassland Regions

  • Horn of Africa Acacia Savannahs.
  • East African Acacia Savannahs.
  • Central and Eastern Miombo Woodlands.
  • Sudanian Savannahs.
  • Northern Australia and Trans-Fly Savannahs.
  • Terai-Duar Savannahs and Grasslands.
  • Llanos Savannahs.
  • Cerrado Woodlands and Savannahs.

2.  Temperate Grasslands, Savannahs and Shrubland - Temperate Grasslands, Savannahs and Shrublands is a Biome whose predominant vegetation consists of Grasses and/or shrubs. The climate is temperate and semi-arid to semi-humid. They differ largely from Tropical Grasslands in the annual temperature regime as well as the types of Species found here. Generally speaking, these regions are devoid of trees, except for riparian or gallery Forests associated with streams and rivers. The soil here is fertile with rich nutrients and minerals. The Fauna here includes large grazing Mammals, Carnivores and Birds.

Grassland Regions

  • Northern Prairie of North America.
  • Patagonian Steppe in South America.
  • Daurian Steppe in Asia.

3.  Flooded Grasslands and Savannah - Flooded Grasslands and Savannahs are a Biome, generally located at subtropical and tropical latitudes, which are flooded seasonally or year-round. Everglades, Pantanal, Sahelian flooded Savannahs, Zambezian flooded Savannahs, and the Sudd are the major Flooded Grasslands and Savannah Ecoregions of the World. These areas support numerous Plants and Animals which are adapted to the unique hydrologic regimes and soil conditions. These support large population of migratory and resident water-birds along with various Reptiles and Amphibians. The temperature in these regions is warm with  nutrient rich soil.

Grassland Regions

  • Sudd-Sahelian Flooded Grasslands and Savannahs in Central Africa.
  • Zambezian Flooded Savannahs in in Africa.
  • Rann of Kutch Flooded Grasslands in India and Pakistan
  • Everglades Flooded Grasslands in North America.
  • Pantanal Flooded Savannahs in Central South America.

4.  Montane Grasslands and Shrubland - Montane Grasslands and Shrublands are a Biome which are located above the tree line and are commonly known as Alpine Tundra, which occurs in mountain regions around the World. It  includes high elevation (montane and alpine) Grasslands and shrublands, including the Puna and Paramo in South America, sub-alpine Heath in New Guinea and East Africa, Steppes of the Tibetan Plateaus, as well as other similar sub-alpine habitats around the World. The Plants and Animals of Tropical Montane Paramos display striking adaptations to cool, wet conditions and intense sunlight. Characteristic Plants of these habitats display adaptations such as rosette structures, waxy surfaces, and hairy leaves. A unique feature of many wet tropical montane regions is the presence of giant rosette Plants from a variety of Plant families, such as Lobelia (Afrotropic), Puya (Neotropic), Cyathea  (New Guinea), and Argyroxiphium  (Hawaii). The most extensive Montane Grasslands and shrublands occur in the Neotropic Paramo of the Andes Mountains. This biome also occurs in the mountains of east and central Africa, Mount Kinabalu of Borneo, highest elevations of the Western Ghats in South India and the Central Highlands of New Guinea. Where conditions are drier, one finds Montane Grasslands, Savannahs, and Woodlands, like the Ethiopian Highlands, and Montane Steppes, like the Steppes of the Tibetan Plateau.

Grassland Regions

  • Ethiopian Highlands in North-eastern Africa.
  • Southern Rift Montane Woodlands in South-eastern Africa.
  • East African Moorlands in Eastern Africa.
  • Drakensberg Montane Shrublands and Woodlands in Southern Africa.
  • Central Range Subalpine Grasslands in Central New Guinea.
  • Kinabalu Montane Scrub in South-east Asia.
  • Northern Andean Paramo in Northwestern South America.
  • Central Andean Dry Puna in Western South America.
  • Tibetan Plateau Steppe in Central Asia.
  • Middle Asian Montane Steppe and Woodlands in Central Asia.
  • Eastern Himalayan Alpine Meadows in South-Central Eurasia.

Distribution

Grasslands occur naturally on all continents except Antarctica.

General Characteristics of Grasslands

Domination of Short Plants - Grasslands generally have very short season, the climate is too dry and the soil too poor. This condition limits the growth of woody and large Plants. However this condition favours the growth of small Plants like Grass and Shrubs which dominate this type of Habitat. Another factor which favours short Plants is the maintenance of these habitats by fire and grazing, which prevent the succession of the Grassland vegetation toward Tropical Deciduous Forest or Temperate Forest. However in the absence of heavy Mammalian grazing and especially of regular fires Woody Plants, shrubs or trees, may occur on some Grasslands forming Savannahs, Scrubby Grassland or Semi-Wooded Grassland, such as the African Savannahs or the Iberian Dehesa. Such Grasslands are sometimes referred to as Wood-Pasture or Woodland. Grassland vegetation can vary in height from very short, as in chalk downland  where the vegetation may be less than 30 cm (12 in) high, to quite tall, as in the case of North American tall-grass Prairie, South American Grasslands and African Savannah.

Short Growing Season - Natural Grasslands, whether Tropical or Temperate occur in environments in which growing conditions are favourable for only a short season.
In Tropical Grasslands the growing season is usually the rainy season or, in some cases, the season when the ground is not waterlogged or submerged. In Temperate Grasslands the growing season is usually the short period between the cold, damp winter and the hot, dry summer. Perennial Grasses, relying on subterranean reserves of stored food for rapid shoot growth, are well adapted to exploiting such brief growing seasons, reaching their maximum size and completing their seeding within a few weeks. Their aboveground parts then die back, providing potential fuel for the Grass fires that typify these environments. The underground perennating (surviving from one season to the next) roots and rhizomes of the Grasses, however, are relatively well protected from fire.

Fast Growth of Grass - Grasses are specialists when it comes to regrowth. Their growing points are situated low down near the soil enabling them to grow back in spite of grazing or overgrazing. Many Grass Species can grow back quickly after a fire has swept through the Grassland, and some have seeds that can grow after being burned in a fire Grasslands tend to produce larger amounts of new growth if subjected to some type of repeated disturbance, usually grazing or fire, that prevents the accumulation of a thick layer of dead litter. Where such a layer is allowed to develop, it retains nutrients in a form not immediately available to roots and acts as a physical barrier for new shoots growing from the soil surface toward the light; in temperate Grasslands this layer acts as thermal insulation, slowing the spring warming of the soil. This has obvious implications for grazing management of these systems. Grasslands can therefore support a high density of grazing Animals.

Mostly Hot and Dry Areas - Grassland climates are varied, but all large regions of Natural Grassland are generally hot, at least in summer, and dry. In general, Tropical Grasslands receive 500 to 1,500 millimetres (20 to 60 inches) of rain in an average year and in every season experience temperatures of about 15° to 35° C (59° to 95° F). The dry season may last as long as eight months. An excess of rainfall over evaporation, leading to ephemeral river flow, occurs only during the wet season. The tropical Grassland climate overlaps very broadly with that of Savannah. Temperate Grasslands have cold winters and warm summers with rain or some snow.

Balance between different Plants - A dynamic balance commonly exists between Grasslands and related vegetation types. Droughts, fires, or episodes of heavy grazing favour Grassland at some times, and wet seasons and an absence of significant disturbances favour woody vegetation at others. Changes in the severity or frequency of these factors can cause a change from one vegetation type to another.

Changing Appearances - Grasslands change their appearance throughout the year. In winter (or in the tropical dry season), Grasslands look drab and lifeless. In the Temperate Grasslands, spring brings about a transformation as tender shoots emerge, the Grass starts growing, and the first flowers bloom. A similar change is seen in Tropical Grasslands when the onset of the rainy season changes the landscape from dull brown to bright green.

Specialised Plants - The Plants of Grasslands have adapted themselves to survive the prevalent conditions. Grasses generally have pollen that is spread by the wind and are as such not much dependant on other organisms for pollination. Some Plants have bad-tasting and poisonous chemicals which prevent them from being eaten by Animals. They also have thick latex sap contained in their leaves or stem and upon breakage, they ooze the gummy sap. If this is tapped by an insect , it hardens in the air and gums up the insect's mouth parts. Milkweeds and Dogbane are such Plants. The Stinging Nettle Plant can cause a painful feeling in the Animal that touches it. Also, a kind of Grass can cut the tongue of the Animal that eats it. In addition, there is also a kind of Poison Ivy. During a fire, while above-ground portions of Grasses may perish, the root portions survive to sprout again as Grasses grow from near their base, not from tip, thus are not permanently damaged from grazing Animals or fire. Extensive root systems prevent grazing Animals from pulling roots out of the ground.

Some of the  different kinds of Grasses

  • Cocksfoot.
  • Upright Brome.
  • Tor Grass.
  • Sheep's Fescue.
  • Crested Dog's-Tail.
  • Common Quaking-Grass.
  • Common Fox-Tail.
  • Rough Meadow Grass.
  • False Oat-Grass.
  • Blue Moor-Grass.
  • Yorkshire Fog.

Some of the different kinds of Grassland Flowers

  • Salad Burnet.
  • Meadow Buttercup.
  • Red Campion.
  • Cuckoo Flower.
  • Cowslip.
  • Sainfoin.
  • Field Gentian.
  • Meadow Saffron.
  • Harebell.
  • Knapweed
  • Bee Orchid.

Grassland Adapted Animals - The Animals that live in Grasslands have adapted themselves to dry, windy conditions. Most of the Animals found in Grasslands are grazers which eat  a variety of Grasses and other Plants. Some Animals, such as Bison, have broad, flat-topped teeth and digestive systems especially adapted to feed on Grasses. The colour of many Grassland Animals blends in with the Plants helping them to catch a prey or escape a predator. Most of the Animals on the Savannah have long legs or wings to be able to go on long migrations. Many burrow under ground to avoid the heat or raise their young. The Savannah is a perfect place for birds of prey like hawks and buzzards. The wide, open plain provides them with a clear view of their prey, hot air updrafts keep them soaring, and there is the occasional tree to rest on or nest in. Animals don't sweat to lose body heat, so they lose it through panting or through large areas of exposed skin, or ears, like those of the elephant. Grasslands also benefit other Animals by providing them with their habitats and food. With the interaction between Grasslands and Animals, the existence of Grasslands is made possible because without the grazing by Animals, they will be colonized by shrubs quickly and become woodland.

Some of the Grassland Animals

  • Chaffinch.
  • Skylark.
  • Rook.
  • Pronghorn Antelope.
  • Gray Wolf.
  • Badger.
  • Red Kangaroo.
  • Mole.
  • Woodmouse.
  • Leaf Bug.
  • Ladybirds.
  • Ground Beetles.
  • Greenflies.
  • Earwigs.
  • Earthworms.
  • Centipedes.
Origin of Grasslands

Grasslands arose during the period of cooling and drying of the global climate, which occurred during the Cenozoic Era (65.5 million years ago). In the Miocene and Pliocene Epochs (5.332 million to 2.588 million years ago), which spanned a period of about 25 million years, mountains rose in western North America and created a continental climate favourable to Grasslands. Ancient Forests declined and Grasslands became widespread. Following the Pleistocene Ice Ages (2 million to 11 thousand years ago), Grasslands expanded in range as hotter and drier climates prevailed Worldwide. The Grass family itself (Poaceae or Gramineae) evolved only early in this era. The date of earliest appearance of Grasslands varies from region to region. In several regions a succession of vegetation types can be recognized in the Cenozoic fossil record, as climate dried out progressively. For example, in central Australia during the past 50 million years Tropical Rainforest gave way successively to Savannah, Grassland, and, finally, Desert. In some places expansion of Grasslands to something approaching their modern extent occurred only during the extremely cold, dry intervals—called ice ages in north temperate regions—of the past two million years. Other Grassland types occur in places too cold for trees to grow—i.e., beyond the Forest limits of high mountains or at high latitudes. A characteristic type of Grassland in cool, moist parts of the Southern Hemisphere is Tussock Grassland, dominated by tussock or bunch Grasses that develop pedestals of matted stems, giving the vegetation a lumpy appearance. Tussock Grasslands occur at various latitudes.

However not all natural Grasslands, however, arise from climate-related circumstances. Woody Plants may be prevented from growing in certain areas for other reasons, allowing Grasses to dominate. One cause is seasonal flooding or water-logging, which is responsible for the creation and maintenance of large Grasslands in parts of the highly seasonal subtropics and in smaller areas of other regions. One of the best examples of a seasonally flooded subtropical Grassland is the Pantanal in the Mato Grosso region of Brazil. Across an area of 140,000 square kilometres (54,000 square miles), dry Grasslands prevail for half of each year and shallow wetlands for the other, with small Forest patches restricted to low rises that do not flood during the wet season. In many other areas where climate is suitable for Forest growth, very shallow or infertile soils may prevent tree growth and result in development of Grassland.

Importance of Grasslands
  • Grassland are an important part of ecosystem as they cover nearly one third of the earth’s land surface and supply three quarters of the energy that the World needs. They support an amazing variety of Animals and Plants which are important components of the Grassland Habitat and maintain a rich biodiversity. Some Species are endemic to these Habitats and as such these Habitats should be conserved.
  • No other habitat is as agriculturally useful to humans as Grasslands. Soils tend to be deep and fertile, perfect for crop land or pastures. Much of the North American Prairie lands have been converted into one of the richest agricultural regions on Earth. According to an estimate one hectare of natural Grassland can provide four persons’ requirements of Wheat. If properly managed Grasslands can be mutually beneficial to Humans as well as to local Fauna and Flora.
  • Grasslands separate Forests from Deserts. Grasslands act as barrier towards desertification of land as they have Plants which bind the soil and prevent erosion of the land.
  • Grasslands are a source of income through Tourism as well. The increasing number of tourists add to the revenues of most countries where they are found.
  • Grassland are important for researchers and scientists as Grasslands are needed to be fully understood so that they can benefit Humans in innumerable ways. Certain adaptations of Plants towards harsh climates are and can be utilised to develop better quality of Plants.
  • Certain Animal Species use various strategies and techniques to survive in Grasslands and these can be applied in scientific research and development for the benefit of mankind.
List of Grasslands
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