Introduction
•At one time, grasslands covered about 42% of the land surface of the world, today, however, much of it is under cultivation and its cover is reduced to 19% of the total land area of the world.
•There are two main types of grasslands:
1.Grasslands variously known as Prairies (in North America); Veldt (in South Africa): Steppe (in Asia); Puszta (in Hungary); Pampas (in Argentina and Uruguay) from one group. These are. tree-less grasslands and are characterized by the predominance of grasses adapted to dry conditions.
2.Savannas (from Spanish word “Sabana” which means meadow) or Tropical grasslands form another group. These are grasslands with scattered big trees and shrubs. Tropical savannas are found in South Africa, South America, Southeast Asia and Australia. Savannas cover about 8% of the land surface of the world.
Grasslands
•Grasslands naturally develop in regions with cold winters, hot summers and seasonal rainfalls (more annual rainfall than desert· but not enough to support forest life). Generally, the rainfall lies between 30 – 75 mm per year.
•Grasslands typically appear in the interior of continents. Grasslands are open land communities with limited moisture conditions, irregular rainfall, sharp seasonal and diurnal variations in temperature and high solar radiations.
•Grassland soils are highly characteristic; dark in color and contain large amount of humus. The extensive root system of grasses allows them to recover quickly from seasonal drought, occasional fires and grazing by large mammals which occur frequently in this biome.
•Fauna
•As the name implies, dominant vegetation consists of grass which can be divided into two groups, the tall grass more than 1.5 meter high found in moist areas and the short grasses, grown in clumps, and found in drier areas.
•Typical animals in grasslands tend to be quite small, with the exception of a few very Farge herbivore mammals such as Bison and Pronghorn in North
•America; Wild horse, Wild ass, Antelope in Eurasia; Antelope, Zebras in Africa; kangaroos and wallabies in Australia.
•Most herbivores of grasslands characteristically aggregate into herds or colonies; this aggregation provides some kind of protection against predators.
•Carnivores of grasslands relatively small, such as badgers, foxes, ferrets, wolves, etc. Rodents, such as, rabbits, gophers, squirrels, mice, shrews are predominant.
•The characteristic birds of this biome are chicken, hawks, owls, pigeons, etc. Lizards and snakes are common.
Savannas
• Location; Savannas cover much of Central Africa, South “Africa, Malaysia, North, Australia, West Indies and parts of South America.
•Savanna is comparatively rich in number of plant species. Vegetation is dominated by tall perennial grasses which may reach 2 meter in height and commonly referred to as “Elephant grass”.
•The trees found in association with it are quite distinctive. They are relatively low growing and may be deciduous or evergreen.
•Temperature is high, seldom falling below 21° C. rainfall comes in summer and ranges between 38 – 150 mm.
•Three seasons are generally recognized namely,
•cold dry season,
•hot dry season.
•warm rainy season.
•The fauna of savanna is very rich compared to other types of grasslands.
•The fauna of savanna mainly consists of large herbivores. The tropical grasslands of Africa have herbivores like zebra, antelope, giraffe, elephant, gazelle, monkey, ape, rhinoceros, hippopotamus, etc. and carnivores like lions, tigers, hyaenas, wolves, jackals, etc.
The tropical grasslands of Malaya include, gibbons, tapirs, antelopes, elephants, etc.
Whereas in Australian savanna, kangaroos and wallabies are dominant.
Desert Ecosystem
•Deserts are defined as lands where evaporation rate is high, and rainfall is very scanty. Deserts occupy roughly 30% of the land surface area of the earth.
•Deserts may be classified as under:
a) Low rain fall desert; Atacama
b) Hot deserts e.g. Sahara (Africa); Kalahari (Africa); Thar and Cholistan (Pakistan); Arabian (Saudi Arabia); Libyan (Libya); Rajasthan (India) and many others.
c)Cold deserts etc. Ladakh (India), Gobbi (Mongolia); Alps (Italy). .
d)Low nutrient deserts e.g. North American deserts.
e)High salt content deserts e.g. Chile, South American and Australian deserts.
•Generally hot deserts have a rainfall of less than 25 mm per year.
•The driest deserts of the world are those of Central Australia and Sahara (Africa) where annual rainfall is less than 2 mm. These deserts have no or little vegetation.
•Cold deserts occur at high elevations where temperature is very low, but rainfall is very scanty.
Characteristics
•Deserts are mostly confined to tropical regions. Deserts are characterized by:
a) Low rainfall and high evaporation rate,
b) High intensity bf scorching sunlight,
c)Wide fluctuation in temperature, from hot day to cool night; the days are hot because of the lack of cloud cover but the nights are cool because heat escapes easily into the atmosphere,
d)Dust storms are of common occurrence, particularly in afternoon; these result due. to lack of moisture and extremes of temperature, causing an increase in the air movement, and,
e)Vegetation is sparse due to scarcity of water.
Flora and Fauna
•The desert is a harsh environment. “Animals and plants in this habitat have evolved ways to circumvent aridity and high temperature.
•Desert animals avoid heat by becoming nocturnal in their habit; by seeking shady places; or by sleeping daytime in underground borrows.
•Vegetation is largely composed of thorny bushes, perennial succulents and rapidly growing herbaceous plants.
•In most hot deserts, there occurs plant like Cacti, Acacia, Euphorbias, Pricky peers, etc. Fauna is very poor.
•There are few large mammals,’ such as, camels, antelopes and sheep, small mammals such, as, rodents of various kinds are abundant.
•Carnivores are represented by wolves, jackals, foxes, etc. Reptilian fauna consists of lizards and snakes. The avifauna include birds like partridges, quails, bustards, sand grouses and vultures.