claass 9 english medium geography ch 5 notes
Answers
• Relief, Climate and Ecosystem are three factors for biodiversity.
• Relief
=> Land: The nature of land influences the type of vegetation. Fertile lands supports agriculture while undulating and rough terrains have grassland and woodlands which give shelter to a variety of wild life.
=> Soil: Different types of soils provide basis for different types of vegetation. The sandy soils of the desert support cactus and thorny bushes while wet, marshy, deltaic soils support mangroves and deltaic vegetation. The hill slopes with some depth of soil have conical trees.
• Climate
=> Temperature: The character and extent of vegetation are mainly determined by temperature along with humidity in the air, precipitation and soil.
=> Sunlight: Due to differences in latitude, altitude, season and duration of the day there is variation in duration of sunlight.
=> Precipitation (Rains): Areas of heavy rainfall have more dense vegetation as compared to other areas of less rainfall. In India, almost the entire rainfall is brought in by the advancing southwest monsoon (June to September) and retreating northeast monsoons.
Ecosystem
• All the plants and animals in an area are interdependent and interrelated to each other in their physical environment, thus, forming an ecosystem.
• A very large ecosystem on land having distinct types of vegetation and animal life is called a biome.
• Importance of Forests:
=> These are renewable resources and play a major role in enhancing the quality of environment.
=> They modify local climate, control soil erosion, regulate stream flow, support a variety of industries, provide livelihood for many communities and offer panoramic or scenic view for recreation.
=> It controls wind force and temperature and causes rainfall. It provides humus to the soil and shelter to the wildlife.
Types of Vegetation
(i) Tropical Evergreen Forests
(ii) Tropical Deciduous Forests
(iii) Tropical Thorn Forests and Scrubs
(iv) Montane Forests
(v) Mangrove Forests
• Tropical Evergreen Forests:
=> These forests are restricted to heavy rainfall areas of the Western Ghats and the island groups of Lakshadweep, Andaman and Nicobar, upper parts of Assam and Tamil Nadu coast.
=> They grow in an area of 200 cm of rainfall with a short dry season.
=> The trees reach great heights up to 60 metres or even above.
=> The forests appear green all the year round because there is no definite time for trees to shed their leaves.
=> Common animals found in these forests are elephants, monkey, lemur and deer. Plenty of birds, bats, sloth, etc.
• Tropical Deciduous Forests
=> Most widespread forest in India.
=> These are also called the monsoon forests and spread over the region receiving rainfall between 200 cm and 70 cm.
=> Trees of this forest-type shed their leaves for about six to eight weeks in dry summer.
=> These forests are further divided into two types: Moist and Dry deciduous.
=> Moist deciduous: Found in areas receiving rainfall between 200 and 100 cm. Present mostly in the eastern part of the country
=> Dry deciduous: Found in areas having rainfall between 100 cm and 70 cm. Present in the rainier parts of the peninsular plateau and the plains of Bihar and Uttar Pradesh. There are open stretches in which Teak, Sal, Peepal, Neem grow.
• Tropical thorn forests and Scrubs
=> These are found in the region of with less than 70 cm of rainfall.
=> The natural vegetation consists of thorny trees and bushes. Acacias, palms, euphorbias and cacti are the main plant species.
=> Trees are scattered and have long roots penetrating deep into the soil to get moisture. The stems are succulent to conserve water. Leaves are mostly thick and small to minimize evaporation.
=> Common animals are rats, mice, rabbits, fox, wolf, tiger, lion etc
• Montane Forests
=> Montane forests have a succession of natural vegetation belts in the same order as we see from the tropical to the Tundra region.
=> Between a height of 1000 and 2000 metres
=> Between 1500 and 3000 metres, temperate forests containing coniferous trees like pine, deodar, silver fir, spruce and cedar, are found.
=> At higher elevations, temperate grasslands are common.
=> At high altitudes, generally more than 3,600 metres above sea-level, alpine vegetation found which have silver fir, junipers, pines and birches trees common.
=> Near snow line, shrubs and scrubs, they merge into the Alpine grasslands which are used extensively for grazing by nomadic tribes like the Gujjars and the Bakarwals.
=> The common animals found in these forests are Kashmir stag, spotted dear, wild sheep, jack rabbit, Tibetan antelope, yak, snow leopard, squirrels, Shaggy horn wild ibex, bear etc.
• Mangrove Forests
These forests are found in the areas of coasts influenced by tides where mud and silt get accumulated. Dense mangroves are the common varieties with roots of the plants submerged under water. In the Ganga- Brahamaputra delta, sundari trees are found, which provide durable hard timber.