Terrestrial Ecosystems UPSC

Terrestrial Ecosystems

The interrelations between organisms and environment on the land constitute “Terrestrial Ecology”. 

Due to variation in the topographic features of valleys, mountains and slopes, certain differences occur. 

These differences are reflected in both the material and biotic diversities. 

Altitudinal and latitudinal variations cause shifts and differences in the climatic patterns. 

Due to varied climate, the plant and animal life existing in dif-ferent terrestrial areas vary which result in differentiation of ecosystem as segments within the large biosphere. 

The most important limiting factors of the terrestrial ecosys-tems are moisture and temperature.

Terrestrial Ecosystems Includes following :-

1. Tundra Ecosystem

2. Forest Ecosystem

3. Grassland Ecosystem

4. Desert Ecosystem

1. Tundra Ecosystem

• Tundra means a “barren land” since they are found where environmental conditions are very severe. 

• There are two types of tundra :- arctic and alpine.

A. Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line in the northern hemisphere. It occupies the northern fringe of Canada, Alaska, European Russia, Siberia and island group of Arctic Ocean. On the south pole, tundra is very small since most of it is covered by ocean .

B. Alpine tundra occurs at high mountains above the with respect to Arctic mountains are found at all latitudes there-fore alpine tundra shows day and night temperature variations.

Note:-

Mammals of the tundra region have large body size, small tail and small ear to avoid the loss of heat from the surface. The body is covered with fur for insulation. Insects have short life cycles which are completed during favourable period of the year.

2. Forest Ecosystem

The nature of soil, climate and local topography determine the distribution of trees and their abundance in the forest vegetation. 

Forests may be evergreen or deciduous. 

They are distinguished on the basis of leaf into broad-leafed or needle leafed coniferous forests in the case of temperate areas.

The forest ecosystems have been classified into three major categories: 

A. Coniferous forest

B. Temperate forest

C. Tropical forest.

Forest type in India

1st Type :

Tropical Evergreen Forest

Distribution :

Western Slope of Western Ghat hills of North East, Andaman and Nicobar Islands.

Climate :

>200 cms rainfall.

Species :

Rosewood, Mahagani, Aini, Ebony.

2nd Type :

Semi Everygreen forest

Distribution :

Western Slope of Western Ghat hills of North East, Andaman and Nicobar Islands.

Climate :

Less Rainier parts of the same.

Species :

White-cedar, Hollocks, Kail.

3rd Type :

Moist Deciduous Forest.

Distribution :

Foot hills of Himalayas, Eastern slopes of Western Ghats and Odisha.

Climate :

100-200cms.

Species :

Teak, Sal, Shisham, Hurra, Mau, Amla, Seoul, Kusum, Sandalwood.

4th Type :

Dry Deciduous Forest

Distribution :

Rainier regions of Peninsula, Plains of UP and Bihar.

Cliamte :

70-100cms.

Species :

Teak in higher rainfall regions, and Tendu, Palas, Amaltas, Bel, Khair, Axlewood in lower rainfall regions.

5th Type :

Tropical Thorn Forest

Distribution :

Semi-arid regions of South West Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, Uttar Pradesh.

Climate :

<50cms

Species :

Babool, Ber,Wild date palms, Khair, Neem, Khejri, Palas, Tussocky (Grass >2m).

6th Type :

Littoral and Swamp Forest

Distribution :

Reservoirs of Deccan Plateau, lagoons of South West Coast, Saline expanses of Rajasthan, Gujarat, Kutch, freshwater lakes and reservoirs of Gujarat etc.

Climate :

150-200cms.

Species :

Mangroves, Variety of Birds.

3. Grassland Ecosystem

The grasslands are found where rainfall is about 25-75 cm per year, not enough to support a forest, but more than that of a true desert.

Types of Grassland

Based on climatic conditions there are 4 major types of grasslands found in the different regions of the Indian subcontinent.

1) semi-arid zone 

• It covers the northern portion of Gujarat, Rajasthan (excluding Aravallis), western Uttar Pradesh, Delhi and Punjab. 

• The topography is broken up by hill spurs and sand dunes.

2) dry sub humid zone 

• It covers the whole of peninsular India (except Nilgiri). 

3) moist sub humid zone 

• It covers the Ganga alluvial plain in Northern India. 

• The topography is level, low lying and ill-drained. 

4) Humid montane regions 

• This extends to the humid montane regions and moist sub-humid areas of Assam, Manipur, West Bengal, Uttar Pradesh, Punjab, Himachal Pradesh and Jammu and Kashmir. 

• The savanna is derived from the humid forests on ac-count of shifting cultivation and sheep grazing.

4. Desert Ecosystem

• Deserts are formed in regions with less than 25 cm of annual rainfall, or sometimes in hot regions where there is more rainfall, but unevenly distributed in the annual cycle.

• Because water is the dominant limiting factor, the productivity of a given desert is almost directly de-pendent on the rainfall. Where soils are suitable, ir-rigation can convert deserts into productive agricultural land. 

• As the large volume of water passes through the irrigation system, salts may be left behind that will gradually accumulate over the years until they become limiting, unless means of avoiding this difficulty are devised.

Adaptation of Plants and Animals to desert ecosystem

A. These plants conserve water by following methods:

• They are mostly shrubs.

• Leaves are absent or reduced in size.

• Leaves and stem are succulent and water storing.

• In some plants even the stem contains chlorophyll for photosynthesis.

• Root system is well developed and spread over large area.

B. The animals are physiologically and behaviorally adapted to desert conditions

• They are fast runners.

• They are nocturnal in habit to avoid the sun’s heat dur-ing day time.

• They conserve water by excreting concentrated urine.

• Animals and birds usually have long legs to keep the body away from the hot ground.

• Lizards are mostly insectivorous and can live without drinking water for several days.

• Herbivorous animals get sufficient water from the seeds which they eat.

• Camel is known as the ship of the desert as it can travel long distances without drinking water for several days.

• Mammals as a group are poorly adapted to deserts but some species have become secondarily adapted. A few species of nocturnal rodents can live in the desert without drinking water.

Desert Ecosystem in India

• The climate of this region is characterised by excessive drought, the rainfall being scanty and irregular. 

• The winter rains of northern India rarely penetrate into the region.

• November to March is characterized by extreme varia-tions of temperature and the temperature is frequently below freezing point at night. 

• During April to June the heat are intense, frequent scorching winds prevail with great desiccating.

• The relative humidity of the atmosphere is always low.

• The climate is hostile to all vegetation, only plants and animals possessing special adaptations being able to establish themselves.