Terrestrial Ecosystem- 1 | Environment for UPSC CSE PDF Download

Introduction

• 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 different terrestrial areas vary, resulting in differentiation of ecosystem as segments within the large biosphere. 
• The most important limiting factors of the terrestrial ecosystems are moisture and temperature.

Tundra

• Tundra means a "barren land" since they are found where environmental conditions are very severe. There are two types of tundra- arctic and alpine.
• Distribution: Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line in the northern hemisphere. It occupies 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 the ocean.
• Alpine tundra occurs at high mountains above the concerning Arctic mountains are found at all latitudes. Therefore, alpine tundra shows day and night temperature variations.
• Flora and fauna: Typical vegetation of arctic tundra is cotton grass, sedges, dwarf heath, willows, birches and lichens. Animals of tundra are reindeer, musk ox, arctic hare, caribous, lemmings and squirrel.
• Most of them have a long life, e.g. arctic willow has a life span of 150 to 300 years. They are protected from chillness by the presence of thick cuticle and epidermal hair. 
• Mammals of the tundra region have a large body size, small tail, and small ear to avoid heat loss from the surface. The body is covered with fur for insulation. Insects have short life cycles which are completed during the favourable period of the year.

What is Forest Ecosystem?

• The forest ecosystem includes a complex assemblage of different kinds of biotic communities. Optimum conditions such as temperature and ground moisture are responsible for the establishment of forest communities.
• The nature of the soil, climate and local topography determines the distribution of trees and their abundance in the forest vegetation. Forests may be evergreen or deciduous. They are distinguished based on leaf into broad-leafed or needle leafed coniferous forests in temperate areas.
• The forest ecosystems have been classified into three major categories: coniferous forest, temperate forest and tropical forest. These forest biomes are generally arranged on a gradient from north to south latitude or high to a lower altitude.

1. Coniferous forest (boreal forest)

• Cold regions with high rainfall, strong seasonal climates with long winters and short summers are characterized by boreal coniferous forest
• This is characterized by evergreen plant species such as Spruce, fir and pine trees, etc. and by animals such as the lynx, wolf, bear, red fox, porcupine, squirrel, and amphibians like Hyla, Rana, etc
• Boreal forest soils are characterized by thin podzols and are rather poor. Both because the weathering of rocks proceeds slowly in cold environments and because the litter derived from conifer needle (leaf ) is decomposed very slowly and is not rich in nutrients.
• These soils are acidic and are mineral deficient. This is due to the movement of a large amount of water through the soil, without a significant counter-upward movement of evaporation, essential soluble nutrients like calcium, nitrogen and potassium which are sometimes leached beyond the reach of roots. This process leaves no alkaline oriented cations to encounter the organic acids of the accumulating litter.
• The productivity and community stability of a boreal forest are lower than those of any other forest ecosystem.

2. Temperate deciduous forest

• The temperate forests are characterized by a moderate climate and broad-leafed deciduous trees, which shed their leaves in fall, are bare over winter and grow new foliage in the spring.
• The precipitation is fairly uniform throughout.
• Soils of temperate forests are podzolic and fairly deep.

3. Temperate evergreen forest

• Parts of the world with a Mediterranean climate is characterized by warm, dry summers and cool, moist winters.
• These are commonly inhabited by low broad-leafed evergreen trees.
• Fire is an important hazardous factor in this ecosystem, and the adaptation of the plants enables them to regenerate quickly after being burnt.

4. Temperate rain forests

• The temperate rain forests exhibit a marked seasonality concerning temperature and rainfall.
• Rainfall is high, and fog may be very heavy. It is an important source of water than rainfall itself.
• The biotic diversity of temperate rain forests is high as compared to another temperate forest. However, the diversity of plants and animals is much low as compared to the tropical rainforest.

5. Tropical rain forests

• Tropical rain forests occur near the equator.
• Tropical rain forests are among the most diverse and rich communities on the earth.
• Both temperature and humidity remain high and more or less uniform.
• The annual rainfall exceeds 200 cm and is generally distributed throughout the year.
• The flora is highly diversified
• The extreme dense vegetation of the tropical rain forests remains vertically stratified with tall trees often covered with vines, creepers, lianas, epiphytic orchids and bromeliads.
• The lowest layer is an understory of trees, shrubs, herbs, like ferns and palms.
• Soil of tropical rainforests are red latosols, and they are very thick.
• The high rate of leaching makes these soils virtually useless for agricultural purposes. Still, when left undisturbed, the rapid cycling of nutrients within the litter layer, formed due to decomposition, can compensate for the soil's natural poverty.
• Undergrow this restricted in many areas by the lack of sunlight at ground level.

6. Tropical seasonal forests

• Tropical seasonal forests also known as monsoon forest occur in regions where total annual rainfall is very high but segregated into pronounced wet and dry periods.
• This kind of forest is found in South East Asia, central and south America, northern Australia, western Africa, and the Pacific and India's tropical islands.

7. Subtropical rainforest

• Broad-leaved evergreen subtropical rain forests a re-found in regions of fairly high rainfall but fewer temperature differences between winter and summer 
• Epiphytes are common here. 
• Animal life of the subtropical forest is very similar to that of tropical rainforests.

Indian Forest Types

India has a diverse range of forests from the rainforest of Kerala in the south to the alpine pastures of Ladakh in the north, from the deserts of Rajasthan in the west to the evergreen forests in the north-east. Climate, soil type, topography, and elevation are the main factors determining the type of forest. Forests varied according to their nature and composition, the type of climate they thrive, and its relationship with the surrounding environment.

Champion and Seth Classification of Forest

Champion and Seth classify forest types in India into sixteen types.

1. Tropical Wet evergreen forests

• Wet evergreen forests are found along the Western Ghats, the Nicobar and Andaman Islands, and the northeastern region. Tall, straight evergreen trees characterize it. The more common trees found here are the jackfruit, betel nut palm, Jamun, mango, and hollock. 
• The trees in this forest form a tiered pattern: shrubs cover the layer closer to the ground, followed by the short structured trees and the tall variety. Beautiful fern of various colours and different varieties of orchids grow on the trunks of the trees.

2. Tropical Semi-evergreen forests

• Semi-evergreen forests are found in the Western Ghats, Andaman and Nicobar Islands, and the Eastern Himalayas. Such forests have a mixture of the wet evergreen trees and the moist deciduous trees. The forest is dense and is filled with a large variety of trees of both types.

3. Tropical Moist deciduous forests

• Moist deciduous forests are found throughout India except in the western and the north-western regions. The trees are tall, have broad trunks, branching trunks and roots to hold them firmly to the ground. Some of the taller trees shed their leaves in the dry season. There is a layer of shorter trees and evergreen shrubs in the undergrowth. These forests are dominated by sal and teak, along with mango, bamboo, and rosewood.

4. Littoral and swamp

• Littoral and swamp forests are found along the Andaman and Nicobar Islands and the delta area of the Ganga and the Brahmaputra. They have roots that consist of soft tissue so that the plant can breathe in the water.

5. Tropical Dry deciduous forest

• Dry deciduous forests are found throughout the northern part of the country except in the North-East. It is also found in Madhya Pradesh, Gujarat, Andhra Pradesh, Karnataka, and Tamil Nadu. The canopy of the trees does not normally exceed 25 metres. The common trees are the sal, a variety of acacia, and bamboo.

6. Tropical Thorn forests

• This type is found in black soil areas: North, West, Central, and South India. The trees do not grow beyond 10 metres. Spurge, caper, and cactus are typical of this region.

7. Tropical Dry evergreen forest

• Dry evergreens are found along Tamil Nadu, Andhra Pradesh and Karnataka coast. It is mainly hard-leaved evergreen trees with fragrant flowers, along with a few deciduous trees.

8. Subtropical Broad-leaved forests

• Broad-leaved forests are found in the Eastern Himalayas and the Western Ghats, along the Silent Valley. There is a marked difference in the form of vegetation in the two areas. In the Silent Valley, the poonspar, cinnamon, rhododendron, and fragrant grass are predominant. In the Eastern Himalayas, the flora has been badly affected by the shifting cultivation and forest fires. These wet forests consist mainly of evergreen trees with a sprinkling of deciduous here and there. There are oak, alder, chestnut, birch, and cherry trees. There are a large variety of orchids, bamboo and creepers.

9. Subtropical Pine forests

• Pine forests are found in the steep dry slopes of the Shivalik Hills, Western and Central Himalayas, Khasi, Naga, and Manipur Hills. The trees predominantly found in these areas are the chir, oak, rhododendron, pine, sal, amla, and laburnum in the lower regions.

10. Subtropical Dry evergreen forests

• Dry evergreen forests normally have a prolonged hot and dry season and a cold winter. It generally has evergreen trees with shining leaves that have a varnished look. These forests are found in the Shivalik Hills and foothills of the Himalayas up to 1000 metres.

11. Montane Wet temperate forests

• In the North, Montane wet temperate forests are found in the region to the east of Nepal into Arunachal Pradesh, receiving a minimum rainfall of 2000 mm. There are three layers of forests in the North: the higher layer has mainly coniferous, the middle layer has deciduous trees such as the oak, and the lowest layer is covered by rhododendron and Champa.
• In the South, it is found in parts of the Niligiri Hills, Kerala's higher reaches. The forests in the northern region are denser than in the South. We can find rhododendrons and a variety of ground flora here.

12. Himalayan Moist temperate Forest

• This type spreads from the Western Himalayas to the Eastern Himalayas. The trees found in the western section are broad-leaved oak, brown oak, walnut, rhododendron, etc. In the Eastern Himalayas, the rainfall is much heavier and therefore the vegetation is also more lush and dense. There are a large variety of broad-leaved trees, ferns, and bamboo. Coniferous trees are also found here, some of the varieties are different from those found in the South.

13. Himalayan Dry temperate Forest

• This type is found in Lahul, Kinnaur, Sikkim, and other parts of the Himalayas. There are predominantly coniferous trees and broad-leaved trees such as the oak, maple, and ash. At higher elevation, fir, juniper, deodar, and chilgoza are found.

14. Subalpine forest

• Subalpine forests extend from Kashmir to Arunachal Pradesh between 2900 to 3500 metres. In the Western Himalayas, the vegetation consists mainly of juniper, rhododendron, willow, and black currant. In the eastern parts, red fir, black juniper, birch, and larch are the common trees. Due to heavy rainfall and high humidity, the timberline in this part is higher than that in the West. Rhododendron of many species covers the hills in these parts.

15. Moist Alpine scrub

• Moist alpines are found all along the Himalayas and on the higher hills near the Myanmar border. It has a low scrub, dense evergreen forest, consisting mainly of rhododendron and birch. Mosses and ferns cover the ground in patches. This region receives heavy snowfall.

16. Dry alpine scrub

• Dry alpines are found from about 3000 metres to about 4900 metres. Dwarf plants predominate, mainly the black juniper, the drooping juniper, honeysuckle, and willow.

Importance of Forest

From the air we breathe, the food we eat to the paper and wood we use depends directly on the forest. Without forests, most of the areas would have been deserts

• Forests keep up the natural balance.
• Forests purify the air
• Forests provide a microclimate
• Forests indirectly play a role in precipitation
• Forests prevent floods
• Forests prevent soil erosion
• Forests provide medicinal properties
• Forests provide us with fuel and timber
• Forests provide raw materials for industries