Table of Contents
- 1 Natural Ecosystem
- 2 Biomes or Terrestrial Ecosystems
- 2.1 Tundra Biome
- 2.2 Taiga or Boreal Biome
- 2.3 Temperate Deciduous Biome [North Western Europe]
- 2.4 Temperate Rainforest Biome
- 2.5 Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA
- 2.6 Steppe or Temperate Grassland Biome
- 2.7 Temperate Deciduous Biome [Mediterranean Region]
- 2.8 Tropical Deciduous Biome [Monsoon Climate]
- 2.9 Savanna or Tropical Wet and Dry Biome
- 2.10 Tropical Rain Forest Biome
- 2.11 Desert Biome
- A natural ecosystem is an assemblage of plants and animals which functions as a unit and is capable of maintaining its identity. There are two main categories of ecosystems.
- Ecosystems found on land e.g. forest, grasslands, deserts, tundra.
- Arctic and Alpine Tundra Biome
- Taiga or Boreal Biome [Coniferous forests]
- Temperate Deciduous Biome [North Western Europe]
- Temperate Rainforest Biome
- Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA
- Temperate Deciduous Biome [Mediterranean Region]
- Tropical Deciduous Biome [Monsoon Climate]
- Savanna or Tropical Wet and Dry Biome
- Tropical Rain Forest Biome
- Steppe or Temperate Grassland Biome
- Savanna or Tropical Wet and Dry Biome [Tropical Grasslands]
- Tropical and Mid Latitude Desert Biome
- Plants and animal community found in water bodies. These can be further classified into two sub groups.
- Fresh water ecosystems, such as rivers, lakes and ponds.
- Marine ecosystems, such as oceans, estuary and mangroves.
Biomes or Terrestrial Ecosystems
- The terrestrial part of the biosphere is divisible into enormous regions called biomes, which are characterized, by distinct climate [precipitation and temperature mainly], vegetation, animal life and general soil type.
- [They are nothing but ‘Climatic Regions’ http://www.pmfias.com/climatic-regions-upsc-ias-geography/ explained under Geography Section]
- No two biomes are alike. The climate determines the boundaries of a biome and abundance of plants and animals found in each one of them. The most important climatic factors are temperature and precipitation.
- There are two types of tundra – arctic and alpine.
- Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line (taiga) 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.
- Alpine tundra occurs at high mountains above the tree line. E.g. High ranges of Himalayas, Andes, Alps etc.
- The tundra climate is characterized by a very low mean annual temperature.
- In mid-winter temperatures are as low as 40 – 50 °C below freezing.
- Precipitation is mainly in the form of snow and sleet.
- There are no trees in the tundra (Ground is frozen). Lowest form of vegetation like mosses, lichens are found here and there.
- Coastal lowlands support hardy grasses and the reindeer moss which provide the only pasturage for reindeers.
- In the brief summer, berry-bearing bushes and Arctic flowers bloom.
- In the summer, birds migrate north to prey on the numerous insects which emerge when the snow thaws.
- Insects have short life cycles which are completed during favourable period of the year.
- Animals like the reindeer, arctic fox, wolves, musk-ox, polar bear, lemming, arctic hare, arctic willow live in tundra region.
- Reptiles and amphibians are almost absent.
- Most of the animals have 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 or fur.
- Mammals of the tundra region have large body size and small tail and ear to avoid the loss of heat from the surface [less surface area = less heat loss = less food required to produce heat].
Taiga or Boreal Biome
- Summers are brief and warm reaching 20-25 °C whereas winters are long and brutually cold – 30-40 °C below freezing.
- Typical annual precipitation ranges from 38 cm to 63 cm.
- It is quite well distributed throughout the year, with a summer maxima.
- In winter the precipitation is in the form of snow.
- Boreal forest soils are characterized by thin podozols and are rather poor.
- This is 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. Moreover conifers don not shed their leaves frequently.
- Most podzols are poor soils for agriculture due to the sandy portion, resulting in a low level of moisture and nutrients.
- Some are sandy and excessively drained. Others have shallow rooting zones and poor drainage due to subsoil cementation.
- A low pH (acidic) further compounds issues, along with phosphate deficiencies and aluminium toxicity.
- The low pH (acidic) factor is due to excessive leaching of alkaline oriented cations which if present would neutralize the organic acids of the accumulating litter.
- The predominant vegetation is evergreen coniferous forest.
- Conifers are evergreen plant species such as Spruce, fir and pine trees, etc.
- The conifers require little moisture are best suited to this type of sub-Arctic climate.
- The productivity and community stability of a boreal forest are lower than those of any other forest ecosystem.
- Animals found in this region include Siberian tiger, wolverine, lynx, wolf, bear, red fox, squirrel, and amphibians like Hyla, Rana, etc.
Characteristics of Coniferous forests
- Unlike the equatorial rain forests, Coniferous forests are of moderate density and are more uniform. The trees in coniferous forests grow straight and tall.
- Almost all conifers are evergreen. There is no annual replacement of new leaves as in deciduous trees.
- The same leaf remains on the tree for as long as five years. Food is stored in the trunks, and the bark is thick to protect the trunk from excessive cold.
- Conifers are conical in shape. Their conical shape and sloping branches prevent snow accumulation. It also offers little grip to the winds.
- Transpiration can be quite rapid in the warm summer. So, leaves are small, thick, leathery and needle-shaped to check excessive transpiration.
- The soils of the coniferous forests are They are excessively leached and very acidic.
- Humus content is also low as the evergreen leaves barely fall and the rate of decomposition is slow.
- Under-growth is negligible because of the poor soil conditions.
- Absence of direct sunlight and the short duration of summer are other contributory factors.
- Coniferous forests are also found in regions with high elevation [Example: The forests just below the snowline in Himalayas].
- But on very steep slopes where soils are immature or non-existent, even the conifer cannot survive [Example: Southern slopes of Greater Himalayas].
Temperate Deciduous Biome [North Western Europe]
- Moderately warm summers and fairly mild winters.
- The mean annual temperatures are usually between 5° C and 15° C.
- Winters are abnormally mild. This is because of the warming effect brought by warm North Atlantic Drift. [Eastern Australian warm current in case of New Zealand]
- Rainfall occurs throughout the year with winter maxima.
- Adequate rainfall throughout the year.
- As in other temperate regions there are four distinct seasons.
- Winter is the season of cloudy skies, foggy and misty mornings, and many rainy days from the passing depressions. (Trees shed their leaved in winter to prevent snow accumulation and protect themselves from severe cold)
- Spring is the driest and the most refreshing season when people emerge from the depressing winter to see everything becoming green again.
- This is followed by the long, sunny summer.
- Next is the autumn with the roar of gusty winds; and the cycle repeats itself.
- This type of climate with its four distinct seasons is something that is conspicuously absent in the tropics. [Rainforest == Only Rainy season, Tropical Monsoon == Summer, Winter and Rainy, Tropical Savanna == Summer (rains) and Winter]
- Soils of temperate forests are podozolic and fairly deep.
- The natural vegetation of this climatic type is deciduous forest.
- The trees shed their leaves in the cold season.
- This is an adaptation for protecting themselves against the winter snow and frost.
- Shedding begins in autumn, the ‘fall’ season. Growth begins in spring.
- Some of the common species include oak, elm, ash, birch, beech, and poplar.
- In the wetter areas grow willows (Light weight cricket bats are made from willows. In India willows are found in Kashmir).
- Most animals are the familiar vertebrates and invertebrates.
Temperate Rainforest Biome
- Temperate rain forests receive an annual precipitation of 200 cm, mostly due to on shore westerlies.
- Precipitation occurs in the form of fog, rain as well as snow. Fog is quite common and is an important source of water.
- This is a small biome in terms of area covered. The main stretch of this habitat is along the northwestern coast of North America from northern California though southern Alaska. There are also small areas in southern Chile, New Zealand, Australia and a few other places around the world.
- Big coniferous trees dominate this habitat, including Douglas fir, Western red cedar, Mountain hemlock, Western hemlock, Sitka spruce and Lodgepole pine.
- In addition to the trees, mosses and lichens are very common, often growing as epiphytes.
- Grizzly Bears are the common mammals found in Alaska.
Sub-Tropical Deciduous Biome in Eastern China, South Eastern USA
- Characterized by a warm moist summer and a cool, dry winter (one exception: winters are also moist in Natal Type).
- The mean monthly temperature varies between 4° C and 25° C and is strongly modified by maritime influence.
- Rainfall is more than moderate, anything from 60 cm to 150 cm.
- There is the fairly uniform distribution of rainfall throughout the year.
- Supports a luxuriant vegetation.
- The lowlands carry both evergreen broad-leaved forests and deciduous trees [hardwood].
- On the highlands, are various species of conifers such as pines and cypresses which are important
- Perennial plant growth is not checked by either a dry season or a cold season.
Steppe or Temperate Grassland Biome
Name of the Temperate Grassland
|Pustaz||Hungary and surrounding regions|
|Prairies||North America [between the foothills of the Rockies and the Great Lakes]|
|Pampas||Argentina and Uruguay [Rain-shadow effect]|
|Bush-veld (more tropical)||Northern South Africa|
|High Veld (more temperate)||Southern South Africa|
|Downs||Australia: Murray-Darling basin of southern Australia|
- Climate is continental with extremes of temperature.
- Temperatures vary greatly between summer and winter.
- The average rainfall may be taken as about 45 cm, but this varies according to location from 25 cm to 75 cm.
Natural Vegetation of Steppe Climate
- Greatest difference from the tropical savanna is that steppes are practically treeless and the grasses are much shorter.
- Grasses are fresh and nutritious. This is typical of the grass of the wheat-lands in North America, the rich black earth or chernozem areas of Russian Ukraine and the better watered areas of the Asiatic Steppes.
- Polewards, an increase in precipitation gives rise to a transitional zone of wooded steppes where some conifers gradually appear.
- Does not have much animal diversity.
- Horses are common in Asian Steppes.
Temperate Deciduous Biome [Mediterranean Region]
- Parts of the world that have Mediterranean type of climate are characterized by warm, dry summers and cool, moist winters.
- Trees with small broad leaves are widely spaced and never very tall.
- Regions with adequate rainfall are inhabited by low broad leafed evergreen trees [mostly evergreen oaks].
- Fire is an important hazardous factor in this ecosystem and the adaptation of the plants enable them to regenerate quickly after being burnt.
- Plants are in a continuous struggle against heat, dry air, excessive evaporation and prolonged droughts.
- They are, in short xerophytic [drought tolerant], a word used to describe the drought-resistant plants in an environment deficient in moisture.
Tropical Deciduous Biome [Monsoon Climate]
- Unlike equatorial wet climate, monsoon climate is characterized by distinct wet and dry seasons associated with seasonal reversal of winds.
- Floods in wet season and droughts in dry season are common.
- Usually there are three seasons namely summer, winter and rainy
- Monthly mean temperatures above 18 °C.
- Temperatures range from 30-45° C in summer.
- In winters, temperature range is 15-30° C with mean temperature around 20-25° C.
- Annual mean rainfall ranges from 200-250 cm. In some regions it is around 350 cm.
- Places like Cherrapunji & Mawsynram receive an annual rainfall of about 1000 cm.
Tropical Monsoon Forests
- Also known as drought-deciduous forest; dry forest; dry-deciduous forest; tropical deciduous forest.
- Teak, neem, bamboos, sal, shisham, sandalwood, khair, mulberryare some of the important species found here.
Savanna or Tropical Wet and Dry Biome
- This type of biome has alternate wet and dry seasons similar to monsoon climate but has considerably less annual rainfall.
- Also, there is no distinct rainy season like in monsoon climate. [Only two seasons – winter and summer. Rains occur in summer].
- Floods and droughts are common.
- Vegetation, wildlife and human life are quite different from monsoon climate regions.
- Mean annual rainfall ranges from 80 – 160 cm [Rainfall decreases with distance from equator].
- Mean annual temperature is greater than 18° C.
- The monthly temperature hovers between 20° C and 32° C for lowland stations.
Natural Vegetation of Savanna Climate
- The savanna landscape is typified by tall grass and short trees.
- The grasslands are also called as ‘bush-veld’.
- The trees are deciduous, shedding their leaves in the cool, dry season to prevent excessive loss of water through transpiration, e.g. acacias.
- Trees usually have broad trunks, with water-storing devices to survive through the prolonged drought.
- Many trees are umbrella shaped, exposing only a narrow edge to the strong winds.
- In true savanna lands, the grass is tall and coarse, growing 6 to 12 feet high. The elephant grass may attain a height of even 15 feet.
- Grasses appear greenish and well-nourished in the rainy season but turns yellow and dies down in the dry season that follows.
- As the rainfall diminishes towards the deserts the savanna merges into thorny scrub.
Animal Life of the Savanna
- There are two main groups of animals in the savanna, the grass-eating herbivorous animals and the fleshing-eating carnivorous animals.
- The herbivorous include the zebra, antelope, giraffe, deer, gazelle, elephant etc. [most of the National geographic and Animal Planet documentaries on wild animals are shot in savanna regions] and carnivorous animals include the lion, tiger, leopard, hyena, panther, jaguar, jackal etc..
- Species of reptiles and mammals including crocodiles, alligators, giant lizards live together with the larger rhinoceros and hippopotamus in rivers and marshy lakes.
Tropical Rain Forest Biome
- Also known as ‘The Hot, Wet Equatorial Climate’, ‘Equatorial Rainforest Climate’.
- The regions are generally referred as ‘Equatorial Rainforests’, ‘Equatorial Evergreen Forests’, ‘Tropical Moist Broadleaf Forest’, ‘Lowland Equatorial Evergreen Rainforest’.
- Temperature is uniform throughout the year.
- The mean monthly temperatures are always around 27° C with very little variation.
- There is no winter. [Typical to Equatorial Rainforest Climate]
- Precipitation is heavy and well distributed throughout the year.
- Annual average is always above 150 cm. In some regions the annual average may be as high as 250 – 300 cm.
- High temperature and abundant rainfall support a luxuriant tropical rain forest.
- In the Amazon lowlands, the forest is so dense that it is called ‘selvas’. [selvas: A dense tropical rainforest usually having a cloud cover (dense canopy)]
- Unlike the temperate regions, the growing season here is all the year round-seeding, flowering, fruiting and decaying do not take place in a seasonal pattern.
- The equatorial vegetation comprises a multitude of evergreen trees that yield tropical hardwood, e.g. mahogany, ebony, dyewoods etc.
- In the coastal areas and brackish swamps, mangrove forests
- All plants struggle upwards (most ephiphytes) for sunlight resulting in a peculiar layer arrangement [Canopy].
Epiphyte (Commensalism – Epiphyte benefits without troubling the host): An epiphyte is a plant that grows harmlessly upon another plant (such as a tree) and derives its moisture and nutrients from the air, rain, and sometimes from debris accumulating around it.
Q1. Which of the following is/are unique characteristic/characteristics of equatorial forests?
- Presence of tall, closely set trees with crowns forming a continuous canopy
- Coexistence of a large number of species
- Presence of numerous varieties of epiphytes
Select the correct answer using the code given below:
- 1 only
- 2 and 3 only
- 1 and 3 only
- 1, 2 and 3
Answer: Too easy. d) All
- Deserts are regions where evaporation exceeds precipitation.
- There are mainly two types – hot like the hot deserts of the Saharan type and temperate as are the mid-latitude deserts like the Gobi.
- They include the biggest Sahara Desert (3.5 million square miles), Great Australian Desert, Arabian Desert, Iranian Desert, Thar Desert, Kalahari and Namib Deserts.
- In North America, the desert extends from Mexico into U.S.A. and is called by different names at different places, e.g. the Mohave, Sonoran, Californian and Mexican Deserts.
- In South America, the Atacama or Peruvian Desert is the driest of all deserts with less than 2 cm of rainfall annually.
- The temperate deserts are rainless because of either continentiality or rain-shadow effect. [Gobi desert is formed due to continentiality and Patagonian desert due to rain-shadow effect]
- Amongst the mid-latitude deserts, many are found on plateau and are at a considerable distance from the sea. These are Ladakh, The Kyzyl Kum, Turkestan, Taklimakan and Gobi deserts of Central Asia, drier portions of the Great Basin Desert of the western United States and Patagonian Deserts of Argentina etc..
- The Patagonian Desert is more due to its rain-shadow position on the leeward side of the lofty Andes than to continentiality.
Rainfall (Both Hot and Cold deserts)
- Deserts, whether hot or mid-latitude have an annual precipitation of less than 25 cm.
Temperature of Hot deserts
- There is no cold season in the hot deserts and the average summer temperature is high around 30°C.
- The highest temperature recorded is 77° C in 1922 at A1 Azizia, Libya.
- The predominant vegetation of both hot and mid-latitude deserts is xerophytic or drought-resistant.
- This includes the cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacias.
- Trees are rare except where there is abundant ground water to support clusters of date palms.
- Most desert shrubs have long roots and are well spaced out to gather moisture, and search for ground water. Plants have few or no leaves and the foliage is either waxy, leathery, hairy or needle-shaped to reduce the loss of water through transpiration.
- The seeds of many species of grasses and herbs have thick, tough skins to protect them while they lie dormant.