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EnE-Biodiversity 2.2.1: Biomes
Presented by Dr. Roman Saini
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Biomes
Biomes
Biomes
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Biomes are the largest recognisable sub division of the terrestrial ecosystem
(geographically and climatically defined)
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It is an assemblage and association of plants and animals that form a regional
ecological unit of sub continental dimensions.
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Contiguous areas with similar climatic conditions on the Earth, such as
communities of plants, animals, and soil organisms etc.
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Biomes defined by: plant structures (trees, shrubs, etc.), leaf types (broadleaf
and needleleaf), plant spacing (forest, woodland, savanna), and climate
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Not defined by genetic, taxonomic, or historical similarities (ecozones are)
Biomes distribution
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Distribution is governed by
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a) annual variation in temperature
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b) minerals availability
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c) rainfall
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d) availability of sunshine
There exist a close parallelism between latitudinal and altitudinal zonation
of biomes. ALTITUDE mimics latitude.
Patterns and Trends in biodiversity
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Altitude mimics latitude. BD increases towards equator and with
increasing humidity.
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As we move away from equator towards the pole, in general, the species
diversity decreases (Latitudinal gradient)
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A tropical forest in amazon region will have 10-20 times more species of
plants, than a forest in temperate region.
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Because of this massive biodiversity, these amazonian rain forest of
South America produce and release huge amount of oxygen into the
atmosphere and hence are called as the Lungs of the Earth.
Why high diversity in tropics?
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Due to undisturbed environment: As speciation is generally a function
of time, temperate regions were disturbed by ice age and glaciation,
while tropics were left relatively undisturbed.
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In short, less seasonal, more constant and predictable environment.
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More resources available like sunlight, which leads to higher
productivity, development of specific ecological niches and hence, leading
to higher biodiversity.
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Species Area Relationship: Within a region, the number of species do
increase with increase in explored areas but only up to a limit.
Forest: 1) Tropical rainforest; 2) Tropical deciduous; 3) Temperate deciduous;
4) Temperate coniferous
Grasslands: 5) Tropical grasslands (SAVANNA); 6) Temperate grasslands
(steppes)
7) Desert Biome
8) Mediterranean Biome
9) Tundra Biome
10) Temperate Monsoon type
11) Cool temperate East Margin type
Tropical Rainforest
Tropical Rainforest
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aka Tropical wet forests/ Tropical moist broadleaf forests/ Lowland
equatorial evergreen rainforest
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Distribution 0-28° N & S i.e between Cancer and Capricorn
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GREATEST EXTENT- South America (Amazon), Central America, Africa (Congo),
SE Asia (Malaysia, Indonesia etc.), islands in Pacific, Caribbean and Indian
Ocean
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CLIMATE: Temperature: 25-30°C (>18°C all 12 months). Seasonal range is
rarely > 3°C
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Ex: INDIA 1) Western Ghats; 2) North East; 3) A & N islands
Tropical Rainforest
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Rainfall
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Cloudy weather condition especially in the afternoon
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It rains almost everyday 3-4 pm
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Relative humidity is high
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Heavy rainfall throughout the year 175-200 cms (never <168 and can be >
1000 cms)
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The term season is meaningless and the term weather and climate are
interchangeable
Stratification/ Layering/ Hierarchy /
Vertical Pattern/ Multi-Layered
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Forest floor: receives only 2% of sunlight; only adapted plants can grow here;
contains decaying plant and animal matter, which disappears quickly, because
the warm and moist conditions promote rapid decay by fungi and bacteria
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Understory layer: between canopy and forest floor
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Canopy layer: primary layer of the forest forming a roof over the two remaining
layers. Contains the majority of the largest trees (30–55 m in height). Tall,
broad-leaved evergreen tress are the dominant plants
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Emergent Layer: 55-80 m, tolerate hot temp and winds, crowned eagle and
large flying fox etc. Gaps
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VEGETATION
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Very high density of BD are found in the forest canopy, because it
supports a rich flora of epiphytes, including orchids, bromeliads,
mosses and lichens
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Epiphytes are plants which grow on outside of the other plants using
them just for support. Also they attach to trunks & obtain water,
other resource like minerals from rain, soil, debris etc. that deposits
on the supporting plants
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Great species diversity but few individual of each species
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Trees are broad leaves, never experience a seasonal leaves fall because
season are unknown in the environment of continuous warmness and
moistness
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SELVA soil is relatively lacking in nutrients (significant leaching), 2
types: ultisols (well weathered, acidic red clay soils, -ve Ca+K) and
oxisols (acidic, old, rest all points same, but are well drained
compared to ultisols)
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Economic exploitation is difficult because of high density, high
humidity, poisonous snakes and mixed species distribution
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Tress are hardwood type and important species are Mahogany,
Rosewood, Cinchona etc
DESERT BIOME
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Desert: Its not a vegetation, rather a climatic term. It refer to areas with
annual precipitation less than 25 cm annual rainfall or Evapotranspiration
losses are higher than precipitation
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Xerophytic vegetation. 4 general types of adaptations:
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1. Roots are modified in shape or size to enable to seek widely for moisture.
Sometimes taproots extends to ordinary depth to reach moisture. Also root
modification may involve the growth of large number of thin air like rootlets to
penetrate small pore spaces in soil
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2. Stems are sometimes modified into fleshy, spongy structure that can store
moisture. Plants with such fleshy stem are called succulents
DESERT BIOME
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3. Leaf modification take many forms i.e. hard and waxy, white and shiny,
spines
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4. The most remarkable adaptation involves the plant’s reproductive cycle
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Many xerophytic plants lie dormant for years without perishing
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When rain eventually arises they pass through an entire cycle of
germination, flowering, fruiting and seed dispersion in only a few days
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Deserts are of 2 types: Hot and Cold (Cold Coastal type is a subtype)
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Hot deserts. They are mostly subtropical. Ex:
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Sahara: North Africa
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Arabian Desert: Middle East
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Kalahari Desert: Southern Africa (Angola, Botswana, Namibia and South
Africa)
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Great Sandy Desert, Great Victoria Desert, Gibson Desert, Simpson
Desert: Australia
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Dasht-e Kavir (Great Salt/ Namak Desert ), Dasht-e Lut (emptiness): Iran
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Kalahari Desert: Southern Africa (Angola, Botswana, Namibia and South
Africa)
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Sonoran and Mojave: USA (Sonoran also in Mexico)
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Thar Desert: India and Pakistan
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Hot desert lie in 20-30° N & S latitude, occupy the western side of
continent in trade wind belt
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Very high temp, clear sky and almost absence of rain. Ex:
Death valley in California
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Large daily range of temp.
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Low humidity and high evaporation
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Halophytic adaptation (to survive in salty depression)
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Westerlies also leads to their warmness
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Cold Desert. They are beyond the subtropics towards the polar side.
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Gobi desert: East Asia in Mongolia and China
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Antarctica (may be excluded under certain classification)
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Patagonian Desert: South America (Argentina and Chile)
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Taklamakan Desert: China
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Kyzyl Kum: Central Asia (Kazakhstan, Turkmenistan and Uzbekistan);
Karakum Desert: Turkmenistan
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Colorado Plateau, Great Basin Desert: United States
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Cool Coastal type: Namib Desert in Southern Africa (Angola and
Namibia) and Atacama Desert in South America (Chile and Peru)
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