Important facts about Biomes/Major Ecosystems



Biomes are major ecosystems delimited by "particular climates or geographical areas, e.g. Marsh, Desert, Tundra, Pond, and Sea.


It is transitional or overlapping zone between two biomes where plants/animals of both the biomes are found.

Major Biomes:

They are of two types, terrestrial and aquatic. The terrestrial biomes include tundra, taiga, deciduous forest, tropical rain forest, chaparral tropical savannah, grassland and desert. Aquatic biomes include ocean, lake, pond, marsh and stream.

(A) Tundra/Arctic Tundra:

It lies north of 60° N in North America, Europe and Asia. Precipitation is 25 cm/yr, mostly as snow. Winter temperature is - 30° to - 40°C. Summer is for 45-75 days with highest temperature of 10°C. Ponds, pools, marshes, bogs occur during summer. Lower part of soil is under permafrost. Tundra is arctic desert with mosses {e.g. Sphagnum), lichens (Cladonia), grasses, sidges, dwarf willow (Salix), dwarf birch (Betula) and a few shrubs. Amphibians and reptiles are absent. Arthropods and worms appear during summer. Common animals are lemmings, Snow Grouse, Snow Owl, Arctic Fox, Polar Bear, Arctic Hare, Caribou, and Reindeer.

Polar Bear hibernates during winter while Reindeer and Caribou migrate to less cold areas. (a) Alpine/Alpine Tundra: ft is treeless area on high mountains (above 3500 m) which has snow for long months; ft is well drained and sloppy. Plants include lichens, mosses, and grasses herbs, small shrubs (e.g. Artemesia, Primula) and dwarf tress (Juniperus). Animals are Snow Leopord, Snow Bear, Mountain Goat, and migratory birds.

(B) Taiga/North Coniferous Forest:

Taiga occurs in temperate areas (mostly Northern Hemisphere, parts of New Zealand) with precipitation both as snow and rain (variable), Winters are chilly while summers are pleased. Marches have cotton grass and Sphagnum. Vegetation consists of evergreen conifers-Deodar (cectrus), Larch, Juniper, Spruce, Fir, Pine, Hemlock, and Yew. They are adapted to severe cold winters.

The needle like leaves lose very little in transpiration. Being green, they continue to manufacture food, broad- leaved Birch, Maple, Poplar and Aspen occur at places. Lichens, mosses, ferns and herbs are abundant. Ground has thick covering of fallen needles which later decay slowly. Fauna includes Wolf, Deer, Rabbit, Hare, Weasel, Elk, Beaver, Pumas, Raven, Muskrat, Porcupine, Lynx, Grouse and Jay. Migration from Tundra (Reindeer, Caribou) and from here to warmer places is quite common.

(c) Temperate Deciduous Forests:

The areas have warm summer and moderately cool winter. Rainfall is 75-150 cm. Dominant trees are Oak, Elm, Birch, Maple Ash, Chestnut, Hickory, Beech, Poplar and Magnolia. Conifers occur at places. Shrubs, herbs, ferns, mosses, lichens, grasses vines, and epiphytes are abundant. Most trees shed their leaves during autumn or fall making the soil brown. A mixed coniferous- broad leaved forest occurs in Indian hills between 1500-3500 m. Trees height can reach 30-40 m. Fauna consists of Deer, Fox, Beeves, Wild Cat, Raccoon, Opossum, Squirrel, Rabbit, Hare, Snakes, Lizards, Salamanders, Thrushes, Owls, Sparrows, Song birds.

(D) Tropical Deciduous Forests:

Climate is warm with alternate wet and dry periods. Rainfall is 100-200 cm. Vegetation includes broad leaved trees which shed their leaves during dry season, e.g. Butea, Bonbax, Shorea, Dalbergia. Famous Sal (Shorea), Teak (Tectona) and Sandal (Santalum) forests of India belong to their category. Animal's population is similar to evergreen tropical forests.

(E) Tropical Evergreen/Rain Forests:

The biome occurs over equatorial/ subequatorial regions with abundant warmth and rainfall (200-1000 cm/yr) almost throughout the year. The forest are impenetrable (= jungle) with maximum diversity, 200 types of trees in one hectare, 70-80% of all insects and 80-85% of all birds. Productivity is also maximum 12,000 k cal/m2/yr as compared to 2000 k cal/ m2/yr for taiga. The forests occur in famous Congo basin of Africa and Amazon basin in South America. In India, they occur in Western Ghats, Assam (Asom) and Andamans. Vegetation shows stratification, (layering), emergent tree layer (50 m or more), understory tree layer, shrub layer and ground layer. Epiphytes, climbers, mosses, ferns and orchids are abundant.

Trees include Cinnamon, Mahogony, Ebony, Rosewood, Rubber Tree, Nutmeg, Artacarpus, and Fig etc. Palms, plantains and bamboos occur here and there. Fauna consists of Deer, Goat, Antelope, Tapir, Elephant, Leopard, Jaguar, Snakes, Lizards, Monkeys, Lemurs, Bats, Sloths, Parakeets, Toucan, Birds of Paradise and several others. Chaparral: It is a broad-leaved shrub-forest (sclerophyllous or thick leaved shrubs and small trees) found in Mediterranean and pacific coast of several countries with winter rain and dry summer. Bush fires are common. Several plants are fire resistant including Sage, Arctostaphylos, Adenostemma and Coenothus. Trees of Oak and Eucalyptus, (in Australia) occur at places. Fauna consists of rabbits, chipmunks, deer, tiger, rats, snakes, lizards and birds.

(F) Tropical Savannah:

It is a warm climate plain with coarse grasses, scattered shrubs and trees, seasoned rain (wet and dry periods) and frequent fire. Savannah is named after dominant tree like Acacia, Phoenix, and Eucalyptus. Hoofed herbivores are quite common. Animals include Antelope, Zebra, Giraffe, Goat, Gazelle, Rhino, Elephant, Fox, Wolf, Lion, Tiger, and Kangaroo (in Australia).

(G) Grassland:

Grasses are dominant with non-graminaceous herbs, scattered bushes and occasional tree, e.g. prairies of USA/ Canada, Pampas of South America, Steppes of Eurasia, Tussocks of New Zealand and Veldts of South Africa. There is hot summer, cold winter, seasonal 25-75 cm rainfall. Grasses can be short or long. Fauna consists of Deer, Elk, Bison, Wolf, Prairie Dog, Bear, Bighorn Sheep, Rabbit, Mice, Budges, Coyote, Burrowing owl.

(H) Desert:

It occupies about 1/5 of land. It lacks rain (less than 25 cm) due to either being present in rain shadow (area beyond high mountains which cut of clouds, e.g. Tibet), lack of cloud intercepting mountains (e.g. Thar) or leging away from cloud seeding regions.

Death Valley (Great Western Deserts) of USA, Sahara (Africa), Gobi, Arabian and Thar of Asia. Rajasthan lies in the Thar Desert. Deserts can be cold (e.g. Tibet, Gobi) and hot (e.g. Thar, Sahara). Ground is sandy or rocky. Vegetation is sparse consisting of Cacti, euphorbia (succulents) Acacia, Phoenix, Tamarix, Echinops, Aerua etc. Animals are Kangaroo Desert Rat, Hare, Fox Jackal, Cat, Rattle Snake, Coral Snake, lizards (Gila, Monster, and Horned Lizard), spiders, scorpions, locusts, ants, wasps and a number of birds like Swifts, Swallows, Quails, Doves, etc. Camel is adapted to desert conditions as it can protect its eyes and nostrils from dust, has insulated spreading feet, and is capable of tolerating dehydration up to 40% with highly reduced urine output.

(I) Oceanic Biome:

Oceans occupy 75% of earth's surface with salinity of 3.5% (0.5% in Red Sea and 1% in Baltic Sea), temperature of 28°C on surface in equatorial region (colder below) and 0°C near poles (warmer below). Continental shelf is gradually sloping (0%) sea shore up to 160 km and depth of 8200 m. It passes into continental slope (3°-6°) which leads to ocean floor at a depth of 6 km-1Okm.

There littoral zone in continental shelf and a neritic zone above the same. The open seal pelagic part is differentiated into photic zone (up to 200 m depth, light penetrates the zone), aphotic zone (200-2000 m depth; little light) and abyssal zone (dark zone), epipelagic (photic zone), mesopelagic (alphotic zone), bathy belagic (2000 m to near ocean floor and abyssopelagic (ocean floor).

(J) Open Ocean:

Productivity is 1000 k cal/ m2/yr. The surface has phyto- plankton (diatoms, dinoflagellaes, other unicellular and multicellular algae, and some luminescent flagellates), 300 plankton (protozoans larvae, crustaceans) and neuston (photosynthetic like Sargassum, phagotrophic like some crabs, gastropods, jelly fishes, physallia). The surface as well as lower part has necton/nekton or swimming animals like turtles, snakes, squids, fishes, marine birds, etc. producers are absent in deep water. The abyssal zone contains only carnivores/predators. Some of them have luminescent organs (e.g. Devil Fish, Hatchet Fish), baits (e.g. Angles Fish), large heads (Granadier Fish, Gulper Eel). The benthonic region has scavengers and decomposes.

(K) Coastal Region:

Productivity is 2000-6000 k cal/m2/yr. The important producers of coastal regions are Dictyota, Ulva, Fucus, Polysiphoria, Enteromorpha, Cladophora, Zostena (the only seed plant) besides phytoplankton. Consumers include Zooplankton, biralves, snails, crabs, barnades, sponges, bryozoans, Nereis, Star Fish, Sea Urchin tunicates etc. In littoral zone there are strong waves. Attached algae include Laminaria, Macrocystis, Neroecystis, Alaria, Gelidium, & Corallian. Lithothamnion, consumer of the area are sponges, corals, polychaetes, tunicates and sea anemones. Nekton of the neritic zone also visits the area. Neritic zone (constant water, pelagic) has plankton, neuston and necton. Coral reef is the area of maximum productivity and diversity.

(L) Estuary:

Tidal mout of river/coastal bay where there is mixing of fresh and sea water. Highly productive due to turbulence. There are fluctuations in temperature and salinity. Species found are phytoplankton (blue-green algae, green algae, diatoms, din flagellates), zooplankton (protozoan's, crustaceans, rotifers), nekton (fishes and some crustaceans) and benthos (attached algae, snails, clams, prawns etc.)

(M) Pond/Lake Biome:

Ponds and lakes are stationary fresh waters. Deep lakes and brackish lakes are oligotrophic with sparse biota due to little circulation of nutrients. Shallow lakes and ox-bow (from main stream of river) lakes are atrophic with rich biota and quick circulation of nutrients. Ponds are generally shallower with depth less than 2 m. Producers includes phytoplankton (e.g. diatoms, desmids, Chlorella, Chlamydomonas, Spirogyra, Oedogmium, Zygnema, free floating macrophytes (e.g. Lemna, Pistia, Azolla, suspended macrophytes (e.g. Utricularia, Ceratophyllum, Hydrilla), submerged, anchored plants (e.g. Scirpus, Sagittaria, Phragmites).

Consumers comprise zooplankton (ciliates, flagellates, rotifers, small crustaceans like cyclops and Daphnia, larvae), necton (e.g. Water Boatman, Water Spider, Diving Beetle, amphibians, turtles, fishes) and benthon (e.g. snails, clams, mussels, crabs, prawns). A number of decomposers also occur on the bottom. Water birds include Duck, Heron, Crane and Kingfisher.

(N) Marsh Biome:

It is turbid muddy biome with little planktons. Flora includes emergent hydrophytes (e.g. Typha, Phragmites), Sphagnum and Eichhornia. Fauna consists of snails, mosquito larvae, some insects and frogs.

(O) Lotic/River Biome:

It has high speed and low temperature in upper reaches. Water becomes muddy during rains. Detritus form land constitutes important component of food. Produces grow along shallow banks with very slow moving water. They include attached algae, encrusting diatoms, aquatic mosses (e.g. Fontinalis) submerged seed plants, reeds, water grasses etc. Consumers are more abundant including flatworm's nymphs, larvae, snails, fishes, otter, mink, muskrat, crocodile etc.

(P) Man-Made/Artificial Ecosystem:

They include aquaria, dams, parks, gardens, orchards, plantations, human settlements and agriculture. Artificial or man-made ecosystems have little diversity (generally monocultures), little recycling of nutrients and no self regulatory mechanisms. Agriculture (crop raising, animal husbandry) has created an agro ecosystem which differs from place to place depending upon climate, latitude, topographic and seraphic factors.

Agro ecology is the study of relationships between agricultural crops and there surrounding animate as well as inanimate environment. Biotic community is rich when crop is in the field-crop, weeds, pests, birds, pollinators, nematodes, earth worms, insects, rodents, birds and decomposers.

Since, there is little circulation of nutrients, agro ecosystem is artificially irrigated, provided will biogenetic nutrients, protected from weeds, pests and pathogens. There is little accumulation of biomass. Manure is, therefore added. Technology is being increasingly used in creating new varieties, sowing and reaping.