10 Earths Major Biomes: Distribution and Biotic Components

V.K. Garg

Module 22 Earths Major Biomes: Distribution and Biotic Components

Objectives: To learn about distribution and biotic components of Earths Major Biomes

LEARNING OBJECTIVES

• The concept of biomes and biogeographic realms
• Major terrestrial biomes of the world as per the World Wildlife Fund (WWF) classification
• To understand distribution and biotic components of different Biomes

22.1.Introduction

Biomes are large geographical regions of earth which have characteristics types of biotic communities that are shaped by the climate of the region. On the basis of global analysis for conservation of terrestrial ecosystems, Olson et al. (2001) unified the biome concept. The terrestrial world has been divided into 14 biomes and eight biogeographic realms. Nested within14 biomes are 867 ecoregions that reflect finer regional-scale patterns of ecological organization that are shaped by local geography and climate, being different from one another by the unique collections of ecosystems and species assemblages that have evolved there (Hoekstra et al. 2005). The Biome Classification System has been developed by The Nature Conservancy and the World Wildlife Fund (WWF). This classification is being used by the National Geographic Society (www.nationalgeographic.com/) and the Millennium Ecosystem Assessment (www.millenniumassessment.org/). WWF defines an ecoregion as a “large unit of land or water containing a geographically distinct assemblage of species, natural communities, and environmental conditions”.

According to Olson et al. (2001), the 14 terrestrial biomes/ Major Habitat Types show the diverse types of organisms that are adapted to life on land, ranging from mangrove forests by the sea to the alpine meadows of the Himalayas. Biomes represent broad habitat and vegetation types and span across biogeographic realms. For example, the tundra biome is found in both Palearctic and Nearctic realms. Biomes are useful units for assessing global biodiversity and ecosystem services because they stratify the globe into ecologically meaningful and contrasting classes The eight biogeographic realms and the 14 major biomes (major habitats) are listed in Table 22.1 and illustrated in Fig.22.1. Each biogeographic realm contains a range of major biomes. The Indo-Malayan, Oceanic, and Neotropical realms are dominated by tropical forest and grassland biomes (Fig. 22.1). The polar realms (Palearctic, Nearctic) contain higher proportions of tundra and boreal forest. The Afrotropics are dominated by tropical grasslands. Oceania is composed mostly of low, tropical islands and is dominated by tropical forest and tropical grassland biomes.

11.2.Tropical and Subtropical Moist Forests (TSMF)

Tropical and Subtropical Moist Forests (TSMF) are mainly located around the belt at the equator extending between the Tropics of Cancer, and Capricorn (Fig. 22.2). These forests are distributed in the Amazon basin in South America, the Congo basin and other lowland regions in Africa, and on the mainland and the islands of Southeast Asia, and the Northern tip of Australia. Forest composition is dominated by semi-evergreen and evergreen tree species. The largest number of ecoregions falls within the TSMF, 35% of all terrestrial ecoregions (Olson et al. (2001), reflecting the biological richness and complexity of tropical moist forests. They also vary in habitat from swamp to dry land as well as in elevation, i.e. from lowland to montane rainforest and cloud forest. Tropical montane cloud forests are found in Central America, South America, Africa, Southeast Asia, and the Caribbean. There’s even cloud forest on the side of Mt. Kilimanjaro in Tanzania.

Tropical rainforests cover about 6% of the Earth’s total land surface area. The largest continuous areasof tropical rain forests are found in the Amazon basin of South America. In India, they are found mainly in the Western Ghats region. The rainforests have evolved over the course of 50 to more than 100 million years. They exhibit great variation in climate ranging from evergreen rainforests where there is minimal variation in precipitation and temperature, to rainforests with seasonal variations of drier periods. Some general characteristics of tropical rain forests are given in Box 22.1.

The canopy layer is the primary layer of the forest forming a roof over the two remaining layers. The emergent layer is unique to tropical rainforests. The emergent layer consists of very tall trees reaching heights of 45 – 55 m; although (a few species grow to height up to 60–70 m). The dense canopy layer further down absorbs most of the sunlight, but along the trunks and stems grow dense lianas, lichens, mosses, ferns and flowering plants. The air in the lower layer is stagnant and humid, There are large woody climbers or lianas extending from the ground to the canopy; orchids, other epiphytes, and stranglers are abundant. The understory layer lies between the canopy and the forest floor.

There is high diversity of animal and plant species in tropical rainforests. Flora is highly diverse, as many as 100 different tree species can be found within one square kilometer; 40 to 100 tree species per ha is common. Mostly trees are evergreen, with large dark green leaves, many of trees are with buttressed roots (may reach as far as nine m up the trunk), Plants such as orchids, bromeliads, vines (lianas), ferns, mosses, and palms grow luxuriantly in tropical forests.

There are several millions of different animal species, and insects, reptiles, amphibians and mammals in these forests. Mammals and reptiles are predominantly arboreal (living in canopy), and nocturnal. Birds are present in great diversity in the upper strata of the rain forest. All levels of these forests contain an unparalleled diversity of invertebrate species. The forest canopy has unique community of insects, amphibians, reptiles, birds, and mammals. Animals in the canopy often play an important role in forest functioning, particularly in seed dispersal.

Tropical montane cloud forests are distinctive forest vegetation on tropical mountains that are frequently or persistently immersed in ground-level clouds (Fahey et al. 2016). The potential global area of cloud forest is approximately 0.26 per cent of the Earth’s land surface. The cloud forests are found along mountainsides (generally between 1,000 and 3,000m, but as low as 500m in the tropics. In tropical montane cloud forests, climbers may be vines, lianas, or palms, while epiphytes may be bromeliads, orchids, mosses, lichens, or ferns. The hemi-epiphytes include the strangler figs, while mistletoe is the most common of the hemi-parasites. They are the natural habitat of the wild relatives of many crop species.

22.3. Tropical and Subtropical Dry Forests

Tropical and Subtropical Dry Forests are found in southern Mexico, southeastern Africa, central India, Indochina, Madagascar, New Caledonia, eastern Bolivia and central Brazil, the Caribbean, valleys of the northern Andes, and along the coasts of Ecuador and Peru.

These forests occur in climates that are warm year-round, exhibit long dry seasons which last several months that varies with geographic location. Deciduous trees dominate these forests, and during the drought a leafless period occurs, which varies with the tree species. The dry forests of central India and Indochina are notable for their diverse large vertebrate faunas (Corbett and Hill, 1992; Stewart-Cox, 1995). Chhota-Nagpur dry forests have diverse large vertebrate faunas including tigers, elephants. These forests are dominated by teak with species such as Tectona grandis, Shorea robusta, Anogeissus latifolia,etc. The endemic Cycad (Cycas beddomei) is an endangered species, reported to occur in the Tirupati-Kadapa Hills in Andhra Pradesh State, northwest of Madras in eastern Peninsular India from 300 to 900 m.

These forests are less biologically diverse, are a home to a wide variety of wildlife including monkeys, large cats, parrots, various rodents, and ground dwelling birds. Dry forests of Madagascar and New Caledonia are also highly distinctive because of the presence of endemics and a large number of relictual taxa. In Madagascar Dry Forests, there is high degree of endemism, and a large number of relict taxa. The world’s most endangered tortoise, the Angonoka tortoise (critically endangered as per

IUCN criteria) is found around Baly Bay in northwestern Madagascar (http://www.iucnredlist.org/details/9016/0). This species has a very restricted distribution over an area of only 66 km2 comprised of dry deciduous forest, savanna, and mangrove swamps.

The Atlantic Dry forests of South America are fairly dense, up to 25 to 30 m high, the most remarkable tree is Cavanillesia arborea (Malvaceae), which is endemic and is bat-pollinated and the seeds are wind-dispersed. The Hawaii’s Dry Forests harbor Native Hibiscus trees and several rare endemic plants.

22.4. Tropical and subtropical coniferous forests

These forests occur predominantly in North and Central America, low levels of precipitation and moderate variability in temperature. These forests are characterized by a thick, closed canopy. The ground is often covered with fungi and ferns. Shrubs and small trees compose a diverse understory. These forests are characterized by diverse species of conifers, which are adapted to the variable climatic conditions. Many migratory birds and butterflies spend winter in tropical and subtropical conifer forests. Mesoamerican Pine-Oak forests are most extensive subtropical coniferous forests; rich diversity of plant and animal species especially birds, conifers, reptiles, and amphibians show restricted distribution. Mexico harbors the world’s richest and most complex subtropical coniferous forests. The conifer forests of the Greater Antilles contain many endemics and relict taxa. Subtropical conifer forests of Indochina are incorporated into the dry and moist forests of the region.

22.5. Temperate broadleaf and mixed forests (TBMF)

Temperate forests occur in areas with distinct warm and cool seasons, which give them a moderate annual average temperature (3 to 16 °C). It is one of the major biome on Earth. TBMF are richest and most distinctive in central China and eastern North America. Some other globally unique ecoregions are the Caucasus, the Himalayas, southern Europe, and the Russian Far East.

Forests in the temperate regions experience a wide range of variability in temperature and precipitation.

Species such as oak (Quercus spp.), beech (Fagus spp.), birch (Betula spp.), and maple (Acer spp.) are the main components in these forests. There are four layers in the forest: a canopy composed of mature full-sized dominant species, a slightly lower layer of mature trees, a shrub layer, and understory layer of grasses and other herbaceous plants. Most biodiversity is concentrated much closer to the forest floor.

The Eastern Himalayan Broadleaf and Conifer Forests are found ranging from the lowlands to the foothills of the Himalayas in northern India, Nepal, and Bhutan. The Eastern Himalayan temperate

forests are home to the highly endangered golden langur, lesser panda , clouded leopard, Himalayan black bear and the goat antelope called Takin (Budorcas taxicolor). Endangered endemic plants include many orchid species and maple species.

The western Himalayan temperate forests are made up of Western Himalayan broadleaf forests; and Western Himalayan subalpine conifer forests. Characteristic plant species in the region include conifers including Blue pine (Pinus wallichiana), Spruce (Picea smithiana), Yew (Taxus wallichiana), and Fir (Abies pindrow); subalpine broadleaved species such as Birch(Betula utilis) and Rhododendron (Rhododendron campanulatum), some endemic shrubs.

Russian Far East Temperate Forests are very distinct, high level of endemism in plants and invertebrates; form a critical area for the conservation of Amur tigers (Panthera tigris spp altaica) and leopards (Panthera pardus).

The temperate rain forests of Tasmania are very complex and harbour relict species from the time when the island was part of the supercontinent Gondwanaland. Many endemic genera and some unique species in the alpine flora, 500 year-old Nothofagus, trees can be found here, and a rich diversity of lichens.

22.6. Temperate coniferous forests

Temperate rain forests only occur in seven regions around the world – the Pacific Northwest, the Validivian forests of southwestern South America, the rain forests of New Zealand and Tasmania, the Northeastern Atlantic (small, isolated pockets in Ireland, Scotland, and Iceland), southwestern Japan, and those of the eastern Black Sea. Temperate evergreen forests are common in the coastal areas of regions that have mild winters and heavy rainfall, or inland in drier climates or montane areas.

Temperate evergreen vary markedly in their kinds of plant life. In some, needle leaf trees dominate, while others are home primarily to broadleaf evergreen trees or a mix of both tree types.Many tree

species like pine, cedar, fir, and redwood occur in these forests. The understory also contains a wide variety of herbaceous and shrub species. Temperate conifer forests sustain the highest levels of biomass in any terrestrial ecosystem.

Nevada ecoregion is home to the Giant sequoia (Sequoiadendron giganteum), naturally grow only in a narrow strip of mixed conifer forest on the western slopes of the Sierra Nevada mountains, primarily between 5,000 and 7,000 feet in elevation. Giant sequoias are the largest trees on in terms of total volume. Yosemite Toads are small olive green toads, with black spotting, which are endemic to the Sierra Nevada Mountains.

22.7. Boreal forest/ taiga

Boreal coniferous forests are found between 50 °N to 70 °N and are regulated by long dry, cold winters and short, warm summers. Averages precipitation is 100 in/yr, mostly in the form of snow, soil poor in nutrients and very acidic and growing season is very short. Extensive tracts of boreal forest exist in the northern part of North America and Eurasia the northern, the largest expanses being in central and eastern Russia.

The dominant trees of the boreal forests are evergreen spruces (e.g. Picea glauca), firs (e.g., Abies balsamea) , larches (Larix spp.) or pines in most areas, while cedar and some species of deciduous trees (Betula spp. and Populus spp) are common. The nutrient poor soils favor the preponderance of conifer species (Abies, Picea, Larix, and Pinus). Ground cover in Boreal Forests is dominated by mosses and lichens. Animals adapt for cold winters; burrow, hibernate, warm coat, insulation, etc. Thus, the forest is essentially two-layered. The vegetation is reduced to open pine woodlands in arid mountains, bogs or muskegs in humid subarctic areas, woodland in the far North, and wind-sheared shrub community (Krummholz) toward the timberline ( see Singh et al. 2015).. Characteristic animals are moose, wolverine, lynx, and several kinds of snowshoe hares, finches and wood warblers. Large-scale migrations of caribou, or reindeer (Rangifer tarandus) and intact predator assemblages can still be found in some regions.

22.8. Tropical and subtropical grasslands, savannas and shrub-lands

This biome is characterized by rainfall levels ranging from 90-150 cm per year. Grasslands and savannas are of widespread occurrence within the subtropics and tropics, such as the savannas of Africa, and the compos and llanos of South America and in Mediterranean climate (dry summers and  relatively warm, wet winters). The largest areas of savannas are found in Africa. Afrotropical savannas include the Horn of Africa Acacia Savannas, East African Acacia Savannas, Central and Eastern Miombo Woodlands, and Sudanian Savannas.

Some characteristics of the savannahs are : i) a continuous or near-complete cover of a mostly grassy herbaceous stratum, ii) tree and shrub strata varying from a total canopy cover (savannah woodland) to open grassland; iii) marked seasonal contrasts with periodic annual fires typical of dry seasons iv) mostly nutrient-poor soils. Terai-Duar savannas and grasslands occur in southern Asia including Bangladesh, Bhutan, India, and Nepal http://wwf.panda.org/about_our_earth/ecoregions/teraiduar_savannas_grasslands.cfm. These grasslands contain the world’s tallest grasses and have the highest densities of tigers, rhinos, and ungulates anywhere in Asia. The dominant grass of the floodplains is Saccharum , or elephant grass, and supports a number of habitat specialists such as the Bengal Tiger (Panthera tigris tigris)) and its prey base, the Chital (Axis axis).

The most threatened tropical savanna in the world is the Cerrado, a large region that occupies the center of South America and is biologically rich (Silva and Bates 2002). Both the Cerrado and the Llanos occur in South America represent complex habitats and exhibit high level of endemism in plants (Fig.22.3). It is also the second largest South American biome and the Cerrado is among the 36 terrestrial hotspots. Australia’s tropical savannas are the landscapes of dense grass and scattered trees that cover almost one-quarter of the continent. The tropical savannas of northern Australia and southern New Guinea exhibit distinct species assemblages.

22.9. Temperate grasslands, savannas and shrublands

The main temperate grasslands include the pampas of South America, the steppes of Eurasia, prairies of North America, and the veld in Southern Africa. Broadly speaking, they occur in areas where rainfall (25-75 cm per year) is intermediate between those of deserts and forests. Climate is typical continental, with long, cold winters and hot summers. In comparable climate of Australia, there occur grassy woodlands with Eucalyptus.

Biodiversity in these habitats includes a number of large grazing mammals and associated predators in addition to burrowing mammals, numerous bird species, and a great diversity of insects. Among large mammals, ecological equivalents in different continents include the bison and pronghorn in North

America, the wild horse and ass and taiga antelope of Eurasia, the larger kangaroos of Australia, and the zebras, antelopes, and others of the warm-temperate grasslands of Africa. Many prairie animals are burrowers. For example, Black-tailed prairie dogs build extensive underground ‘towns’, which soon become temporary and permanent shelter for burrowing owls, jackrabbits, snakes, and many other species. The Patagonian steppe and grasslands are notable for distinctiveness at the generic and family level, high endemism of vascular species and regionally distinctive communities of mammals, birds, and plants.

The Daurian steppe region is most intact example of an undisturbed steppe ecosystem and is also one of the last areas in the Palearctic that still supports stable herds of larger vertebrates. The region has a distinct flora and fauna, with a number of endemic species.

22.10. Flooded grasslands and savannas

The flooded savannas and grasslands occur in the Everglades, Pantanal, Sahelian flooded savannas, Zambezian flooded savannas, and the Sudd-Sahelian Flooded Grasslands and Savannas.(http://wwf.panda.org/about_our_earth/ecoregions/about/habitat_types/selecting_terrestrial_ec oregions/habitat09.cfm) .

The Everglades flooded grasslands: The Everglades are the world’s largest rain-fed flooded grassland on a limestone substrate, and feature some 11,000 species of seed-bearing plants, 25 varieties of orchids, 300 bird species, and 150 fish species.

The Pantanal flooded savannas, one of the largest continental wetlands globally (Fig.3), supports large diversity of fish, birds, mammals, reptiles, amphibians, butterflies, and plants. The flooded savannas in southern South America are comprised of a mosaic of flooded grasslands and savannas, gallery forests, and dry forests.

Zambezian Flooded Savannas, The Okavango Delta and associated flooded grasslands and savanna habitats constitute the Zambezian Flooded Savannas. There is a rich diversity of birds, and significant populations of the African elephants.

flooded grasslands: In India, flooded grasslands occur in Rann of Kutch, Gujarat. Expanses of mangroves and desert vegetation comprise portions of this ecoregion. Among the threatened mammals present within the ecoregion are – Leopard (Panthera pardus), Asiatic wild ass (Equus hemionus), and striped hyena.

22.11. Montane grasslands and shrub-lands

Montane grasslands and shrublands are located above the tree line (the upper limit of tree growth), are commonly known as alpine tundra, and occur in mountainous regions around the world. This major habitat type includes the Puna and Paramo in South America, subalpine heath in New Guinea and East Africa, and the steppes of the Tibetan Plateau. The paramos of the northern Andes are the most extensive examples of this habitat type. The plants and animals of tropical montane paramos show adaptations to cool, wet conditions and intense sunlight. In winters, many of larger animals migrate to lower elevations, while smaller animals either hibernate or remain in shelter in meadows.

The montane grasslands of the Tibetan Plateau still support relatively intact migrations of Tibetan antelope (Pantholops hodgsonii) and Tibetan wild ass (Equus kiang).

22.12.Tundra

The tundra is a treeless polar desert found primarily in Alaska, Canada, Russia, Greenland, Iceland, and Scandinavia in northern hemisphere (Fig.22.4), and Antarctica in southern hemisphere. The region has long, dry winters and extremely frigid temperatures. Most precipitation falls in the form of snow during the winter. Histosols (bog soils, and organic soils with more than 20% organic matter) and entisols, with little profile development are major soil orders. The top (15 – 60 cm) soil thaws in summer and freezes in winter, and beneath this soil is the permanently frozen parent material, called permafrost.

The Tundra vegetation is composed of lichens, mosses, grasses, sedges and heaths as well as dwarf shrubs. Vegetation is generally scattered, although it can be patchy reflecting changes in soil and moisture gradients. Musk ox, caribou and reindeer (in Eurasia), polar bears, the arctic hare, and lemming are predominant mammals; longspurs

larks are characteristic birds. The majority of large vertebrates leave Tundra in winters; the birds migrate to the south, and only lemmings and arctic ground squirrels to stay. There is a seasonal concentration of breeding waterfowl and shorebirds, as well as caribou.Reindeer herding is one of the most extensive forms of human interactions with tundra ecosystem.

22.13 Mediterranean Forests, woodlands and shrubland

The Mediterranean biome is a global conservation priority because of high plant species diversity. The biome has mild climate and proximity to the ocean. The Mediterranean biome includes the Mediterranean Basin, the western United States (California) and Mexico (northwest Baja), central Chile, the cape region of South Africa, and south and southwestern Australia (Fig.22.5). The Lowland Fynbos are found roughly below 300 m elevation within the Cape Floristic Region, South Africa, is a fire-dependent ecosystem characterized by high shrubs diversity, canopy seed storage (serotiny), and ant seed dispersal (myrmecochory) (Cowling et al., 1996). The Mediterranean landscape and the natural vegetation (matorral) in Chile has been strongly affected by human activities such as logging,

Mediterranean biome supports five global biodiversity hotspots. These hotspots are (i)The California Floristic Province, (ii) the Cape Floristic Region, (iii)the Mediterranean Basin, (iv) Southwest Australia, and(v) the Chilean Winter Rainfall-Valdivian Forests (Klausmeyer and Shaw, 2009; Myers et al. 2000; http://www.cepf.net/resources/hotspots/Pages/default.aspx). These regions are characterized by high plant diversity accounting for 20 percent of the plant species out of which more than half are endemic. Scrub communities can be quite species-rich and diverse, as is the case with those occurring on mountain slopes and the upper margins of desert plains in North America. They may include prickly pear, Acacias, Agave, etc., or a tree woodland. Lizards and snakes are common fauna in chaparral, though mammals may also be many such as gray fox, wood rats, kangaroo rats, and small rodents. The Fynbos of South Africa show high degree of endemism.

22.14. Desert and dry shrubland

Deserts occur in specific latitudes (25–35° north and south of the equator). Desert Biome can be defined climatologically as the sum of all the arid and hyper-arid areas of globe; biologically, as the ecoregions that contain plants and animals adapted for survival in arid environments, and physically as large contiguous areas with bare soil and low vegetation cover (UNEP 2006).

Deserts are dry places where less than 250 mm of rain falls in a year resulting in sparse growth of vegetation. They are often regions of extreme temperatures where living conditions are hostile. Temperature variability is also extremely diverse in these regions. Many deserts, such as the Sahara in Africa, are hot all year-round, whereas Asia’s Gobi, become quite cold in winter. The vast land area of Sahara in northern Africa, the Arabian Peninsula, the west coast of South America, and parts of Australia, India and southwestern United States are the typical areas of deserts.

The vegetation cover is poor (mainly shrubs), yet plant diversity can be high. All plants have evolved to minimize water loss; cacti are a representative example of this ability. Desert soils are usually poor because plant growth and productivity is low and the litter layer is almost absent. The true deserts are primarily subtropical, occurring generally in climates drier than those of semidesert scrub. In extremely arid climate, with precipitation below 120mm per year, vegetation cover is very sparse and the vast bare ground surface (sand, stone and salt crust). Plant forms range from typical low shrubs, to some very distinctive plants and lichens in areas with fog.

Warm semi-desert scrubs occupy dry warm-temperate and subtropical climates.

22.15. Mangroves

The mangrove ecosystems are found in the inter-tidal zones of sheltered shores, estuaries, creeks, backwaters, lagoons, marshes and mud-flats, along the tropical coastlines of Asia, Australia and Americas (Fig.21.6). They stretch from the intertidal zone up to the high-tide mark. These forests are comprised of 12 genera comprising about 73 species of salt-tolerant trees.

The dominant salt-tolerant, sclerophyllous broadleaved trees form a unique ecosystem with associated plants, including epiphytic and terrestrial ferns, orchids, lichens, non-mangrove halophytes, sea grasses and seaweeds, and fauna such as fish, shrimp, shellfish, crabs, lobsters, reptiles and birds. Many organisms colonise mangrove roots such as sponges, clams, algae and oysters. In India, important mangrove areas are in the Sundarban, Bhitarkanika, Krishna and Godavari delta of Andhra Pradesh, Andaman and Nicobar Islands, Gulf of Kachchh, and the Pichavaram-Vedaranyam area of Tamil Nadu coast ( see Singh et al. 2015). The coastal zone of the mainland of India and that of Andaman and Nicobar Islands is endowed with the presence of extensive and diverse mangroves. The Sundarbans mangrove forest, one of the largest such forests in the world, lies on the delta of the Ganges, Brahmaputra and Meghna rivers on the Bay of Bengal. The area is known for its wide range of fauna, including 260 bird species, the Bengal tiger and other threatened species such as the estuarine crocodile and the Indian python.

Summary

• Biomes are large geographical regions of earth such as tundra or tropical grasslands and savannas which have characteristics types of biotic communities.
• The WWF biome classification divides terrestrial world into eight biogeographic realms and 14 biomes.
• Tropical and Subtropical Moist Forests, dominated by semi-evergreen and evergreen deciduous tree species, are distributed in the Amazon basin in South America, the Congo basin and other lowland regions in Africa, and on the mainland and the islands of Southeast Asia, and the Northern tip of Australia.
• Tropical and Subtropical Dry Forests occur in climates that are warm year-round, and may receive several hundred centimeters of rain per year, exhibit long dry seasons that varies with geographic location.
• Tropical and Subtropical Coniferous Forests, occur predominantly in North and Central America, are characterized by diverse species of conifers.
• Temperate broadleaf and mixed forests is one of the major biome on Earth; species such as oak (Quercus spp.), beech (Fagus spp.), birch (Betula spp.), and maple (Acer spp.) are the main components in these forests.
• Boreal coniferous forests are found between 50 °N to 70 °N and are conditioned by long dry, cold winters and short, warm summers.
• The Tropical and Subtropical Grasslands, Savannas, and Shrublands biome is characterized by rainfall levels ranging from 90-150 cm per year; savannas in Africa have world’s richest fauna of grazers and browsers.
• The main temperate grasslands include the pampas of South America, the steppes of Eurasia, prairies of North America, and the veld in Southern Africa.
• Montane grasslands and shrublands are located above the tree line, and occur in mountainous regions around the world. They are tropical, subtropical, and temperate.
• The tundra is a treeless polar desert found in the high latitudes in the Polar Regions, the vegetation is composed of sedges and heaths as well as dwarf shrubs.
• The Mediterranean-type biome is characterized by hot and dry summers, while winters tend to be cool and moist. Most plants are fire adapted, and dependent on this disturbance for their persistence.
• Deserts occur in latitudes from 25–35° north and south of the equator,evaporation exceeds rainfall; rainfall less than less than 250 mm per year. Many deserts, such as the Sahara in Africa, are hot all year-round, whereas Asia’s Gobi, become quite cold in winter.
• Mangroves occur in the waterlogged, salty soils of the tropical coastlines of Asia, Australia and Americas.

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