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1. Details of Module and its Structure

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Subject Name Botany

Paper Name

Module Name/Title

Module Id < Major Terrestrial Biomes >

Pre-requisites

Objectives Biomes>

Keywords , ,

Structure of Module / Syllabus of a module (Define Topic / Sub-topic of module )

Terrestrial Ecosystem ,, ,,,< Conifer forrest>,< Tundra> ,

2. 2. Development Team

Role Name Affiliation

National Coordinator

Subject Coordinator < Prof. Sujata Bhargava >

Paper Coordinator < N.S.R. Krishnayya >

Content Writer/Author (CW) < Swati Diwakar >

Content Reviewer (CR) Language Editor (LE)

TABLE OF CONTENTS

Introduction

1. Tropical Forests

(i) Tropical Rain Forest

(ii) Tropical Dry Forest

2. Tropical Savanna

3. Temperate Grassland

4. Dessert

5. Temperate Shrubland

6. Temperate Forest

7. Conifer forrest

8. Tundra

9. References

e-Text Major Terrestrial Biomes

INTRODUCTION Terrestrial ecosystems can be grouped into broad categories called biomes. Ecologists F. E Clements and V. E. Shelford in 1939 coined the term Biomes for regions with similar distribution of plant, animals and environmental conditions. Biome is one of the largest recognizable ecological units on Earth. There are eight major terrestrial biomes: i. Tropical forest ii. Tropical Savanna iii. Temperate grasslands iv. Desert v. Chaparral (shrublands) vi. Temperate forest vii. Conifer forest (Taiga or boreal forest) and viii. Tundra Figure 1: Biomes on Earth

FIGURE 1 The distribution of the biomes types is influenced by the mean annual temperature and mean annual precipitation (Figure 1 and 2). Boundaries between the biome are broad and merge into each other. These categories reflect the relative contribution of three general plant life-forms: Trees, Shrubs and Grasses. These plant forms represent adaptations under different environmental conditions. Within the broad classes of forest ecosystems, leaves are classified into two categories based upon their existence on the trees: Deciduous (leaves that live for only a single growing season or year and Evergreen (leaves that live beyond a year). Similarly, Evergreen leaf types are also classified into two categories: broadleaf type characteristic of tropical rain forests and needle-leaf type characteristic of environment with short growing seasons.

Figure 2: Distribution of World’s major Terrestrial Biomes

1. Tropical forests (i) Tropical Rain Forests Ecosystems characteristic of warm, wet climates with no distinct seasonality are dominated by broadleaf evergreen trees and are called tropical rain forest (Figure 3). The tropical rainforests of the world are famous for the greatest number of plants and animals than any other biome on Earth. Tropical forests characterize the equatorial zone. These are found in tropical America, west Africa, Congo basin of Africa and in the Indo-Malayan region of Asia. Climate: Tropical rain forests are restricted to warm temperatures and high rainfall areas in equator between 10° North and South. Average temperatures range from 25-27° C and it varies little from month to month. Annual rainfall ranges from about 2000-4000 mm. Vegetation: Most plants growing in tropical rainforests are woody-stemmed trees and climbers. The tropical rainforest is a broad-leaved evergreen forest with a complex, multi-storeyed structure. The vertical

structure of the forest is divided into five general layers: emergent trees, high upper canopy, low tree stratum, shrub understory and a ground layer of herbs and ferns. Conspicuous in the rain forest are the lianas or climbing vines, epiphytes growing up in trees and stranglers growing downward from the canopy to the ground. Many large trees develop buttresses for support. Tropical rain forest supports high levels of primary productivity.

Figure 3: Tropical Rain Forest Animal life: Tropical rain forest harbours a great diversity of plants and animals. It covers only 6% of the land surface but accounts for >50 % of all known plants and animal species. The richest area is the lowland tropical forest of peninsular Malaysia containing around 7900 species. Soil: Rainforest soil are nutrient poor, acidic, thin and low in organic matter as the heavy rains leach nutrients from rain forests soils and rapid decomposition in the warm, moist rain forest climate keeps the soil organic matter low. Soils are oxisols characterised by advanced weathering and so have high clay content, deficient in calcium and phosphorus. Tropical soils tend to be bright red in both A and B horizon due to oxides of iron along with oxides of aluminium and manganese.

(ii) Tropical Dry Forests Tropical dry forest includes semi-evergreen, dry evergreen, semi deciduous forests. This is a series of plant communities along an environmental gradient toward increasing aridity. Tropical dry forests of all types are found in climate regions that are warm year round and experience several months of severe drought during low sun period. They are often neglected as attention focuses on

the wet evergreen forests of the tropics. They deserve treatment as separate biome because it hosts a different group of plants and animals that do either neighboring tropical savannas or rainforests.

Figure 4: Tropical Dry Forest The broadleaf evergreen forests are replaced by the dry tropical forests. Dry tropical forests undergo varying lengths of dry season. During the dry season, the drought deciduous trees and shrubs drop their leaves (Figure 4). New leaves are grown at the onset of the rainy season. The largest proportion of tropical dry forest is found in Africa and South America. Most dry tropical forests have been lost to agriculture and grazing and other disturbances.

2. Tropical Savanna Tropical Savannas are characteristic of semiarid regions with seasonal rainfall. The term Savannas is used to describe range of vegetation types in the drier tropics and subtropics (Figure 5). Climate: Tropical savannas occur north and south of tropical dry forests within 10° to 20° North & South of the equator. Savannas are associated with a warm continental climate with distinct seasonality in precipitation and a large variation in total rainfall per year. Seasonal drought combines with another important physical factor, fire. Fire helps maintain the tropical savannah as a landscape of grasslands and scattered trees.

Figure 5: Tropical Savanna Vegetation: It is characterized by a vegetation cover of grasses with scattered shrubs or trees. Such vegetation is characteristics of regions with alternating wet and dry seasons. Frequent fires have selected for fire resistance in the savanna flora. Savannas are characterised by two layer vertical structure due to the ground cover of grasses and the presence of shrubs or trees. Productivity and decomposition is savanna ecosystems are closely tied to the seasonality of precipitation. Animal life: Savannas support a large variety of herbivores. The tropical savanna is populated by wandering animals that move in response to seasonal and year-to year variations in rainfall and food availability. The African Savanna is dominated by a large and diverse ungulate fauna of atleast 60 species such as wildebeest, giraffes, and zebras. The wandering consumers of the Australian savannas include kangaroos. Living on the herbivore fauna are large number of carnivores such as Lion, leopard, cheetah and Hyena. Soil: Deeply weathered, low nutrient acidic soil are characteristic of such biomes.

3. Temperate Grasslands The natural grasslands of the world occur in the multitudes in midcontinent regions, where annual precipitation declines as air masses move inward from the coastal environments. In the northern hemispheres, examples of such regions are Prairies of North America and Steppes of central Eurasia. In the southern hemisphere, grasslands are represented by the pampas of Argentina and veldt of high plateaus of southern Africa.

Figure 6: Temperate Grassland Climate: Natural grasslands occupy regions where rainfall ranges from 25-80 cm per year. The temperate grasslands climate is one of the recurring droughts and the diversity of vegetation cover reflects the difference in the amount of rainfall. The maximum precipitation usually occurs in summer during the height of the growing season. The grasslands are tallest and most productive where mean annual precipitation is greater than 800 mm and mean annual temperature in above 15° C winters in temperate grasslands are generally cold and summers are hot. Vegetation: The most visible feature of grassland is tall, green and short lived herbaceous growth that develops in springs and dies in autumn (Figure 6). Drought and high summer temperatures encourage fires. Grassland consists of an ephemeral herbaceous layer that arises from crowns, nodes and rosettes of plants hugging the ground. The height of the vegetation varies from about 5cm in dry, short grass prairies to over 200 cm in the wetter, tall grass prairies. The ground layer and below ground root layer are the other two major strata of grasslands. They have highly developed roots layer that extend deep into the soil. Animal Life: Grasslands support a diversity of animal life with both invertebrate and vertebrate herbivores including grazing ungulates and burrowing mammals. The Prairies were once dominated by migratory herds of bison (Bison bison), prong horn antelope (Antilocarpa americana) and prairie dog (Cynomys sp.). Pampas deer (Ozotoceros bezoarticus) and guanaco (Lama guanicoe) are the two major herbivores in pampas. The African grassveldt once supported migratory herd of

wildebeest (Connochatetes taurinus) and Zebra along with their carnivores such as Lion (Panthera leo), leopard (Panthera pardus). Soil: Temperate grassland soils are derived from a variety of parent materials. The best temperate soils are deep, basic or neutral, and fertile and contain large quantities of organic matter. Dominant soil: Mollisol.

4. Desert Deserts are structurally simple-scattered shrubs, ephemeral plants and open, stark topography. Climate: The arid regions of the world occupy from 25-35% of Earth’s landmass. Much of this lies between 15° to 30° latitude. Deserts result from dry descending air masses with in these regions, the rain shadows of coastal mountain ranges and remoteness from oceanic moisture. Temperate deserts lie in the rain shadow of mountain barriers or are located far inland where moist air from oceans rarely enters. Temperatures are high during summer but drop o freezing during winters. Lack of precipitation is the distinctive characteristics of all deserts. Water loss in deserts due to evaporation and transpiration by plants exceeds precipitation during most of the year. Desserts are differentiated based on difference in moisture, temperature, soil drainage, topography. There are hot deserts and cold deserts. Most of the arid environments are found in northern hemisphere. Sahara, the world’s largest desert is an example of hot desert. Other examples include Thar Desert in northwest India, Chihuahuan desert in Mexico, Atacama in South America. Cool deserts include great basin of North America, Gobi, Takla makan and Kara kum desert region of Turkmenistan. Similarly, the deserts of the southern hemisphere all lies within the subtropical high pressure belt that mirrors that of the northern hemisphere. Examples include Kalahari in Botswana. The most extensive region of arid land in the southern hemisphere is found in Australia where more than 40% of the land is classified as desert.

Figure 7: Desert Vegetation: The hot desert ranges from those lacking vegetation to ones with some combinations of chenopods, dwarf shrubs and succulents. (Figure 7 and 8). Areas of favorable moisture support tall growths of acacia sp, saguaro, yucca and ephemeral plants. Both plants and animals adapt to the scarcity of water by either drought evasion or drought resistance. Desert plants may be deep rooted woody shrubs such as prosopis and tamarix. Other perennials have shallow roots that extend no more than a few centimeters below the surface. The infrequent rainfall along with high rates of evaporation limits the availability of water to plants so the primary productivity is low. Animal life: Despite their aridity, desert ecosystems support a surprising diversity of animal life such as beetles, ants, locusts, lizards, snakes birds and mammals (mostly herbivores) and carnivores such as foxes and coyotes although in low abundance. Most desert animals use behavior to avoid environmental extremes. Soils: Desert soils are generally so low in organic matter that they are sometimes classified as lithosols, which means stones or mineral soil. They contain high concentrations of salts. Most desert spoils are poorly developed aridisols and entisols.

Figure 8: Vegetation and animal life in desserts

5. Temperate shrub lands Mediterranean climates support temperate shrub lands. Temperate shrub lands are found in five widely disjunct regions along the western margins of the continents between 30 to 40 degrees latitude. Regions include areas bordering Mediterranean Sea, central Chile, cape region of south Africa and south-western and southern Australia. The wide geographic distribution of Mediterranean shrubland is reflected in the diversity of names for this biome. In western north America it is called chaparral. In Spain, the most common name is matoral, in south Africa it is called as fynbos and as mallee in Australia

Figure 9: Temperate shrub lands Figure 10: Fynbos plant

Climate: The climate is cool and moist during fall, winter and spring whereas summers are hot and dry. About 65% of rainfall takes place during winter months. Winter temperature averages from 10- 12°C with a risk of frost. The combination of dry summers and dense vegetation rich in essentials oils, creates ideal conditions for frequent and intense fires. Vegetation: These are dominated by evergreen shrubs and sclerophyllus trees that have adapted to the summer drought and cool, moist winters (Figure 9 and 10). These regions support xeric broadleaf evergreen shrubs and dwarf trees. Much of the Mediterranean region in southern Europe and northern Africa is dominated by oak and cork oak. Mediterranean shrub community in mallee is dominated by low growing eucalyptus with broad sclereophyllous leaves. The shrub community Chaparral dominated by scrub oak. Matorral shrub communities in central Chile. For the most part, these shrub lands lack understory and ground litter and are highly inflammable. Shrubs have a densely branched, woody structure and low height. Trees have thick fire resistant bark. In contrast shrubs are rich in oils and burn readily but re-sprout rapidly. Animal Life: Shrub communities support complex of animal life. Chaparral supports mule deer, coyotes and jackrabbits and sage grouse. Australia mallee is rich in mallee fowls, gray kangaroo and wallaby. Soil: Soils of Mediterranean woodlands and shrublands are generally of low to moderate fertility and are considered fragile. Soils are typically Alfisols, deficient in nutrients.

6. Temperate Forests Forest ecosystems dominate the wetter regions of the temperate zone. The largest living organisms on earth the sequoias of western north America and the giant Eucalyptus of southern Australia live in temperate forests. The deciduous forests over Europe and Asia have been cleared over centuries for agriculture. In North America, deciduous forests are still widespread. Majority of this biome lies between 40° and 50° of the equator. Climate: Temperate forests occur where temperatures are not extreme and where annual precipitation averages from about 650mm to over 3000mm. These forests generally receive more winter

precipitation than temperate grasslands. Deciduous trees usually dominate temperate forests where the growing season is moist and atleast 4 months long. Where winters are more severe or the summers drier, conifers are more abundant than deciduous trees.

Figure 11: Temperate Forest Figure 12: Giant Sequoia Vegetation: Humid mid-latitude regions are dominated by broadleaf deciduous trees (Figure 9). Mild, moist climates of the southern hemisphere temperate evergreen forests become predominant. They include various types such as beech-maple and Oak-Hickory forest. In the broadleaf deciduous forests of the temperate region the end of growing season is marked by the autumn colours of foliage shortly before the trees enter into leafless winter period. The trees resume growth in spring with increasing temperatures and day lengths. The deciduous forests usually have four vertical layers or strata. The upper canopy, lower canopy or understory, shrub layer and ground layer of herbs, ferns and mosses. Animal life: The diversity of animal life is associated with this vertical stratification. Soil: Temperate forest soils are usually fertile. They are generally neutral or slightly acidic and rich in both organic matter and inorganic nutrients. Differences in climate, bedrock have reflected in the variety of soils present: Alfisols, Inceptisols and ultisols are important

7. Conifer Forests Conifer forests dominate the cool temperature and boreal zones. The largest expanse of conifer forest or the largest vegetation formation on Earth is the boreal forest or Taiga (Russian for “land of little sticks”). This belt of coniferous forest, encompassing the high latitudes of the northern

hemisphere covers about 11% of Earth’s terrestrial surface. Conifer forests dominated by needle- leaf evergreen trees are found primarily in a broad circumpolar belt across the northern hemisphere (Figure 13). In North America, the boreal forests cover much of Alaska and Canada. In Eurasia, the conifer forests begin in Scotland and Scandinavia and extends to northern Japan covering Siberia.

Figure 13: Conifer Forest Climate: A cold continental climate with strong seasonal variation dominates taiga. The summers are short, cool and moist. Winters are long, harsh and dry with a prolonged period of snowfall. Fires are recurring events in the Taiga. Precipitation in boreal forest is moderate, ranging from about 200 to 600mm. Vegetation: In central Europe extensive coniferous forests are dominated by Norway spruce. In North America, conifer forests are dominated by spruce and fir and pine at lower elevations. Spruce, and pine dominate boreal forest with successional communities of birch and poplar. Ground cover below spruce is mostly moss; in open spruce and pine stands, the cover is mostly lichens. Taiga is also a region of cold lakes, bogs, rivers and alder thickets. All of the boreal trees both broadleaf and conifers are well adapted to fire. Compared to temperate forests, boreal forests have low Net Primary Productivity as they are limited by low nutrients, cooler temperatures and short growing season. Animal life: The boreal forest has a unique animal community. Caribou (Rangifer tarandus) inhabit open sruce- lichen woodlands. Moose (Alces alces) elk in Eurasia is the largest of all deer. Snowshoe hare

(Lepus americanus) the arboreal red squirrel, quill bearing porcupine. Preying on these are the wolf, lynx, pine martin and owls. This biome is also inhabited by black bears and grizzly bears in North America and the brown bear in Eurasia. Taiga is also the habitat of seed eating birds such as crossbills, grosbeaks, American redstart and siskins. Soil: Boreal forest soils tend to be of low fertility, thin and acidic. Soils are primarily spodosols.

8. Tundra Low precipitation and cold temperatures define arctic tundra. The name tundra comes from Finnish tunturi meaning a treeless plain. Tundra encircles the north pole. The arctic tundra extends beyond the tree line at the far north of the Northern Hemisphere. Climate: It is characterized by low precipitation, low temperature, a short growing season, a perpetually frozen subsurface (the Permafrost). At lower latitudes, alpine tundra occurs in the higher mountains of the world. Has a severe environment of rock strewn slopes, bogs, meadows, and shrubby thicket. It is a land of strong winds, snow, cold, and widely fluctuating temperatures. Precipitation in tundra varies from less than 200mm to 600mm.

Figure 14: Tundra Vegetation: The arctic tundra falls into two broad types: tundra with upto 100% plant cover and wet to moist soil and polar desert with less than 5% plant cover and dry soil (Figure 15). The number of species tends to be few and growth rates are slow. Low ground is covered with a complex of cotton grasses, sedges and sphagnum. These plants exploit the long days of summer by photosynthesizing during

the 24-hr day light period. Arctic plants propagate themselves almost entirely by vegetative means. Structurally most of the tundra vegetation is underground. Root to shoot ratio of vascular plants range from 3:1 to 10:1. The lichens are eaten by reindeer and caribou. Animal life: The tundra holds fascinating animal life, even the diversity of species is low. Invertebrates are concentrated near the surface, abundant populations of white segmented worms, collembolas, flies. Summer in the arctic tundra brings hordes of black flies and deer flies. Dominant vertebrates on the tundra are herbivores including lemmings, hare caribou, musk ox. Major carnivores are the wolf, weasels, lemmings, Arctic fox and Snowy owl. Soil: Soil formation is slow in cold tundra climate. Rates of decomposition are low and as a result organic matter accumulates in deposits of peat and humus.