Terrestrial ecosystem

its a presentation on the key aspects of Terrestrial Ecosystem. Its types, characters, soil horizon, soil microflora . Its curated specifically to help environmental microbiology students to ubderstand the key aspects of various Eco biomes . Hope it helps the students and faculties to grasp the knowledge and spread among people, the awareness to protect our precious Ecosystem .

1. T errestrial Ecosystem Mr. Abhirup Ganguli Assistant Professor Dept. of Biotechnology Swami Vivekananda Institute of Modern Sciences 1

2. A terrestrial ecosystem is a type of ecosystem found only on landforms. Five major terrestrial ecosystems exist: Tundra Taiga Forest Grassland Deserts. 2

3. Tundra: Two types of tundra exist: arctic and alpine . The Arctic tundra is located in the Arctic Circle, north of the boreal forests. Alpine tundras occur on mountain tops. Both types experience cold temperatures throughout the year. Because the temperatures are so cold, only the top layer of soil in this terrestrial environment thaws during the summer; the rest of it remains frozen year round, a condition known as permafrost. Plants in the tundra are primarily lichens, shrubs, and brush. Tundras do not have trees. Most animals that live in the tundra migrate south or down the mountain for the winter. 3

4. Alpine Tundra Arctic Tundra 4

5. Taiga Ecosystems: Another type of forest ecosystem is the taiga, also known as northern coniferous forest or boreal forest. It covers a large range of land stretching around the northern hemisphere. It is lacking in biodiversity, having only a few species. Taiga ecosystems are characterized by short growing seasons, cold temperatures, and poor soil. This terrestrial environment has long winter days and very short summer days. Animals found in the taiga include lynx, moose, wolves, bears and burrowing rodents. 5

6. Taiga Biome in Winter Season Taiga Biome in Summer Season 6

7. Forest Ecosystems: About one third of the Earth's land is covered in forest. The primary plant in this ecosystem is trees. Forest ecosystems are subdivided by the type of tree they contain and the amount of precipitation they receive. Some examples of forests are temperate deciduous, temperate rainforest, tropical rainforest, tropical dry forest and northern coniferous forests. Tropical dry forests have wet and dry seasons, while tropical rain forests have rain year-round. Both of these forests suffer from human pressure, such as trees being cleared to make room for farms. Because of the copious amounts of rain and favorable temperatures, rainforests have high biodiversity. 7

8. Tropical Rainforest Temperate Deciduous Forest 8

9. Grassland Ecosystems Temperate grasslands include prairies and steppes. They have seasonal changes, but don't get enough rainfall to support large forests. Savannas are tropical grasslands. Savannas have seasonal precipitation differences, but temperatures remain constant. Grasslands around the world have been converted to farms, decreasing the amount of biodiversity in these areas. The prominent animals in grassland ecosystems are grazers such as gazelle and antelope. 9

10. Savanna Grassland 10

11. Desert Ecosystems: The amount of rainfall is the primary abiotic determining factor of a desert ecosystem. Deserts receive less than 25 centimeters (about 10 inches) of rain per year. Large fluctuations between day and night temperature characterize a desert's terrestrial environment. The soils contain high mineral content with little organic matter. The vegetation ranges from nonexistent to including large numbers of highly adapted plants. 11

12. The Sonora Desert ecosystem contains a variety of succulents or cactus as well as trees and shrubs. They have adapted their leaf structures to prevent water loss. For instance, the Creosote shrub has a thick layer covering its leaves to prevent water loss due to transpiration. One of the most famous desert ecosystems is the Sahara desert, which takes up the entire top area of the African continent. The size is comparable to that of the entire United States and is known as the largest hot desert in the world with temperatures reaching over 122 degrees Fahrenheit. 12

13. Sahara Desert Algeria Gobi Desert Mongolia 13

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15. Soil Profile: Formation of Soil: The soil has taken thousands of years to form. Soil formation takes place in the following ways: Big rocks break down into smaller rocks by continuous action of wind and rain. It takes many years for these rocks to break down into smaller rocks. Rocks are mainly broken by two types of weathering- physical weathering and chemical weathering. A number of natural force, called agents, work to break down the parent rock into tiny particles of soil. 15

16. These agents include wind, water, the sun’s heat, and plants and animals. These pieces get further broken down to form sand and silt and, ultimately, into finer particles and the process continues. This process is very slow. It takes thousands of years to form a just 1cm layer of soil. These fine particles form the top layer of the soil. Components of Soil Profile: A soil horizon makes up a distinct layer of soil. The horizon runs roughly parallel to the soil surface and has different properties and characteristics than the adjacent layers above and below. 16

17. The soil profile is a vertical section of the soil that depicts all of its horizons. The soil profile extends from the soil surface to the parent rock material. The regolith includes all of the weathered material within the profile. The regolith has two components: the solum and the saprolite . The solum includes the upper horizons with the most weathered portion of the profile. The saprolite is the least weathered portion that lies directly above the solid, consolidated bedrock but beneath the regolith. 17

18. Horizons of the Soil: There are 5 master horizons in the soil profile. Not all soil profiles contain all 5 horizons; and so, soil profiles differ from one location to another. It consists of the following horizons: O) Organic surface layer: Litter layer of plant residues, the upper part often relatively undecomposed , but the lower part may be strongly humified . A) Surface soil: Layer of mineral soil with most organic matter accumulation and soil life. Additionally, due to weathering, oxides (mainly iron oxides) and clay minerals are formed and accumulated. 18

19. It has a pronounced soil structure. But in some soils, clay minerals, iron, aluminium, organic compounds, and other constituents are soluble and move downwards. When this eluviation is pronounced, a lighter coloured E subsurface soil horizon is apparent at the base of the A horizon. A horizons may also be the result of a combination of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil. In this case, the A horizon is regarded as a " biomantle ". 19

20. B) Subsoil: This layer has normally less organic matter than the A horizon, so its colour is mainly derived from iron oxides. Iron oxides and clay minerals accumulate as a result of weathering. In a soil, where substances move down from the topsoil, this is the layer where they accumulate. The process of accumulation of clay minerals, iron, aluminium and organic compounds, is referred to as illuviation. The B horizon has generally a soil structure. 20

21. C) Substratum: Layer of non- indurated poorly weathered or unweathered rocks. This layer may accumulate the more soluble compounds like CaCO 3 . Soils formed in situ from non- indurated material exhibit similarities to this C layer. 21

22. R) Bedrock: R horizons denote the layer of partially weathered or unweathered bedrock at the base of the soil profile. Unlike the above layers, R horizons largely comprise continuous masses (as opposed to boulders) of hard rock that cannot be excavated by hand. Soils formed in situ from bedrock will exhibit strong similarities to this bedrock layer. 22

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24. View of a road cut in Maui. Road cuts are excellent ways to observe the layers, or horizons, within a soil profile. This particular soil profile is well developed and consists of many layers. 24

25. Illustrated differences in soil profiles. The soil profile at the left is the Hamakuapoko Series, which is an old soil with distinct profile development. The soil profile at the right is the Keahua Series. The Keahua Series is an arid soil, which also shows two horizons in the soil profile. 25

26. Soil Microflora: Microorganisms are very small forms of life that can sometimes live as single cells, although many also form colonies of cells. A microscope is usually needed to see individual cells of these organisms. Many more microorganisms exist in topsoil, where food sources are plentiful, than in subsoil. They are especially abundant in the area immediately next to plant roots (called the rhizosphere), where sloughed-off cells and chemicals released by roots provide ready food sources. These organisms are primary decomposers of organic matter, but they do other things, such as provide nitrogen through fixation to help growing plants, detoxify harmful chemicals (toxins), suppress disease organisms, and produce products that might stimulate plant growth. Soil microorganisms have had another direct importance for humans—they are the source of most of the antibiotic medicines we use to fight diseases. 26

27. Bacteria Bacteria live in almost any habitat. They are found inside the digestive system of animals, in the ocean and fresh water, in compost piles (even at temperatures over 130°F), and in soils. Although some kinds of bacteria live in flooded soils without oxygen, most require well-aerated soils. In general, bacteria tend to do better in neutral pH soils than in acid soils. In addition to being among the first organisms to begin decomposing residues in the soil, bacteria benefit plants by increasing nutrient availability. For example, many bacteria dissolve phosphorus, making it more available for plants to use.  Bacteria are also very helpful in providing nitrogen to plants, which they need in large amounts but is often deficient in agricultural soils. 27

28. You may wonder how soils can be deficient in nitrogen when we are surrounded by it—78% of the air we breathe is composed of nitrogen gas. Yet plants as well as animals face a dilemma similar to that of the Ancient Mariner, who was adrift at sea without fresh water: “Water, water, everywhere nor any drop to drink.” Unfortunately, neither animals nor plants can use nitrogen gas (N 2 ) for their nutrition. However, some types of bacteria are able to take nitrogen gas from the atmosphere and convert it into a form that plants can use to make amino acids and proteins. This conversion process is known as nitrogen fixation . 28

29. Some nitrogen-fixing bacteria form mutually beneficial associations with plants. One such symbiotic relationship that is very important to agriculture involves the nitrogen-fixing rhizobia group of bacteria that live inside nodules formed on the roots of legumes. These bacteria provide nitrogen in a form that leguminous plants can use, while the legume provides the bacteria with sugars for energy. People eat some legumes or their products, such as peas, dry beans, and tofu made from soybeans. Soybeans, alfalfa, and clover are used for animal feed.  Clovers and hairy vetch are grown as cover crops to enrich the soil with organic matter, as well as nitrogen, for the following crop. 29

30. In an alfalfa field, the bacteria may fix hundreds of pounds of nitrogen per acre each year. With peas, the amount of nitrogen fixed is much lower, around 30 to 50 pounds per acre. The actinomycetes, another group of bacteria, break large lignin molecules into smaller sizes. Lignin is a large and complex molecule found in plant tissue, especially stems, that is difficult for most organisms to break down. Lignin also frequently protects other molecules like cellulose from decomposition. Actinomycetes have some characteristics similar to those of fungi, but they are sometimes grouped by themselves and given equal billing with bacteria and fungi. 30

31. Fungi Fungi are another type of soil microorganism. Yeast is a fungus used in baking and in the production of alcohol. Other fungi produce a number of antibiotics. We have all probably let a loaf of bread sit around too long only to find fungus growing on it. We have seen or eaten mushrooms, the fruiting structures of some fungi. Farmers know that fungi cause many plant diseases, such as downy mildew, damping-off, various types of root rot, and apple scab. Fungi also initiate the decomposition of fresh organic residues. They help get things going by softening organic debris and making it easier for other organisms to join in the decomposition process. Fungi are also the main decomposers of lignin and are less sensitive to acid soil conditions than bacteria. 31

32. None are able to function without oxygen. Low soil disturbance resulting from reduced tillage systems tends to promote organic residue accumulation at and near the surface. This tends to promote fungal growth, as happens in many natural undisturbed ecosystems. Many plants develop a beneficial relationship with fungi that increases the contact of roots with the soil. Fungi infect the roots and send out root-like structures called hyphae (see figure). The hyphae of these mycorrhizal fungi take up water and nutrients that can then feed the plant. The hyphae are very thin, about 1/60 the diameter of a plant root, and are able to exploit the water and nutrients in small spaces in the soil that might be inaccessible to roots. 32

33. This is especially important for phosphorus nutrition of plants in low-phosphorus soils. The hyphae help the plant absorb water and nutrients, and in return the fungi receive energy in the form of sugars, which the plant produces in its leaves and sends down to the roots. This symbiotic interdependency between fungi and roots is called a mycorrhizal relationship. All things considered, it’s a pretty good deal for both the plant and the fungus. The hyphae of these fungi help develop and stabilize larger soil aggregates by secreting a sticky gel that glues mineral and organic particles together. 33

34. Algae Algae, like crop plants, convert sunlight into complex molecules like sugars, which they can use for energy and to help build other molecules they need. Algae are found in abundance in the flooded soils of swamps and rice paddies, and they can be found on the surface of poorly drained soils and in wet depressions. Algae may also occur in relatively dry soils, and they form mutually beneficial relationships with other organisms. Lichens found on rocks are an association between a fungus and an alga. 34

35. Protozoa Protozoa are single-celled animals that use a variety of means to move about in the soil. Like bacteria and many fungi, they can be seen only with the help of a microscope. They are mainly secondary consumers of organic materials, feeding on bacteria, fungi, other protozoa, and organic molecules dissolved in the soil water. Protozoa—through their grazing on nitrogen-rich organisms and excreting wastes—are believed to be responsible for mineralizing (releasing nutrients from organic molecules) much of the nitrogen in agricultural soils. 35

36. Relative amounts of bacteria and fungi: All soils contain both bacteria and fungi, but they may have different relative amounts depending on soil conditions. The general ways in which you manage your soil—the amount of disturbance, the degree of acidity permitted, and the types of residues added—will determine the relative abundance of these two major groups of soil organisms. Soils that are disturbed regularly by intensive tillage tend to have higher levels of bacteria than fungi. So do flooded rice soils, because fungi can’t live without oxygen, while many species of bacteria can. Soils that are not tilled tend to have more of their fresh organic matter at the surface and to have higher levels of fungi than bacteria. 36

37. Because fungi are less sensitive to acidity, higher levels of fungi than bacteria may occur in very acid soils. Despite many claims, little is known about the agricultural significance of bacteria versus fungal-dominated soil microbial communities, except that bacteria-prevalent soils are more characteristic of more intensively tilled soils that tend to also have high nutrient availability and enhanced nutrient levels as a result of more rapid organic matter decomposition. 37

38. Mycorrhizal fungi Mycorrhizal fungi help plants take up water and nutrients, improve nitrogen fixation by legumes, and help to form and stabilize soil aggregates. Crop rotations select for more types of and better performing fungi than does mono cropping. Some studies indicate that using cover crops, especially legumes, between main crops helps maintain high levels of spores and promotes good mycorrhizal development in the next crop. Roots that have lots of mycorrhizae are better able to resist fungal diseases, parasitic nematodes, drought, salinity, and aluminum toxicity. Mycorrhizal associations have been shown to stimulate the free-living nitrogen-fixing bacteria azotobacter , which in turn also produce plant growth–stimulating chemicals. 38

39. THANK YOU 39