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. TERRESTRIAL 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:
i. Tundra
ii. Taiga
iii. Forest
iv. Grassland
v. Deserts.
2

3.  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.  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.  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.
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8. Tropical Rainforest
Temperate Deciduous
Forest
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9.  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.
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10. Savanna Grassland 10

11.  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.
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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.
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13. Sahara Desert
Algeria
Gobi Desert
Mongolia
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14. 14

15. SOIL PROFILE:
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.
 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. 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 CaCO3.
 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

23. 23

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.
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26.  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.
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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.
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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 (N2) 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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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39. THANK YOU
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