The document discusses several key biogeochemical cycles - carbon, oxygen, nitrogen, sulfur, phosphorus - and how they function in ecosystems. It also covers energy flow through ecosystems. Some key points: 1. Biogeochemical cycles circulate essential nutrients through biotic and abiotic components of ecosystems. This maintains the supply and circulation of nutrients that ecosystems depend on. 2. Carbon, oxygen and nitrogen cycles are gaseous nutrient cycles, with the atmosphere and oceans as main reservoirs. Sedimentary nutrient cycles include sulfur and phosphorus, with soil, rocks and minerals as primary sources. 3. Energy from the sun drives biogeochemical cycles and flows through ecosystems via photosynthesis, food chains,

1. Raymond C. Baldonado
Biogeochemical Cycles

2. Biogeochemical Cycles
• Nutrients and water are essential for
ecosystems to continue functioning
• Living organisms need 30-40 elements for
normal development
• The chemical elements or nutrients flow from
the nonliving to the living and back to the
nonliving components of the ecosystem in a
more or less cyclic path

3. Biogeochemical Cycles
• Nutrients that are required by organisms,
primarily autotrophs, may be classified into:
1. Macronutrients- are required in relatively
large amounts and they include:
 Carbon, Hydrogen, Oxygen, Nitrogen,
Potassium, Calcium, Magnesium and Sulfur
and Phosphorus

4. Biogeochemical Cycles
2. Micronutrients- are required in small
quantities, among the are:
 Iron, Manganese Copper, Zinc, Boron, Sodium
and so on
• These nutrients have to cycle in ecosystems
because the continued functioning and
maintenance of an ecosystem depends on the
supply and circulation of these nutrients

5. Biogeochemical Cycles
Biogeochemical cycles have two basic types:
1. Gaseous Nutrient Cycle- the main source of
nutrients are the atmosphere and the oceans.
The gases which are most important for life
are nitrogen, oxygen and carbon dioxide
These three gases in stable quantities of 78%,
21% and 0.03%, respectively
Example: Nitrogen, Oxygen and Carbon Cycles

6. Biogeochemical Cycles
2. Sedimentary Nutrient Cycle- the main sources
are soil, rocks and minerals
The mineral elements that living organisms
require come initially from inorganic sources
Mineral salts come directly from the Earth’s
crust through weathering
Example: Sulfur Cycle, Phosphorus Cycle

7. Biogeochemical Cycles
• Both Gaseous and Sedimentary Nutrient
Cycles involve biological and non biological
processes
• Both are driven by the flow of energy through
the ecosystem
• Both are tied to Water/Hydrologic Cycle

8. CARBON CYCLE

9. Carbon Cycle
• Carbon is the basic building block element of
large molecules necessary for life
The source of carbon for plants is the carbon
dioxide in the atmosphere and dissolved
carbon dioxide in water
Carbon also occurs in the earth’s crust as
carbonate rocks such as limestone
Volcanos can return carbon dioxide to the air
and water during eruptions

10. Carbon Cycle
 The carbon is converted from carbon dioxide into
sugars by green plants and into organic molecules by
photosynthesis
 From there the carbon is transferred through ingestion
along the food chains to herbivores and carnivores
 At each stage part of the carbon stored in the complex
food molecules is broken down through respiration to
release energy and carbon is cycled back as carbon
dioxide to the air and water
 The remaining carbon is returned to the air and water
when an organisms die and decay

13. OXYGEN CYCLE

14. Oxygen cycle
• It is the most important element of the human
body, makes up about 65% of the mass of the
human body
• The three main reservoirs are the air,
ecosystems and Earth’s crust
• The main driving factor of the oxygen cycle is
the process of photosynthesis
• The oxygen cycle is interconnected with the
carbon dioxide

15. Oxygen cycle
The autotrophs uses carbon dioxide, water
and sunlight to produce food and releases
oxygen to the atmosphere
The animals then breathe in the oxygen and
breathe out carbon dioxide that is needed
again by the plants in manufacturing food
Decaying matters release carbon dioxide that
also used by the plants for photosynthetic
process

18. NITROGEN CYCLE

19. Nitrogen Cycle
• Nitrogen is an important element because it is
a constituent of some biological molecules
Most of the nitrogen in living organisms does
not enter directly from the atmosphere.
Instead, the nitrogen fixing bacteria in the
soil, algae in water and in roots of leguminous
plants converted the gaseous nitrogen into
nitrates, some are fixed by lightning

20. Nitrogen Cycle
These nitrate salts dissolve in soil water and are
absorbed by plants and converted into nucleic
acids and proteins
When animals (herbivores) feed on these plants,
some nitrogen is passed to the animals and
eventually to other animals (carnivores)
When the organisms die their nitrogen is
converted to ammonia gas and soluble
ammonium salts by saprotrophic fungi and
bacteria

21. Nitrogen Cycle
These are converted by nitrifying bacteria
either into nitrite the to nitrate
Plants can absorb the dissolved ammonium or
the nitrate to begin the nitrogen cycle again
Some of the nitrate is converted to nitrogen
by denitrification of bacteria

24. Nitrogen Cycle
Four Special Processes involved in the Nitrogen
Cycle:
1. Nitrogen fixation
Atmospheric nitrogen is converted to nitrates
Accomplished physio-chemically and by nitro-
fixing bacteria
2. Aminification
Nitrates are converted to ammonia and ammonia
compounds
Accomplished by bacteria and fungus of decay

25. Nitrogen Cycle
• Four Special Processes involved in the Nitrogen
Cycle:
3. Nitrification
Ammonia compounds and ammonia are
converted to nitrates
Accomplished by nitrite and nitrate bacteria
4. Denitrification
Nitrates are converted to atmospheric nitrogen
Accomplished by denitrifying bacteria

26. SULFUR CYCLE

27. Sulfur Cycle
• Sulfur has both gaseous and sedimentary
phases
• Sedimentary sulfur comes from the weathering
of rocks, runoff and decomposition of organic
matter
• Gaseous sulfur are from decomposition of
organic matter, evaporation of oceans and
volcanic eruptions

28. Sulfur Cycle
A significant portion of the sulfur released to
the atmosphere is a by-product of the burning
of fossil fuels
Sulfur enters the atmosphere mostly as
hydrogen sulfide, which quickly oxidizes to
sulfur dioxide
Sulfur dioxide reacts with moisture in the
atmosphere to form sulfuric acid, carried to
Earth in precipitation

29. Sulfur Cycle
Plants incorporate it into sulfur-bearing amino
acids
Consumption, excretion and death carry sulfur
back to soil and aquatic sediments, where
bacteria release it in inorganic form

32. PHOSPHORUS CYCLE

33. Phosphorus Cycle
• In living organisms phosphorus is an
important component of nucleic acids, cell
membranes, teeth and bones
• This cycle is interesting because unlike the
previous cycles, it lacks an atmospheric
component
• The major reservoir is sedimentary rock in the
earth’s crust

34. Phosphorus Cycle
Phosphorus is absorbed by plants from the
soil as dihydrogenphosphate or
hydrogenphosphate
It is then passed to animals, that is, herbivores
and then carnivores.
It is eventually returned to the soil, rivers and
oceans as animal excretion or through
decomposition after death

37. Biogeochemical Cycles are
Interconnected

38. Biogeochemical Cycles are Linked
• The nutrients that cycle are all components of
living organisms, constituents of organic matter
• The stoichiometric relationships among various
elements involved in plant processes related to
carbon uptake and plant growth have an
important influence on the cycling of nutrients in
ecosystems
• Interconnection of different biogeochemical
cycles may always lead to equilibrium state within
the biosphere

40. Energy Flow in the Ecosystem

41. Energy
• Energy is a very mysterious concept
• It is involved in every single event in the
universe from the humans to photons
• Energy is everywhere
• Energy never appears from or disappears into
nothing
• Energy can always be counted for

42. Energy Concept
• Earth is an open system
• For life to exist, the earth must constantly receive
inputs of energy from the sun and make outputs
of heat energy
• Energy from the sun maintains all of the life
processes in the earth ecosystem
• Only 50% of the sunlight reaching the earth’s
upper atmosphere to earth’s surface
• Heat from the earth is constantly rising and
passing to outer space

43. Energy Concept

44. Energy Flow
 In every ecosystem, the main source of energy is the
sunlight or solar radiation
 Light energy enters the ecosystem when it is absorbed
by plants
 It is the passed through the ecosystem as food plants
for animals that consume each other
 Energy absorbed and transferred through the
ecosystem in this way is eventually converted into heat
 This heat, which is exactly equivalent to the solar input,
finally leaves the ecosystem and is lost in space

45. Solar energy
•Energy used in
photosynthesis
Food
production and
consumption •Energy lost in
respiration
Heat
Energy Input
Ecosystem
Energy output

46. Energy Flow
All energy are controlled by two very general
laws: Two Laws of Thermodynamics
1. First Law of Thermodynamics
• States that energy can be transformed from one
form to another but can never be created nor
destroyed
2. Second Law of Thermodynamics
• States that each time energy is transformed, it
tends to go to from a more organized and
concentrated form to a less organized and more
dispersed form

47. Food Chains
• Through this process, food energy flow in
ecosystem
Two Major Food Chains:
1. Grazing food chain- is where energy is passed
through living organisms and is represented as:
Plant—Animal--Animal
2. Detritus food chain- is where energy is passed
from dead organisms or organic matter to
decomposers and is represented as:
Dead matter--Decomposer

49. Trophic Levels
• In ecosystem, organisms that obtain food from
plants by the same number of steps are said to
belong to same trophic level
Green plants occupy the first trophic level
Herbivores are in the second trophic level
Carnivores are in the third trophic level
Tertiary consumers are in fourth trophic level
Decomposers can belong to any trophic level
depending on their food sources

51. Ecological Energy Pyramid
• Pyramid of energy shows the flow of energy in
the trophic levels
• It is always upright, that is, it can never be
inverted because of the Second Law of
Thermodynamics about transformation or
transfer of energy
• There can never be the same amount or more
energy flowing or being passed from a lower
trophic level to the next upper trophic level

53. Human Implication to:
Water Cycle
Biogeochemical Cycle
Energy Flow

54. Human Implication on
the Water Cycle and
Biogeochemical Cycle
A. Human disturbance of the
Nutrient Cycle
B. Increase in volume and rate of
nutrient cycle
C. Increase in volume and decrease
in rate of nutrient cycle
D. Reduction in volume and
increase in rate of nutrient cycle
E. Reduction in volume and rate of
nutrient cycle
F. Addition of synthetic materials
to the nutrient cycle
G. Collapse of the nutrient cycle

55. Roles of Water in
Biogeochemical
Cycles
1. Dissolved nutrients are carried
from the earth’s surface either into
the ground or into the ocean
2. Atmospheric nutrients are often
brought to the earth’s surface in
rainwater
3. Nutrients held in rocks are
gradually released by weathering
accomplished by rain, by erosion
through flowing water and by
freezing and defrosting ice
4. Nutrients are usually dissolved in
water when they are absorbed into
the roots of plants
5. Water is critical in accomplishing
the various chemical changes that
nutrients undertake as they pass
thru the bio phase of their cycle

56. 1. Keeps the earth warm enough
so that chemical reactions are
possible
2. Makes it possible for living
organisms to carry on their vital
processes
3. Powers the atmospheric,
geological and water cycles
4. Energy is needed by the plants
to pump water and
consequently to extract
dissolved nutrients from the soil
5. Bacteria require considerable
amount of energy to carry out
their vital processes and thereby
change nutrients from one form
to another
Functions of Energy
Flow in Facilitating
Biogeochemical Cycles

57. 1. The effect of humans on net
primary productivity is generally
to reduce the productivity of
wild system and to increase that
of cultivated system
2. Energy intensification in
cropping has been accompanied
by a substitution of fossil fuels
for human and animal power
3. In forest system, there is a
varying relationship between
crop maturity and economic
return
Human Implication to
Energy Flow