1. Biogeochemical cycle
BFT 1023
Chapter-13
Dr. Md. Shafiqur Rahman
UMK

2. Biogeochemical cycles
biogeochemical cycle, any of the natural
circulation pathways of the essential
elements of living matter. These elements in
various forms flow from the nonliving
(abiotic) to the living (biotic) components of
the biosphere and back to the nonliving
again. In order for the living components of a
major ecosystem (e.g., a lake or forest) to
survive, all the chemical elements that make
up living cells must be recycled continuously.

3. Biogeochemical cycles
Each cycle can be considered as having a
reservoir (nutrient) pool—a larger, slow-
moving, usually abiotic portion—and an
exchange (cycling) pool—a smaller but more
active portion concerned with the rapid
exchange between the biotic and abiotic
aspects of an ecosystem.

4. Biogeochemical cycles
Biogeochemical cycles can be classed as
gaseous, in which the reservoir is the air or
the oceans (via evaporation), and
sedimentary, in which the reservoir is the
Earth’s crust. Gaseous cycles include those of
nitrogen, oxygen, carbon, and water;
sedimentary cycles include those of iron,
calcium, phosphorus, and other more
earthbound elements.

5. Biogeochemical cycles
Gaseous cycles tend to move more rapidly than
do the sedimentary ones and to adjust more
readily to changes in the biosphere because
of the large atmospheric reservoir. Local
accumulations of carbon dioxide, for
example, are soon dissipated by winds or
taken up by plants. Extraordinary and more
frequent local disturbances can, however,
seriously affect the capacity for self-
adjustment.

6. Biogeochemical cycles
Plants and some animals obtain their nutrient
needs from solutions in the environment.
Other animals acquire the bulk of their needs
from the plants and animals that they
consume. After the death of an organism, the
elements fixed in its body are returned to the
environment through the action of decay
organisms and become available to other
living organisms again.

7. Biogeochemical cycles
Biogeochemical Cycle : the cycling of
chemical elements required by life between
the living and nonliving parts of the
environment. Some examples of these
chemical elements are H2O, P, S, N2, O2 and
C. Or
Biogeochemical cycles: the movement (or
cycling) of matter through a system

8. Biogeochemical Cycle
These elements cycle in either a gas cycle
or a sedimentary cycle; some cycle as
both a gas and sediment.

9. Biogeochemical Cycle
Gas Cycles: Sedimentary
Carbon Phosphorus
Nitrogen Sulfur
Oxygen

10. Biogeochemical Cycle
• In a gas cycle elements move through
the atmosphere. Main reservoirs are the
atmosphere and the ocean.
• In a sedimentary cycle elements move
from land to water to sediment. Main
reservoirs are the soil and sedimentary
rocks.

11. Biogeochemical cycles
In general... we can subdivide the Earth
system into:
atmosphere
hydrosphere
lithosphere
biosphere

12. Biogeochemical cycles
Elements (carbon, nitrogen, oxygen) or
molecules (water)
so the movement of matter (for example
carbon) between these parts of the
system is, practically speaking, a
biogeochemical cycle

13. Biogeochemical cycles
The Cycling Elements:
macronutrients : required in relatively large amounts
"big six":
carbon
hydrogen
oxygen
nitrogen
phosphorous
sulfur

14. Biogeochemical cycles
other macronutrients:
potassium
calcium
iron
magnesium

15. Biogeochemical cycles
micronutrients : required in very small
amounts, (but still necessary)
boron (green plants)
copper (some enzymes)
molybdenum (nitrogen-fixing bacteria)

16. Biogeochemical cycles
Biogeochemical cycles are part of the
larger cycles that describe the
functioning of the whole Earth (not
just the surface parts)

17. Biogeochemical cycles
Geological cycle consists of:
tectonic cycle
rock cycle
hydrologic cycle
biogeochemical cycles

18. Biogeochemical cycles
The hydrologic cycle and the
biogeochemical cycles. These are the
cycles in which humans interact the
most

19. The hydrologic cycle

20. The hydrologic cycle

21. The carbon cycle
The carbon cycle is one of the most important to
humans because it is important to our existence:
-- one of the primary elements forming human
tissues
-- necessary to plants, the basis of human food
and because it is important to the climate system
which sets the background for our environment:
-- carbon dioxide (CO 2 ) and methane (CH 4 ) are
greenhouse gases which help set global
temperatures

22. Biogeochemical cycles
photosynthesis is the basis of life on Earth...
carbon dioxide + water + sunlight _
organic material (sugar) + oxygen
-- respiration is the reverse of photosynthesis...
organic material + oxygen =
carbon dioxide + water + energy
animals and plants respire, releasing energy for other
activities... decay is also a form of respiration

23. Biogeochemical cycles
Introduction to the Nitrogen Cycle
Important cycle because:
-- nitrogen is a necessary nutrient
-- nitrogen is part of acid rain

24. Biogeochemical cycles
The Phosphorus Cycle
Important because:
-- Phosphorus is a necessary, limiting nutrient
-- Phosphate runoff causes eutrophication
Phosphorous is a strongly limiting nutrient
because it cannot be transferred from the
ocean to plants very effectively.

25. Basic Concepts
in Nutrient Cycling
Movement through the atmosphere is generally rapid
-- Movement through the soils is generally slow
-- Movement from terrestrial biosphere to the ocean
(via stream flow, usually) must be replaced by
movement either through the atmosphere (such as
with nitrogen and carbon) or by weathering (such as
with phosphorous or calcium).

26. Biogeochemical cycles
Humans clearly disrupt many, if not all biogeochemical
cycles...and in the process threaten many ecosystems.
In the absence of humans, are the biogeochemical
cycles stable? Probably not...
Life has existed for about 3.5 billion years, and a
complete breakdown has not occurred since oxygen
became available about 1.5 billion years ago.
Change is a part of natural biogeochemical cycles
resulting in periods of abundant biota and periods of
scarce biota (both ocean and land).