Introduction to Geography
People, Places, and Environment, 4e
Edward F. Bergman
William H. Renwick
Chapter 4: Biogeochemical
Cycles and the Biosphere
Victoria Alapo, Instructor
Geog 1010
Biogeochemical Cycles

Pathways by which energy & matter are transformed &
recycled in Earth systems. See Fig. 4-1, pg 133 (next
slide).

In the Atmosphere, hydrosphere, lithosphere e.g. water cycle.

Law of conservation of energy and matter – “matter cannot
be destroyed or created under ordinary conditions, but it
may be changed from one form to another”.

Two important biogeochemical cycles
 Hydrologic cycle
 Carbon cycle
Hydrologic Cycle

Flows (cycles) of water among land (lithosphere),
sea (hydrosphere) and air (atmosphere). See next
slide, but use the simpler version for exam.

Water changes between 3 states, but the amount
remains constant.
 Gas
 Solid
 Liquid

All living things are primarily water
Water Storage and Sources on Earth
Water Budget

An accounting of inflows and outflows of
water within a given system over some time
period.

Evapotranspiration

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Sum of evaporation and transpiration
Seasonal variation

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Low in winter
High in summer
Local water budgets

Compares precipitation and evapotranspiration
Vegetation and Hydrologic
Cycle

Trees and forests require large amounts of
water. E.g. one tree in the Amazon can
transpire an average of 1000 liters per day
into the atmosphere!

Therefore, trees play key role in returning
rainwater to the atmosphere
 So deforestation affects water balance of
regions. Ex. Amazon, and other parts of
the world.
The Carbon Cycle

Processes that cycle carbon and oxygen
between the environment and living things (next
slide).

Photosynthesis


Respiration


Opposite reaction of photosynthesis (Oxygen is used)
Combustion

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Determined by climate/ more in summer
Coal, oil, natural gas
Industrial Revolution
The lithosphere stores carbon (from 1000s of
years e.g. coal).
Soil

Is a dynamic, porous layer of mineral and
organic matter

Six principal components of soil

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Rocks and rock particles
Humus
Dissolved substances
Organisms
Water from rainfall
Air
Soil Formation

Weathering

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
The first step in soil formation
Mechanical and chemical
Soil horizons (next slide)


Layers of substances found in soils
Formed through vertical movement of water,
minerals and organic matter
Soil Horizons
Types of Soils

Soil orders

11 orders (next slide)

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47 suborders
230 great groups
1,200 subgroups
6,000 families
Thousands of soil series
There’s nothing simple about “ordinary dirt”!
USDA Natural Resource Conservation Service
maps (soils maps used in Planning Commissions &
by farmers).
Ecosystem

Includes all living organisms and the
physical area in which they exist

Fundamental elements

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Producers
Consumers
Decomposers
Material/energy needed for production
Food Chains

Food that plants produce are distributed via
a food chain (distribution)

Trophic level – each step in the food chain.

Biomagnification – e.g. when persistent
chemicals remain in animal tissues and
magnifies as it goes up the food chain. As
in the case of humans, lions, etc.
Food Chains

These 3 are all “consumers” (i.e. they’re just
types of consumers):
Herbivores
Carnivores
Omnivores

What category does a “Venus fly trap” fall in???
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Community Succession

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Sequence – how comm. succession happens
Succession – each plant community is succeeded
by a new one until…
Climax community – when the community or
environment becomes stable
Biomes

Named for dominant vegetation/climate
Major Biomes

Forest

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
Tropical & temperate rainforest (based on location).
Boreal – needle leaf/coniferous evergreen found
closer to poles e.g. Alaska & Canada. Called Taiga
in Russia.
Savannah – Woodland & Scrubland
Location of the Serengeti National Park (“Safari”) found
in Tanzania & Kenya – also a world heritage site.

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Grassland – Prairies
Desert
Tundra
Human & Natural Effects on
the Environment

Humans influence ecosystems

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37% of land area = cropland or pasture
(see next slide)
Desertification – when a previously nondesert area becomes one over time. E.g.
fringes of the Sahara, etc. See further
slide. This could be due to misuse by
humans or because of global warming.
Desertification Hazard
The most severe desertification hazards are in northern Africa,
central Australia, and the southwestern parts of Africa, Asia, North America,
and South America (the fringes of the major deserts of the world).