Transcript TROPHIC STRUCTURE

TROPHIC STRUCTURE
READINGS:
FREEMAN
Chapter 54
ECOSYSTEM
ECOSYSTEM
COMMUNITY
PHYSICAL ENVIRONMENT
ECOSYSTEM
• Consists of a community and its physical
environment.
• The non-living (abiotic) components of an
ecosystem include air, water and soil.
• Ecosystem scientists seek to study the
physics and chemistry of how energy flows
and nutrients cycle.
• Among the practical problems that they
address are global warming and pollution.
ECOSYSTEM
• Matter and energy are
continually moving
from the physical
environment through
living things and back
into the physical
environment.
• Energy flows.
• Matter recycles.
ECOSYSTEM
The muscle you move
when you blink is
powered by the energy
you borrowed from a
plant or animal that in
turn got it from the sun.
It is now dissipated in
the form of low grade
heat; no longer to be
used by an other living
or non-living thing.
ECOSYSTEM
Each breath you
take is a reminder of
the fact that matter
cycles. The oxygen
you take from the air
is combined with the
carbon you got from
a plant or animal
and put back into
the air.
TROPHIC STRUCTURE
• Trophic structure is
the pattern of
movement of energy
and matter through
an ecosystem.
• It is the result of
compressing a
community food web
into a series of
trophic levels.
TROPIC STRUCTURE
For example, the
biomass of all species
found in the green and
brown food webs from
Hubbard Brook could
be combined into
producer and consumer
groups to form a trophic
structure diagram.
Some of the Producers in the Hubbard
Brook Ecosystem
Some of the 1o Consumers in the
Hubbard Brook Ecosystem
Some of the Decomposers and
Detritivores in the Hubbard Brook
Ecosystem
Most Species Occupy More Than One
Trophic Level in the Hubbard Brook
Ecosystem
TROPHIC STRUCTURE
2O & HIGHER LEVEL
CONSUMERS
1O
CONSUMERS
PRODUCERS
• The result of combining all
producers and consumers
in Hubbard Brook would
be a biomass pyramid.
• Since consumers can be
at several trophic levels,
the fraction of the food
they consume at each
trophic level is determined
and proportioned among
levels.
TROPHIC STRUCTURE
2O & HIGHER LEVEL
CONSUMERS
DECOMPOSERS
1O
CONSUMERS
PRODUCERS
Detritivores (species
that feed on the dead
remains of organisms)
are also known as
decomposers. These
include bacteria, fungi
and invertebrate
animals of numerous
species.
ECOLOGICAL PYRAMIDS
ECOLOGICAL PYRAMIDS
BIOMASS PYRAMIDS
PYRAMIDS OF PRODUCTIVITY
(ENERGY PYRAMIDS)
BIOMASS PYRAMIDS
• In a biomass pyramid each tier represents the
standing crop biomass (total dry weight of all
species) included in a trophic level.
• In general, most such pyramids narrow
sharply from producers at the base to the top
level consumers.
• In a few exceptions, primary consumers
outweigh producers.
BIOMASS PYRAMID
• As mentioned earlier,
biomass is the dry
weight (-water) of living
matter.
• It is most often
expressed as
grams/square meter
(g/m2).
• This pyramid was among
the first constructed.
BIOMASS PYRAMID
2O& HIGHER
CONSUMERS (11*)
1O CONSUMERS(132*)
PRODUCERS (703*)
CORAL REEF in ENIWETOK ATOLL
* (g/m2)
BIOMASS PYRAMID
2O& HIGHER
CONSUMERS (O.01*)
1OCONSUMERS(0.6*)
PRODUCERS (470*)
OLD FIELD in GEORGIA
* (g/m2)
BIOMASS PYRAMIDS
(* g/m2)
(4*)
2O … (2.3*)
(11*) 1O (22*)
(96*) P (170*)
UNFERTILIZED
FERTILIZED
WEBER LAKE, WISCONSIN
BIOMASS PYRAMIDS
(32*) 1O
(16*)
P
(21*)
(4*)
LONG ISLAND SOUND
ENGLISH CHANNEL
Producers have a lower standing crop due to being
much smaller and having a much higher rate of
reproduction.
PYRAMIDS OF ENERGY
(PRODUCTIVITY)
• The transfer of energy from one trophic level
to the next is never 100% efficient.
• Therefore, all pyramids of energy are “bottom
large”. No exceptions.
• Ecological efficiencies of transfer from one
trophic level range from 5% to 20%.
• Thus, 80% to 95% of the energy at one
trophic level is never transferred to the next.
PYRAMID OF ENERGY
• This is the energy
pyramid for Silver
Springs, Florida.
• Energy units are in
kilocalories, or you
known them as food
calories or large
calories (Calories).
• This is an annual or
average year estimate;
per year.
PYRAMID OF ENERGY
• This is a hypothetical
energy pyramid.
• It assumes a 10%
efficiency of energy
transfer across all
trophic levels, except in
the conversion of solar
energy (only 1%
efficient).
• Note energy units are in
joules (J). 1 J = 0.239
cal.
Why Is Energy Transfer Not 100%
Efficient?
• When energy is changed from one form to
another, some is degraded in the form of
heat. This law of thermodynamics is true for
all physical-chemical systems, including living
ones.
• One ecologist summarized this fact by the
statement: “There is no such thing as a free
lunch.” All physical transactions come at a
cost of energy.
Why Is Energy Transfer Not 100%
Efficient?
• Entropy explains why food chains have limits
to their length.
• As Freeman (2005) points out low and high
productivity ecosystems were equally likely to
contain only four trophic levels.
• Although it is popular to speak of “energy
loss”, this energy is simply degraded as a low
grade heat.
• Energy flows; it can not be recycled.
MEASURING NET ANNUAL
PRIMARY PRODUCTION
• Field measurement of
annual net primary
production entails random
plot assignment, clipping
and sorting vegetation,
drying and weighing plant
material.
• Data is often reported as
grams of biomass per
square meter per year or
kilocalories per square meter
per year or Joules per
square meter per year.
NET PRODUCTION, GROSS
PRODUCTION & RESPIRATION
• Plants accumulate matter (and energy)
through photosynthesis (gross production).
• Plants use matter (and energy) during
respiration (respiration).
• Net production = Gross production Respiration
• Production (Gross or Net) is either expressed
in units of mass (g /m2 /year) or energy (kcal
/m2 /year).
Net Primary Production and
Evapotranspiration
• Moisture and
temperature influence
the rate of net primary
production.
• Measures of the rate
at which water
evaporates from the
land and transpires off
plants are highly
correlated with net
primary production.
Variation in Annual Net
Primary Production
• The effect of precipitation
(water) is seen as one travels
from east to west through the
NA grassland biome.
• The tallgrass prairies of Illinois
(top) receive about 36 inches
per year.
• Short grass prairies of
western Kansas get only
about 15 inches.
• Average annual temperatures
are only slightly higher in
western Kansas.
NET PRODUCTION IN SOME
MAJOR BIOMES
BIOME
Net Production / Unit Area
( grams / meter 2 / year)
RANGE
AVERAGE
Desert & Semi-desert
0-250
40
Artic & Alpine Tundra
10-400
140
Coniferous Forest
400-2,000
800
Deciduous Forest
600-2,500
1,250
Grassland
200-1,500
600
Tropical Forest
1,000-3,500
2,000
Net Productivity in Marine
Ecosystems
• The most productive
ecosystems on the
planet are found in
coral reefs and marine
algal beds.
• Some of the least
productive ecosystems
are found in the open
ocean.
Net Productivity in Marine
Ecosystems
Although open ocean
has the lowest net
primary productivity,
the percentage of
earth’s productivity is
greater than tropical
forests due to it
occupies nearly 65%
of the planet’s surface.
Measuring Net Productivity in
Marine Ecosystems
• A global view of marine
productivity is provided
by sensors that
measure various
wavelengths of light
from satellites.
• A more detailed of the
biota involved in net
production is obtained
by direct sampling of
the water column.
Iron Fertilizer Increases
Marine Primary Productivity (I)
• Marine phytoplankton are
the major contributors to
photosynthesis and thus
primary production.
• Freeman (2005) describes
an experiment designed to
increase productivity by
these algal species. See
Figure 54.5 on page 1247.
Iron Fertilizer Increases Marine
Primary Productivity (II)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Iron Fertilizer Increases Marine
Primary Productivity (III)
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
TROPHIC STRUCTURE
READINGS:
FREEMAN
Chapter 54