Transcript Ecosystem Processes

Chapter 19
Ecosystem
Essentials
Robert W. Christopherson
Charlie Thomsen
Vocalic Eruption in Iceland
Flight Cancellation
Earth’s Major Plates
Arrows represent 20
million years of
movement.
Figure 11.17
Biosphere
The space on Earth where life exist forms a
sphere which extends from ocean floor to
~8km altitude into the atmosphere.
Ecosystem: A self-sustaining association of
living plants, animals and microbes and their
nonliving physical environment.
1) Natural ecosystems are open systems with respect to energy and
matter.
2) Ecosystem boundaries often function as transition zone, not sharp
demarcations.
3) Natural ecosystems can varying significantly in size
Ecology
Ecology is the study of the relationship
between organisms (human beings, plants,
animals, microbes) and their environment.
a) the living organisms have impacts on the environment.
lichens/mosses grow on rocks  soils
growth of trees  add litter to soils  more fertile soil
wolfs eat deer  reduce deer population  less grazing
b) through altering the environment, their impacts also have feedbacks
to themselves.
lichens/mosses grow on rocks  soils  higher plants to grow 
lichens/mosses compete out
Wolfs eat deer  reduce deer population  less food for wolf 
Humans as Most the Active Agent
Deforestation:
 timber  economic gains  better life  more people
 more space for agriculture  more food  more people
 loss of other lives  loss of resources
 soil erosion  land degradation  less food
Agriculture
 more food  more people
expansion  loss of other land (grass, forest, wetland …)
fertilization/pesticide  more food  pollution  disease
Urban expansion
 better living  more people
expansion  loss of other lands
Fossil fuel use
 better living  more people
 global warming/pollution 
Ecosystem Components
Like any system in general, it is made up of several
components, each function independently yet in
concert.
biotic
individuals  population  Communities
producers (plants), consumers (animals), decomposers
Abiotic Ecosystem Components
soils, light, heat (temperature), water, air
As ecosystems are open systems, there are constant flow of
energy and matter through the system to keep the system
alive.
Biotic and Abiotic Components
Figure 19.2
Small Leaves do the Big Job: Photosynthesis
6CO 2  6H 2 O    C6 H12O 6  6O 2 
light/Chloroplast
CO2
Underside
H2O
stoma
Losing water is the price to pay for gaining CO2
Plants also keep cool with transpiration
(1) cools leaves
(2) brings nutrients to where they are needed
Stomatal Regulation
1. Stoma opens when light shine on the leaf, thus opens during the day to
absorb CO2 and closes during night to prevent unnecessary water loss.
2. Stoma closes when there is limited water in the soil.
3. Stoma closes when the air is too dry, i.e. high vapor pressure deficit.
4. Stoma closes to save water when CO2 concentration is high in the air.
Gross Primary Production and Respiration
GPP: Gross Primary Production, the amount of carbohydrate
(C6H12O6) produced through photosynthesis is called GPP.
Plant Respiration: All living organism needs energy to stay
alive. Plants do too. Plants use about 50% of GPP they
produce to stay alive. The respiration is the opposite process
of photosynthesis. We call this respiration as autotrophic
respiration (Ra).
C6 H12O6  O2 
 CO2  H 2O  Energy
Autotrophic respiration is use for two purpose:
(1) to keep living tissues alive, called maintenance respiration.
(2) To realize growth, call growth respiration.
Note: Energy is not heat energy as said in the textbook, but energy in the
form plant can use, ATP (Adenosine Triphosphate)
Net Primary Production
NPP: Net Primary Production is the balance of GPP after plant
respiration (autotrophic respiration) is taken away.
NPP = GPP – Ra
NPP is the part of photosynthesis product that can be used for
growth, including
Leaves
Branches
Stems
Roots
Part of NPP become food resources available for the
consumers ( herbivores, carnivores, humans)
Biomass vs. Net Primary Production
Biomass
The dry weight of the living organisms. e.g. the total dry weight
of leaves, branches, stems, and roots would be the biomass of a
tree, not including the dead leaves or stems on the floor.
For plants, Biomass is the accumulated NPP that stays as part
of the living organism. Due to litter fall and mortality, Biomass
is less than the annual NPP added up. Biomass is a cumulative
figure, NPP is an annual figure.
For forests, the biomass eventually levels off as the addition of
growth from NPP breaks even with loss of biomass due to litter
fall and mortality.
Net Primary Productivity
Satellite measure of chlorophyll concentration
Figure 19.7
Carbon Cycle and Balance
Input: 6.3 (fossil) + 1.6 (landuse)=7.9
Output: 1.4 +1.7 =3.1
Balance: 7.9-3.1 = 5.8
Actual increase seen: 3.2
Missing 2.2 C in the atmosphere: missing sink
Figure 19.10
Energy/Matter Flow in Ecosystems
Producers, Consumers, and Decomposers
Producers: Plants on land
Phytoplankton in oceans
Consumers: Primary (herbivores), secondary
(carnivores), tertiary (carnivores),
omnivores
Decomposers: bacteria and fungi
Energy, Nutrient,
and
Food Pathways
Figure 19.13