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Ecosystems and Restoration Ecology
Ecosystems and Restoration Ecology: Chapter 55
consists of all organisms living in a community and the abiotic factors with which they interact.
Range from microcosm's (aquariums) to large areas like lakes
All ecosystems dynamics involve
Energy flow (through ecosystems)
Chemical cycling (cycles within ecosystem)
Physical laws govern energy flow and chemical cycling
Conservation of Energy
First law of thermodynamics: energy cannot be created or destroyed, only transformed.
Energy enters ecosystem as solar radiation, is conserved, leaves organisms as heat, is transferred to chemical energy by plants.
Second law of thermodynamics: every exchange of energy increases the entropy of the universe.
Energy conversion is not completely efficient, some is always lost as heat.
Conservation of Mass
Law of conservation of mass: matter cannot be created or destroyed
Chemical elements are recycled
Ecosystems are open systems that absorb mass and energy and release heat and waste products.
Energy, Mass, and Trophic Levels
Autotrophs: create their own food.
use photosynthesis or chemosynthesis to build their own molecules to use as an energy source.
Heterotrophs: depend on the output of primary producers.
herbivores, consume primary produces
carnivores that eat herbivores
carnivores that eat carnivores.
consumers that derive their energy from
nonliving organic matter.
Prokaryotes and fungi
Decomposition connects to all trophic levels
is the amount of light energy converted to chemical energy by autotrophs during a given time period.
An ecosystems energy budget is set by the extent of photosynthetic production.
The global energy budget is limited by the amount of solar radiation that reaches Earth's surface.
Only a small fraction of solar energy is of a usable wavelength for photosynthesis.
Gross primary production (GPP)
is the total primary production of the ecosystem.
Measure of the conversion of chemical energy from photosynthesis per unit time
Net primary production (NPP)
is GPP minus the energy primary producers use for respiration
On average its about half the GPP
Only NPP is available to consumers
Greatly varies in different ecosystems
All ecosystems NPP contributes to the total NPP on Earth
Tropical rain forests, estuaries, and coral reefs are most productive ecosystems per unit area
Marine ecosystems are unproductive per unit area, but since they are such a great volume they contribute to the global NPP a lot.
Net ecosystem production (NEP)
is a measure of the total biomass accumulation during a given time period.
GPP - total respiration of all organisms in an ecosystem
Estimated by comparing the flux of carbon dioxide and oxygen in an ecosystem.
In Aquatic Ecosystems
Primary production is controlled by light and nutrients
Light limitation: depth of light affects primary production in the photic zone
Nutrient limitation: a
is the element that must be added for production to increase in an area.
Nitrogen and phosphorus are most limited
Adding nutrients to lakes has ecological impacts. Sewage run off can cause
which can cause many fish to die. Phosphorus also limits cyanobacterial growth, so phosphate-free detergents have become more common.
In Terrestrial Ecosystems
Primary production is affected by temperature and moisture.
Production increases with moisture.
Actual evapotranspiration: total amount of water transpired by plants and evaporated from a landscape. It is affected by precipitation, temperature, and solar energy. It is related to net primary production.
Soil nutrient is often the limiting factor
Nitrogen is most common limiting agent, phosphorus is also (primarily in older soil).
Adaptations help plants access limited nutrients:
Mutualism with nitrogen-fixing bacteria
Root hairs to increase surface area
Enzymes that increase the availability of limiting nutrients.
Energy transfer between trophic levels is only 10% efficient
is the amount of chemical energy in food converted to new biomass during a given period of time.
= (Net secondary production X 100%)/(Assimilation of primary production)
Birds and mammals efficiency = 1-3%
Fishes = 10%
Insects and microorganisms = <40%
is the percent of production transferred from one level to the next.
Range from 5-20%
Multiplies over the food chain's length
About 0.1% of energy from photosynthesis reaches a tertiary consumer
A pyramid of net production represents the loss of energy with each transfer in a food chain.
A biomass pyramid shows the dry weight of all organisms in one trophic level.
Usually a decrease at higher trophic levels
is a ratio of the standing crop biomass to production.
nutrient circuits in ecosystems that involve biotic and abiotic components.
All elements cycle between organic and inorganic reservoirs.
Decomposition and Nutrient Cycling Rates
Decomposers play a key role in chemical cycling since rates at which nutrients cycle vary with rates of decomposition.
Rate of decomposition is controlled by temperature, moisture, and nutrient availability.
Rapid decomposition = low levels of nutrients in the soil
Returns degraded ecosystems to a more natural state.
Over time biological communities can recover from disturbances.
Restoration ecologists try to initiate or speed up recovery.
is using living organisms to detoxify ecosystems
Often uses prokaryotes, fungi, or plants that can take up and sometimes metabolize toxins.
uses organisms to add essential materials to a degraded ecosystem.
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