Ecology: Lecture 4 Flashcards
What is ecosystem function?
- Species interactions
- Energy and nutrient flows
Ecosystem function is…?
How an ecosystem works
- How they operate in terms of creating biological matter and maintaining the livability of earth.
Humans are altering ecosystem function and what does it mean?
As we change the function, it will impact the ability of earth to support life and different kinds of life.
What is ecosystem function defined as?
- Species interactions
- Energy and nutrient flow
What do species interactions do for ecosystem function?
Species interactions (and different kinds of them) structure ecosystems, resulting the ecosystems that we see and the interconnections within sand between ecosystems.
Ecosystem function is also how an ecosystem….?
It is how an ecosystem works.
- How ecosystems operate in terms of creating biological matter and maintaining the livability of the planet.
Are humans altering function?
As we change the function of an ecosystem, it will impact the ability of earth to support life and different kinds of life.
What are primary producers?
They are autotrophs, turning light into biomass
What are primary consumers?
Primary consumers are herbivores
What are secondary consumers?
They are predators
What are decomposers?
Organisms that break down dead organisms.
What are detritus?
They are dead organisms - a vital source of nutrients. They make the environment/ecosystems sustainable.
Living and non-living components of an ecosystem?
Living organisms and dead organisms are biotic features.
The physical environment is an abiotic feature.
Living component?
Group of organisms that process energy and nutrients in similar ways.
- Move nutrients in similar ways (eat similarly)
The components are affected how?
- Trophic/energy/nutrient flows between organisms.
- Energy/nutrient flows between the organisms and the environment.
How are the components connected?
- Organism to organism
- Organism to physical environment
What is ecosystem function characterized by?
Ecosystem function is characterized by the connections between components and the flow of energy and nutrients.
How can we measure ecosystem functioning?
We can measure ecosystem functioning as these connections and rates of flow. I.e How fast/effiecient are ecosystems? Their components? Using their material?
Ecosystem energetics?
Ecosystems (and life) are powered by the sun.
What do primary producers do?
Primary producers capture radiant energy (photosynthesis) and
store chemical energy (molecular bonds in organic compounds)
- Radiant energy is contained in light beams
- Chemical energy is carbs, ATP, sugars, etc.
- Their energy is then available for other organisms to consume.
How do ecosystems transfer energy?
Ecosystems transfer chemical energy through consumption (transfer to consumers) and death (transfer to detritus)
How do ecosystems lose heat?
Ecosystems lose heat energy through respiration
Is energy flow in ecosystems a perfect loop?
No, it is not!
One-way energy flow in ecosystems: enters as radiant energy, stored and transferred as chemical energy, leaves as heat energy
Energy flow in ecosystems?
We can compare ecosystem energy flows:
- Amount of energy reaching ecosystem
- Efficiency of energy capture
- Transfer rates
- Rates of energy loss
How much energy goes to each trophic level?
~ 10% of energy goes from one trophic level to the next level.
- This means that there is 10% efficiency
- This is due to a loss of material, respiration, or the biomass of the predator.
How does energy flow affect animals?
Every time an animal grazes or predates on another organism, there is a loss of energy.
Ecosystem nutrient cycling?
Circular flow of nutrients: Nutrients mostly retained. Cycle between
organisms and physical environment
Carbon and ecosystem cycling?
Plants get CO 2 from atmosphere and convert to organic carbon
(Org C). Org C transferred among components. CO 2 returned to
atmosphere through respiration.
What plays an important role in nutrient cycling?
Decomposers play an important role in nutrient cycling.
Examples of decomposers?
Dung beetles, Invertebrates, fungi, bacteria
What do decomposers do?
They obtain chemical energy and nutrients from detritus (dead organisms)
- They return some nutrients to the physical environment.
How can we compare ecosystem nutrient cycles?
- Nutrient stores in physical environment (soil)
- Efficiency of nutrient uptake (some are adapted to certain environments)
- Transfer rates
- Retention of nutrients.
Ecosystem health?
A healthy ecosystem processes and transfers energy and nutrients.
- Fueled by energy from outside the ecosystem
- Cycle and recycle nutrients from and to the physical environment
When might an ecosystem be unhealthy?
An ecosystem might be “unhealthy” if it is less able to:
- Obtain or transfer energy (loss of primary producers)
- Cycle or retain nutrients (whale shit)
Rate of primary production - ecosystem function?
The rate that the primary producer biomass is built:
- Energy capture and nutrient uptake
- Death rates and why they die
- Plant respiration (heat loss)
Rate of secondary production - ecosystem function measures?
Rate that the consumer biomass is built (consumption of primary):
- Energy and nutrient transfer
- Death rates
- Respiration
- How much animal abundance is supported by primary producers
Rate of decomposition - ecosystem function measures?
Rate of decomposition:
- Rate that inorganic nutrients are released from detritus.
- How effective are detriphors at decomposition in terms of releasing nutrients and pushing back into nutrient cycles.
Reasons to care about ecosystem health and function?
- Feeding ourselves
- Natural ecosystems
- We are changing the rates
Feeding ourselves?
- Primary production: how fast can we grow food?
- Secondary production: how fast can we turn plants into animals?
- Decomposition: nutrient supply for growing plants
Natural ecosystems?
- Primary production: plant/tree abundance and recovery after damage (hurricanes, etc).
- Secondary production: animal diversity and abundance
- Decomposition: nutrient supply that animals rely on.
We are changing the rates?
- Deforestation: primary production
- Use of fertilizers: modify nitrogen cycle
- Greenhouse gas emissions and climate change (burning fossil fuels, nitrogen cycle)
We NEED to learn about these rates and how we are changing them + the consequences and how we can quantify them.
Net Primary Production (NPP)?
- Rate that plant biomass increases in an ecosystem (how much and fast are primary producers growing).
- Synthesizes many rates.
Biomass?
Amount (mass) of organic matter present in an ecosystem.
Gross Primary Production (GPP)?
Total light energy captured by plants to be utilized.
Autotrophic Respiration (Ra)?
Energy lost as heat due to plant respiration.
Net primary production (NPP)?
Plant growth rate (energy accumulated as biomass).
NPP = GPP - Ra
- This equation is used to compare different ecosystems.
Units of NPP and GPP?
Energy: joules/time
Biomass: kg/time
- We can approximate this with satellites!
Equations for GPP and NPP?
NPP = GPP - Ra
GPP = NPP + Ra
Net Ecosystem Production (NEP)?
Energy (biomass) accumulated in all ecosystem components (per unit time)
- includes animals and plants
What energy is accumulated/looked at?
- Plants capture energy
- Energy is stored as biomass in all components
- Heat energy is lost from all components
What does NEP help us understand?
It helps us understand broad scale change over time in an ecosystem.
What is total respiration (Rt)?
Heat (biomass) lost from ALL components.
NEP equation?
NEP = GPP - Rt
NEP > 0 vs NEP < 0?
NEP > 0 Ecosystem biomass increasing
NEP < 0 Ecosystem losing biomass
Positive NEP?
- Ecosystem biomass is increasing
- Ecosystem absorbs more CO2 than it releases
- Helps lower atmospheric CO2 (simulate change)
Negative NEP?
- Ecosystem biomass is decreasing
- Ecosystenm releases more CO2 than it absorbs
- Contributes to increasing atmospheric CO2
NEP and NPP are?
large scale measures of ecosystem productivity.
NEP is a useful measure of what? q
IT is a useful measure for both the ecosystem and then understanding the contributions in terms of locking up carbon.
What limits NPP in terrestrial ecosystems?
- Temperature/light (latitude and elevation)
- Moisture
- Soil nutrients
- Limiting nutrient: Nitrogen
Nitrogen is essential for life?
Forms of organic nitrogen: DNA, proteins.
Forms of nitrogen?
- Atmospheric N2 gas
- NH4+ (result of N-fixation)
- NO3- (result of nitrification)
Biotic components?
Trees, plants, air.
Decomposition?
Organic N ~> NH4+
Assimilation?
NH4+ ~> Organic N
NO3- ~> Organic N
Process of the nitrogen cycle?
- N2 is exposed to nitrogen fixing bacteria, resulting in N-fixation.
- NH4+ is exposed to nitrifying bacteria, resulting in Nitrification
- NO3- is exposed to denitrifying bacteria, resulting in Denitrification.
Physical reservoirs in Nitrogen cycle?
Soil water and the atmosphere.
Terrestrial plant growth is?
Nitrogen limited. Plants can’t use N2, it HAS to be NH4+ or NO3-
Pristine Nitrogen fixation?
Lightning = 5 Tg/yr
N-fixing bacteria = 80 Tg/yr
Human Input Nitrogen Fixation?
Agriculture = 195 Tg/yr
Burning fossil fuels = 25 Tg/yr
Who dominates the nitrogen cycle and why/how?
We now dominate the cycle to sustain ourselves:
- Growing legumes and soybeans and chickpeas increases Tg/yr
- Soil fertilizer brings in NH4 & NO3
Legume crops?
60 Tg of fixed N per year - almost as much as the natural cycle.
- Symbiosis between root nodules containing N-fixing bacteria in Soybeans.
Manufacturing and using fertilizer fixes what?
Manufacture and using fertilizer fixes ~135 Tg of N per year. This is the largest component of the nitrogen cycle.
- Brings more food to people and security, BUT….
Consequences of applying N fertilizer?
Long term impacts of excessive nitrogen inputs:
* High nitrate (NO 3- ) levels in soil
water – can be toxic to livestoc
* Loss of nutrients from soil (e.g.
calcium)
* Pollution of aquatic ecosystems (fertilizer runoff and affects coral reefs & algal blooms in lakes).
Coastal marine environments?
In coral reefs, runoff chokes the reef and encourages macroalgal growth.
- High primary production due to phytoplankton and algae
- Algal blooms use up O2 and fish die.
Eutrophication?
Excessive primary production due to overload of nutrients
Decomposition of algae?
Leads to oxygen depletion. This is a dead zone, with low O2, fish will die.
Fertilizer summary?
- Fertilizer converts N2 to forms that
plants can use (NH 4+ and NO 3- ) - Overuse leads to increased NO 3- levels in soil water
- Excess nitrogen ends up in aquatic
ecosystems - Eutrophication and oxygen-depletion in freshwater and coastal habitats
Fossil fuel use?
- Burning fossil fuels adds nitrogen to atmosphere
- Nitrogen deposited back into ecosystems
Humans and nitrogen cycle?
Through the application of fertilizer
and burning fossil fuels, humans
have hugely increased the amount
of available nitrogen
Legume crops: N2 ~> NH 4+
Fertilizer: N2 ~> NH 4+ + NO 3-
Fossil fuels: Org N ~> NO 3-
