Ecosystem Energetics Flashcards
What is the basis of a natural ecosystem?
the energy source
Aside from being involved in nutrient cycling themselves, what makes bacteria so critical in energy transformation?
mitochondria and chloroplasts (organelles in eukaryotic organisms involved in energy transformation) evolved from bacteria
What are the major sources of energy for an ecosystem?
sunlight in the form of photons
or
some organisms can intake energy from geothermal or hydrothermal environments (not light related)
What other type of energy can photons be converted into?
heat
chemical energy (ATP)
What effect does the transformation of photons into heat energy have?
the heat energy warms the surface of the earth and the oceans
it drives the water cycle
it causes the wind and water currents
What governs the flow of energy in ecosystems?
the laws of thermodynamics
What is potential energy?
energy that is stored and available for and capable of doing work
ex. the ball at the top of a hill has stored energy
ex. potential energy stored in chemical bonds is released when wood burns
What is kinetic energy?
the energy of motion
it does work and acts as a force on an object to displace it
ex. the energy acting on the ball as it rolls down the hill
ex. kinetic energy is produced as heat and light as wood burns
What is the first law of thermodynamics?
energy is conserved
ie., it is not created or destroyed
it can change from one form to another
move from one place to another
it can act on matter in multiple ways
but there is never a gain or loss in total energy
What is the second law of thermodynamics?
when energy is transferred, entropy (disorder) increases and it’s in a form that can’t do work (loses capacity)
What happens to energy when it is transferred from one organism to another?
some energy will be stored in living tissues
some energy will be lost as heat
entropy will increase
If entropy increases with energy transfer, according to the second law of thermodynamics, how do ecosystems maintain order and energy?
ecosystems are open systems, which the second law of thermodynamics doesn’t apply to
the law only applies to systems within which no energy or matter is exchanged with the environment
the constant input of energy (mainly sunlight) in ecological systems contradicts the effects of entropy and maintains order and conserves energy
What is primary production?
the energy that is fixed in the system during photosynthesis
the rate at which autotrophs transform CO2 from the atmosphere or water into organic compounds
What are the 2 types of autotrophs?
chemoautotrophs
photoautotrophs
What are chemoautotrophs? give an example
primary producers that fix CO2 from their environment using energy from chemical compounds (oxidation of electron-donating molecules)
ex. Nitrosomonas europea use ATP to fix CO2
ex. Thiobacillus hydrothermalis use sulphur
What are photoautotrophs? give an example
primary producers that fix CO2 from their environment using energy from sunlight
ex. trees, herbs, mosses, Lamprocystis purpurea, Gammaproteobacteria, Cyanobacteria, Chloroflexus
What are the 2 measurements of primary productivity in a natural system?
gross primary productivity (GPP)
net primary productivity (NPP)
what is GPP?
Gross Primary Productivity is the TOTAL rate of photosynthesis by autotrophs
this includes energy converted for the organism’s own respiration
What is NPP? what is it’s formula?
Net Primary Productivity is the rate of energy storage in the form of organic molecules AFTER energy is used for cellular respiration (loss of energy)
NPP = GPP - Respiration
units: kcal/m^2/yr or g/m^2/yr
can be calculated from the Standing Crop Biomass accumulation
What is the standing crop biomass accumulation?
scientist makes multiple transects at different elevations and measures the diameter at breast height of the 4 closest trees to the transect as well as notes down the identification
How is NPP measured in aquatic systems?
the light/dark bottle method
Explain the light/dark bottle method that’s used to measure NPP in aquatic systems
used to measure the production and consumption of oxygen
light bottles are used to estimate NPP: they contain an incubated water sample with autotrophs - if photosynthesis surpasses respiration, dissolved oxygen will accumulate
dark bottles are used to estimate respiration: they contain the same sample incubated for the same time - if there’s no photosynthesis, and only respiration, the dissolved oxygen should decline
How can the light/dark bottle method be used to determine the amount of dissolved oxygen produced by photosynthesis?
the light bottle will have both photosynthesis and respiration occurring, whereas the dark bottle will only have respiration
to get the total amount of O2 that was produced by photosynthesis (GPP), you have to subtract the amount of O2 consumed by respiration (the purpose of the dark bottle)
What is the purpose of the dark bottle?
To learn how much O2 is consumed during respiration so it can be subtracted from the value found in the light bottle to determine the amount of O2 produced by photosynthesis
the dark bottle is the control
What is a microcosm?
a small representation of a larger system
ex. the light and dark bottles with samples containing autotrophs
What are the biases of studying microcosms?
they are removing the medium and study organisms from the actual environment, so they are removing natural inputs and contributing factors so it may not be representative of reality
Why do we like microcosm studies?
they are generally less $$
simple
reliable
they could be used for bioremediation and isolation of bacteria
Which bottle is the experimental one and which is the control?
the light bottle is the experimental
dark bottle is control
How do environmental factors effect NPP in terrestrial ecosystems?
Temperature and precipitation are major influencers of NPP
NPP increases with increasing precipitation and temperature (ex. tropical wet forests)
How is solar radiation related to average annual temperature?
How are the effects of temperature and precipitation on primary productivity related?
generally:
as precipitation increases, NPP increases; as temperature increases, NPP increases
ex. Low NPP, more extreme temperatures, lower ppt in Kelowna
higher NPP, moderate temperatures, higher ppt in Victoria
highest NPP, moderate-cold temperatures, highest ppt in Tofino
How does NPP vary across different ecosystems?
It depends on the particular climate
higher ppt tends to increase NPP
elevation will have an effect because temperature and moisture levels will change
Describe the biome diagram by Whittaker
precipitation (cm/yr) on x axis
air temperature (C) on y axis
the diagram shows and relates climates of terrestrial biomes to one another in terms of their ppt and temperature
Where on Whittaker’s biome diagram would Victoria be?
~temperate forest
between 100-230 cm/yr ppt
between 18-2 C
rough ^^^
Where on Whittaker’s biome diagram would Tofino be?
temperate wet forest
between 150-450 cm/yr ppt
between 18- -5C
Where on Whittaker’s biome diagram would Kamloops be?
desert
<50 cm/yr ppt
between 30- -15C
Order the 4 biogeoclimatic zones on Vancouver island in terms of temperature and NPP
alpine mountains: lowest temp (-10-0), lowest NPP
mountain hemlock: lower temp (-10-0), lower NPP
Coastal Western Hemlock: mid temp (~10), mid NPP
Coastal Douglas-fir: mid temp (~10), mid NPP
How does the length of the photosynthetic period per day affect NPP?
In latitudes closer to the equator, the photosynthetic period is longer = higher NPP
as you move up or down latitudes toward either of the poles, the photosynthetic periods become shorter = lower NPP
Describe the basics of photosynthesis
photoautotrophs uptake CO2 and water to convert energy from the sun into chemical energy
stomata in cells open to intake CO2
water is lost while stomata is open (evapotranspiration)
roots uptake water from the environment
How might photosynthesis (NPP) be affected by amount of water in environment?
while stomata are open for intake of CO2 from environment, water vapor molecules are being lost from the photoautotroph
so if there’s less ppt, the plant may have to adjust how long the stomata are open (or what time of day, when it’s less hot etc) = less photosynthesis
if there’s more ppt, the more water can be replaced by the roots of a plant and the stomata can be open for longer = more photosynthesis
What is evapotranspiration?
when water is lost through transpiration via stomata in plant cells
What does the amount of water available in the environment limit?
rate of photosynthesis
the number of leaves that a plant can support
On a global level, what level of NPP do coastal ecosystems have?
intermediate
On a global level, what areas tend to have the lowest NPP?
higher and lower latitude areas as well as higher elevations
On a global level, what areas tend to have the highest NPP?
regions closer to the equator / mid-latitudes
how is world NPP calculated in terms of biomes?
for each biome, the area (10^6km^2) is multiplied by its mean NPP per unit area (g/m^2/yr) = world NPP (10^9 mt/yr)
What is the relative NPP? how is it calculated?
it’s the amount of NPP that is stored in the biomass of a biome type
calculated by:
mean NPP/mean biomass per unit area (g/g/yr)
If a biome type (ex. boreal forest) has a higher relative NPP than another (ex. temperate evergreen forest), what does this suggest?
the boreal forest is more productive per unit of biomass than the temperate evergreen forest
order the 7 ecosystems on VI from lowest to highest relative NPP
temperate evergreen
boreal forest
woodland/shrubland
tundra and alpine meadow
algal beds and reefs
estuaries
lake and stream
Which terrestrial ecosystem found on VI has the highest relative NPP?
lakes and streams
How does the availability of essential plant nutrients affect ecosystem productivity?
essential plant nutrients affect the rate of nutrient uptake, photosynthesis, and plant growth
How is NPP affected by soil nutrient availability?
increase in soil nutrient availability = increase in NPP
What example was provided to show that NPP increases with soil nutrient availability?
forest on Blackhawk Island, Wisconsin
with increasing mineralization of nitrogen (increasing soil nitrogen availability), the number of primary producers increases = increasing NPP
How could we measure the mineralization of Nitrogen in the soil?
create a transect for the primary producers in the area of interest
collect soil samples from each quadrat
create a microcosm with N15 isotope and NH4+
use mass spectroscopy to follow the % of N15 and graph
where the graph plateaus, mineralization is occurring
What theory does the Blackhawk Island, Wisconsin, study provide evidence for? Explain
Liebig’s Law of the Minimum
that nitrogen is the limiting element in soil systems because aboveground productivity increases as nitrogen availability increases
What else increases with increasing soil nitrogen availability?
organic matter
Will a recently burned forest have higher or lower nitrogen mineralization?
lower
What is PAR?
photsynthetically active radiation
In aquatic systems, how is photosynthetically active radiation affected by water depth?
PAR declines exponentially with water depth
How is the rate of photosynthesis and GPP of phytoplankton affected by PAR?
photosynthesis and GPP of phytoplankton are highest when PAR is at an intermediate level
How is respiration affected by water depth?
it’s not really affected, it stays relatively constant regardless of depth
