Carbon cycle and movement Flashcards
C inputs? (what controls productivity)
GPP
photosynth
calvin cycle
what is GPP? photosynth?
Gross Primary Production (GPP): ecosystem-level photosynthesis
Photosynthesis – conversion of atmospheric CO2 to carbon products by plants
CO2 + 2H20 + light energy à CH20 + H20 + O2
describe the calvin cycle
Calvin cycle: Light independent cycle – energy molecules to fix carbon dioxide
molecules
what controls productivity
Net photosynthesis by leaves (leaf level
rimary Productivity (GPP & NPP) (ecosystem level)
how does nitrogen affect growth
Provide budling blocks to build photosynthetic enzymes
factors to leaf level
Net photosynthesis by leaves (leaf level)
a) Light
b) Nitrogen
c) Water
d) Temperature
e) CO2
factors of ecosystem level
Primary Productivity (GPP & NPP) (ecosystem level)
a) Leaf area
b) Seasonal length
how do plants respond to limitation by light
Plants can respond via acclimation – physiological responses to the environment and adaptation
– change of population in allele frequency
net photosynth vs irradence graph: LUE?
Plants can respond via acclimation – physiological responses to the environment and adaptation
– change of population in allele frequency
net photosynth vs irradence graph: light saturated?
Light saturated = # of chloroplasts are maximized
- Increase of light = excess photons creating free radicals which degrade
thus decrease photo-oxidation (photosynthesis
top canopy effect on light?
Top canopy (lots of light) has smaller thick leaves to withstand radiation where shade leaves are
thick and big to absorb light radiation
- Because access to light is limiting thus they don’t allocate as much
energy to enhance capture of those photons and concentrate energy to
provide more photosynthetic structures
- Top leaves reduce the surface area to enhance heat balance in lea
rubisco?
an enzyme used my primary producers to convert CO2 into organic compounds (light
compensating for carbon that is lost in oxidization
how is photosynthesis measured? activity levels?
Photosynthesis is measured by microcopy through wavelength of activity.
- Shade leaf is equally active at all wavelengths. Light that is hitting
leaves is narrow because top leaves absorb some waves
- Top canopy leaf is most active with blue wavelength. Light that
reaches canopy is a broader spectrum thus it is beneficial to have all
wavelength photons.
what is shade tolerence? isat?
Shade tolerance: ability of a plant to tolerate low light levels
- Light spectrum is niched
- Photosynthesis increases over a wider range of light levels
- Light saturation = Isat
- Summation of species creates a broader Isat for the community
- The Isat is different for each species, but the community shows a broader Isat
level, thus plants maximizing by their own different levels = summation of
species. Enhances by plants being varied in their light responses
why is nitrogen important? how is NPP increased?
Nitrogen is in plant proteins and enzymes and is the foundation of energy molecules thus
allocation is important
Increase N in leaf (allocated to photo structures) = Increase NPP
Increase N = Increase photosynthetic rate b/c used to make enzymes or other photosynthesis
structures
what is the trade off to increase NPP in leaves
Trade off à stomata used to exchange CO2
- Less precipitation = closed stomata b/c risk of desiccation even at the
cost of photosynthesis
- As N increases = Stomata conductance increases (rate of gas exchange
and transpiration determined by the physical structure of stomata)
- More N = Open stomata more = Higher photosynthesis and
transpiration
short term leaf response to water limitation
Short term responses:
1. Reduce stomatal conductance (tradeoff between photosynthesis and water loss)
2. Wilting, shedding leaves
long term water responses
. Reduce leaf area (transpiration)
optimal temp range for photosynth?
Optimal range for photosynthesis:
Temperature: 15-25 degrees
Tropical: 30-35 degree
why are too low and too high temps bad leaf level
Low temperature is limited by rate of chemical
reactions
High temperature creates enzyme inactivation and
destruction of photosynthetic pigments
how do plants adjust CO2
Plants physiologically and morphologically adjust so that CO2 diffusion and biochemical
limitations on photosynthesis are equal
CO2 limiting factors? look at graph
Principle of limiting factors:
a) Photosynthesis à process limited by >1 factor
b) Rate of governed by most limiting factor
c) Other factors will adjust to match
what raises rate of photosynth
igher CO2 concentration; higher temperature = rate of photosynthesis
what are the impacts of increasing CO2 concentration?
Reduced stomatal conductance of water; reduced plant water use; increased rate of carbon
fixation and photosynthesi
photosynthetic traits that influence carbon gain- limiting?
Thick, long-lived leaves (decrease of biomass)
- Low leaf nitrogen
- Low stomatal conductance
- Low photosynthetic capacity
photosynthetic traits that influence carbon gain- ample?
Thin leaves, high turnover (increase of biomass)
- High leaf nitrogen
- High stomatal conductance
- Low photosynthetic capacity
why are plants central to the carbon cycle?
Plants are central to carbon cycle because with the emergence of plants they changed the
atmosphere and change the oxygen levels from 15%to 21%.
shade intolerence?
Sun acclimated/adapted
species (shade intolerant)
Photosynthesis increases over a
wider range of light levels
Trade-off = high respiration
rates (higher LCP)
Relationship between leaf life span and traits that increase photosynthesis
Inverse relationship between
leaf lifespan & traits that
increase photosynthesis
Long-lived leaves contain many
non-photosynthetic compounds
- Herbivore protection
- Desiccation resistant
how are plant interactions measured?
Measured in productivity of leaves: Allocation and structure of leaves (photosynthesis structures)
– leaf area index
how do canopy processes change over light intensities
Canopy processes increase range of light intensities over which LUE curve continues to increase
* Canopy as a whole utilizes a wider range of light intensities while still having net photosynthetic rate that is higher (than sunlit or shaded leaves alone)
sunlit vs shaded leaves + canopy
○ Sunlit - typically higher in the canopy
§ Have a basic photosynthetic response where net PP begins to decrease at a certain level of light (breakdowns of enzymes, disruption of metabolic processes at too high heat/light)
○ Shaded leaves - within canopy
Increases linearly as light begins to hit the shaded leave
describe NPP
Net primary productivity (NPP) – NPP = GPP – RR
-Difference between energy fixed and respiration rate
describe GPP+ how it varies
Gross Primary Production (GPP) – Energy store during photosynthesis
-Varies diurnally and seasonally in response to proximate controls: light, water, nitrogen,
temperature, carbon dioxide
what determines GPP variation? where and when is it highest?
Variation is determined by:
1. Quantity of photosynthetic tissue (leaf-area)
2. Duration of tissue activity (season length)
Croplands and deciduous forests have the highest GPP within the growing season of
April to August
what is LAI? what does it effect?
Leaf Area Index (LAI) –one half of the total amount of leaf material in a canopy
compared to ground area
- Affects light (PAR) penetration through canopy
- Main driving force of net primary production, water and nutrient use
and carbon balance
- Canopy absorbs 79% of PAR, low vegetation absorbs 2% of PAR,
middle absorbed 7% of PAR
- Boreal forest reflects 10% of PAR
why is NPP half of GPP
NPP is about half of GPP because most ecosystems have similar efficiencies converting
photosynthate to NPP
respiration and plant growth?
Respiration – provides energy for plants to grow and maintain biomass and acquire nutrients
R plants = R growth + R maintenance + R ion
Each component involves oxidation of carbohydrates to make ATP
why does respiration impact plant growth?
- Growth – cellulose and lignin are important compounds made by biosynthesis and
contribute to the standing carbon pool - Maintenance – Energy for replacing proteins, membranes, and other tissues; increase
temp=increase tissue turnover; accounts for 50% of total plant respiration - Ion transport – gradient required for nutrient uptake
compensation point?
Compensation point – where light intensity is at the point where the rate of photosynthesis is
equal to the rate of respiration
why are terrestrial plants important to NPP biomes : life zone
Life zone – volume of space an organisms can potentially occupy. The ocean has a
greater volume, however terrestrial plants outweigh the ocean in terms of productivity
because they are not nutrient limited like oceans.
Coastal terrestrial areas have increased primary production because they are moist
and have more rainfall
why are terrestrial plants important to NPP biomes : precip
Precipitation – overall trend of increasing temperature, increases primary production
(excluding deserts)
- Quadratic relationship meaning once you get 2000 mm of rain, there is
a decreases in primary production
- Too much water = saturated reduces the availability of oxygen to the
roots creating water logging thus they stop up taking water and grow
slower. Increases water also create deficiency of nutrients because
draining through profile (especially phosphorus)
biome differences in NPP?
Biome Differences in NPP
The prairies have relatively fast primary production because of being adapted to a short growing
season.
Species are adapted to their local conditions such that they can’t use extra resources creating
limitations because they don’t have the mechanism to enhance P
what creates variation in NPP
Precipitation – spatial variation depending on where the biome is located has different
levels of precipitation while temporal variation does not respond to additional
precipitation due to adaptations
- Dry locations are limited by water such that not enough water
decreases PP
- Wet locations are limited by water such that too much water decreases
PP; limited by oxygen
- Tropical forests are limited by phosphorous because it is drained out of
the soil
What happens to NPP within a plant?
- Growth within plant it takes 40 -70% of net primary production
New roots (30-40%,) ; leaves (10-30) - Root secretions use 20 to 40% of net primary production
Transferring to mycorrhizae (10-30%), root exudates – nutrients released (leaked)
into soil usually sugars (might be selecting for specific microbes) (10-30%) - Losses to herbivores, mortality, and fire (1-40%)
- Volatile emissions (0-5%)
plant allocations to NPP?
Allocation to different parts influences survival, growth, and
reproduction
Leaves – Photosynthesis
Stem – Support
Roots – Uptake of nutrients and water
Flower and seed – Reproductio
measures of plant allocation of NPP
Root: Shoot Ratios
How plant allocate efforts: Response of plant to
Minimize limitation of nutrients = grow roots
Minimize limitation of access to sunlight = grow shoo
what does NPP allocation change by?
- Seasonal changes – resources and energy that would normally go onto leaves gets
absorbed into plants and stored for next year’s leaf growth - Leave budget – on individual level making localized decisions (keep or drop leave)
depends on whether the maintained cost greater than benefits of maintain it = leaf will be
dropped (allocate energy to other parts of plant)
allocation of growth of tissue by biomes. good vs bad conditions?
tropical forests and boreal forests – allocation to below ground (20%)
Deserts and grasslands – allocation to below ground (50%)
Good growth conditions – primary competition is less – more shoots
Bad growth conditions –increase completion of resources – more below ground
what are carbon fluxes
Ecosystem carbon balances:
Net ecosystem production (NEP) = GPP – (R plant + R heterotr + R F disturb + F leach
