Carbon cycle and movement

Question 1

C inputs? (what controls productivity)

Answer 1

GPP
photosynth
calvin cycle

Question 2

what is GPP? photosynth?

Answer 2

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

Question 3

describe the calvin cycle

Answer 3

Calvin cycle: Light independent cycle – energy molecules to fix carbon dioxide
molecules

Question 4

what controls productivity

Answer 4

Net photosynthesis by leaves (leaf level
rimary Productivity (GPP & NPP) (ecosystem level)

Question 5

how does nitrogen affect growth

Answer 5

Provide budling blocks to build photosynthetic enzymes

Question 6

factors to leaf level

Answer 6

Net photosynthesis by leaves (leaf level)
a) Light
b) Nitrogen
c) Water
d) Temperature
e) CO2

Question 7

factors of ecosystem level

Answer 7

Primary Productivity (GPP & NPP) (ecosystem level)
a) Leaf area
b) Seasonal length

Question 8

how do plants respond to limitation by light

Answer 8

Plants can respond via acclimation – physiological responses to the environment and adaptation
– change of population in allele frequency

Question 9

net photosynth vs irradence graph: LUE?

Answer 9

Plants can respond via acclimation – physiological responses to the environment and adaptation
– change of population in allele frequency

Question 10

net photosynth vs irradence graph: light saturated?

Answer 10

Light saturated = # of chloroplasts are maximized
- Increase of light = excess photons creating free radicals which degrade
thus decrease photo-oxidation (photosynthesis

Question 11

top canopy effect on light?

Answer 11

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

Question 12

rubisco?

Answer 12

an enzyme used my primary producers to convert CO2 into organic compounds (light
compensating for carbon that is lost in oxidization

Question 13

how is photosynthesis measured? activity levels?

Answer 13

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.

Question 14

what is shade tolerence? isat?

Answer 14

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

Question 15

why is nitrogen important? how is NPP increased?

Answer 15

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

Question 16

what is the trade off to increase NPP in leaves

Answer 16

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

Question 17

short term leaf response to water limitation

Answer 17

Short term responses:
1. Reduce stomatal conductance (tradeoff between photosynthesis and water loss)
2. Wilting, shedding leaves

Question 18

long term water responses

Answer 18

. Reduce leaf area (transpiration)

Question 19

optimal temp range for photosynth?

Answer 19

Optimal range for photosynthesis:
Temperature: 15-25 degrees
Tropical: 30-35 degree

Question 20

why are too low and too high temps bad leaf level

Answer 20

Low temperature is limited by rate of chemical
reactions
High temperature creates enzyme inactivation and
destruction of photosynthetic pigments

Question 21

how do plants adjust CO2

Answer 21

Plants physiologically and morphologically adjust so that CO2 diffusion and biochemical
limitations on photosynthesis are equal

Question 22

CO2 limiting factors? look at graph

Answer 22

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

Question 23

what raises rate of photosynth

Answer 23

igher CO2 concentration; higher temperature = rate of photosynthesis

Question 24

what are the impacts of increasing CO2 concentration?

Answer 24

Reduced stomatal conductance of water; reduced plant water use; increased rate of carbon
fixation and photosynthesi

Question 25

photosynthetic traits that influence carbon gain- limiting?

Answer 25

Thick, long-lived leaves (decrease of biomass) - Low leaf nitrogen - Low stomatal conductance - Low photosynthetic capacity

Question 26

photosynthetic traits that influence carbon gain- ample?

Answer 26

Thin leaves, high turnover (increase of biomass) - High leaf nitrogen - High stomatal conductance - Low photosynthetic capacity

Question 27

why are plants central to the carbon cycle?

Answer 27

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%.

Question 28

shade intolerence?

Answer 28

Sun acclimated/adapted species (shade intolerant) Photosynthesis increases over a wider range of light levels Trade-off = high respiration rates (higher LCP)

Question 29

Relationship between leaf life span and traits that increase photosynthesis

Answer 29

Inverse relationship between leaf lifespan & traits that increase photosynthesis Long-lived leaves contain many non-photosynthetic compounds - Herbivore protection - Desiccation resistant

Question 30

how are plant interactions measured?

Answer 30

Measured in productivity of leaves: Allocation and structure of leaves (photosynthesis structures) – leaf area index

Question 31

how do canopy processes change over light intensities

Answer 31

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)

Question 32

sunlit vs shaded leaves + canopy

Answer 32

○ 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

Question 33

describe NPP

Answer 33

Net primary productivity (NPP) – NPP = GPP – RR -Difference between energy fixed and respiration rate

Question 34

describe GPP+ how it varies

Answer 34

Gross Primary Production (GPP) – Energy store during photosynthesis -Varies diurnally and seasonally in response to proximate controls: light, water, nitrogen, temperature, carbon dioxide

Question 35

what determines GPP variation? where and when is it highest?

Answer 35

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

Question 36

what is LAI? what does it effect?

Answer 36

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

Question 37

why is NPP half of GPP

Answer 37

NPP is about half of GPP because most ecosystems have similar efficiencies converting photosynthate to NPP

Question 38

respiration and plant growth?

Answer 38

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

Question 39

why does respiration impact plant growth?

Answer 39

1. Growth – cellulose and lignin are important compounds made by biosynthesis and contribute to the standing carbon pool 2. Maintenance – Energy for replacing proteins, membranes, and other tissues; increase temp=increase tissue turnover; accounts for 50% of total plant respiration 3. Ion transport – gradient required for nutrient uptake

Question 40

compensation point?

Answer 40

Compensation point – where light intensity is at the point where the rate of photosynthesis is equal to the rate of respiration

Question 41

why are terrestrial plants important to NPP biomes : life zone

Answer 41

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

Question 42

why are terrestrial plants important to NPP biomes : precip

Answer 42

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)

Question 43

biome differences in NPP?

Answer 43

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

Question 44

what creates variation in NPP

Answer 44

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

Question 45

What happens to NPP within a plant?

Answer 45

1. Growth within plant it takes 40 -70% of net primary production New roots (30-40%,) ; leaves (10-30) 2. 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%) 3. Losses to herbivores, mortality, and fire (1-40%) 4. Volatile emissions (0-5%)

Question 46

plant allocations to NPP?

Answer 46

Allocation to different parts influences survival, growth, and reproduction Leaves – Photosynthesis Stem – Support Roots – Uptake of nutrients and water Flower and seed – Reproductio

Question 47

measures of plant allocation of NPP

Answer 47

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

Question 48

what does NPP allocation change by?

Answer 48

1. Seasonal changes – resources and energy that would normally go onto leaves gets absorbed into plants and stored for next year’s leaf growth 2. 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)

Question 49

allocation of growth of tissue by biomes. good vs bad conditions?

Answer 49

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

Question 50

what are carbon fluxes

Answer 50

Ecosystem carbon balances: Net ecosystem production (NEP) = GPP – (R plant + R heterotr + R F disturb + F leach