carbon and ecosystem productivity (terrestrial lecture 2)

Question 1

Define biome

Answer 1

areas of vegetation characterised by the same life form
- WHAT grows there

geographic/climate descriptions

 - WHERE it grows
  e. g. tropical rainforest/boreal forest

Question 2

How to measure:

• leaf productivity
• wood productivity
• root productivity
• net ecosystem CO2 exchange

Answer 2

leaf: litter traps
wood: allometric calibration
root: ingrowth cores/ mini rhizotrons

net ecosystem CO2 exchange: eddy covariance towers

Question 3

What does NASA MODIS do?

What does GOSAT do?

Answer 3

MODIS: Moderate Resolution Imaging Spectroradiometer

• measures reflection of Earth surface
• calibrated for LAI (leaf area index) or fPAR (fraction of photosynthetically active radiation absorbed by leaf canopies

GOSAT: Greenhouse Gases Observing Satellite
- measure CO2 & methane in atmosphere

Question 4

How do we estimate global GPP from space?

Define PAR, fPAR, pLUE

Answer 4

Solar induced fluorescence shows photosynthesis

GPP = PAR x fPAR x pLUE

PAR = photosynthetically active radiation
fPAR = fraction of photosynthetically active radiation absorbed by leaf canopies
pLUE: photosynthetic light-use efficiency

Question 5

Tropical rainforests vs Boreal forests

leaf type, ecosystem characteristic, C uptake, C turnover rate

Answer 5

Tropical rainforests

• evergreen broadleaves
• wet tropics
• high C uptake year round
• rapid C turnover

Boreal forests

• evergreen needleleaves
• v cold winters
• seasonal C uptake
• slow C turnover

Question 6

What are the climate controls on NPP?

What controls biome productivity? Relation to climate correlation?

Answer 6

NPP correlates with climate across biomes

Relationship with precipitation is a humpbacked curve, temperature more linear

Growing season length and leaf area are main control on biome productivity, climate correlation is via these factors

Question 7

Observing photosynthesis seasonality from space:

• how to measure
• effect on temperate evergreen conifer ecosystems

Answer 7

photosynthesis correlates with the chlorophyll:carotenoid ratio - CCL (chlorophyll:carotenoid spectral index)

seasonality in photosynthesis controls seasonal variation in GPP in temperate evergreen conifer systems