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Lecture 4

Lecture 4-biob50.docx


Department
Biological Sciences
Course Code
BIOC50H3
Professor
Marc Cadotte
Lecture
4

Page:
of 2
Lecture 4: (19-01-12)
Primary producers only give about 1% of their energy to others
There’s less and less energy as you go up the chain (10000-100-10)
Photosynthesis: organisms convert solar energy into chemical energy, they take up CO2
and synthesize compounds
Primary production;
Measure the amount of carbon in order to measure the energy in organisms
o GPP: it depends on climate and LAI (what area of ground is covered by leaves)
The space between the lines is getting smaller and smaller (as more leave
layers, the amount of carbon dioxide is increasing)
o NPP: GPP-respiration (amount of biomass gained by plant, whatever energy is not
used by the plants gets turned into biomass)
Higher temperature: large NPP (and much lower in deserts)
It’s hard to detect for belowground (lifecycle is short and hard to measure-
so people use tubes with a camera into the soil and get a sense of how
many roots are there and the amount of biomass)
Measuring: just take a tape and measure them (but if it is large place, you measure
chlorophyll concentrations) or you use NDVI (difference between visible light and near-
infrared)
Just like roots, phytoplankton have a short life span (if you measure the amount of
carbon, carbon come and die quickly because they don’t accumulate)
o People grow phytoplankton in light and no light and measure the amount of CO2
and O2 (the difference equals to NPP)
o The chrophyll is concentrated in coastal (near shore areas because there is
upwelling- water is bringing in nutrients)
o We get max primary production near the equator becomes of the climate (global,
terrestrial)
Environmental controls on NPP:
Water and temperature affects NPP (in places that are already moist do not benefit from
adding more water where places with no water will benefit)
Increase in temperature, there a growth in NPP
Nutrients are also important (nitrogen is important for plants)
Alpine (depending on which side of the mountain you are on, it can be really wet or dry),
wet: increase in biomass was driven by increasing the biomass of the dominant species
and the opposite was true for dry meadow
Experiment done in Experimental Lakes Area in Ontario (p.421): what limits primary
production in lakes: Phosphorus was limiting growth (he compared two lakes, and it
changed colour with the addition of P): some cleaning products contained P which was
flushing out into lakes and killing fishes, etc (dead zones are low in O)
In open ocean, the growth is limited by N not P
In equatorial Pacific Ocean, it is limited by iron (read p.422-423 in detail)