Production

Question 1

What is Primary Production?

Answer 1

• the fixation of energy by autotrophs in a ecosystem
• amount of energy fixed by autotrophs over an interval of time (measured as a rate -e.g., kgC per km2 per unit time)
• is the gateway for energy and nutrients entering food webs

Question 2

What is the biggest source of primary production?

Answer 2

photosynthesis by plants, phytoplankton and cyanobacteria
- also can occur via chemosynthesis by some species of bacteria

Question 3

What is the Redfield Ratio?

Answer 3

• ratio at which elements are fixed by plants during photosynthesis
• 106C:16N:1P

Question 4

What are the two measures of primary production?

Answer 4

1. gross primary production (GPP)
2. net primary production

Question 5

Gross Primary Production

Answer 5

• total amount of energy fixed by all autotrophs in an ecosystem
• GPP = photosynthesis

Question 6

Net Primary production

Answer 6

• the total amount of energy fixed by all the autotrophs in the ecosystem, minus the cost associated with its function
• only refers to the amount of energy available to the consumers in an ecosystem

Question 7

How can we quantify primary production?

Answer 7

NPP is estimated by increase in plant biomass in experimental plots and scaling up to the whole ecosystem
- harvest techniques (DBH)

Question 8

What is remote sensing?

Answer 8

• science of acquiring information about the Earth’s surface without being in contact with it
• sensing and recording of reflected or emitted energy
• cameras/sensors mounted to satellites, planes and drones take photos and record reflected light vs absorbed light

Question 9

What is remote sensing really telling us?

Answer 9

quantifies wavelengths that are reflected off of the earth’s surface (aka light)

Question 10

NDVI

Answer 10

• normalized difference vegetation index
• ration of near red to red reflectance (“greeness”)
• basically assessing chlorophyll concentrations - a spectral signature that may be a proxy of GPP/NPP

Question 11

What is NDVI used for?

Answer 11

used to estimate CO2 uptake and NPP, deforestation, desertification, atmospheric pollution and other phenomena

Question 12

Values of NDVI?

Answer 12

• will always be a value between -1 and +1
• an area with nothing growing = NDVI of zero
• NDVI <0 suggest lack of dry land

Question 13

Terrestrial NPP

Answer 13

• generally limited by temperature and moisture
• highest rates of terrestrial primary productivity occur in warm, moist conditions

Question 14

Actual Evapotranspiration

Answer 14

• AET
• total amount of water that evaporates and transpired during given time period (usually a year)

Question 15

How does soil fertility influence NPP?

Answer 15

NPP can be increased by adding nutrients to the soil

Question 16

Liebig’s Law of the Minimum

Answer 16

plant growth is not limited by the total amount of all soil nutrients available but by the soil nutrient variable that is present in the lowest quantity

Question 17

Marine NPP usually greatest near the shores of oceans where:

Answer 17

• nutrients from the terrestrial runoff arrive
• nutrients arise from disturbance of bottom sediments
• nutrient upwellings arrive from the greater water depths