5.10

Question 1

Give the definition and units of GPP

Answer 1

Gross Primary Production - rate of energy made into organic molecules during photosynthesis
kJ m-2 y-1

Question 2

Give the definition and units of NPP

Answer 2

Net Primary Production - rate of energy made into biomass
kJ m-2 y-1

Question 3

Give the definition of R

Answer 3

Respiration - release of energy for metabolic use
kJ m-2 y-1

Question 4

Give the formula to show the relationship between GPP, NPP and R

Answer 4

NPP = GPP - R

Question 5

The GPP of a grassland is 10,200 kJ m-2 y-1. The efficiency of energy transfer from GPP to NPP is 35%. Calculate the values of NPP and R.

Answer 5

NPP - 10,200 x 0.35 = 3,570 kJ m-2 y-1
R - 10,200 - 3,570 = 6,630 kJ m-2 y-1

Question 6

Producers have an energy intake of 14,526 kJ m-2 y-1 and fix 4657 kJ m-2 y-1 as biomass. Calculate how much energy is lost via respiration.

Answer 6

NPP = GPP - R
R = GPP - NPP
R = 14,526 - 4,657 = 9,869 kJ m-2 y-1