gross, net and primary productivity

how can biomass be measured ?

• in terms of mass of carbon

• dry mass of tissue in a given area

how can you estimate energy store in dry biomass ?

using a calorimeter

what is gross primary production (GPP) ?

the chemical energy store in plant biomass in a given area/ volume

What is net primary production (NPP) ?

the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account

what is net primary production available for plants ?

available to other trophic levels in the ecosytems such as herbivores & decomposers

what are producers ?

• photosynthetic organisms

• manufacture organic substances using light, energy, water & CO2

• e.g. green plants & algae

what are consumers ?

• obtain their energy by feeding on other organisms

• producers →primary consumers → secondary consumers → tertiary consumers

what are decomposers ?

• bacteria & fungi that break down complex materials in dead organisms into simple components

• releases valuable mineral ions e.g. nitrates can be absorbed by plants

what is biomass ?

light energy captured by plants & used to make glucose

why is such a small amount of sun energy converted into organic matter ?

• 90% reflected back into space

• not all wavelengths absorbed can be used for photosynthesis

• some may not fall onto chlorphyll

what does NPP have to do with animals ?

this chemical energy is available to other trophic levels in the ecosystem

how to calculate NPP for plants ?

GPP - R

r = respiratory losses

GPP = gross primary production

what is net production for consumers ?

N = I - (F + R)

N = net production

I = chemical store of ingested food

R = energy lost in respiration