Net primary prductivity and efficiency of biomass transfer

what is net primary productivity

• The rate at which the light is used to make organic material by producers is determined by the rate of photosynthesis.

• Small percentage of light from the sun results in production of plant material. 1-3%

why energy lost from sun to plant

• Light passes through leaves or is reflected away

• Light hits non-photosynthetic parts of the plant e.g. bark or flowers

• Light is a mixture of wavelengths and only certain wavelengths are absorbed in photosynthesis

• Plants release energy during respiration, some of which is lost to the environment in the form of heat

what is gross primary productivity

Gross primary productivity in plants is the rate at which it produces biomass by

We can measure it in units gC m-2year-1 grams of carbon assimilated per metre squared per year.

Could also look at energy kJ m-2year-1photosynthesis.

why net primary productivity difficult to measure?

Productivity is difficult to measure. The mass of samples should be taken and then these are scaled to represent theecosystem.

why biomass used in plants

• Plants use 25% of the biomass they produce in respiration.

They do this to release energy for their own metabolic needs.

• They respire and they breakdown glucose to make ATP.

Respiration is exothermic. It increases the internal energy store of surroundings. The remainder of the material is stored in new plant tissue. The energy stored in biomass is known as net primary productivity.

GPP-R = NPP

why different ecosystems will lead to differences in NPP?