2.3 NPP vs GPP
Net Primary Productivity
an ecosystem's NPP is the rate at which plants accumulate dry mass (actual plant material) usually measured to g m -2. This glucose produced in photosynthesis has two main fates. -Some provides for growth, maintenance and reproduction (life processes) with energy being lost as heat during processes of respiration. -The remainder is deposited in and around cells as new material and represents the stored dry mass - this store of energy is potential food for consumers within the ecosystems.
Primary Productivity
autotrophs are the base unit of all stored energy in any ecosystem. Light energy is converted into chemical energy by photosynthesis using chlorophyll within the cells of plants.
Productivity
is the conversion of energy into biomass over a given period of time. It is the rate of growth or biomass increase in plants and animals. It is measured per unit area per unit time, eg per metre^2 per year. (m^-2 yr^-1)
Biomass
is the living mass of an organism or organisms but sometimes refers to dry mass.
Secondary
is to do with animals
Gross Primary Productivity
[GPP] is the total gain in energy or biomass per unit area per unit time by green plants. It is the energy fixed (or converted from light to chemical energy) by green plants by photosynthesis. But, some of this is used in respiration so...
Gross Productivity
[GP] is the total gain in energy or biomass per unit area per unit time. It is the biomass that could be gained by an organism before any deductions.
Net Primary Productivity
[NPP] is the total gain in energy or biomass per unit area per unit time by green plants after allowing for losses to respiration. This is the increase in biomass of the plant - how much it grows - and is the biomass that is potentially available to consumers (animals) that eat the plant. NPP = GPP - R where R = respiratory loss
Primary
in ecology means to do with plants.
Gross Primary Productivity
plants are the first organisms in the production chain. They fix light energy and convert it to sugars so it is theoretically possible to calculate a plant's energy uptake by measuring the amount of sugar produced (GPP).
Net
refers to the amount left after deductions are made, eg costs of production or deductions of tax and insurance from a salary. It is what you have left and is always lower than the gross amount.
Gross
refers to the total amount of something made as a result of an activity, eg profit from a business or salary form a job.
Net Productivity (NP)
results from the fact that all organisms have to respire to stay alive so some of this energy is used up in staying alive instead of being used to grow.
