1,300
g C/m²/yr
52
%
1,300
g C/m²/yr
52
%
The Net Primary Productivity (NPP) Calculator determines the rate at which an ecosystem produces and stores biomass, after accounting for the energy used by plants for their own respiration. NPP represents the net amount of carbon fixed by autotrophs that is available to heterotrophs in the food web.
NPP is a fundamental measurement in ecosystem ecology, as it drives all consumer production and decomposition. It varies widely among ecosystems, from less than 100 g C/m2/yr in deserts to over 2,000 g C/m2/yr in tropical rainforests and productive estuaries.
Net Primary Productivity is calculated as:
NPP = GPP - Ra
Where:
The NPP/GPP efficiency ratio shows what fraction of total photosynthesis is retained as biomass. Typically, plants use 40-60% of GPP for respiration, so NPP is 40-60% of GPP.
Inputs
Results
NPP = 2500 - 1200 = 1300 g C/m2/yr. This forest retains 52% of its gross production as biomass.
Inputs
Results
Desert NPP is very low at 50 g C/m2/yr. Plants use 75% of GPP for respiration due to harsh conditions.
Net Primary Productivity is the rate at which producers (primarily plants) accumulate biomass after subtracting the energy they use for respiration. It represents the energy available to all other organisms in the ecosystem and is measured in grams of carbon per square meter per year.
NPP determines the energy base of the entire food web. Higher NPP supports more consumers, greater biodiversity, and more complex trophic structures. It is also critical for understanding carbon cycling, climate change effects, and ecosystem services like carbon sequestration.
Tropical rainforests (1,000-2,200 g C/m2/yr), estuaries, and coral reefs have the highest NPP. Agricultural lands can also be highly productive. The open ocean has low NPP per unit area but contributes enormously to global NPP due to its vast extent.
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