Gross and net primary productivity.

GPP split into respiration and NPP; NPP is what herbivores and decomposers can use.

Set GPP and R so that NPP is exactly 1200 kcal m⁻² yr⁻¹ while respiration takes more than half of GPP.

Writing NPP = GPP + R.

• Every ecosystem needs a steady supply of solar energy to keep working.
• Primary production is the organic matter (biomass) that plants make by photosynthesis on a unit of area over a stated period. It is expressed as weight (g m⁻²) or energy (kcal m⁻²).
• Productivity is the rate of biomass production, expressed as g m⁻² yr⁻¹ or kcal m⁻² yr⁻¹, so that different ecosystems can be compared.
• Gross primary productivity (GPP) is the rate at which organic matter is made in photosynthesis. Plants use a considerable part of it in respiration.
• Net primary productivity: GPP − R = NPP, where R is the respiration loss. NPP is the biomass available to heterotrophs (herbivores and decomposers).
• Secondary productivity is the rate at which consumers form new organic matter.
• Primary productivity depends on the plant species of an area, environmental factors, nutrient availability and the photosynthetic capacity of plants, so it differs between ecosystems.
• The annual NPP of the whole biosphere is about 170 billion tons (dry weight) of organic matter.
• Oceans cover about 70 per cent of the surface but produce only 55 billion tons of it; the rest is produced on land.

Teaching this idea? Put the simulation on your own page or LMS with this code.