2.3 Flows of energy and matter

Solar constant

The amount of solar energy reaching the top of the atmosphere of Earth being 1400 watts per second.

Productivity

The conversion of energy into biomass over a given period of time.

• Rate of growth of biomass in plants and animals

• measured in unit area per unit time

Primary

Dealing with plants

Gross primary productivity (GPP)

The total gain in energy or biomass per unit area per unit time by green plants.

• Energy converted from light to chemical energy

• Doesn’t consider anything loss

Net primary productivity (NPP)

Total gain in energy or biomass per unit area per unit time by green plants after allowing for losses to respiration

• Increase in biomass of plant

• Calculated with NPP = GPP-R

  • R = respiration

Secondary

Dealing with animals

Net secondary productivity (NSP)

The total gain in energy or biomass per unit area per unit time by consumers after allowing for losses to respiration.

• NSP = Energy in the food ingested - Energy lost in egestion (feces) - energy used in respiration

• Carnivores assimilate 80% of energy in diet and egest less than 20%

• Herbivores 40% of energy in diet and egest 60%

Biogeochemical cycle

The pathway through which a chemical substance moves through biotic and abiotic components of Earth. It includes processes like photosynthesis, respiration, decomposition, and nutrient cycling.

Carbon cycle

THe presence of organic and inorganic carbon molecules in both human-made and natural processes such as combustion, fossil fuels, soil microorganisms, photosynthesis, respiration, all part of the carbon cycle.

Carbon fixation

Carbon Fixation

When carbon dioxide from the atmosphere is converted into organic compounds by plants during photosynthesis. T

Nitrogen cycle

When nitrogen is converted between its various chemical forms in the environment, including nitrogen fixation, nitrification, assimilation, ammonification, and denitrification.

Nitrogen fixation

When atmospheric nitrogen is made available to plants through the fixation of atmospheric nitrogen.

• Done by nitrogen fixing bacteria, cyanobacteria, lightning and the industrial Haber process.

Nitrification

The process of nitrifying bacteria in the soil converting ammonium into nitrites and then nitrites into nitrates which can be absorbed into plants

Denitrification

The opposite of nitrification where denitrificating bacteria convert nitrates, nitrites and ammonium into nitrogen gas that escapes into the atmosphere.

Decomposition

The breakdown of dead organisms by detrivores and saphotrophs into proteins and nitrogen ions.

• These are then absorbed into plants

Assimilation

When living organisms take in nitrogen and build it into complex molecules.

Trophic efficiency

The efficiency of transfer from one trophic level to the next.

Anthropogenic

A process, effect or activity derived from humans

Maximum sustainable yield

The largest crop or catch that can be taken from the stock of a species (forest, shoal of fish), without depleting the stock.

Energy subsidy

The additional energy that has to be put into the system other than the natural energy there

• Energy other than the sun for farming

  • Human and animal labor

  • system without energy subsidy will die

Gersmehl’s nutrient flow model

A model that shows the relationship between biomass, litter and soil

• Biomass is nutrients in vegetation and animals

• Litter is nutrients in dead organisms and leaves

• Soil is nutrients in decomposing matter and soil humus