#2 Why, even though tropical rain forests make up so little of the earth's surface and open oceans so much of it, do both have similar net primary productivity?

NPP, GPP, R, What the?

• GPP: Gross Primary Production: Total (Gross) primary production in an ecosystem or the amount of light energy that is converted to chemical energy by photosynthesis per unit time.

• NPP: Net Primary Production: Is equal to GPP minus the energy used by the primary producers for respiration.

• NPP = GPP − R(espiration)

To ecologists, net primary production is the most important measurement because it represents the storage of chemical energy that will be available to consumers in the ecosystem.

For example, in forests, the net primary production can be as little as one- fourth of the gross primary production. This is because trees have large masses to support, including trunks, branches and roots, so more energy is spent in respiration in forests that herbaceous/crop communities.

Net primary production can be expressed as energy per unit area per unit time (J/m2/yr) or asbiomass (weight) of vegetation added to the ecosystem per unit area per unit time (g/m2/yr).

PLANTS AND ALGEA – AUTOTROPHIC PRIMARY PRODUCERS CONVERTING ENERGY OF SUNLIGHT INTO CHEMICAL ENERGY FOR METABOLIC PRCESSES

Herbivores

CONSUMERS

CARNIVORES

Tropical rainforests are among the most productive terrestrial ecosystems and contribute a large portion of the planet’s overall net primary production. Estuaries and coral reefs also have very high net primary production,but their total contribution to global net primary production is relatively small because theseecosystems cover only about one-tenth the area covered by tropical rain forests. The open ocean contributes more net primary production than any other single ecosystem, but this is because of its very large size; net primary production per unit area is relatively low.

SO TROPICAL RAINFORESTS ACTUALLY HAVE A HIGHER PRODUCTION THAN OCEANS BECAUSE OF THE DENSE VEGETATION AND OPTIMAL CLIMATIC CONDITIONS, WHILE OCEANS HAVE A LOWER AMOUNT OF PRODUCTION BUT ON THE WHOLE PRODUCE MORE ENERGY BECAUSE OF THEY COVER SUCH A VAST AREA.

THE HIGH PRODUCTION OF TROPICAL FORESTS PER UNIT AREA