Agricultural ecosystems

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What is an agricultural ecosystem?

They are ecosystems developed by humans; comprising of domesticated animal and plants used to produce food for mankind.

Humans are often the third or fourth trophic level in natural ecosystems, so recieve little of the energy absorbed from the Sun.

Therefore, agriculture ensures as much as possible of the Sun's availible energy is transferred to humans. This channels more energy directly into the human food chain, so productivity is upped. 

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Key words

Productivity- The rate at which something is produced

Gross Productivity- The rate at which plants assimilate chemical energy

Net productivity- Remaining energy left after some 20% is used for respiration

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Differences between natural and agricultural ecosy

Natural:

-Solar energy only

-Lower productivity

-More species diversity

-More genetic diversity within a species

-Nutrients are recycled naturally with little help from outside addition

-Populations are controlled naturally (e.g. competition)

-Natural climax community

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Differences between natural and agricultural ecosy

Agricultural:

-Solar + energy from food and fossil fuels

-Higher productivity

-Lower species diversity

-Less genetic diversity within a species

-Limited natural recycling supplemented by pesticides (artificial)

- Populations controlled naturally along with pesticides and cultivation

- Artificial community - prevented from reaching natural climax.

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Energy input (agricultural ecosystem)

To prevent a climax community, agricultural ecosystems need aditional energy sources to increase productivity.

This comes in two forms:

1) Food (farmers expending energy)

2) Fossil fuels (due to mechanised farming, fuel used to plough, harvest, transport)

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Productivity (agricultural ecosystem)

In agricultural ecosystems, additional energy is used to reduce the effect of limiting factors on growth; e.g. light, minerals, CO2.

By using pesticides and fertilizers to add essential ions.

The energy is used to exclude other species so the crop has little competition for resources so productivity is increased.

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