Ecological Techniques

Module 5

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The Quadrat

This is simply a metal, plastic or wooden square!

Measuring 0.5m x 0.5m

Or 1m x 1m

It is used for estimating numbers in an ecosystem where the organisms are fixed in position (like plants) or relatively static

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How to use a quadrat

Quadrats are usually used to study the distribution of plants in a fairly uniform area

Such as a rocky shore, a field or a heathland

The quadrat must be placed randomly

Randomness is important to avoid bias

If a method to generate randomness is not used it is very difficult to avoid bias

If your estimating the number of daisies in a field it would be difficult to know where to place the quadrat

It would be tempting to place it where there were lots of daisies and to avoid places where there are not very many

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Random numbers

The area to be studied needs to be marked out with ropes or string, marked at 1m intervals. (knots are a good way of doing this)

Random numbers can be generated using a calculator

Random numbers can also be generated by putting pieces of paper with numbers on into a container, two numbers are taken out which represent the coordinates of the marked area

The quadrat is placed in the appropriate grid

Or we can define the area that you are studying (string, rocks etc)

Walk into the defined area

A random number is chosen (taking a number out of a hat)

A method of chossing a random direction is chosen (a straw in a bottle-spun round, a roulette wheel type device)

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Random number continued

Having randomly chosen the direction and a number, the person doing the study walks that number of paces

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