A quadrat sample used to measure the percentage cover of certain species.
A quadrat is a measured and marked rectangle, often a square, used in ecology to isolate a sample.
When an ecologist wants to know how many organisms there are in a particular habitat,it would not be feasible to count them all.Instead,he would be forced to count a smaller representative part of the population,called a sample.Sampling of plants,or animals that do not move much(such as snails),can be can be done using a sampling square called a quadrat. A suitable size of a quadrat depends on the size of the organisms being sampled.For example,to count plants growing on a school field,you could use a quadrat with sides 0.5or 1 meter in length. It is important that sampling in an area is carried out at random,to avoid bias. For example,if you were sampling from a school field, but for convenience only placed quadrats next to a path,this might not give you a sample that was representative of the whole field.It would be an unrepresentative,or bias,sample.It usually consists of a 100 squares. One way you can sample randomly is to place the quadrats at coordinates on a numbered grid.
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