what is a quadrat
The usual sampling unit is a quadrat. Quadrats normally consist of a square frame, the most frequently used size being 1m (see picture below). The purpose of using a quadrat is to enable comparable samples to be obtained from areas of consistent size and shape.For instance, you cannot compare data obtained using a circular quadrat, with data obtained using a square quadrat. The difference in shape of the sampling units will introduce variations in the results obtained.). right: A quadrat is used to sample the species present in a habitat.