In many biodiversity studies, the area you're working with can be too large to count every plant or animal present. The practical solution is to take samples using quadrats.
Quadrats are sample areas (usually squares or rectangles) marked out on the ground and used to record the number of species present or count individuals of various species. They are useful for studying plants and slow moving animals. In situations where the quadrats are fixed in position they can be used to detect changes over time.
Quadrats can be any size. For instance a one metre square quadrat can be useful to count individual small plants in order to monitor a direct seeding project. On the other hand, a ten metre square quadrat will be more suitable for recording plant species present in mature bushland.
You can make the quadrat, depending on size, using:
Quadrat sampling can be done at random, on a grid pattern or at set points along a transect line.
You can do your recording once you have your quadrat in position. Work in pairs for a small quadrat, with one person to observe and one to record. With larger quadrats you may find it helpful to work in a team with three or four people.
Follow these steps to use a 1m x 1m quadrat to estimate a plant population. Your supervisor will help you with this.
In a sample area chosen by your supervisor, place your quadrat at random. You can do this by throwing the quadrat over your shoulder or simply placing it in any location.
Count the number of plants present for the nominated plant species and record these numbers on the recording sheet.
Repeat the above process until you have covered ten areas using your quadrat.
Note: Using your quadrat in 10 different areas will equal 10m².
On your Recording Sheet add up the total number of plants you recorded for each species. This will give you the population density for 10m².
You can then easily calculate the estimated population density for 100m² by multiplying your answer by 10.
An example has been given on the Recording Sheet to help you out.
You can see that the sheet records data on the natural density of two small legume shrubs. This information will be useful in planning future revegetation work in the area.