Sampling Methods
The aim of sampling is to select a sample which is representative of the population. We can either randomly or systematically sample any area.
It may be useful to undertake stratified sampling in certain ecosystems. Stratified sampling is simply the process of identifying areas within an overall habitat, which may be very different from each other and which need to be sampled separately. Each individual area separately sampled within the overall habitat is then called a stratum. If the habitat is fairly uniform, this is unnecessary. Important: if you are looking at vertical strata, then you clearly won’t be using quadrats or transects!
The picture shows stratified random sampling comprising of four strata: woodland, rangeland, corn field, and soybean field.
Both systematic and random sampling can be utilised once you have stratified an ecosystem. Stratified systematic is missing from the diagram, but this could also be done.
Give one limitation of using a line transect to collect data.