Sample units are the members of the population from which measurements are taken during sampling. Sample units are distinct and non-overlapping entities, such as quadrats or transects, individual plants, branches within a plant, etc.
Characteristics of the sample unit have a significant effect on sample accuracy and sample precision (and therefore sampling costs). Sample unit dimensions may also be manipulated to promote a normal distribution in the collected data that will permit the application of conventional analysis of variance models for statistical analysis.
Types of Sample Units
The form of the sample unit must be decided during the planning stages for the inventory or monitoring program because the goals of these efforts will require a particular sample unit. The general goal of inventory or monitoring programs is to describe attributes of the vegetation at a site. Therefore, sample units are usually one of the following types of delineated small-scale area within the general area of interest.
The following aspects of sample units are also important to consider:
References and Further Reading
Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Son, New York, NY. pp 1-40.
Kent, M., and P. Croker. 1992. Vegetation description and analysis. Belhaven Press, London. pp 40-56.