Quadrats are two-dimensional sample units of any size or shape. In some cases, a tape may be laid on the ground at each sampling location to define the quadrat, but more often the quadrat is a frame created from narrow steel or plastic piping and carried from one sampling location to the next. Quadrats are used to measure most vegetation attributes in most vegetation types.
Permanent quadrats are a useful technique when the site is repeatedly sampled to monitor changes in a vegetation attribute, such as frequency or density. Quadrat location may be marked by pegs or by following a grid system. Although labor-intensive to establish, the permanent siting of quadrats offers the considerable advantage of removing some of the error associated with different placement of the sample unit at each sampling event. Therefore, these techniques are most suitable for small scale studies, but are generally impractical for large scale inventory or monitoring programs.
References and Further Reading
Austin, M.P. 1981. Permanent quadrats: An interface for theory and practice. Vegetatio 42:11-21.
Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Son, New York, NY. pp 19-40.
Goldberg, D.E., and R.M. Turner. 1986. Vegetation change and plant demography in permanent plots in the Sonoran Desert. Ecology 67:695-712.
Kent, M., and P. Choker. 1992. Vegetation description and analysis. Belhaven Press, London. pp 40-44.
Roshier, D., Lee, S., and F. Boreland. 1997. A digital technique for recording plant population data in permanent plots. Journal of Range Management 50:106-109.