Arrangement of Points

Observations based on single points, such as the step point method, tend to take less time to record and give a more precise estimate of cover than do the same number of points sampled as a group, such as the point frame method.

However, this generalization should be reevaluated for each situation, because if individual sampling points are widely spaced or difficult to locate, grouped points can generate time advantages and greater sampling efficiency. Measurements obtained from single points are also more accurate, whereas groups of points may overestimate cover in vegetation with patchy spatial patterns. Randomly located points are more desirable for the statistical analysis of cover data, but systematic allocation following a randomly determined starting point is generally more practical.

References and Further Reading

(Note: pdf files require Adobe Acrobat (free) to view)

Bonham, C.D. Measurements of terrestrial vegetation. John Wiley Sons, New York, NY. pp 110-111.

Greig-Smith, P. 1983. Quantitative plant ecology. Academic Press, New York, NY. pp 41-45.

Goodall, D.W. 1952. Some considerations in the use of point quadrats for the analysis of vegetation. Australian Journal of Scientific Research 5:1-41.

Fisser, H.G., and G.M. Van Dyne. 1966. Influence of number and spacing of points on accuracy and precision of basal cover estimates. Journal of Range Management 19:205-211. (pdf)

Kemp, C.D., and A.W. Kemp. 1956. The analysis of point quadrat data. Australian Journal of Botany 4:167-174.