Quadrats Arranged as a Group of Subsamples to Determine Density
When the sampling layout for density involves quadrats arranged as a group of subsamples under the principles of systematic sampling, the group of quadrats (usually positioned to traverse an area) forms the sample unit. Density for each quadrat group must be calculated by obtaining a total group tally and then dividing by the number of quadrats, before dividing this value by the quadrat area to standardize the units of measurement. These sample means for each quadrat group comprise the values used in the statistical analysis of density data, and usually have a smaller sample variance compared to data from randomly located quadrats to determine density.
References and Further Reading
Bonham, C.D. 1989. Measurements for terrestrial vegetation. John Wiley Sons, New York. pp. 145-146.
Bureau of Land Management. 1996. Sampling vegetation attributes. Interagency Technical Reference, BLM/RS/ST-96/002+1730. pp. 101-102.
Lindsey, A.A. 1955. Testing the line-strip method against tallies in diverse forest types. Ecology 36:485-495.