Wandering Quarter Method
The wandering quarter method was developed by Catana in the 1950's as a plotless technique to estimate density. Adapted from the point-center quarter method, the wandering quarter method is based on non-parametric statistical procedures. Therefore, its validity is not restricted to species following random spatial patterns, and it is less sensitive to bias when plants exhibit contagious or regular arrangements.
In the wandering quarter procedure, a starting point is selected and then a compass is used to decide a direction to proceed from that point. From the first plant encountered, a 90° exclusion angle is determined forwards along the directional line (centered to form a 45° angle either side of the line). The nearest plant within this exclusion angle is identified and its distance is measured and recorded. This procedure is repeated after progressing to that plant, keeping the exclusion angle at the same alignment as at the starting point.
Density is calculated by nonparametric techniques which use sample mean and modal values to identify the scale of the contiguous spatial pattern and to determine distances within and between pattern clumps. Details of these mathematical techniques are described in Bonham (1989) or Catana (1953). The complicated computational requirements are a disadvantage of the wandering quarter method.
References and Further Reading
(Note: pdf files require Adobe Acrobat (free) to view)
Becker, D.A., and J.J. Crockett. 1973. Evaluation of sampling techniques on a tall-grass prairie. Journal of Range Management 26:61-65. (pdf)
Bonham, C.D. 1989. Measurements for terrestrial tegetation. John Wiley Sons, New York. pp. 169-174.
Catana, A.J. 1953. The wandering quarter method of estimating population density. Ecology 44:349-360.
Lyon, J.L. 1968. An evaluation of density sampling methods in a shrub community. Journal of Range Management 21:16-20. (pdf)