  This document is an introduction to the use of the point-centered quarter
method. It briefly outlines its history, its methodology, and some of the
practical issues (and modifications) that inevitably arise with its use in the
field. Additionally this paper shows how data collected using point-centered
quarter method sampling may be used to determine importance values of different
species of trees and describes and derives several methods of estimating plant
density and corresponding confidence intervals.
  New to this version is a revision of Appendix D which now includes R Shiny
Apps to carry out many of these calculations. References to data sets in the
previous version that are no longer publicly available have been removed. These
have been replaced with examples and exercises which demonstrate the use of the
R Shiny Apps and the earlier R scripts.
