Quantitative Analysis by the Point-Centered Quarter Method

TL;DR

This paper introduces the point-centered quarter method for ecological sampling, explaining its history, methodology, practical issues, and how to analyze data to estimate plant density and importance values, enhanced with R Shiny Apps for calculations.

Contribution

It provides a comprehensive overview of the point-centered quarter method, including new R Shiny Apps for data analysis and updated practical guidance.

Findings

Methods for estimating plant density and confidence intervals

Use of R Shiny Apps for data analysis

Practical modifications for field use

Abstract

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.