Calculating Importance Values Using the Point-Center Quarter Method


Instructions for Using the PCQM Calculator

  1. If you are not familiar with importance value calculations, you should first read the PDF file of Quantitative Analysis by the Point-Center Quarter Method.

  2. Enter the data into the calculator in the same manner.
  3. Press the "Do Calculations" button at the top of the calculator.
  4. The mean basal area, number of trees per hectare, the relative density, relative cover (also known as the relative dominance), the relative frequency, and the importance value (sum of the last three items) for each species will appear at the bottom of the input table.
  5. Estimates of the mean distance between trees (without regard to species) and the absolute density of all trees are also calculated.

Format of Data Table

PointQuarter SpeciesDistance (m)DBH (cm)DBH (cm)DBH (cm)DBH (cm)
11Acacia1.16
.2Eucalyptus1.648
3Casuarina2.315
4Callitris3.011
21Eucalyptus2.865
2Acacia0.986
3Casuarina3.716
4Casuarina2.29
31Acacia2.84
2Acacia1.16
3Acacia3.26
4Acacia1.45
41Callitris1.319
2Casuarina0.822
3Casuarina0.712
4Callitris3.17
51Acacia1.57
2Acacia2.45
3Eucalyptus3.327
4Eucalyptus1.736

Additional Notes:


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