Principles of Vegetation Measurement & Assessment
and Ecological Monitoring & Analysis


Veg Sampling
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Module 6 - Frequency or Abundance

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Lesson Instructions

  1. Read through the Overview and Learning Objectives.
  2. Complete the Required Reading.
  3. Read and review the Lectures.
  4. Visit suggested Internet Sites in the lectures.
  5. Check the schedule for the required Assignment.
  6. Complete assignments and submit by Blackboard:
       Content Summary due by Midnight on Tuesday, October 09.
    Data Summary
    due by Midnight on Tuesday, October 16.

ReadingSuggested Further Reading:


  • Sampling to Estimate Frequency, Chapter 12 (pp 206-215), Monitoring Plant & Animal Populations by C.L. Elzinga et al. 2001. (Blackwell Science).

  • Frequency & Cover, Chapter 4 (pp 89-130),

    Measurements of Terrestrial Vegetation by Charles Bonham (Wiley)



Suggested Internet Sites:

Learning Materials


Required Reading:


Slides Lecture




What this Lesson Covers


The easiest and most objective measurement in vegetation sampling is to simply declare if a plant is present or not.  When several plots or quadrats are examined then the proportion of plots in which you declare a plant "present" is known as Frequency.  In other words, if you examine a bunch of plots across a landscape and you find a particular plant in 75% of the plots, then, the plant's frequency is 75%. The challenge in using frequency when assessing plant communities is not in the estimating... it is in the analysis.

In this module, we will examine how to measure Plant Frequency and give decision guidelines for when to measure frequency instead of other plant attributes.  Plus, we will include a few tips for analysis of frequency data.

Learning Objectives

After this module you will be able to:

  • Understand the what plant frequency is and when to use it for vegetation assessment. 

  • Explain the difference between frequency, density, and cover.

  • Understand the advantages and challenges in using frequency for characterizing vegetation.

  • Compare single quadrat versus nested quadrat techniques

  • Analyze frequency data when comparing plant communities.