Principles of Vegetation Measurement & Assessment
and Ecological Monitoring & Analysis


Veg Sampling
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Pitfalls and Problems

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Readings & Instructions

  1. The section covers Chapter 4 of Measuring and Monitoring Plant Communities.
  2. This lesson provides an introduction to what the term monitoring means as it is applied to natural resources. Brown text highlights key words.
  3. Read through the Text and work through the Summary Questions at the end of the text.

monitoring Challenges

Monitoring: Pitfalls and Problems

Some sage advice -- Once monitoring has started, be willing to adapt the objectives and methods with reality. No matter what you plan for it will invariably be different once you arrive in the field!


This unforeseen condition could be as simple as planning for 20 days of work and because of weather or transportation problems you only get 12 days. Another example could be that once you start collecting data you find that one of the measurements you want to make at each plot takes twice as long as you thought it would. Therefore, depending on its value to your dataset, it may not be worth the extra collection time, especially since without the measurement you would be able to sample more plots. Another common an unforeseen occurrence is that during preliminary analysis of your data (before data collection is completed), you may find that the measurements you have collected do not provide the necessary information to answer your monitoring questions. In such cases, you will need to re-evaluate and revise your measurements and methodology.

In general, monitoring is not perfect and many factors can ruin your hard sought efforts. A few of the more common reasons include:

  • Poor planning such as arranging fieldwork during late fall, when plants are dormant an difficult to identify therefore obscuring what you are trying to monitor.

  • Poor design by not taking measurements in all representative areas or not including an unaffected area (i.e., a control) and thus not being able to assess whether certain factors are responsible for what you are observing.

  • Inconsistent observations arise by having more than one observer taking measurements, when a standard has not been agreed to or is not being followed. For example, for ocular estimation of shrub cover in a quadrat a standard could involve each observer taking their measurements and comparing their independent results with the known cover measure as measured in a more objective fashion.

  • Problems can occur when data is entered incorrectly into data sheets or is typed incorrectly into the analysis software.

  • Incorrect inferences about what the data means can occur when it is not analyzed correctly because the person does not have the necessary skills.

  • Finally, nature sometimes does that which we donít expect. We could have the best plan and design in the world, and a wildfire could pass through the week before we planned to sample.


** An excellent overview of common problems encountered in monitoring is presented in Appendix 1 of Measuring & Monitoring Plant Communities.

Implement Monitoring as a Pilot Study


Photo - K. Launchbaugh

It is always a good idea to envision difficulties in data collection or analysis.  A successful monitoring protocol ensures that:

  • Necessary and useful information will be collected.

  • Time and resources will not be wasted by collecting data that is not related to the objectives or does not give the intended information.

To avoid these pitfalls, it is wise to plan a pilot study that includes a "real world" trial of the monitoring protocol to expose problems while the protocol can be revised to address these problems. 


On pages 20-21 of Measuring and Monitoring Plant Communities, Elzinga, Salzer, and Willoughby suggest 4 steps to testing out a field protocol in a Pilot Study:

1. Collect field data and evaluate field methods.

  • Is the sampling unit you selected the right size or shape?

  • Is the transect the right length? 

  • Is it difficult to determine the species of interest?

  • Can you get to the sites you want to examine?

2. Analyze pilot study data.

  • Are objectives of power and precision met?

  • How many sampling units or sites will you need to examine differences between sites or repeated measures?

  • Is the level of difference or change you expected to see realistic?

3. Reassess time and resources.

  • Will you be able to conduct the study in the time you have allotted?

  • Do you have enough people or other resources to meet the objectives?

  • Can technologies or other resources be secured to meet the goals of the project?

4. Review - Solicit review of the results of your pilot study.

  • Do the parties involved still agree with the way the monitoring is proposed?

  • Will those involved be able to abide by the results?

  • Are there better ways to accomplish your monitoring objective?

Summary Questions

  1. Explain why should you never use a calendar to precisely plan each hour of each day for fieldwork?
  2. Describe six factors that could cause problems in your monitoring protocol.

Advanced Questions:

  1. Describe four different sources of errors that could arise due to mistakes in data recording or entry into an analysis software.
  2. Describe three ways in which poor planning or design of a monitoring protocol may produce incorrect inferences.

***Again, these questions are just to get you thinking. You do not need to write formal answers to these questions.

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