Principles of Vegetation Measurement & Assessment
and Ecological Monitoring & Analysis


Veg Sampling
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Natural Resources Measurements

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Readings & Instructions

  1. This lesson provides an introduction to scales and terms used to describe vegetation measurements. Brown text highlights key words.
  2. Read through the Text and work through the Summary Questions at the end of the text.

Measurements and Plant Attributes

Natural Resource Measurements

Once the decision to monitor a resource has been made, it is necessary to then decide how best to measure the features of interest. A natural resource inventory is where we take measurements to obtain dimensional or physiological information about the resource. For example, we could be interested in quantifying the amount of carbon sequestered by a forest in a given year or the amount of water used by a shrub species in a semi-arid landscape.

A natural resource inventory can be defined as the process of estimating a specific natural resource (e.g., tree height, grass cover, etc.) as precisely as your available resources (time, money, personnel, etc.) can permit. In forestry, a forest inventory normally focuses on assessing the volume or value of standing trees to use for different forest products. In rangeland management, shrublands and grasslands are assessed to determine attributes such as carrying capacity for livestock or wildlife, invasive plants, and rare or endangered species. Vegetation characteristics from forest, woodlands, shrublands, and grasslands may also be inventoried and assessed to characterize fuel load for prescribed fire or fire risk.


Clearly, there is never enough time, money, or resources to measure the characteristics of every feature of the vegetation in your area of interest. A further limiting factor may be that the extent of your study area may be too large or too remote for your available personnel to accurately inventory in the allotted time. This is why we typically measure a subset of plants called a sample.


Plant Attributes to Measure


There are many ways to measure plants, but, there are only about 6 "attributes" that are commonly measured.  Vegetation attributes are characteristics of vegetation that can be measured or quantified referring to how many, how much, or what kind of plant species are present. The most commonly used attributes are:

  • Plant Species or Type - What kind of plant was it?

  • Frequency - Was the plant there or not?

  • Density - How many plants were there?

  • Biomass - How much did the plants weigh?

  • Cover - How much of the ground surface did they cover?

  • Structure - How tall were the plants and how were branches and leaves arranged?

We can also make observations about health, condition or vigor of individual plants or plant communities.  And we can combine the above attributes to create variables such as species composition, biodiveristy of the site, or similarity with historic measurements or other sites.


**The major plant attributes will be more fully described in later portions of this class.

Natural Resource Measurements: Taking Care

Two important introductory concepts of natural resource measurements are to:

  • Use your time wisely, and

  • Don't discard discoveries. 


Because time is nearly always a limiting factor, are there ways and strategies to make wise decisions about what to measure?  Can field and data analysis habits be gained that will create as much useable data possible?


YES... of course. There are several steps you can follow to make the best use of your time:

  • Clearly specify each objective.

  • Be familiar with the possible and appropriate tools for each task.

  • Practice the correct use of each tool before going to take field measurements.

  • Take repeated measurements.

  • Record measurements on carefully designed field forms.

  • Check that your answers are sensible.


Importantly, if a correctly applied measurement produces an unexpected value -- donít ignore or remove it. The apparently incorrect measurement may be a new discovery.  In general, data points should never be removed unless you have a really good reason (e.g., contaminated sample). In essence, a considerable quantity of important scientific discoveries have been made due to apparent mistakes that produced unexpected results.

Summary Questions

  1. Discuss and describe three potential reasons as to why we might only measure a sample of tree heights within a forest when performing an inventory?

  2. Explain why you should never simply discard unexpected data.

Advanced Questions:

  1. Describe two national programs that actively collect and use inventory data in natural resources, including their objectives and what measurements they collect.

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