Part 5—Compare Biodiversity of Local Forest Plots

Step 1 – Analyze and Compare Data From Two Forest Plots in the Auburn Woods (FIA Plot #2 to FIG Plot)

  1. If necessary, launch My World and open the Maine forest project file from part 4.
    2. If you had trouble making the selections or saving the project file, then use this completed (and saved) project file. Maine_Forest_Part_4.m3vz ( 17.6MB Jun30 10). Right-click or control-click (Mac) the link above to download the file.


  2. Make the Auburn FIA Plot, Site #2, the active selection, and click on the Histogram button.
  3. In the histogram window, use the View Histogram/Bar Chart for Field drop-down menu to change the selection to "Species." A histogram appears showing the relative abundance of the 5 tree species in the plot.
  4. Use the species histogram that My World created, to identify the two most abundant species of trees. (They are the ones with the most records)
  5. Calculate the relative percentage of the total represented by each of the two most abundant tree species using the "Statistics" data table found beneath the histogram.
  6. Click the Save as JPEG button to save the histogram for comparison to the Excel chart that you made in part 2.
  7. Return to your results from Part 2: Step 2 (the Excel pie chart) and recall the two most abundant tree species from the Forest Inventory Growth (FIG) Plot. Next review the Forest Inventory Analysis Plot #2 histogram from My World. Compare the FIG Plot to the FIA Plot.

The predominant tree species consistent between both plots is the Red Maple. However, the second most abundant tree species varies between the two datasets: Red Oak vs. Balsam Fir.

In the FIG Plot there is more species richness, one measure of diversity, than in the FIA Plot – Site 2. The FIG plot has many more types of trees. However, Red Maple is the dominant tree species found in both plots. There are a number of differences between the plots. Red Oak is more numerous in the FIG Plot than in the FIA Plot. Both Balsam Fir and Hemlock are plentiful within the FIA Plot, whereas there are few Balsams and no Hemlocks in the FIG Plot.

When a limited number of species of one type dominate in an area, as described by the sample data for a site, then the overall biodiversity is low. For simple computational purposes, a determination of the combined percentage for the two most dominant tree species can be used to estimate biodiversity; for example, if the combined percentage of the two most dominant tree species is greater than 50%, then the biodiversity of the area is low.

Step 2 – Analyze and Compare Data From Twenty Forest (Auburn FIA) Plots To Data From One Forest Plot (All Auburn FIA Plots to Auburn FIG Plot)

Question: How does one plot (Auburn FIA Plot #2), compare to the larger forest sample of 20 plots (Auburn FIA)?

  1. In My World create a histogram of the "Species" data for the entire FIA data set (Auburn_FIA2.csv).
  2. Compare the FIG Plot Excel pie chart (generated in Part 2) to the histogram for the entire FIA Plot dataset. Describe any differences in tree types between each site.

The advantage of examining a group of 20 plots as compared to a single plot is that the larger dataset would be more representative of the area, and would therefore characterize a more accurate depiction of the biodiversity of the area. Localized, small datasets are typically too restrictive to provide representative information about biodiversity.

For example, a local FIG plot may be located in an atypical section of terrain compared to the larger locality; this could result in significantly different numbers and types of tree species between a site plot and the larger area plot. In this case, the larger FIA dataset exhibits more biodiversity than the FIG plot.

Key Point: Biodiversity increases with a larger sample size.

If you had trouble making the selections or saving the project file, then use this completed (and saved) project file. Maine_Forest_Part_5.m3vz ( 17.6MB Jun30 10). Right-click or control-click (Mac) the link above to download the file.