Jump to [Introduction] [Investigation strategies] [Analysis] [Conclusions] [Extensions] IntroductionHave you ever wondered if the trees in your backyard have always been there? Although plants don’t actually move, the wind, birds, and insects distribute their seeds, which allow new trees to grow in different areas. To pollinate the flowers that produce the scattered seeds, many plants release large amounts of pollen in the air. Some pollen gets buried and preserved in sediments of nearby lakes, ponds, swamps, and bogs. By sampling the sediments and extracting this pollen, scientists can track the movements of a species of plant. The goal of this particular investigation is to see how the population changes in time for a species of plants you choose in an area that you select.
Each year, pollen from nearby plants (trees, grasses, shrubs) is deposited in
ponds, lakes, swamps, and bogs ![]() Pollen is unique for each species of tree and other plants. If the plants around the pond change, so will the type of pollen deposited in the water. Scientists study the pollen buried with the sediments to
estimate which types of plants lived near the pond at the time the pollen was deposited with the sediments. Materials and Preparation
Color Key
Next analyze each map using AnalyzingDigitalImages, which is available as part of the DEW software bundle. A how-to manual about the different tools inAnalyzingDigitalImages is included with the download. Before making measurements, you must first find the intensities of the colors you wish to measure. In the 'Mask Color' tab panel of AnalyzingDigitalImages, draw a box over one (and only one!) of the colors you are going to measure. The intensities of this color should appear in the color bars below the heading on the left. For example, select the dark green color above, which indicates spruce covered 40-100% of the local area. On the menu bar at the top, click ‘Save Color Masks,' and then save it as one of the colors. Do this for every color you wish to measure (most PollenViewer maps of single plant species contain 6 colors–see example above). This makes it easy to recall each color setting for every map without having to reset the color every time. Once all the colors and the area box are set, you can begin making measurements of the amount of the plant in your selected area. Use the ‘Apply Color Mask’ option in the menu bar to recall a specific color. The image will become black and white. The pixels matching the color you selected will be shown in black and everything else will be white. A percentage of highlighted pixels within your selected box will appear on the bottom of the screen. To save this measurement, click on ‘Measurements’ in the menu bar and select 'Save Measuremet.' Choose the name and place for the new folder. Until you create a new file, every measurement will be saved under this folder. A window will pop up where you can place extra data. For example, you could write the name of the species, how many years ago this picture is from, what color you were analyzing, etc. Click ‘Save’, and the measurement is saved in the text file you created. Choose another color and repeat the process with every color you have chosen. In the File menu select ‘Open Picture’ to pick the next map in the sequence. Remember to always make sure the box size and location do not change. By clicking ‘Keep Settings’ when selecting a new map, the area box remains exactly the same as before.
After making the measurements, it is time to analyze the data. First, you must transfer the text file of the measurements into an EXCEL spreadsheet. To do this, open EXCEL and click ‘Open’ in the File Menu on the toolbar. Find the name of the text file and open it. There are windows that appear so you can change the settings, but this is not necessary because they are already set for the transfer. Click ‘Finish’ and the spreadsheet will appear.
The data saved is in several categories:
The number you will be working with is the percentage of pixels having the specific color highlighted in the box, located in column Z. But what does that color mean? The color represents the percent coverage of the species in that area. For example, the dark green color used in the spruce maps represents 40-100% coverage of spruce in that pixel. Double check what the colors represent for your species back at the Pollen Viewer website.
To make a graph, highlight the columns of data and click on the ‘Chart Wizard’ icon. Look at the graphs you made. Do they make sense? If you compare the average percentage to the maximum percentage, they cannot cross paths. The average cannot be more than the maximum. If this happens, you need to go back through your data to find out what went wrong. Drawing ConclusionsWhen did the dominant species of plants move into your area? Are there peaks in the coverage of plants in your area? Research as to why there might have been a swift increase or decrease in the population of your species. Sometimes drastic changes are due to the climate, and sometimes to humans or other factors. See what you can find in order to make sense of the conclusions you have drawn from the data. See if you can expand are your data. Did you use the average percentage, the maximum, and the minimum? Could you include other species of plants? How does the ice retreating affect the population growth of the species? Have fun exploring! ExtensionsResearch the plants that lived in your selected area. What are their growth characteristics? Were the trees predominantly deciduous or coniferous at different periods of time? What are the shapes of leaves of the different trees? Bark texture? When did one plant type replace another? When did deciduous trees replace coniferous trees? |