Eyes in the Sky II > GIT Web Course > Module 2 > Week 5 > Using GIS to Analyze and Predict Invasions > Using AEJEE to Analyze and Predict Invasions

Week 5: Monitoring Invasive Species

Using AEJEE to Analyze and Predict Invasions

Tamarix forest in riparian zone. Image courtesy of Steve Dewey, Utah State University, United States.
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Key Investigation Questions:






Introduction

Tamarix, or saltcedar, grows as a woody shrub or small tree. It was introduced to the United States in the 1850's as an ornamental plant capable of erosion control. It successfully adapted and quickly spread into wetlands displacing native trees such as cottonwood, willow and mesquite. Now, Tamarix has invaded nearly all the watercourses and wetlands in the Southwest US. As one of the most successful and common invasive species in the United States, it has overtaken nearly one million acres of habitat. Since it can transpire as much as 300 gallons of water per day, it is capable of causing a wetland to completely dry up. Additionally, Tamarix has a tendency to increase the salinity of the soils in which it grows and it is of little or no value to wildlife. Although Tamarix is difficult to eradicate, in locations where it has been eliminated native vegetation and wildlife have returned and flourished.

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Launch AEJEE and Orient the Map for the Investigation

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Investigate the Tamarix Invasion in the United States

Where is the present Tamarix invasion and how far has it spread across the United States? top of page

Where is the Tamarix invasion the most severe?

Tamarix can be found throughout the Southwest United States. Some states have more of a Tamarix problem than others, but because Tamarix spreads easily and is very difficult to eradicate, plant biologists are keeping a close eye on the situation.

Zoom and Pan around the map to get a better idea of the extent of the invasion and to answer the following questions.

  1. In which states has Tamarix been sighted?
    Tamarix has been sighted in the following states:
    • California,
    • Oregon,
    • Idaho,
    • Montana,
    • Wyoming,
    • Nebraska,
    • Kansas,
    • Oklahoma,
    • Texas,
    • New Mexico,
    • Arizona,
    • Utah,
    • Colorado.

  2. What relationship do you see between rivers and Tamarix?
    In general, Tamarix follows rivers.
    Note: The US Rivers layer in AEJEE does not contain all rivers in the United States. So although you see Tamarix in parts of Nevada and California, the map is not displaying the invaded river.
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Create a Spatial Query to Investigate the Extent of the Invasion

Buffer Southwest states to investigate the extent of the invasion

Make US States the Active layer and select Arizona with the Select Feature > Polygon selection tool.

select feature close up
  1. Make US States the Active layer.
  2. Click and hold on the Select Feature select features button tool. Choose the Polygon selection tool. (Pictured to the right.)
  3. Click just inside the state boundary of Arizona.
  4. Release the selection tool, Arizona (AZ) should now be highlighted. If you get several states, try again. Hint: You might need to zoom into the states to get more accurate results.
    1. Make US States the Active layer by clicking its name.
    2. Click and hold on the Select Feature tool. Choose the Polygon selection tool.
      1 select feature AZ
    3. Click just inside the state boundary of Arizona.
      2 clicking inside AZ
    4. Release the selection tool, Arizona (AZ) should now be highlighted. If you get several states, try again. Hint: You might need to zoom into the states to get more accurate results.
      3 AZ selected
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Use the Buffer buffer tool icon tool to select the records from the Tamarix database that are contained within the boundaries of the state of Arizona. This is a type of spatial query that is called "containment".

buffer box 2 Buffer dialog box.
  1. Click on the Buffer tool in the toolbar. The buffer dialogue box will open. (Pictured right)
  2. Set the Buffer Distance to 1.
  3. Set the Buffer Units to Meters.
  4. Check the box "Use the buffer to select features from this layer".
  5. In the pull down menu of layers, choose Tamarix.
  6. Click OK. The buffer dialog window will automatically close and the selected points will be displayed on the map.
    1. Click on the Buffer tool in the toolbar. The buffer dialogue box will open.
    2. Set the Buffer Distance to 1.
    3. Set the Buffer Units to Meters.

    4. setting buffer to i meter
    5. Check the box "Use the buffer to select features from this layer".
    6. In the pull down menu of layers, choose Tamarix.

    7. buffer box
    8. Click OK. The buffer dialog window will automatically close and the selected points will be displayed on the map.
      Tamarix Selected on map

Discover the results of the selection

  1. Return to the map and make Tamarix the active layer.
  2. Open the Attribute Table of Tamarix.
  3. How many results are have been selected?
    Right click to open the attribute table of Tamarix.
    r click
    3333 Tamarix are recorded within the state of Arizona.
    attribute table open and map

Repeat this entire process with several other Southwestern States to find the next most invaded state.

Tamarix Records:
AZ - 3333 records
NM - 422 records
UT - 326 records

Clear the selections by clicking on the Clear All Selection Clear Selections button.

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Focus on Arizona Tamarix

As you just discovered, Arizona's Tamarix invasion is the severe. Now, you'll investigate the specific Arizona rivers that have been invaded by Tamarix.

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Add Satellite Data to Connect Tamarix Spread with Vegetation Index

By using the satellite data of vegetation health the scientists at NASA and USGS are able to use habitat preferences, such as moist soils and low elevations, to begin to predict where Tamarix plants were most likely to appear in the future.

Adjust the layers on the map for the investigation.

Plants are sensitive to their environment and so they serve as a good indicator whenever there is change. Scientists routinely produce global NDVI maps to help them monitor and investigate shifts in plant growth patterns that occur in response to climate changes, environmental changes, and changes caused by humans. Farmers and resource managers also use NDVI maps to help them monitor the health of our forests and croplands. So these maps are useful both for scientific research as well as societal benefit.

Notice that the in Arizona the Tamarix invasion prefers the lower elevations where there is more desert. It is found in the river corridors and other low lying wet areas.

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Add Elevation to the Map to Solve the Puzzle

So far we have observed that Tamarix invasion patterns follow the river corridors and also other areas that appear to have healthy green vegetation in the satellite NDVI image. So, why doesn't Tamarix invade everywhere? What is the missing element in the puzzle?

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Resources


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