Controlling invasive species (Part 2/2)

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Students will learn and evaluate two sampling protocols.

Big Idea

Are you being invaded by invasive plants? Find out ways to measure and evaluate your land.

What Students will Learn in this Lesson

1 minutes

In this lesson, students will apply what they learned yesterday about invasive plants.  Students will sample an area of land near our campus for an invasive plant.  They will use two protocols that ecologists use to determine the distribution of a potentially invasive plant.  Then using the data they collected, students will develop a plan of action for controlling the spread of the invasive plant. This is day two of a two day lesson. Here is an overview of what students will learn today. 

Check For Understanding

5 minutes

Briefly poll students about whether or not they think we have a problem with Garlic mustard in our area.  Explain to them that we will use several protocols to determine:

  • If Garlic mustard is present.
  • If it is present, that the amount of Garlic mustard present is sufficient to deem it invasive.  

Explain to students that it will be important to take complete data.

  • For example, if no Garlic mustard is present, then the data sheet should be filled with zeros.
  • An empty data sheet is not acceptable. 

Also, explain to students the importance of following the protocol exactly so that the results will be reliable from year to year.  

  • If students are not at the exact location from year to year, it would be impossible to determine if the Garlic mustard were spreading.  
  • Therefore, they need to mark the accurate GPS location.  

Field Work: Initial Plot Description

10 minutes

Once students have arrived at the field site, they will need to sit quietly for ten minutes and make an initial plot description.  First, they need to describe what they see at the field site.  To help them with their site description, ask the following questions:

  • What types of plants do you first notice (grasses, forbs, or trees)?
  • What is the overall density of vegetation?  Is the area overgrown or sparse?
  • What types of animals do you see?
  • What types of evidence of animals do you see (scat, tracks, nests)?
  • What are the weather conditions today?

Students should end their description with a sketch.  

Next, students should close their eyes and listen for two minutes.  They need to describe what they hear in their lab notebooks. 

  • What types of animal sounds do they hear?

Possible answers:  grasshopper sounding, cows mooing

  • What types of abiotic factors do they hear 

Possible answers:  wind blowing, water running 

When time has been called, ask students to read some of their descriptions of the field site. 


Field Work: Average Species Density

10 minutes

For this protocol, each student group will need:


Students should first decide on how many plots will be sampled in the area.  Plots should be determine beforehand to ensure random selection methods.  If this cannot be done, then one student should stand with his or her back to the area being sampled.

He or she should toss an orange survey flag, while his or her partner watches the area to determine where the survey flag lands. Students should carefully walk to the area where the survey flag has landed and lay the quadrat frame on the ground.  One student should count the number of stems for each of the plant groups on the data sheet (trees, forbs, grasses) in each plot while his or her partner records the data.  Students should take special note of any Garlic mustard that they see.  

This protocol should be repeated for each plot that is surveyed.  

(Note: In my classes, I typically have student pair each sample a plot.  I do this because one person can count while the other records data.  The accepted standard in Invasion Ecology is a minimum of ten plots or one 1m^2 plot per 100m^2. This allows for statistical analysis to be apply.  However, in small classes like mine [N=4], it is very difficult to count 10 plots. One might opt for only having students count one plot and then determining what you can with the data you have. It could be a good object lesson about data reliability or sampling bias due to the low plot numbers.)


Analyzing Your Findings: Plot Sampling Data Summary

10 minutes

Students should analysis of the data collected in each plot and determine the species density per plot.  They should 

  • Calculate the total number of plants counted in each plot.
  • Calculate the total number of forbs, grasses, and trees. 
  • Calculate the total number of garlic mustard.
  • Determine the density of each plot by dividing the total number of each group by the total number of plants.  (i.e.:  number of forbs/total number of plants)
  • Record information in the data table on the provided worksheet.


Next students should determine the average species density per site by

  • Determining the average species density per site, add the density of each plot and divide by the total number of plots. 
  • Using this average density to compare the different groups of plants that they counted. 


Once students have calculated the average species density per site, have them consider the  following questions: 

  • How much variability was found in the overall class results?
  • What might be some reasons for any variability that was seen?
  • Was the species density similar in all of the plots counted by the class? 
  • Look at the site and consider if the average species density was a good representation of what was seen.  Why or why not?
  • If the average species density was not a good representation of the site, would sampling more plot help better understand the plant distribution at the site?


Field Work: Surveying Using A Transect

10 minutes

For this protocol, each student group will need: 

  • tape measure
  • compass
  • datasheet
  • pencil
  • quadrat
  • orange survey flags


At least ten transects should be sampled today.  Student will establish a transect along which they will sample Garlic mustard. Transect surveys are another method to determine differences in plant populations as you move from one habitat to another. For this transect survey, students will start at the walking trail and move west following a straight line. To determine a straight line, students should use the compass and the tape measure. 

Once students have established a straight line for 25 meters.  They should mark sampling areas every five meters with survey flags.  Then, at 0 meters from the trail, they should lay the quadrat to the right of the transect tape. Students should count the total number of Garlic mustard within the quadrat.  They record that number in the data table on the provided worksheet. Next, students should lay the quadrat to the left of the transect tape and count all of the Garlic mustard within the quadrat.  Students should repeat this procedure at 5, 10, 15, 20, and 25 meters from the trail along the quadrat tape.  


Analyzing your Findings: Transect Survey Summary

10 minutes

Once students have completed collecting the transect data, they should clean up the area and go back to the classroom.  Using Logger Pro, students should graph the number of Garlic mustard to the right and left of the transect as compared with distance from the trail.  Once they have generated the graph, have students consider  the following questions:

  • What happens to the amount of Garlic mustard as you move further away from the trail? 
  • Based on all of the observations and data collected today, do you feel that our nature area has been invaded by Garlic mustard?


Putting It All Together: A Summary of Findings and a Plan of Action

15 minutes
Bring students back together and ask for student groups to explain their findings. 
(Note:  We determined that we did have monocultures in parts of our natural area.)
Next, discuss management options for the area.  Have students should consider how to control the unwanted species, but still protect the native species already present.  Students should develop and implement a management plan for the nature area.  

(Note:  My students decided that we should make the trails in our nature area wider. They noticed a lot of poison ivy. After consulting a professional, it was recommended that individual plants be sprayed and larger plants be physically removed. We hired a professional to do this several times throughout the summer.  To control Garlic mustard, students decided that it was best to pull the plants since spraying could damage many of the native plants we wanted to continue to grow in the area.)