Preparation: Depending on the age of your students, you can either have students run their own transects and identify quadrats along the transect, or complete this activity as a class. Make sure students know how to positively identify poison ivy and point out any known patches. Also remind students of general safety procedures in the field, including checking themselves for ticks after walking through woods or tall grass.
Engage: Ask students to name as many invasive plants as they can; most students know at least one plant, even if it is not from their local area. Make a list on the board. Ask if any students know the impacts of any of these invasives. Hand out the “Invasive Plant Survey” worksheet. Before beginning, ask students to predict whether there will be more native or invasive plant species in your survey area, and whether native or invasive plants will suffer more herbivory (predation).
Explore: Hand out a copy of the invasive plant cards to groups of students, along with the student handout. Give them enough time to explore a trail or forest edge near the schoolyard.
Set up a transect of at least 25 meters along which students can measure out small quadrats. Each group of students will sample plants in at least one quadrat along the transect. Depending on the number of groups in your class, you may have to do more than one quadrat (or transect!). The class should sample at least 6 quadrats along a 25 meter length (at 0m, 5m, 10m, 15m, 20m, and 25m). Each quadrat along the transect should measure at least 50cm on each side.
Note: Depending on the size of your class, you may want to have more than one transect, or a longer transect. You can have students investigate one quadrat, or more than one, depending on how much time you have available.
In each quadrat, students identify the invasive plants present (if any), estimate the abundance of the invasive plant, and identify the habitat type. Finally, students estimate the percent herbivory of invasive and native plants by collecting five leaves from two different native and invasive plants. Instruct students not to take leaves from any plant with four leaves or fewer. Remind them that leaves are the food-production factories for plants. Taking the leaves back to the classroom, the students use the transparency sheets with the grids to estimate how much herbivory has taken place. Any herbivory should be counted, but fungal damage should not.
Explain: Invasive plants are a problem throughout the world, and New York harbors a large number due to the high volume of shipping traffic in the state. Although some invasive plants continue to be sold in garden centers and nurseries, awareness is helping reduce the incidence of accidental introductions. Invasive plants tend to be successful because they reproduce in high numbers, can tolerate a range of soil types and weather conditions, and generally are free of natural predators found in their native range. While there is some evidence that native predators eventually learn how to eat invasive plants, some species are well protected (such as Japanese barberry, which has lots of thorns) or are toxic to competitors (such as Tree of Heaven, which emits toxins through its roots). Generally, native plants suffer higher rates of herbivory than invasive species, although this tends to change over time.
Extend: Students can upload their distribution and abundance results to iMap Invasives (NY iMap Invasive Species), where their data will be added to others’ in our region and made available to help land managers develop better invasive management strategies.
Evaluate: Collect student lab sheets. Pay attention to how students are thinking about dispersal, and what students think about how the invasive/native plant community may change in the coming years. This will help you understand whether students are thinking about human-mediated pathways of dispersal, and how a community may change due to the presence (or absence) of an invasive or native species.
NY Invasive Species Clearinghouse
USDA: Invasive Species- National Economic Impacts
Cornell: National Costs of Invasive and Non-native Species