Roads & Plant Diversity

How do roads impact plant communities?

Lesson plan by Mardi Sicular-Mertens

General Information
Objectives
  Preparation
  Background Information
Procedure
Assessment
Materials
Possible Extensions

Location: A native perennial grassland traversed by a road.  Accessible sites in the Bay Area include Vollmer Peak in Tilden Regional  Park, Russian Ridge in the Mid-Peninsula Open Space, and San Bruno Mountain State and County Park.

Time Allotment:  Allow one hour in the classroom, and a full day in the field.

Grade Level:  9-12

Objectives:

1. To gain understanding of human impact on the environment, and of interactions between development and the natural community.

2. To develop students’ skills in qualitative and quantitative observation.

3. To gather, analyze, and graph data.

Preparation:

In the classroom: Students, working in groups of four, construct the quadrats using materials listed.  Quadrats should be diassembled for transport and reassembled in the field.  The quadrat is one meter square, and each one meter rod is painted red for half of its length to mark off quarters.

Background Information:

Roads have an impact on surrounding habitat.  The expected result is that near the road two to three species will dominate the canopy cover, whereas farther from the road more species will share the space more equally.


Procedure:

In the field:  Students, working in groups of four, will take three sets of five samples each.  The first set will be directly adjoining the road, the second will be four generous paces from the road, and the third set will be twenty generous paces from the road.

The first step is to assemble the quadrat and to lay it down flat on the earth adjoining the road.  The next step is for the students to inspect the plants.  For each plant they can differentiate, they are to make up a short descriptive name, such as fuzzy-leaf, or yellow-spotted flower, or short, rough grass.  They should record these names on the data sheet, under plant species observed. ( Warning:  Warn the students to look for similar characteristics in a plant that may be tall or short.  It could be the same type of plant.) Then, using the markings on the quadrat, the students will estimate what percent of the area they see from above is covered by the plant.  The students will repeat the process for a total of five roadside quadrats, 1-5.

The students will repeat the process at four paces and at twenty paces from the road.

Quadrats 6-10 are completed at four paces, and quadrats 11-15 at twenty paces from the road.

Organizing the data:  The students should make a table for each sample set, showing plant name and mean percent canopy cover for each plant.  The students will then make three graphs, one for each sample set.  The x axis consists of plant names, and the y axis of mean percent canopy cover.  The plants must be listed in order from highest mean percent cover to lowest mean percent cover for each plant type at each distance from the road.

The students should write a conclusion, describing their basic findings for each sample set and making generalizations from their graphs.  What patterns do they see?  Can they suggest any possible reasons for the differences?

Assessment:

Organizing the data:  The students should make a table for each sample set, showing plant name and mean percent canopy cover for each plant.  The students will then make three graphs, one for each sample set.  The x axis consists of plant names, and the y axis of mean percent canopy cover.  The plants must be listed in order from highest mean percent cover to lowest mean percent cover for each plant type at each distance from the road.

The students should write a conclusion, describing their basic findings for each sample set and making generalizations from their graphs.  What patterns do they see?  Can they suggest any possible reasons for the differences? 

Teach students to identify five major weeds and five major native plants they will encounter at the field site.  Have them compare presence of natives and weeds in their three sample sets.