Field Trip to San Bruno
A Journey Back in Time to an Aboriginal Prairie
Lesson plan by Mardi Sicular-Mertens
Grade Level: 9-12
To contrast a weedy annual grassland of introduced species with an undisturbed, ancient plant community of native bunchgrasses and wildflowers
Prior to the arrival of the Spanish, grasslands very different from those of today dominated the landscape of the Bay Area. If we could go back in time and walk through these ancient California stands of grasses, what would we experience?
The native grasses of California are perennial bunchgrasses. They lived for hundreds, possibly thousands of years, resistant to drought, fire, and grazing mammals; they were green year round, with roots up to eighteen feet deep, forming a clumpy discontinuous texture, providing nurturance between for native wildflowers.
The Spanish brought grasses from Spain and the wider Mediterranean, annual grasses which live only for one season, grow close together in continuous fields, and out-compete the native grasses and flowers. Native perennial grasslands in California are among the most endangered ecosystems in the United States: close to 90% have been replaced with the European grasses.
Small examples of these beautiful native grasslands do exist: one such can be found at San Bruno Mountain State and County Park.
Before taking the field trips, the students should do in class exercises in careful qualitative observation.
Activity one: Walk through the weedy wasteland. Stand still and describe the look of the ground around your feet. Describe the general spacing of plants, the amount of bare soil, the smells and sounds and feel of the place.
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?
Show students slides of six common native grasses: Nassella pulchra, Deschampsia cespitosa, Elymus glaucus, Festuca rubra, Muhlenbergia rigens, and Elymus condensata.
Students make observations and a drawing from each slide, then each group of three students is given six plant samples to identify from their own descriptions.