2003-2004 Pittsburg High School

Native and Exotic Grass Experiment

Exotic grasses are replacing native grasslands in California at an alarming rate. This may be because they germinate and grow faster than natives. To test this idea, the students at Pittsburg did an experiment to compare the germination rates of Nasella, a native perennial grass, and Bromus hordeaceus, an exotic annual that is invading California grasslands.

The first task was to prepare the beds for planting. Students cleared the beds from years of rampant weed growth and then worked and smoothed the soil.

Jorge and Nathali work the soil.

Veronica, Joliet, and Kulvir use boards to smooth the soil.

Next the students marked out plots in which they planted either pure natives, pure exotics, a mix of the two, or left the plots empty as a control. Students watered the plots and then covered them with tents to protect the seedlings from the hot Pittsburg sun.

Roberto, Luis, Ricardo, and Tina plant the seeds.

Alberto waters the plots.

Victoria and Karen secure the tents.

Mr. Arbuckle (kneeling) and his students smile with pride at a job well done.

Once the planting was completed, the waiting began...
Before long the grasses germinated and the students began collecting data. Besides counting seedlings, there was always weeding to do. But once the plants took hold, there was no holding back.

Sangileen and Jorge count seedlings.

Anya carefully weeds a plot.

Joliet and Leo take notes at the end of the growing period.

Students gathered the data from each of the plant beds and learned how to graph the data. Analysis of the data supported the hypothesis that the germination rates of the exotics were higher than that of the natives.

Students added their data onto a large data sheet and then graphed the data on the board.

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