Following Fall

By Eve Pranis

"My fourth graders love selecting trees to adopt and explore in depth each year," reports Grand Rapids, MN, teacher Jan Ferraro. Last year a colleague from St. Olaf College and I brainstormed how to develop a technology-based project that integrates our interest in trees while also addressing curriculum standards," she added. The result of their collaborative musing? An Internet-based fall phenology project designed to help students explore changes in the seasons, collect and grapple with data, and share and communicate their experiences with others.

With an eye toward tracking leaf color changes as fall progressed, Jan's students chose the schoolyard trees they would use for their study, then practiced taking random samples of 10 leaves from each tree. "The concept of random sampling was challenging for my fourth graders, some of whom wanted to pick all of the colored leaves," reports Jan. After discussing the concept, students settled on the technique of choosing different locations around the tree, then closing their eyes as they picked to ensure random selections.

Once leaves were gathered twice each week, students used transparencies of square-centimeter grids to determine the approximate percentage of leaves that had changed color. (They marked each square centimeter that was more than half-filled by green as unchanged, and those more than half-filled by another color, as changed.) After calculating the percentage of change for each tree, students averaged their findings, then sent their data to the project's Web site. "Since it was early in the year, students found it challenging to calculate percentages, but they were inspired to work at it since it was part of an interactive project," notes Jan.

By checking the Following Fall Web site, students were able to observe the southerly progression of color change and, combined with additional Internet research on phenology, begin to make some connections about factors that influenced leaf color changes. "We culminated this phase of the project by having each student create his or her own Web page to share what they'd learned," explains Jan. But that was hardly the end. "The kids continued to closely observe changes in their trees throughout the year, and they've been inspired to follow the progression of budding and leafing out right through spring," she adds.

Why Do Leaves Change?

Just as the sky is blue, leaves are, of course, green ... or are they? Leaves are actually many colors naturally, but when they are actively growing, the green chlorophyll pigment involved in photosynthesis masks the other colors. This includes yellow and orange carotenoids, which give the carrot its distinct color. In the fall, daylight and temperature changes slow down photosynthesis and food production and the trees begin to go dormant as a protection from winter conditions. As the chlorophyll breaks down, the green color fades, and the yellow and orange colors are revealed. Chemical changes triggered by cold weather also cause formation of other colors, like vibrant reds and purples.

Whether or not your young sleuths participate in the online Falling Fall project, consider challenging them to explore questions about seasonal changes in trees and other plants. For instance, Do all trees of the same species turn the same colors or degree of color? Do all leaves on one tree turn the same color? Do any factors (e.g., exposure to sunlight) seem to influence when different leaves on a tree turn color? How might weather conditions from year to year affect color changes? Then fill us in on your investigations, research, and connections.

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