Hackberries, Sugarberries, and Those Confusing Red Oaks: Place-Based, Service-Learning in Botany

By DARLENE PANVINI

The hackberry and sugarberry specimens (Celtis spp.) are spread out on one lab bench. The collection of northern red and southern red oaks (Quercus spp.) is on another. Students pore through dichotomous keys, each student with his or her favorite. Comparisons of the presence of pubescence, depth of sinuses, width of leaves, and absence of bristles result in furrowed brows and sighs of frustration. Frustration since we do not have fruits or bark to use in our analyses. Frustration that we did not take better field notes. Frustration that we are at the end of the semester and that finalizing these tree identifications brings us one step closer to exams, which is one step closer to winter break.

I admit to the students that I share their frustration. The author of each key focuses on different traits that lead us to different conclusions. Leaves on each specimen are variable in their characters, complicating our task. As anyone who has ever tried to identify these tree species knows, this difficult and challenging work can be exacerbated by levels of hybridization among the species. I, the professor, the so-called “expert,” do not know the answer. Does my confession of shared frustration further aggravate the students or comfort them?

Welcome to place-based, service-learning. Welcome to the messy world of “doing science.”

The context for this real-life scenario was a service-learning project in my botany course. A 2000-level college course taken by students majoring/minoring in biology and environmental science, the course consists of students from sophomores to seniors. A significant course instructional objective is for students to learn how to collect tree specimens, mount them on herbarium sheets, and use dichotomous keys to identify the species.

For two years now I have paired that objective with a place-based, service-learning activity that I refer to as the “arboretum project.” The first year, students collected tree samples on campus and made herbarium specimens. Fifty tree species were identified. We completed the paperwork to get the campus designated as an arboretum through a local non-profit, The Nashville Tree Foundation, which provides an arboretum certification. Trees were labelled with identification tags, students led tree tours, and informational brochures were created to share tree information with the university and neighborhood communities.

The second year, students traveled during lab time to The Historic Sam Davis Home and Plantation (http://www.samdavishome.org/), a home built in 1810 and preserved by the state of Tennessee as representative of a period working farm. While cotton and hay are still grown on the 160-acre property, the site contains a collection of large trees, some undoubtedly hundreds of years old. A majestic row of red cedars graces both sides of the long entry drive. Maples, oaks, walnuts, dogwoods, elms, and many other species enhance the grounds around the house while osage orange and hackberry fill in the hedgerow between lawn and farm. Working in groups, students were assigned sections of the property to collect tree samples to press and later identify in the lab. They were instructed on the procedures for taking field notes that would become part of the university herbarium collection. Collecting, pressing, recording, identifying, and mounting specimens — this is the work of botanists engaged in doing science. This is place-based learning.

An extra sample from each tree was collected and mounted so that herbarium sheets could be given to the staff at the Sam Davis Home to use for educational purposes and as a historical record of the trees on the property. Trees will soon be labelled with identification markers to enhance visitors’ experiences while learning Tennessee history. We are currently in the process of working with the Tennessee Urban Forestry Council to get the Sam Davis property certified as an arboretum. The board and staff at the Sam Davis Home are developing a nature trail on the property and the labelled trees will add to that amenity. The work of the botany students has met a need by contributing to the knowledge and educational experience of the staff and visitors at the Sam Davis Home. This is service-learning.

Students spent weeks gluing their tree specimens to herbarium sheets and poring through dichotomous keys and websites to identify their trees. 41 species were collected, 84 individual specimens were prepared. They worked within and across their groups to complete this huge task. Each student had a level of independence and accountability. They knew that their work would be assessed based on the accuracy of identification, quality of herbarium preparation, and peer review of their contribution to the project. A final exam lab practical would require each student to be able to identify the family, genus, and species of any of the specimens in their collection and to be able to key out unknown tree samples. They jokingly hoped that I would put a Ginkgo specimen on the lab practical as it is an easy species to identify (and I did!).

Back to that day in the lab: most of the trees have been identified and I have approved them as complete. Now we are left with these few that are more challenging to discern. We lay out the samples of hackberry, sugarberry, northern red oak, and southern red oak. Agreement is reached on the set of defining characters that we will use to distinguish these species. Each student examines the specimens again and presents a rationale for identification and then, by tallying votes, the samples are designated with a genus and specific epithet. Satisfaction that we have reached consensus!

I encourage the students by stating that perhaps one of them will someday become an expert on these species and develop a better method of identification. I talk about the promise of genomics as a tool for plant taxonomy and systematics. But, I hold back and don’t state the obvious: that this genetic variability among living organisms, including among individuals of the same species, is what drives us to be biologists. That wanting to know, describe, and predict this incredible variation is the provocative beauty of scientific discovery. I don’t articulate this thought because I want the students to arrive at this understanding, each in his or her own time. By engaging in the process of doing science through place-based service-learning, I am confident that they will.

Darlene Panvini, Ph.D., is a Professor and Department Chair in Biology at Belmont University in Nashville, TN. She teaches biology and environmental science courses. Several of her courses include service-learning projects and all include substantial hands-on, in-the-field activities for students. Her research with undergraduates focuses on the impact of exotic species on native ecosystems.

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