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Bryophytes: Small Plants with a Big Impact

Though you may not know what bryophytes are, you’ve almost certainly seen them if you’ve spent time outside in Door County.

Bryophytes – according to Keir Wefferling, UW-Green Bay’s herbarium curator and an assistant biology professor – are plants that don’t have tracheids, or specialized water-conducting vessels. Without tracheids, plants can’t get very tall.

“[Bryophytes] are never woody, per se, and they don’t have elongated stems,” Wefferling said. “They can’t really climb like a vine or hold themselves aloft.” 

Instead, they tend to stay close to the ground, obtaining water and nutrients largely from the air rather than a root system. The bryophyte umbrella includes liverworts, hornworts and, perhaps most recognizable, mosses. 

Some bryophytes die back with the frost, but many are perennial and continue photosynthesizing and shedding spores throughout the winter. This one is sphagnum capillifolium, or small red peat moss. Photo by Keir Wefferling.

These plants may be small, but they have a big impact on their surrounding environment. 

“They’re these little ecosystem engineers, building hummocks and fixing carbon, and providing substrate for all kinds of invertebrates,” Wefferling said. They can also provide information on air quality, water quality and substrate conditions.

Despite bryophytes’ ecological importance, bryology remains an understudied field, which, according to Wefferling, may be because they’re more difficult to study than other plants.

“Very small, microscopic details allow us to identify the species,” he said. “In some cases, even different genera are impossible to tell apart in the field.”

Wefferling wants to promote understanding of these often-overlooked plants, so he’s working toward integrating bryophytes into floristic quality assessments: tests that researchers use to calculate the quality of plant communities in specific areas. To complete these tests, organizations such as the Wisconsin Department of Natural Resources (DNR) do meander surveys during which researchers spend weeks in the field assessing the health and integrity of a site. 

Pleurozium scheberi, or red-stem feather moss, is a common Door County bryophyte. Photo by Keir Wefferling.

“These botanists will go out in the field, and they’ll look at all the vascular plants,” Wefferling said. “They’ll look at all the flowering plants, the ferns, and the lycophytes and the gymnosperms. But to date in Wisconsin, they have not been identifying the bryophytes.” 

The DNR is aware of this gap and wants to fill it, he said, but the department does not yet have the resources to do so. 

Wefferling wants to change that as well, so he’s working on two main projects. 

First, he and a network of bryologists in the Great Lakes area are working together to assign each bryophyte species a coefficient of conservatism, ranging from zero to 10, to measure how easily a plant can withstand human disturbance. Plants that can do so easily are assigned a low number, and plants that are very sensitive are given a high number.

Second, Wefferling has been promoting knowledge about bryophytes. This includes compiling species lists for local sites, collecting and sharing existing resources, and coordinating bryophyte-identification workshops. 

Bryophytes often grow on trees, rocks and the ground – and where they’re growing can help you to identify them, according to Wefferling. “For the most part, those will be different species” growing in different areas, he said. This is fissidens, or pocket moss. Photo by Keir Wefferling.

Though Wefferling’s home base is in Green Bay, his fieldwork often draws him to Door County. Here, there are many sites that are relatively undisturbed by humans, and the peninsula’s distinctive geology creates a variety of ecosystems in which bryophytes can thrive.

“The very shallow soils over the dolomite bedrock create the conditions that allow for the development of these [bryophyte] communities,” Wefferling said. “They’re a joy to visit and do fieldwork in because you’re surrounded by just incredible biodiversity.”

The Ridges Sanctuary is one of Wefferling’s favorite study spots, but he also visits natural areas throughout the peninsula, focusing especially on minerotrophic, peat-accumulating wetlands such as white-cedar swamps, boreal-rich fens and sedge meadows.

He’s also brought his students to Door County on field trips.

“We’re going out and trying to field-identify every bryophyte we encounter, but that’s not always possible because some of the features are microscopic,” Wefferling said. “So we need to take samples and bring them back to the herbarium where I work, and use the microscopes and keys to figure out what we have.”

Wefferling’s studies in bryology were due, in part, to his desire to study outside in natural areas like these. He was fascinated by moss-dominated landscapes and wanted more chances to explore them in his work. 

“I found myself spending more and more time on the computer, and not super happy about that,” Wefferling said. “So this was a way that I saw that would allow me to get outside more, and spend days and days in the field.”

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