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Earth Matters: Falling for cedars

  • Eye-to-eye with an Atlantic white cedar: when the author tripped over a giant sphagnum mound near Rochester, she found the cedar nursery habitat she had been seeking: the moist sphagnum moss below and shade from leatherleaf above was just right for raising young Atlantic white cedar seedlings. PHOTO BY CHRISTINE HATCH

  • PHOTO BY CHRISTINE HATCH

  • Atlantic white cedars, like these on the Atlantic White Cedar Swamp Trail at Marconi Beach near Wellfleet, mature into nearly monoculture forests above a carpet of sphagnum moss. The research study sought to learn how and where they germinate. PHOTO BY CHRISTINE HATCH

  • As Atlantic white cedars mature, they take over the host sphagnum mounds where they germinated, channels form between mounds, and deep shady thickets form that are too dark for other plants to share. Atlantic white cedars are seen on sphagnum mounds near Rochester. PHOTO BY CHRISTINE HATCH

  • The author, upon finding herself eye-to-eye with an Atlantic white cedar after tripping over a giant sphagnum mound near Rochester. She found the cedar nursery habitat she had been seeking: moist sphagnum moss below and shade from leatherleaf above was just right for raising cedar seedlings. PHOTO BY CHRISTINE HATCH



For the Gazette
Monday, October 10, 2022

Sometimes changing your vantage point makes all the difference. It certainly did for me when my students and I were out searching for baby Atlantic white cedars (Chamaecyparis thyoides). Why we were seeking cedars is a longer story.

Before cranberry farming was commercialized in the 1850s all along the Atlantic seaboard, one significant inhabitant of low, marshy peat bogs was the Atlantic white cedar. As some of these cranberry farms are being restored back into freshwater wetlands, researchers have discovered large Atlantic white cedar stumps perfectly preserved in the anoxic, saturated peat beneath them. Large stands of cedars were logged, and the lands were flattened and sanded to make way for large-scale cranberry cultivation.

Cedars are fickle trees that have the misfortune of being very useful to humans. Their wood is lightweight, reasonably strong and rot resistant, making it an excellent building material: shingles, log cabins, long-houses, canoes and more. They’re ideal for structures subjected to the rain and humidity of the coast, which overlaps with cedar’s native habitat from the Carolinas to southern Maine. Agronomists who experimented with growing cedars found that seed germination rate is very low, and conditions must be just right: light but not too light, wet but not too wet. It seemed to matter tremendously if the sprout was on top of a mound, on the side, or at its base. Restoration practitioners rarely bothered with such a difficult tree.

Along came self-taught gardener, grower, scientist and documentarian Glorianna Davenport who had a mission to make sure the native plants were not only included in wetland restorations, but that they were planted as they occur and grow naturally. Our first attempt at using Atlantic white cedars was scattershot: Plant thousands of trees on a grid and see what happens. Cedars on the edges seemed to do better than trees with their roots in the water. And cedars on hummocks could adjust the water around them to suit their needs. We wanted to include these trees in more restorations, but to do so, we had to understand them better, both in the greenhouse and in their native environment, where they are increasingly hard to find.

A cedar swamp is a fascinating place. It’s cool and dark and damp. The forest floor is dense with rolls and waves and green hoodoos of sphagnum. Step in between them and you will sink into a subterranean channel just under the needled and mossy surface. Cedar swamps store large quantities of carbon in stable organic material, they purify water flowing through them and remove excess nutrients, and they provide a cool, wet place for wildlife to retreat from a hot summer day or a wildfire. Curiously though, upon closer examination, a mature cedar forest does not appear to have any baby seedlings growing on the forest floor. Where and how do they germinate? What are the conditions that allow young cedars to flourish?

Historically, Atlantic white cedars migrated northward along the eastern seaboard following glacial retreat and were especially fond of peat-filled kettle holes. A hydrophilic tree, they successfully colonized wet, open areas that other species could not. In addition, our first nations’ forest management favored the trees: frequent, low-intensity controlled burns killed the understory and hardwoods, leaving cedars (whose seeds were protected in the wet peat of the swamp floor) to germinate in the open spaces. These practices, along with the “seed rain” produced by locally dense stands of cedars, produced a vast seedbank reserve in the swamp awaiting germination.

My students and I visited several natural cedar swamps of different ages in hopes of finding out their secrets. In one swamp, we saw how a few plants seemed to dominate the ecosystem, and each existed at a specific level relative to the water: Juvenile cedars rose highest from tall sphagnum mounds, middle height leatherleaf bushes (Chamaedaphne calyculata) skirted around the edges, and a few cranberry vines (Vaccinium macrocarpon) climbed out of the water on smaller sphagnum pillows. But still no cedar seedlings. Where were they?

At another site, tall cedar trees stood out from a monolithic expanse of 7-foot-tall highbush blueberries (Vaccinium corymbosum). In the lower, wetter areas adjacent to the (delicious!) blueberry patch, we navigated 3-foot-tall squishy sphagnum pillows crowned by leatherleaf for a long distance beside the mature cedar forest. When I wasn’t paying attention, I tripped on one, and fell headfirst into the deep gap between pillows. And that’s where I saw them! I found myself face-to-face with my quarry! Several tiny cedar seedlings, only inches tall, were happily growing on top of the crest of the sphagnum pillow in the shade of the leatherleaf. It was perfect! A little shade, a little water, but not too much. Once I saw one seedling, I saw them everywhere: tiny half-centimeter sproutlets, inch-long seedlings, foot-tall yearling trees, up to several feet tall and beginning to dominate the landscape. The baby cedars had been hidden in plain sight all along — all I had to do was fall for them. I can now say I have, and I’m still smitten.

Christine Hatch (she/her) is research-extension Liaison for the Center for Agriculture, Food and the Environment, and extension associate professor of Water Resources and Climate Change in the Geosciences Department at University of Massachusetts Amherst. She is a leader of the RiverSmart Communities project, supporting ecologically restorative flood prevention and remediation in New England. This project is a serendipitous intersection between her work on freshwater wetlands, rivers and flood resilience.