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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

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Cedar roots cling to the cliff cracks of the Niagara Escarpment. The trees grow only an inch every 15 years, making them among the oldest known living trees in the world.

© Gary Fewless, UW-Green Bay

December 2005

Vertically inclined

A forest of ancient, twisted trees grows from the cliffs of the Niagara Escarpment.

Kathryn A. Kahler

A curving rugged ridge of rock
A new small view of old-growth
Hanging forests in Wisconsin
How cedars adapt to hang on
For more information | Rare finds in rough places
Places to see the Niagara Escarpment in Wisconsin

About the time Michelangelo was sculpting in Italy, a white cedar tree took root in a fissure of the Niagara Escarpment in Door County near what would be called Sven's Bluff centuries later. Today, though it lacks the stature of Michelangelo's "David," that cedar still clings – twisted and sculpted by nature – to the dolomite cliff where it rooted 500 years ago. It is one of thousands across the U.S. and Canada comprising a vertical forest, the most extensive old-growth forest east of the Rockies.

A curving rugged ridge of rock

The Niagara Escarpment is the rim of a saucer-shaped geological feature centered under Michigan. The saucer formed from the basin of an ancient inland sea during the Ordovician and Silurian eras some 445 to 420 million years ago. Over the life of the sea, layers of limestone, sandstone and shale were laid down. The Michigan basin sagged in the center under the accumulated weight of sediments. After the sea receded, the exposed layers of the saucer started to erode. The top layers of very hard dolomite limestone had weaker layers of sandstone and shale underneath. As the weaker layers eroded, the hard limestone on top was subject to another strong force – gravity – and crumbled and tumbled downward. This continual process of erosion and gravity over millions of years formed the cliff faces of the escarpment that we see today.

The western edge of the escarpment in Wisconsin curves in a semi-circular ridge northeast from Horicon Marsh, toward the eastern edge of Lake Winnebago and the western shore of Door County. It arcs around Lake Huron, then south through Ontario and ends at Niagara Falls, spanning a total of 650 miles. Some of its edge is underwater or covered by glacial deposits, but much is exposed as cliff outcroppings as high as 200 feet in places. Growing on these vertical cliffs, at the sluggish pace of about an inch every 15 years, are the gnarled and twisted specimens of this ancient forest.

A new small view of old-growth

Discovered some 17 years ago by a team of botanists from the University of Guelph in Ontario, the vertical forest of the escarpment is of major significance to the scientific community. Before the finding, our vision of old-growth forests focused in the Pacific Northwest where massive 1,000-year-old trees grow 350 feet or taller. Escarpment trees, however, escaped human activities like logging, agriculture and, until recently, development because of the sheer inhospitable nature of their home. Finding these ancient stunted cedars clinging to cliff faces opened new doors for researchers in several disciplines. Locked in these tree rings are clues to climate changes long before the birth of our country.

Dr. Douglas Larson, a University of Guelph botanist, headed the discovery team in 1988 that found trees along the escarpment that are no more than 10 feet high, a foot in diameter and as old as 1,032 years on the Bruce Peninsula in Ontario. Aging trees that grow from vertical cliff faces is no easy task. Using rock climbing gear, they rappelled down the cliffs and sampled living eastern white cedar trees (Thuja occidentalis) by boring pencil-sized pieces of wood from the base of their trunks with a tool called an increment borer. Cross sections of fallen dead trees were collected from the base of the cliff as well.

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A cross-section of geological layers in the Niagara Escarpment under the Michigan Basin shows how the rock sagged under the heavy weight of sediments. © DNR

In the laboratory, Larson's team dried the samples and sanded them smooth so they could count the rings, which in these trees can be the width of a hair. It took a microscope and instruments that could measure increments of one-hundredth of a millimeter. They also looked for the presence of charcoal in the rings, which would indicate whether the trees had been subject to fire. Their studies found uneven-aged populations, a large proportion of old trees (100 to 300 years), and very little sign of human disturbance or fire, leading them to conclude "that the entire forested cliff face of the Niagara Escarpment is an intact old-growth forest."

An even more astounding discovery came later in dendrochronological analysis of the samples. This kind of analysis relates both the number of rings and ring width to climatic conditions at the time the rings formed. Eastern white cedar growing from the cliffs formed narrow rings when the previous growing season was warm, and wider rings after cool growing seasons. By cross-dating tree ring samples from living trees, the Canadian researchers were able to create a timeline going back 1,400 years. Further radiocarbon dating of dead trees preserved at the cliff base revealed a chronology dating back to 1300 B.C. The tree ring growth patterns for the 1,400-year timeline showed a regular fluctuation of high and low growth throughout the period, suggesting a corresponding pattern of temperature change.

To see how trees on escarpment cliffs compared to forests on other cliffs, Larson's team conducted field surveys on 21 cliffs in eastern United States and Europe. After sampling hundreds of trees, they found that most U.S. samples were between 160 and 400 years old and were mainly eastern white cedar in the north and eastern red cedar (Juniperus virginiana) in other areas. All were stunted and growing less than one millimeter per year, the slowest growing trees on earth.

Hanging forests in Wisconsin

On a cold mid-March day in 1997, Larson visited Wisconsin. He was invited by Dr. Jeffrey Nekola, who at the time was a UW-Green Bay ecologist specializing in relict snail research. On cliffs, Nekola had found several species of tiny land snails previously thought to be extinct for more than 10,000 years. The cool crevices of the escarpment mimic the Ice Age conditions where these snails once thrived.

The team of Canadian and Wisconsin scientists visited sites at Door County's Peninsula State Park, Ellison Bluff, and a site on private property in Brown County near Greenleaf. Still snow covered, the bluffs didn't offer the best of conditions for rock climbing, but Larson tied onto a tree at the top of Ellison Bluff and rappelled down the 80-foot cliff face anyway.

"We found ancient Thuja occidentalis at Ellison Bluff County Park – 300-plus-year-old trees no larger in diameter than a 50-cent piece," says Nekola. "We saw what looked like millennium-age trees at Eagle Bluff at Peninsula State Park, and I've since seen similar trees at Rock Island. But logistics were such that we couldn't safely age them.

Places to see the
Niagara Escarpment in Wisconsin
Door County Rock Island Door Bluff Peninsula Park Beech Forest, #12
Peninsula Ellison Bluff Peninsula Park White Cedar Forest, #13
Potawatomi Meridian Bayshore Blufflands, #377
Ellison Bluff, #378
Rock Island Woods, #382
Calumet County High Cliff Calumet County Park, Ledge View Nature Center High Cliff Escarpment, #176
Fond du Lac County Oakfield Ledge, #190
Dodge County Ledge County Park Mayville Ledge Beech-Maple Woods, #143

"We also found the world's oldest red cedar at the bluff north of Greenleaf in Brown County, coming in at roughly 1,200 years old. It's the only known tree more than 1,000 years old in the state and is approximately twice as old as the next oldest known red cedar in the world, a tree in the Ozarks," Nekola said.

Since then, others have sampled trees and found a 507-year-old white cedar on Sven's Bluff at Peninsula State Park, and another venerable specimen at Fish Creek south of the park that is 616 years old. Compared to the trees Larson has found on the Bruce Peninsula, Door County trees are generally younger and fewer. However, Wisconsin trees have not been studied as extensively.

Mike Grimm of the Door County office of The Nature Conservancy accompanied Larson at the Ellison Bluff site. "He didn't find anything over 500 years old, but the jury is still out about whether there are trees here that are as old as the ones in Canada," Grimm speculated. "Nobody here has had the time or resources to do the sampling."

The Canadian and Wisconsin vertical forests differ in other ways. Wisconsin's dolomite cliffs are more brittle which may account for fewer trees. In addition, our cliffs are cooler and moister than those of the Bruce Peninsula. Conditions are better suited for plants like ferns and mosses, which are more abundant here.

How cedars adapt to hang on

The trees have maintained their tenuous hold on life for hundreds of years through a delicate balance. Grimm says if they grew faster, they would succumb to the force of gravity. "And if they grew slower, well, they would be dead."

The cedars reproduce by dropping seeds which find small pockets of soil and moisture in cracks and ledges of the cliff face. Once they germinate, the seedlings begin their slow growth, aided by a symbiotic relationship among their roots, fungi and algae living in the rock. The fungi and algae collect phosphorus and nitrogen from the rocks and transfer them to the tree roots.

The cedar's root structure is unusual and may be a key to its success in this marginal environment. Unlike other trees that have nonspecific roots, each of the white cedar's roots is dedicated to a specific section of the trunk. So if one root is damaged when rock fractures and gives way, the tree can isolate the damage and survive. It also explains how the trees get their twisted appearance and sometimes end up growing sideways or downward instead of upward.

This unique root system depends on water seeping through the rock from the top. Grimm describes it as a pipework of vertical and horizontal holes and cracks which, if disturbed or plugged, threaten the delicate balance on which the trees depend.

What poses the greatest threat to that balance? Grimm believes it's condominium and private home development on top of the escarpment.

"Because most of the shoreline property in Door County is pretty much gone [developed], escarpment property that offers a view is the next best thing," says Grimm.

The filtration system that waters the trees isn't the only thing disrupted by construction, however. When homes are built on the cliffs, large trees along the edge of the bluff are often cleared to enhance the view of the water. The bluffs, once cooled and shaded by the trees, undergo an extreme temperature change.

"The mosses and rare ferns that grew in the cool, shady environment simply cook in temperatures that can reach 100 degrees," says Grimm.

A report in 2001 by DNR's Bureau of Endangered Resources on the Niagara Escarpment lists several additional threats to the cliff environment, including land use conflicts, road construction, quarrying, tower construction, recreation, invasive species, groundwater contamination and jurisdictional conflicts. It also describes actions that would help preserve the biodiversity of the escarpment, such as monitoring, removing invasive species, better planning and protection, landowner outreach, and more surveys, including sampling vegetation like the cedar trees.

Grimm believes that while more can be done to protect the cliffs and the vertical forest that grows there, one place where protection is working is in the Bayshore Blufflands, a 500-acre land trust owned by the Door County Land Trust and The Nature Conservancy that was designated a State Natural Area in 2002. The property is located about eight miles southwest of Egg Harbor. Grimm also says some of the most striking parcels of the escarpment are already protected in public ownership providing vistas and paths to gaze up and down at the stubble of small ancient forests on Wisconsin's rocky face.

Kathryn A. Kahler writes from Madison. She is also production and circulation manager for Wisconsin Natural Resources magazine.

For more information
The Niagara Escarpment

University of Guelph, Ontario

DNR Niagara Escarpment Report

Cliff Ecology: Pattern and Process in Cliff Ecosystems, Douglas W. Larson, Uma Matthes and Peter E. Kelly Cambridge University Press, 2000.