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Field & Street



Somewhere east of Dune Acres, nestled among the high dunes that line the Indiana shore of Lake Michigan, is a piece of flat, sandy ground that holds the finest prairie remnant in the state.

This 80-acre parcel is now a part of the Indiana Dunes National Lakeshore. It has been officially named the Lois Howes Prairie in honor of the woman who discovered it.

Lois Howes lived at the dunes for almost 40 years. She arrived in poor health with a doctor's recommendation that she do a lot of walking. Just walking was boring, so she started studying the plants that grew along her path. Over the years, this self-taught naturalist made a number of major discoveries at the dunes, finding rare plants growing in out-of-the-way places, and feeding valuable information to the scientific community.

One of her most important discoveries came not from searching the ground for unusual plants but from checking the tax rolls for Porter County, Indiana. In 1953, she learned that the land now called Cowles Bog was about to be sold to pay back taxes. She went to Dorothy Buell, the president of a new organization called the Save the Dunes Council, and urged her to buy the land on behalf of the council.

Cowles Bog, now a registered natural landmark, had been the site of much of Henry Chandler Cowles's research into the vegetation of the Indiana Dunes. Cowles was on the faculty of the University of Chicago shortly after the turn of the century, and he used to ride the South Shore Railroad to the dunes to study the plant life.

His studies of plant succession at the dunes earned him his place as one of the founders of modern ecology. Northern Indiana was an ideal laboratory for his work because the landscape contained a record of changes through time spread out across space.

Just a few miles inland from the present shore of Lake Michigan, Cowles could walk through forests that had been bare sand beaches just 12,000 years ago. Walking north toward the lake, he crossed successively younger landscapes until he reached the present shore.

Cowles concluded that the changes he saw, while they were influenced by climate, were largely the product of living things altering their environment until they couldn't live in it anymore. Marram grass growing on dunes just beyond the reach of the highest storm waves of winter stabilized the sand, enriched it with humus, and created a bit of shelter from wind and sun. That slight amelioration of the harsh environment of a foredune allowed a sand cherry or a wild grape vine to grow and eventually shade out the grass. In time, pines and oaks, sheltered by the sand cherries, replaced them.

Dorothy Buell realized the importance of saving Cowles Bog, and with a bit of frantic scrounging she raised the money to buy it. The Save the Dunes Council eventually sold it to the National Park Service, which incorporated it into the Indiana Dunes National Lakeshore.

Today, two intellectual descendants of Henry Chandler Cowles are conducting extensive research on the Lois Howes Prairie. Their goal is to discover a management plan that will approximate the natural processes that created and sustained the rare plant communities that first attracted Mrs. Howes.

Kenneth Cole and Noel Pavlovic are research ecologists on the staff of the National Lakeshore's science division. The science division's job is to study the park so that intelligent decisions can be made on how best to manage it. Cole's specialty is paleobotany, the study of the plant communities of the past through the traces they have left behind.

Howes Prairie is actually a very diverse place. The low, flat portions of its 80 acres include a very rich mesic prairie--"mesic" means moderate in moisture--and a wet prairie knee-deep in water in spring. The higher ground on the surrounding dunes is oak savanna, or, on the cool north slopes, oak woods.

Cole's looks into the past suggest that the history of this place began about 4,500 years ago when Lake Michigan was about ten feet higher than its present level. Ten feet more water means that the shoreline, now over half a mile away, was much closer, and that the area around Howes Prairie looked much like the land just back of the beach at the Indiana Dunes State Park or at the National Lakeshore's West Beach: high dunes separated by low, wind-scoured blowouts where almost nothing grows.

Howes Prairie got scoured down to the water table, which is where wind erosion tends to stop since wet sand doesn't blow very easily. The blowout may have held an interdunal pond like those at West Beach today. Some of the plants Lois Howes found at her prairie--rose gentian, for example--also grow along interdunal ponds.

As the lake receded and the land around Howes Prairie stabilized, a pine forest began to grow. Over the course of centuries, oaks began to replace the pines and prairie grasses entered.

Much of this picture of the past comes from a peat sample Kenneth Cole dug out of wet prairie at the Howes site. He took a core sample about ten inches deep, which was as far down as the peat extended. Below that, the soil was pure sand. Paleobotanists are accustomed to working with samples five to ten yards deep, but Cole only had ten inches to work with, so he used it.

First he sliced his sample into layers about a centimeter thick. Carbon dating told him that the peat five inches down was about 1,100 years old and that the bottom of his ten-inch column was about 2,700 years old.

He checked his samples for charcoal to learn the fire history of the area, and then doused them in powerful corrosives such as sulphuric and hydrochloric acids. The acids dissolved almost everything, leaving behind nothing but pollen, one of the most indestructible things on earth.

The pollen grains preserved in the peat are the main clue to what was here in the past. According to Cole's reading of the record, the pine forests, probably a mixture of jack pine and white pine, dominated until about 2,000 years ago.

Oak savanna increasingly replaced the pines after that time. The final destruction of the pines came in 1850 when they were cut for timber.

Fires were always a part of the ecology of the area, but they increased after 1850, perhaps as slash, the branches left behind from logging operations, dried out and became fuel. Ragweed also enjoyed a boom after 1850, probably because plows were beginning to disturb the soils around the dunes, providing a perfect home for this opportunist.

In recent decades, fires have been suppressed. Trees and shrubs, especially oaks, sassafras, and gray dogwood, have begun to invade the prairie. Some of the rare plants Lois Howes found on this site 30 and 40 years ago have vanished, probably because of this invasion.

The shift over the past 2,000 years from pine to oak is just the sort of change that Henry Chandler Cowles would have predicted, and it provides significant evidence for the correctness of his view of the nature of successional change on this landscape. It is especially impressive because it came in spite of a climatic shift in the last thousand years from warm, dry conditions to cooler, moister weather. The climate shift should have favored pine, but the oaks came to dominate nonetheless.

Cole and Pavlovic have created an experimental management plan for the Howes Prairie. They have divided it into three sections, each including portions of all four plant communities. One of these sections will be left unburned as a control. Another will be burned every year, and the third will be burned every other year.

Each section will be monitored to record the changes that occur. Their main problem in the prairie is those invading trees and shrubs. So far, after two years of burning, the gray dogwoods are being driven back but the oaks are thriving. Burned to the ground in spring, they send up new sprouts that can grow five feet tall in the course of the summer. One question for the future of this prairie is whether fire can drive out oak.

Another is whether water is more important than fire in preserving this particular prairie. Cole suspects that periodic flooding played a role in keeping trees and shrubs out of the mesic prairie on the flat ground. Human activities have lowered the water table in much of the region. A lower water table means fewer floods. If the floods stop on Howes Prairie, fire may not be enough to preserve it.

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