Dune Succession Trail Virtual Tour

Take a virtual tour of the Dune Succession Trail at West Beach at Indiana Dunes National Park.

 

This one-mile trail will take you through a diverse landscape built over thousands of years. It traces how the forces of Lake Michigan and the natural process of changing plant communities transform bare sand at the beach to an oak-covered dune.

That process, called ecological succession, is how a natural group of plants gradually alter their environment so much that they are replaced or “succeeded” over time by different species. Succession was a new concept in the late 1800s when University of Chicago professor Henry Chandler Cowles first brought his students here to study it. Using the area as a natural laboratory, he showed that plant communities succeed each other in a predictable pattern. He achieved worldwide recognition not only for himself but also for this sand dune country along Lake Michigan’s coast. Because of his work, the dunes became known as the Birthplace of American Ecology.

Today, the National Park Service continues to study succession and works to protect and maintain these unique places. Please remain on the trail and leave no trace of your visit for the benefit of this and future generations.

 

1. Beach Habitat

The bare sand at the beach seems an unlikely beginning for an oak-covered dune. Yet only a few thousand years ago, the shoreline was a mile inland, south of Route 12. As sand was deposited and the lake receded, plants advanced to join the wind and lake in changing the shape and texture of the land.

Opportunistic scavengers like raccoons and herring gulls patrol the shore for animal or plant debris, while scattered annual plants like sea rocket and beach pea survive the harsh conditions of the lakefront. Lake Michigan’s currents and waves wash in grains of sand to the shore. Water and wind roll the sand inland to the first line of plants, which catch and pile it up. This process formed the long, narrow foredune parallel to the beach.

 

2. Dune-Builders

Marram grass is the first widespread plant away from the beach and most important of the dune-builders. It can be seen on dunes all around the Great Lakes and along both the Atlantic and Pacific coasts. Marram grass not only survives the barrage of sand that the lake and wind bring, but it thrives on the rapid sand burial.

While green blades of grass form the visible part of the plant, most of its growth takes place in specialized underground stems called rhizomes. At least a dozen internodes, the sections between each joint of these stems, develop each year. If sand piles up fast, the internodes will be long. But if summer breezes are gentle and the sand piles up slowly, the internodes will be short. In sheltered places where there is no wind or sand buildup, the underground roots poke above ground where they may die from exposure.

The rhizomes and roots of a single marram grass plant may spread up to 20 feet in all directions. A typical dune, such as the one along which you have just walked, is held together beneath the surface with a dense network of these underground threads.

The cottonwood tree—with its glossy, spade-shaped leaves, is another important dune-builder. Unlike the grass, it needs a low, sheltered spot to sprout; but by the time it is a few feet tall, it can also survive sand buildup. As the tree’s stems are buried, they begin to function as roots; and new stems appear above ground. Although many of the cottonwoods on this trail appear short, some may be only the exposed tips of much larger trees.

 

3. Open Dune Habitat

Nonliving conditions or abiotic factors such as light, wind, and soil moisture affect the path of succession. Because of the more sheltered conditions behind the foredune, you will find new plant communities developing among these older dunes. Little bluestem grass can be found here where the sands are more protected from the lake’s winds. Look for a subtle change in color between the leaves of little bluestem and marram grass. Although little bluestem cannot build dunes, it grows in thick sturdy clumps and can help hold sand in place. Other typical dune plants that grow here beyond the reach of the wind’s main force are sand cherries, distinctive three-leaved hop trees, and an increasingly varied collection of wildflowers. A common dune plant is sand cress. Its tiny white blossoms bloom alongside yellow-flowered puccoon throughout most of the summer months. Shrubby species begin to shade more sand and reduce the soil temperature. As plants die and decay, their remains enrich the soil. Changes in these abiotic factors produce conditions suitable for an even greater variety of trees, grasses, shrubs, and wildflowers.

 

4. Jack Pine Grove

Naturally, jack pine trees do not grow south of Indiana Dunes. The first jack pines flourished here soon after glaciers melted back north around 14,000 years ago, when the region’s climate was much cooler. Ground-hugging arctic bearberries, which thrive beneath the pines, and common juniper bushes are other northern or boreal relicts from this time. Today, nutrient-poor soils and Lake Michigan’s microclimate provide the conditions necessary for their survival.

 

5. Panne

A panne is a unique coastal wetland whose water levels are influenced by rainfall at the surface and Lake Michigan underground. While pannes often have standing water in the spring, they may not even resemble a wetland by summer’s end. They demonstrate how the process of ecological succession is not always an orderly one. Pannes are created as wind carves a channel through a low spot between the dune and lake and blows the sand out down to the water table. Many of the plants and animals in and around this wetland are different from those on the dune slopes, and even from other wetlands in the park. Rosepink, Kalm’s lobelia, and Kalm’s St. John’s wort grow along pannes’ edges, while the Fowler’s toad lays its eggs and passes its tadpole stage in the deeper portions.

 

6. Blowout

This steep-sided valley is called a blowout. Like pannes, blowouts form when wind whistles in through a low spot in the dunes and carves out a depression. Off-trail footsteps have worn away more of the protective vegetation in recent years. Thus, many of the plants you see here are the same you saw beyond the foredune along the beach. Staying on official trails prevents unnatural disturbances that disrupt the process of succession

 

7. Oak Woodland

In summer, the temperature in this woodland is often as much as 10ºF lower than the open slope on which you just walked. Most of the tallest or canopy trees here are black oaks, red oaks, and basswoods. Beneath the tall oaks are slimmer sassafras, dogwoods, and witch hazel shrubs. This variety of trees indicates that this dune is far enough from the lake to be protected from harsh winds and old enough that the soil has been enriched by previous plant communities. But succession’s path can also be changed here. Wind can blow loose sand from the open dune down into these woods, altering the soil and the plants that use it.

 

8. Sand-mined Landscape

The flat expanse that stretches west from this stairway once contained rolling, wooded dunes like those that you have just hiked. In the early 1900s, sand-miners leveled and hauled away the dunes to use the sand for construction purposes. Today, over a hundred years after this disturbance, what was once loose sand has again succeeded into a mix of plant communities not unlike the open dune habitat closer to the beach. Small mounds of sand are stabilized by little bluestem and tall sand reed grass, as well as by sand cherry and hop tree shrubs. If succession is allowed to continue uninterrupted, someday there may be an oak woodland here once again.