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Rare Plants Discovered Near Detroit

Detroit River International Wildlife Refuge is a Reservoir of Biodiversity

January 20, 2016

Oval ladies’ tresses. Photo courtesy of David McAdoo/Creative Commons.

Detroit River International Wildlife Refuge in Michigan initiated a survey this past year of a few of the largest remaining forests in the downriver area, including the renowned Humbug Marsh, which was nearly developed into hundreds of homes, a marina, and a golf course in the late-1990s and is now a part of the international wildlife refuge.

Botanists Brad Slaughter and Mike Penskar with the Michigan Natural Features Inventory, worked with Detroit River International Wildlife Refuge staff to provide an updated and accurate description of what is most unique and critical for protecting in these small forest stands that total less than 500 acres, with one acre being about the size of a football field. They also investigated forests at Oakwoods Metropark and on Grosse Ile.

To understand what features of the forests are most important to conservation, the researchers referenced what the forests were like before the land was settled and converted to agriculture about 200 years ago. They “dusted off” old land records that dated back to 1817 when Joseph Fletcher, of the Federal General Land Office, walked what is today known as Humbug Marsh. While the purpose of these records was originally to document timber values, they provide a baseline for biologists today. A clear sequence was described of the ownership changes that led to degradation of the native forests due to farming, grazing, and cutting over the years. They focused on describing in detail how the original native, healthy forest was a product of the soil, natural drainage, and inferred Native American land-use. They then described what features of the forest persisted after 200 years of intensive land use by French and then other European settlers.

Refuge biologist Greg Norwood notes that, “the species that make up places like Humbug Marsh are perhaps analogous to collections of books in a library – there are those shelves made up of mostly old, rare books that have somehow been left unchanged, collecting dust together for decades.”

“There are also shelves that are more or less represented by mass-produced, commonly-found books that were added recently, which are analogous to the invasive species and generalists. Finally, there are, of course, some shelves that are virtually devoid of books altogether, that are analogous to very few species,” continues Norwood.

The refuge ultimately wants to track those collections of species that have been together the longest and serve as a “reservoir” of biodiversity. It was recently discovered that Humbug Marsh is home to a rare grass-like plant called the hairy-fruited sedge (Carex trichocarpa) and an orchid species called oval ladies’ tresses (Spiranthes ovalis). Records show that these plants have never been found in Wayne County, which has some of the oldest botanical records in Michigan. One sedge species (Carex squarrosa) identified on Grosse Ile had not been found since 1932. The Shumard oak, having never been recorded on the island, was determined to actually be a dominant tree on the remaining forest on the island. In fact, Grosse Ile is one of the strongholds for the Shumard oak in southeast Michigan, a Michigan State-listed special concern species.

The healthiest flatwoods, which are those on Grosse Ile, Oakwoods Metropark, and Belle Isle in Detroit, have a more even mix of old, medium, and new species. Humbug Marsh, which was determined to have had the most disturbance over the years, has a disproportionately higher abundance of new, common species to older, rare ones that have been together for a long time.

“This difference is like that of a collection at an old, ivy-league university library versus one at, say, a new Barnes and Noble, which is disproportionately represented by mass-produced, common books found nation-wide,” Norwood says.

Detroit River International Wildlife Refuge covers 48-miles of shoreline along the lower Detroit River and western basin of Lake Erie. It stretches from southwest Detroit to the Ohio-Michigan border.

Learn more about this and other research at Detroit River International Wildlife Refuge: