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Photo courtesy USDA FOREST SERVICE
Lupine, found in Michigan's savanna, is vital to federally-endangered Karner blue butterflies. |
Savanna in Michigan? Absolutely.
Let's take a pop quiz: Name three things that come to mind when you think of Michigan.
White-tailed deer? Got about 1.5 million of those.
Great Lakes. Yep, five of them.
Massive stands of hardwoods and coniferous forests? On both peninsulas.
How about savanna? Got that too. Seriously.
Michigan's Huron-Manistee National Forest is restoring and maintaining more than 20,000 acres of savanna habitat over the next 50 years, a project that will provide critical habitat for a large number of species including the federally-endangered Karner blue butterfly.
"There is a lot of interest in the Karner blue butterfly, but the savanna work really benefits all kinds of species — including wild turkeys," said Heather Keough, a district wildlife biologist with the U.S. Department of Agriculture.
We're not talking about African-style plains habitat here. Michigan's savanna is a cross between forest and grassland, a visually striking habitat that provides an ideal mix of cover for nesting and escape from predation as well as mixed stands of hardwoods and conifers.
The Huron-Manistee National Forest has managed for savanna habitat since the early 1990s. Savanna restoration, however, has really taken off in the last five years thanks to partnerships with groups like the NWTF.
Savanna habitat is created and maintained by using selective hand cutting, prescribed burning, mechanical removal of vegetation, seeding and habitat protection.
"Savanna restoration is intense and requires a lot of planning," Keough said. "It's expensive, and we want to stretch those dollars as far as we can."
The goal is to protect remnants of naturally occurring savanna while reducing tree and shrub density to promote establishment and growth of native grasses and wildflowers. One key species is wild lupine, a member of the pea family. Lupine produce small purple-blue flowers in early spring that last just a few weeks, with the peak occurring in mid-May.
Lupine are vital to Karner blue butterflies. Dense stands ensure that enough butterflies are produced to maintain a sustainable population.
Two generations of these butterflies are produced each year. The first begins around mid-April, when eggs laid the previous summer hatch. Larvae crawl up the lupine stems to feed on the new leaves, the only food these young caterpillars will eat.
During the lupine's flowering period, first-flight adult butterflies lay eggs on or near the plants. The season's second brood of larvae feed through mid-July, when lupine flowering ends and seed pods are produced.
Second-flight adults emerge through mid-August. Because they cannot depend on lupine flowers for food at that time, they need a variety of mid- to late summer flowering plants for nector. By the time second-flight females lay their eggs, lupine is dying back or is already dormant.
"We are seeing terrific response [to our work] in the plant life," Keogh said. "And that's the first step — plants change first and wildlife follows."
The Huron-Manistee Forest expanded its partnership with the NWTF in 2010 by entering into an agreement to restore 377 acres of habitat. The partnership promotes ecosystem management that benefits wild turkey, Karner blue butterflies and other savanna species.
Volunteer efforts have played a critical role, with 27 partner groups, including the NWTF, contributing 886 volunteer days valued at more than $112,000 since 2007. — Tony Hansen