When in doubt, check the DNR web site at : http://www.michigan.gov/dnr
The answer to your question is at the following link. I took the liberty of a quick copy and paste for easy reference.
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You can camp anywhere on State Forest Property as long as:
the property is not posted "No Camping"
you are more than one mile from a designated State Forest Campground
you follow all State Land Rules
You must also post a Camp Registration Card (PR 4134) at your campsite. To obtain a Camp Registration Card, contact your local DNR Office or e-mail us at DNR-FMD-TREES to request copies be mailed to you.**
** We are unable to fax or e-mail the permit because it is printed on two-part perforated weatherproof card stock.