Sounds to me like you got into an area of slash/release work. The DNR contracts companies out to get the unit down to around 300 trees per acre (TPA). That is about a 12 foot spacing between trees. When you are in an area where alder was planted, normally at 600 TPA, which I believe is the standard planting, then around the six year mark, they go in and remove half of the trees. The initial heavy planting helps the trees grow up rather than branch out. After six years, they are big enough that an adjacent tree 12 feet away will provide enough shade to keep them going up rather than produce low branches. The release treatment allows the fastest growth of the alder plantations and stops fir plantations from being overtopped by alder, which ultimately will kill the fir trees.
On fir planted units, DNR uses the same spacing but leaves an alder (if available) when slash/release treatments are performed. We all know how effective alder is at overtaking a clearcut. Six year post-planting, that leaves a lot of dead six inch alder laying around. If you want to hunt these spots, look for the trails through the slash or work the edges. Forget trying to walk through that stuff. I think the deer still use the area extensively, at least based on the trails I see through the slash.
I believe the private timber companies use more herbicides intended to kill alder at a younger age. Weyco lands are incredibly barren of alder and brush until the fir are well established. Brown and dead - everywhere. They seem to have special cocktails of 2-4D and Glyphosate (round up) herbicides that kill alder extremely well while only causing minor damage to the fir plantation. It seem to make for a lot easier hunting down the road too.
That's my guess about what you are experiencing. Thankfully, the alder rots incredibly quick. 5 - 8 years of ground contact and that stuff will literally melt into the forest floor.
