Sugar maple seedlings have the opposite niche as hemlock seedlings--they are much more likely to survive on thick duff. This is because the seed is larger and has enough energy to grow a more vigorous root that can penetrate the duff. They can compete somewhat better with herbs because they get larger in the first year than hemlock or other conifer seedlings.
Furthermore, (although we know relatively about this), there are apparently mycorrhizas that form relationships with sugar maple that are very abundant in the older leaf litter at the base of the duff. Also, duff formed by hardwood leaves has a relatively high pH and N and P supply, while tip up mounds, rotted and conifer logs are low in nitrogen, creating even more differentiation in survival between maple and hemlock seedlings, since maple requires higher pH and nutrients than hemlock. Also, hardwood leaves can land on top of hemlock seedlings in the fall, and then they are crushed by the snow on top of the leaves. It is important to note, however, hemlock seedlings are not successful in either maple or hemlock duff--they just don't get through to the mineral soil quickly enough and a few days without rain kills them if the leaf litter dries out.
And, of course, the earthworm invasion is changing all of these 'neighborhood effects' that have maintained separate maple and hemlock stands for the last 3,000 years. Fortunately, the park still a large area free of earthworms.
Deer are excluded from a large portion of the Porcupine Mountains, and actually a large surrounding landscape, by deep snow. Last winter, for example, a nearby weather station had 25 feet (7.6 m) of snowfall. This is mostly lake effect snow, when arctic air masses cross Lake Superior, they pick up moisture, which then condenses and precipitates out as snow when the air cools when it reaches land. However, the first mile or so along the lake shore, gets little snow, since the air masses get some distance inland before the snow reaches the ground. There is usually a wall of snow 2-3 m deep a certain distance from the lake. Deer migrate out of the deep snow area and go to the lakeshore during winter, and therefore we have a naturally occurring winter deer exclosure, with contrasting areas of high and low deer browsing during winter. During summer, deer do return to these areas, but at that time they usually eat herbs, and relatively little woody material.