The North is Near

North America is home to the world's farthest southern tundra, on the shores of Hudson Bay.  The flat, apparently barren shores share the same latitude with Edinburgh and Copenhagen, and even the great Siberian tundra lies at least a hundred or so miles north of this.  A combination of a large continental body with deep reaching salt water bodies serve to make nearly all of interior Canada a really cold place for a good portion of the year.  The United States largely escapes the reach of truly northern conditions, although in some places in the north eastern areas and around the Great Lakes, the great boreal forests reach south.  Michigan is where the struggling remnants of a colder forest persist the furthest south, namely in bogs covered in Tamarack and Paper birch.

Swamps can often extend the natural range of forest types and certain trees well beyond the natural limits of their range.  The waterlogged soil can be rich in nutrients, but is usually of marginal quality for many trees.  Pines, for instance, require well drained soils.  Hardwoods like maples, beeches, and oaks require drier conditions, or at least soil that is more on the moist, rather than drained or wet, sides.  As a result, trees of more distant regions can find a more suitable home in these marginal soils, sheltered or cooled more so by the conditions of a swamp.  Baldcypress, for example, grow as far north as Indiana along the Wabash river.  Black spruce can be seen far to the south of their normal limits in small bottomland areas of the Allegheny highlands near Corning, New York.

For the most part though, no one is going to confuse the outer reaches of Detroit with "the north" just because a few tamarack bogs are nestled in with the oaks and hickories.  Things become far more noticeable when such relics of a colder age become the norm across lower areas.

Black spruce, especially on the left in that second picture, are those "Christmas trees" that seem to be missing most of their body.  They are usually missing interior sections of their crown, with but a mass of new growth at the top serving as the only distant evidence that the tree is not dead.  Even close up, the branches bend to the ground and look sickly, hanging off the trunk.  For all their weak appearance, however, they are truly remarkable trees that can withstand arctic temperatures, sourly acidic soils, and will not break under the worst snowfalls.  They can grow in a miniature form even in permafrost, can root peat mats together and stabilize bogs, and can grow either in standing water or dry ground.  They are extremely adaptable, and grow in a range of conditions from the treeline in Alaska all the way down to the New York/Pennsylvania border.  They are marginalized in the temperate southern limits of their range, and are perhaps the best indication that one has arrived in northern lands when they are seen covering vast tracts instead of being shunned in shaded, acid bogs.

This would, of course, place "north" as such:

The nice thing about this proximity to a fair bit of the population in both Canada and the United States is that some rather undeveloped, vast stretches of land are close at hand to those living in some of the biggest cities of the world.  At the same time, warmer areas given life by the great humidity factory of the Gulf of Mexico are not even several hundred miles south of the northern line, and areas there and in between are among the most productive agricultural regions in the world.  North America is just that diverse and amazing!