Crossing the Great Divide (two of them, actually)

In just a few short weeks, I will be making my journey northwestward from the warm tidal area of the southern Chesapeake Bay towards the sandy and wind-driven dunes of the south shore of Lake Michigan.  In doing so, I will be crossing many political boundaries.  For a naturalist, though, I'll be crossing much more than just mere state lines and congressional districts, but I'll be traversing ecological boundaries.

I will likely cross two major geological boundaries on my road trip to the Hoosier State of Indiana.  On the grandest scale, I will start off the in the Chesapeake Bay watershed and move across a great divide into the Mississippi/Ohio River watersheds.  A watershed is simply an area of land that sheds surface water (such as rain or snow) into a larger body of water.  For example, your gutters likely poor into a storm drain which empties out into a nearby stream, and then that stream drains to a river, which then flows to an ocean or a large bay.  A great divide is that "invisible" boundary where, depending upon which side of the boundary you're on, that water from your gutter will end up in one place or another (in my case, I will cross a divide where water will end up flowing into the Mississippi River on one side and the Chesapeake Bay on the other).  Everyone lives in a watershed.

Everyone lives in a watershed.  Think about it.  Everyone.  The concept of a watershed is perhaps the most tangible fact that people can utilize in order to understand that people and ecosystems are all interconnected. In this case, one can no longer consider the concept of being 'interconnected' to be one of new-age, esoteric nonsense.  That flow of water from your gutters, and whatever else may be in it, can and does affect people living downstream.

On my upcoming travels though, I'll be moving across not just  ecosystems and watersheds, but rather I'll be crossing into different ecotones.  Ecotones are a collection of ecosystems that are similar to each other in terms of their biodiversity (the different kinds of life they have there) and/or their climate.  The following photo journal will show you what ecological transitions a naturalist such as myself sees on such a long car trip:

START

As I pull out of the drive way, I'll be leaving a region dominated by lush subtropical foliage in a wind-swept, salty maritime environment.
The southern section of the Chesapeake Bay exhibits characteristics common to the Southeast United
States.  In this photo, lush evergreen vegetation gives way to a windy and salty marine marsh dominated by Saltmarsh Cordgrass (Spartina alterniflora).
I'll then cross over into the mainland areas of the Mid-Atlantic Coastal Plain, a forested area of sandy uplands with slow-moving tidal rivers.
The Mid Atlantic Plain is dominated by a wide variety of larger hardwood trees native to both the northeastern and southeastern United States.  In this photo, a bald cypress (Taxodium distichum) stands tall over various oaks, ashes, and hickories.   A showy and leafy tree, American Holly (Illex opaca) dominates the understory of these stately forests.  
Higher up in the watershed (the Chesapeake Bay watershed), I'll ride along the fall line of the Mid Atlantic Coastal Plain and the Piedmont.  The Piedmont exhibits qualities similar to that of the coastal forests, only the terrain is more rocky and steep.  This allows for large cliffs and overhangs dominated by Virginia Pine (Pinus virginiana) over tumbling waterfalls.  The climate here is somewhat cooler, so northern-growing plants start to blend in with southern-growing plants.
Piedmont community along the fall line of the Potomac River in Maryland.

Now, depending upon which route I take, at some point I will cross into the Northwestern flanks of the Appalachian mountains, which is mostly within the Ohio River watershed.  This marks my first crossing of a great divide.  The ecological communities here look similar to that of the Piedmont, but their higher altitude and colder climate reveal the southern terminus of northern growing North American plants.



Northern white cedars (Thuga occidentalis) and Eastern Hemlock (Tsuga canadensis) line a gorge along an Appalachian stream in southern Ohio indicating the southern extent of northern plant species.

As I continue to move north and west of this hilly and rugged region, an unsettling change begins to occur across the landscape.  The terrain becomes flatter and more open.  The wind picks up and sways my tiny Toyota Corolla around a straight and wide highway.  There are still some trees, but they are now clumped together in various spots across an open field.  The field looks mostly brown and green at this point, but I know that within a few weeks a dazzling array of colorful prairie flowers will surround those clumps of gnarly trees.  I have now crossed yet another great divide.  I am now in the oak-savanna expanses of the southern watershed of the Great Lakes.  
Oak savanna prairie (in winter) at a nature preserve in Northwest Indiana.  In summer, the clumps of oaks become surrounded by a diverse and colorful array of prairie wildflowers.

FINISH

The northern extent of my long road trip ends with somewhat of a paradox.  I have moved northwestward from the warm coastal plain into the cool  and more temperate north country.  Yet my end point - the south shores of Lake Michigan, reveals a plant and animal community I would associate more with the beginning of my trip along the southern shores of the Chesapeake Bay.  Prickly pear cactus (Optunia humufusa) can be seen growing on a sandy coastal dune with small six-lined race-runners (Cnemidophorus sexlineatus) (a type of lizard) scurrying about.  The only obvious clue that I am now much further north is the presence of Jack Pine (Pinus banksiana), which is plentiful along the upland ridges and higher sand dunes.  Anything north of here lies northern hardwood forests  with hardly a trace of what I saw at the start of my adventure.  
Prickly pear cactus on a sand dune near the southern shoreline of Lake Michigan


Jack Pine (seen behind the barren tree on the left side of this photo) growing along a shoreline of Lake Michigan.  The presence of this plant species at the end of my journey across two great divides marks a transition into a northern ecosystem.  

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