From rock, to plant

Beautiful and wild, the cold rocky shoreline of Lake Huron in Michigan's Presque Isle County offers a glimpse of utterly untrammeled wilderness. Of all of the diverse habitats in this region, this spot, at Thompson Harbor State Park, is my favorite. The botanical diversity is stunning, the ecology fascinating, and the birds can be beyond belief. It was not far from this spot where I photographed the Snowshoe Hare which was the subject of THIS POST.

The rock-studded gravelly shoreline spread out before us is not a hospitable environment for most plants. If chlorophyll coursed through your veins, and you were thinking of plunking down roots in this place, you'd be wise to pick a new spot. Take note of the White Cedars and other conifers in the backdrop. They display the Krummholz effect - a stunted twisting of conifers that are subjected to regular strong icy winds. Lake Huron, off to the right, regularly offers up gales and attendant brutal winds that smash and distort the lakeside trees. Not only that, but the rocky plain in the foreground is often pounded by punishing walls of water during storms. Come winter, comes ice. The lake drives piles of it ashore, and the ice scours the shoreline with the force of a fleet of caterpillar bulldozers.

As I said, this is no place to be if you are a refined plant, used to tender soils and balmy climes.

This is the number one botanical tough guy; the grassy-looking plant that dominates the previous photo. It is Baltic Rush, Juncus balticus, and it's the main pioneering plant of No Man's Land: the wave-washed, ice-scoured leading edge of the Huron shoreline. Note how its stems form a perfect line. This is a wonderful example of a rhizomatous plant.

I've unearthed a Baltic Rush so that we might better examine its anchoring system. That thick cordlike root is the rhizome, and the stems arise at regular intervals. This growth habit forms the neat row of stems that we saw in the former photograph. Such a system works well for holding a plant in place when it is subject to extreme forces of disturbance. Plants that are successful at colonization by rhizome often produce relatively few fertile seed, instead putting much of their energy into expansion of the root network.

After a while, islands of comparative tranquility are created by the buffering effect of pockets of Baltic Rush. Other, somewhat lesser plants then gain a tenuous foothold on the beachhead by growing in spots protected by the rush. The purple jots in the foreground are Northern Bog Violet, Viola nephrophylla.
 
Do not be fooled by the violet's elfin, delicate appearance. The plant, at least when inhabiting rocky Huron shorelines, grows in an environment that would quickly kill most plants. It is able to eke out an existence sandwiched in the interstices of rocks, where it is occasionally drenched by raging waves.

As we move back the beach a bit, to slightly more settled lee zones, the plant life diversifies somewhat. This is Indian Paintbrush, Castilleja coccinea, which often grows in association with Bird's-eye Primrose, Primula mistassinica, in these areas.

Eventually, woody shrublets, perhaps most notably Bearberry, Arctostaphylos uva-ursi, gain a foothold. The process of stabilization and transformation from rock to plant is well underway.

Other plants begin creeping in, including what may be the world's most beautiful member of the Iridaceae, the Dwarf Lake Iris, Iris lacustris. This is Michigan's official state wildflower, and its range is limited to shorelines of the upper Great Lakes. The plant is well named on all fronts: it is truly dwarf; those blooms rise only a few inches above the gravel. The specific epithet of the scientific name, lacustris, means "of lakes".

The occasional Pitcher Plant, Sarracenia purpurea, infiltrates damp pockets of the back parts of the gravelly beach. Ohioans and others from points south are invariably delighted to see this botanical carnivore, which is quite rare down our way and persists only in the odd glacial relict bog or fen. Note the other carnivorous plant in the backdrop, righthand corner. It is the so-called English Sundew, Drosera anglica.

The leaves were obvious on my recent visit, but one would have to return to these shores in July to catch the spectacular flowers of Grass-of-Parnassus, Parnassia glauca. In Ohio, we think of this plant as a strict fen specialist. The cold wet calcareous shorelines of Lake Huron have all of the ingredients of a fen, and sport many of the same plant species.

Finally, given enough time - hundreds? thousands? of years? - full blown woody plants will begin colonization of the shoreline, following in the rootsteps of all of the pioneering plants that came before. This is a White Cedar, Thuja occidentalis, and it is among the first trees to step foot onto the shoreline. The conditions are still rugged, even for a tough cedar, and this tree shows the wear and tear that comes with life on the Lake Huron shoreline. This specimen is not particularly robust, but I suspect we might be surprised to learn its true age.

Once the cedars take hold, the process of forestation will increase dramatically. This is an old beach ridge only a quarter-mile aft of the open rocky shoreline featured in the previous photos. Ground Juniper, Juniperus communis, and Creeping Juniper, J. horizontalis, line the path. Other conifers dominate, such as Red Pine, Pinus resinosa, Balsam Fir, Abies balsamea, White Spruce, Picea glauca, and in wetter areas, Tamarack, Larix laricina, and Black Spruce, Picea mariana.

Life is easier, and more diverse, in these nearshore forests than on the open lakeshore. Breeding birds abound, and plant diversity spikes appreciably. Walking through the transition between these places is always fascinating, and our mile round-trip from parking lot to lakeshore and back can easily take several hours. We typically return with an enormous list of flora and fauna, and a better appreciation of Great Lakes ecology.