The Great Smokies

On the way from the Missouri Ozarks to the Great Smoky Mountains of eastern Tennessee and western North Carolina, we spent two days in southern Illinois, as it was not much out of the way, and we’d done no field work in that state before, just driven across it a number of times. We visited two areas in Shawnee National Forest: LaRue – Pine Hills Research Natural Area, and the Simpson Township Barrens. The former contains a set of bluffs at the edge of the Mississippi River floodplain, with nice wetlands at their base, and it has an impressive plant list for an area of its size. The latter is an area of thin soil over bedrock, which suppresses the growth of woody species (trees and shrubs), and so supports a glade-like habitat. Surprisingly, this area, prior to Caucasian settlement, had soils of normal depth and was covered with forest. But it was cleared for farming and erosion took its toll, leaving a landscape that has no means of recovering on other than geological time scales, the production of soil from rock in uplands being an exceedingly slow process.

While in Illinois, we visited Dahlgren, the very small town where Eileen’s mother was born. Eileen asked her the street address of the house in which she lived, and she said they did not have any back then – the postmaster knew where everyone lived. We were able to locate Eileen’s grandfather’s grave, which was in good shape.

We crossed Tennessee to the Great Smokies in two partial days of driving. We made only one stop at a location for Ditch Stonecrop, the only North American species in vascular plant family Penthoraceae. This is not an uncommon plant but just one with which we had never connected. The species was indeed present, but it was not mature enough yet for me to make a truly positive identification. We’ll hope to run into it again later in the season.

Great Smoky Mountains National Park is well known as the most visited national park in the country. It straddles the Tennessee-North Carolina border, located along the Appalachian crest, and has elevations ranging from 875 feet, along the northwest boundary, to 6643 feet at the summit of Clingman’s Dome, about half a mile hike from a paved road. This and other very high areas in the park support a coniferous forest of Fraser Fir and Red Spruce. These trees form a habitat that is physically similar to southern Canadian coniferous forests, though the two species above are replaced by others from the same genera, Balsam Fir and White Spruce. Another notable habitat in the Smokies is the Cove Hardwood Forest, which has a high species diversity of trees, and in which a number of species reach enormous size.  A cove is a valley partially filled with sediments from the mountains around it, producing deep soils and a fairly well-defined, though potentially sloped, floor (unlike a classic V-shaped valley formed by a rapidly cutting river). A third distinctive habitat type is the heath bald, a high-elevation area dominated by shrub rhododendrons, azaleas, and mountain laurel, usually interspersed with small meadow openings. These areas can have spectacular floral displays in early summer. We had good luck with the orange Flame Azalea in Andrews Bald, the most accessible bald in the park (3.6 miles round trip from Clingmans Dome). Less accessible Gregory Bald (11 miles round trip from near Cades Cove) is said to be even better.

The climate of the Smokies practically qualifies as that of a temperate rainforest. The 5000 feet of elevational range wrings moisture from weather systems encountering the mountains, with the rising air cooled below the dew point, and precipitation resulting. The high rainfall maintains a superb collection of cascading streams, many with waterfalls, both of which are major attractions to the numerous tourists. The humidity is also consistently very high, contributing to the renowned biodiversity of the park, particularly noted for its remarkable number of salamander species, which require and thrive in the moist conditions. Another reason for its biodiversity is that the area was just the right distance south of the maximum glacial advance during the last ice age, to serve as a refugium for many more northerly species. With its wide range of elevations, many species were able to find a niche and survive to the present, in addition to providing stock for recolonization of areas father north as the ice receded.

One notable natural phenomenon in the Smokies is the largest display of Synchronous Fireflies, Photinus carolinus, in the world. In this species, at times, individuals will light up at about the same time as their neighbors, so that their lights create a pulse or wave over a large area, punctuated by a dark period that varies with temperature, but averages about 8 seconds. The display is best during a one- to two-week period when the population peaks, often in late May. But predicting the exact date range is difficult because the population emergence is controlled by spring weather. (Specifically, in a plot of temperature versus date, the area under the curve, but above a threshold temperature, must reach a critical value for initiation of the phenomenon.) The National Park Service holds a lottery each year for people to reserve a nighttime parking space at the Sugarlands Visitor Center, from which shuttle buses transport people to and from the area. Another approach is to book a site at the Elkmont Campground, from which the location may be reached on foot (about 3 miles round trip).

The best area is along the Little River Trail (a gated fire road), on the side opposite the river, in places where there is a good view deep into the forest. We viewed from latitude 35.65246, longitude -83.57443, (map link), and based on conversations with others, areas a little farther up the trail were at least as good. But unfortunately, we were a week or so after peak, and the display was rather muted. Around sunset, the abundant and familiar Common Eastern Firefly, Photinus pyralis, began lighting up. Roughly an hour later we were pleased to see a second firefly species, the Blue Ghost (Phausis reticulata), which emits a bluish light and remains lit for several seconds at a time, noticeably longer than the other two species. The Synchronous Firefly display started about an hour later than that, though at the peak of the season they begin earlier, perhaps an hour after sunset. Lights disrupt the display and so should be filtered red or blue and should be used as little as possible.

Some highlights of our two weeks in the park included finally seeing an Eastern Copperhead (a venomous snake in the same genus as Cottonmouths); locating flowering Mountain Camelia (Stewartia ovata), with 2-inch cream blossoms having contrasting deep purple filaments; seeing adult Black Bears foraging on brambles; and watching a bear cub at close range for several minutes. Despite seeing about 156 plant species in the park, we averaged only about one new species per day, as many of the species were familiar from a  few previous trips to the Smokies, several visits to Kentucky, and considerable field time in the Adirondack and Blue Ridge Mountains.

Next up: heading north.