Essay: Recovery
[In April, 2014, on a camp out in the swamp, I spent a day studying the recovery of a 40-year old clearcut in the middle of the park; here are the results].
It has been nearly forty years since logging ended in the Congaree. All total, about 3,600 acres was logged in the swamp from 1969 to 1976. Some of the cutting was light, taking out just a few very large trees; in other places, more heavily selective; and some areas were clearcut, where everything was removed. Some of the selectively-cut sites have now recovered to the point that most people would never know logging had ever taken place. Not so with the clearcuts. They look more like forest now, albeit a young one.
I remember one clearcut well. It was located in the center of the park, next to the “New Road” as we called the one that was punched in almost due south from South Cedar Creek Landing all the way to the river. A section of this old logging road is now part of the Kingsnake Trail, but in 1975 it was a big, wide, and often muddy road large enough to accommodate fully-loaded eighteen-wheeled logging trucks.
This clearcut was a big one, about 240 acres, in the shape of a rectangle. The logging contract stipulated that no cypress was to be cut, perhaps because the Santee River Cypress Lumber Company had made their name by cutting virgin cypress and now wanted to leave some of what remained. I don’t remember much about what this area looked like before it was cut, except it had a good bit of low ground with shallow sloughs and small guts. The cypress was nice but not overly large.
For the first few years after cutting, the site was a thick stand of brush, briars, and vines, thick as hair on a dog’s back as they say, and almost impenetrable, even to a dog. After eight years or so, young tree growth started kicking in, and by year fifteen it looked like a plantation of slender, thickly planted trees. A few years later the clearcut had turned into a young hardwood forest of trees ten inches in diameter and sixty feet tall. Now, with the former clearcut reaching age forty, I wanted to learn a little more about the ongoing recovery process for this stand. To do this, I measured the diameters at breast height (dbh; four and a half feet above ground) for all trees greater than six inches in ten circular plots sixty feet in diameter. In a few cases I also measured the heights of some of the dominant trees.
For this admittedly very small sample, I found nine species of canopy trees, with green ash being by far the most abundant, accounting for nearly half, 47%, of the total. Sugarberry was next with 15% of the total. The remaining seven species, American elm, swamp cottonwood, laurel oak, overcup oak, red maple, sweetgum, and sycamore, combined for the remaining 38%. The one thing that struck me right off was the low number of sweetgums in the sample, only two of sixty-six trees. Normally this aggressive hardwood invader of old fields and clearcuts would be the most abundant, both in terms of numbers and biomass, but its sparsity was probably due to the fact that the site is low with a high water table and poor drainage and more conducive for growing ash than sweetgums.
The other surprise is that I after forty years I expected the tree diameters to be larger, say around 18-20 inches, than an average of 14.6 inches for all species (and somewhat skewed by the large size of the two sweetgums, 22.5 and 20 inches; when not counting these two, the average dbh dropped to 13.8 inches); for green ash, the average dbh was only 11.7 inches.
I suspect diameter growth and the low number of sweetgums had something to do with the soil type, in this case Tawcaw silty clay loam, and not the more fertile and better-drained Congaree loam. For the latter soil, foresters tell me it would not be unusual to grow a twenty-inch diameter sweetgum nearly 100 feet tall in 40 years. This was borne out for the two gums in my sample, growing on slightly higher and better-drained soil, that were 20 and 22.5 inches dbh with the height of the latter being 93 feet. The heights of a few other species were 75 feet each for two red maples; 73 feet each for two sugarberries; 84 feet for a sycamore; and 84 feet for an overcup oak.
With such a high density of young trees at this site, and I only counted the ones greater than six inches dbh, you would expect a sparse ground cover, which was the case. Mostly it was bare soil with scattered light patches of switch cane and a sparse understory of mostly deciduous holly.
It will be interesting to continue to follow the recovery process for this stand, but even with the swamp’s fertility and rapid tree growth, this forty-year-old clearcut will not look like an old- growth forest for many, many years. I only look for confirmation at another nearby site, along the eastern side of Horsepen Gut, which has been undergoing recovery for a hundred years longer than my clearcut, since just after the Civil War. Known as the “Hunt Tract” after Alfred M. Hunt of Columbia (who purchased it from the Weston family in 1861), about 170 acres of this 744-acre tract had been previously cleared and diked by Weston slave labor, probably sometime between the 1820s and 1840s. Diking bottomland crop fields was in response to increased flooding caused by the clearing of native plant cover in the Piedmont for cotton culture. I believe Harry Hampton called this area the “Jim Williams Old Field.”
The trees growing in this old field site are now about 150 years old. They are mostly sweetgum, as would be expected from a site that is nearly 100% Congaree loam. This extraordinarily fertile soil produces gums here averaging thirty inches in diameter (range, 22-40 inches based on a small sample of eleven) and 120-135 feet high. I actually expected the trees to be larger, averaging 36-40 inches in diameter, based on their ages and soil type, but surmise that because of high densities they have been in competition with one another for growing space.
It is a beautiful stand of tall, straight trees that also includes green ash, elm, and sugarberry in addition to sweetgum. But it is still an even-aged forest with nearly all the trees being about the same size since they all grew up together at the same time. In structure, this stand is much different from the old-growth, “all-aged” forest that surrounds it. It would not be the place, for example, to look for a national or state champion sweetgum, oak, elm, or ash. It lacks the complex structure and vegetative layers of old-growth, and there are relatively few tip-up mounds, logs, large limbs and other woody debris on the ground so characteristic of an old- growth forest. How long will it take before this “old field” looks like genuine Congaree old-growth? We don’t really know except that it’s probably measured in hundreds of years.
