Roundtop Mountain, SC    Jess Riddle    May 09, 2006 17:39 PDT  Ents, Last week, Will Blozan, I, and three other Appalachian Arborist employees traveled to Roundtop Mountain in South Carolina to treat a population of Carolina hemlock trees for hemlock woolly adelgid on behalf of SC Department of Natural Resources. The peak lies on the Blue Ridge Escarpment within the 32,000-acre Jocassee Tract and approximately three miles south of the North Carolina state line (L. L. Gaddy A Naturalists Guide to the Southern Blue Ridge Front). Actually neither round nor a mountain in structure, Roundtop Mountain occupies a narrow, east-west ridge of gneiss that juts out from a larger ridge system that contains two of South Carolina's best known peaks: Sassafras Mountain, the highest point in SC at 3560'; and Table Rock featuring sheer cliffs over 900 feet high and another excellent population of Carolina hemlock. Moderately steep, unexceptional slopes occupy the ridge's south side, but numerous rock outcrops, small cliffs, and a few large rock faces and boulderfields cover the upper north slope. The SC DNR singled out the Carolina hemlock population for treatment due to the groves' reputation as one of the finest in the state. That reputation comes from the extent of the stand, stretching for over half a mile along the ridge-crest, and the undisturbed nature of the area. However, even in this stand, Carolina hemlock constitutes only a small proportion of the canopy. Stunted old chestnut oaks form the vast majority of the canopy on the steep, thin soiled slopes, and shade dense thickets of dwarf rhododendron mixed with some mountain laurel. Only galax grows in the dim, dry, acidic environment below the heath shrub layer. Red maple, sourwood, pitch pine, shortleaf pine, downy serviceberry, and sweetleaf also occasionally occur on the upper north slopes. Curiously, table mountain pine, which grows with Carolina hemlock on Table Rock and in Jones Gap State Park, is absent. Heath shrubs also thrive along the ridge crest with rosebay rhododendron, dwarf rhododendron, and huckleberry and blueberry (V. stamineum) occupying separate areas. With the advent of fire suppression, Carolina hemlock has also invaded the midstory on the ridge crest and upper south facing slopes. Those slopes have a higher overstory of mixed second growth hardwoods including white oak, chestnut oak, scarlet oak, silverbell, sourwood, pignut hickory, and mockernut hickory. A description of the forests in the boulderfields and below the cliffs appears in a Roundtop Mountain post from May 2003. At the site, the older Carolina hemlocks grow exclusively in close proximity to exposed rock, most often at the top of cliffs. Those sites offer the fire sensitive species a refuge from fire, and the harsh conditions mean few other species can survive to compete with young hemlocks. The trees begin with scant soil, but often grow large roots across the rock surfaces to reach adjacent forest soils; however, many trees growing on narrow rock ledges are confined to a thin layer of soil composed primarily of organic material derived from fallen leaves and needles. Some trees avoid that situation by root grafting into other hemlocks to indirectly access forest soils. In just a few days, the thin organic soils on rocks may go from saturated to parched and cracked leaving the rockbound trees without access to water. Despite that water stress, the trees apparently frequently attain radial growth rates of 1/8 inch or more. The great solar input to the trees may account for much of that relatively rapid growth. The exposed conditions allow the trees to rapidly reach the canopy and maintain extremely full grows; many trees have branches only a few inches from the ground and live foliage below the level of their bases. Their rocky perches also expose the hemlocks to storms. Some trees quickly develop flat-topped crowns and branches that double-back on themselves. More severe storms snap the tops in some hemlocks leaving the large lower branches to regrow the crown into a claw like structure. A single lightning strike can also damage multiple trees simultaneously on the rocky terrain. However, most trees still maintain full, spruce-like crowns. Trees rarely exceed five feet cbh (two are over seven feet); heights were not measured but likely reach only about 60'. That small size coupled with the observed high growth rates suggests most of the hemlocks at the site are not very old, but many chestnut oaks appear significantly older. Unfortunately, hemlock woolly adelgid threatens to make the hemlocks' life spans much shorter. The plague reached the stand at least two years ago, and has caused major decline in the eastern hemlocks in the surrounding area. However, the adelgid has heavily infested only a minority of the Carolina hemlocks, and even those trees still show vigorous growth. Hence, the trees should respond well to treatment with a systemic insecticide, and the vast majority of the stand, including trees requiring rappelling to access, have now been treated. Jess Riddle RE: Roundtop Mountain, SC   Will Blozan   May 11, 2006 18:10 PDT  Scott, Imidacloprid (soil) treatments are well known to last several years, and the amount needed to control HWA is very small, but slow to get in. Old-growth hemlocks sampled in the Smokies 30 months after one soil treatment had no less than 5X the required levels of imidacloprid to kill HWA. Some trees had several hundred time more than needed. I treated three 28-38" diameter tres in 2002 for HWA and they have not needed a retreatment even though trees nearby have heavy HWA. Hardwoods may be different, but I do not know. Will RE: Roundtop Mountain, SC   wad-@comcast.net   May 11, 2006 19:45 PDT  Will It is my understanding that the chemical has the same action in all plants. I would have to check the label, but I don't think it harms any plants. Lack of moist ground slows uptake. It does not kill mites, and in landscape situations, the mites can explode in population causing more trouble for the hemlocks. Do the Hemlocks down there have HWA, needle scale and mites all on the same tree? That seems to be the norm up here. I kind of understand Lee's input. Something natural has to be found to control the HWA. Keep up the fight though until they find it! Scott   Home