Effects of Clearcutting on Regeneration

The clearcutting regeneration method has been applied in the Southern Appalachians for several decades and research on this technique dates back to the 1920s. The accumulation of knowledge on this regeneration method has revealed several general patterns.

First, species composition following the clearcutting method is generally related to site quality. On high-quality mesic sites and in cove stands, species composition following the clearcutting method is generally dominated by yellow-poplar seedlings, sweet birch seedlings, stump sprouts of red maple, and root sprouts of black locust. It has been observed that stands become increasingly dominated by yellow poplar with development (Beck and Hooper 1986). At elevations of 3,500 to 4,500 feet in the southern Appalachians numerous black cherry seedlings often appear after clearcutting.(Hicks 1998)

On medium-quality sites dominated by upland oak species, species composition following the clearcutting method is generally dominated by the same species that were harvested, primarily white, scarlet, and chestnut oak with several pine species as associates. As previously noted, more sproutable stumps are usually present on such sites than on the better quality cove sites. Also, greater numbers of advance oak seedlings are frequently present due to the less competition from tolerant understory species. Therefore, if the clearcut stand is on southeast or northwest middle and upper slopes, we can expect to have a stand at about age 20 that can be molded into an essentially pure oak stand by thinning. On north and east aspects and lower slopes, the stand composition may be highly variable. (Sander and Graney, 1993)

Second, if advance growth dependent species, e.g. oaks, are desired on these high-quality sites, large advance reproduction of these species must be present at the time of harvest if they are to represented as dominant and codominant stems in the new stand. Herbicide application prior to, during, or immediately after harvest is often necessary to control sources of competing species. (USDA Forest Service 1995)

Third, an opening of at least 1-2 acres in size is required in order to create the openness needed to produce the characteristics of a clearcut (Sander 1992; Dale et al. 1994). Stands smaller than this have a large proportion of their area in a zone around the stand border where reproduction growth will be slow because of the influence of the surrounding trees. (Hicks 1998)

In spite of these general patterns, Loftis (1988b) acknowledges that the type and amount of regeneration following clearcutting can be quite variable, and there are instances where clearcutting has not achieved the desired objectives. For example, Elliott and Swank (1994) reported that a southern Appalachian hardwood stand clearcut in 1939 and again in 1962 showed a decrease in frequency of oaks, due in part to the regeneration strategies that are initiated when clearcutting a very young stand (notably sprouting).(Hicks 1998)

On many sites in the southern Appalachians, the clearcutting method increases unwanted competing or allelopathic vegetation, rather than the desired species (Boring et al. 1981; Leopold and Parker 1985). Horsley (1988) lists a number of woody and herbaceous species as undesirable competing vegetation, including ferns, grasses, brambles, rhododendron, mountain laurel, grapevine, striped maple, sourwood, dogwood, pin cherry, sassafras, and blackgum. It is important, before clearcutting, to assess the potential for such competitive interactions. The options for control vary, according to the type of competing vegetation being managed, but may range from selecting an alternative regeneration system to use of prescribed fire or herbicide treatment before or after cutting. Since most selective herbicides kill broadleaf species, it is not practical to use broadcast spraying after hardwood regeneration has already become established. In such cases, spot spraying, injection, or basal spraying may be required. Both herbicide injection and/or basal spray of individual stems shortly before harvest (Loftis 1985) and cut-stump treatment with herbicides at the tire of the harvest cut have met with success in the southern Appalachians (Zedaker 1987). Cutting competing vegetation without the use of herbicides is not effective due to the rapid regrowth of sprouts from the cut stumps. These treatments are expensive and labor intensive; thus, where such problems are expected, it may not be economically feasible to do them, particularly for the small private landowners typical of the southern Appalachians. Ferns and grasses have an advantage over tree seedlings in highly compacted soils so it is imperative that soil compaction be minimized during logging. (Hicks 1998)

Deer browsing also contributes to the failure of regeneration (Marquis and Grisez 1978). Smaller isolated clearcuts are particularly vulnerable since they serve as an attractant for deer. In addition to using larger clearcuts, leaving slash piles scattered through the clearcut helps in discouraging deer and promotes regeneration success. A last resort for obtaining regeneration in areas with very high deer population levels is fencing (Marquis and Grisez 1978) however, fencing alone may not be enough to ensure regeneration. (Hicks 1998)

In a few situations in the central hardwood region natural regeneration may need to be supplemented by planting or direct seeding following clearcutting (Pope 1993). Plantings can be successful but are expensive and will probably require weed control or protection from deer during the first few years, particularly on good sites (Stout 1986; Walters 1993). Although planting may be desirable under certain circumstances (Davidson 1988), cost and uncertainty of success limit its practice. (Hicks 1998)