Causes of Degraded Hardwood Stands

McGee (1982) indicates that stand degradation can be caused by a variety of factors, including past cutting treatments, fire, and insects and disease.  Site-quality also plays a role in stand degradation. Perhaps the foremost cause of degraded hardwood stands is past harvesting practices.  Many of the present hardwood stands in the eastern United States developed without the benefit of deliberate management; some developed after high-grading-- cutting of best trees and leaving the rest (Ezell 1992).  Also, wildfire was a regular occurrence throughout the hardwood region and still affects important hardwood producing areas.

Insects and diseases also can degrade stands. Infestations of insects such as gypsy moths, elm spanworms, fall cankerworms, and white and red oak borers weaken or kill hardwoods. Cankers, wilts, and rots also cause substantial damage throughout the region. Diseased trees largely populate degraded stands because they are usually passed over in cuttings.

Icestorms and windstorms can also degrade stand quality. Certain stands are more susceptible to ice damage than others; for example, stands containing grapevines, stands dominated by yellow-poplar, or young pole-sized stands can be severely damaged by ice (McGee 1982).

Degraded stands are composed of remnants from previous cuttings, some regrowth of desirable species, and a large proportion of mostly undesirable shade-tolerant species (Ezell 1992). These cull-burdened stands present serious management problems (Trimble 1963) Considering the condition of these stands and the current economic situation, there remain powerful incentives to continue diameter limit cuttings, where the best trees are harvested and the remaining stand is left unmanaged. The average owner has little economic incentive to improve degraded stands as such stands may be worthless for traditional timber products and stand improvement can require considerable investment (McGee 1982).

The Role of Site Quality

The quality of a stand depends heavily on the quality of the site it occupies (Carmean and Boyce 1973). As site productivity decreases so does the quantity and quality of timber produced. In some instances, the growth may be too slow for viable production of high-grade hardwood sawtimber. Also, degraded stands growing on low-quality sites take much longer to respond to improvement treatments. However, substantial acreages of degraded stands are growing on good sites, such as coves and north-facing slopes. These areas have potential to produce high-quality hardwoods and they often escape wildfire (McGee 1982).