Oak Regeneration Challenges

The relative importance of oaks is decreasing within the oak forest region (Johnson 1993). At the forest landscape scale, oak forests are changing ecologically because of widespread successional displacement of oaks by more shade tolerant species, the absence of fire, and the increased mortality of oaks caused by gypsy moth (Lymantria dispar L.) defoliation, and oak dieback and decline. Urban expansion, road construction, conversion of oak forests to pasture and cropland, and accelerated harvesting of oak stands have produced additional losses (Johnson 1993). Northern red oak stands, especially, are currently being heavily logged by private landowners throughout the East because of its high oak lumber value, and are being heavily attacked by pests, including gypsy moth (Lymantria dispar L.) and oak wilt [Ceratocystis sogacearum (Bretz) Hunt.] (Isebrands and Dickson, 1994).

At the heart of this contraction of oak forest acreage in the landscape and of the importance of oaks within oak forests is a serious problem with oak regeneration. Evidence has been accumulating for many years that there is a problem establishing oak regeneration on many sites. This evidence suggests the oak regeneration problem appears to be both geographically widespread and site specific in nature (Table: Upland White Oak)BROKEN-LINK BROKEN-LINK , (Table: Bottomland White Oak) (Table: Upland Red Oak), (Table: Bottomland Red Oak), and (Table: Western Oak Species).

A number of factors are known to contribute to oak regeneration failures. Problems with acorn production, acorn consumption by insects, acorn consumption by animals, poor seedling establishment, damage to seedlings by animals, and damage to seedlings by insects can, in some cases, account for oak regeneration failures. However, overall the major cause of regeneration failure on good sites seems to be the slow juvenile growth rate of oak seedlings and their inability to respond to release. Oaks apparently do not compete efficiently with more tolerant species, especially those in the lower canopies at low light levels, and with well established and/or faster-growing species under open conditions.

Comprehending the options, opportunities, and limitations in managing oak forests requires, among other things, an understanding of oak ecology, the reaction of oaks to environmental stress factors, and the historical relation between oaks, fire, and humans. It is also important to recognize ecological differences among the different kinds of oak forests and how these differences are related to silvicultural and management options. Stands that are superficially similar may react differently to a given silvicultural practice.