Oak Silvics/Ecology

The oak genus (Quercus) is one of between six to nine genera of the beech family (Fagaceae) found worldwide{Rogers 2004}. Of the estimated 400 to 600 species of oak, most are found in the northern hemisphere. Some 200-250 species are found in North, Central, and South America, and 300 or more species are scattered throughout Europe, Asia, and North Africa (Little 1979, Harlow et al. 1991, {Johnson 2002}). Oak is the largest tree genus in the United States and is the most important hardwood. There are 58 recognized native oak tree species in the United States and Canada, one naturalized tree species, and about 10 native oak shrubs. There are about 125 species native to Mexico, 45 species native to Central America, five species in Colombia, and one species in Cuba (Little 1979, D. Smith 1993,{Johnson 2002})

Frequently the greatest challenge in managing oak stands is overcoming the problem of insufficient oak regeneration following natural or anthropogenic disturbances. The key to solving this problem is to identify where the bottleneck(s) occur in the regenration process.  It is important to understand that the barriers may be different within the same oak system as well as being the same across oak systems. Therefore one must understand and appreciate the ecology of oak regeneration which encompasses , the  biology physiology and the dynamics of the newly developing oak stand.  For a comprehensive treatment of the ecology of oak regeneration  from reproduction to population dynamics the reader is directed to Johnson et. al. (2002).    An abbreviated treatment of topics related to oak regeneration ecology is given here.

• Regeneration strategies of oaks. Oak species occur in a variety of ecosystems, ranging from xeric, to mesic, to hydric. This section discusses the different regeneration strategies among oaks in each of these three systems. The three forms of oak reproduction (seedlings, seedling sprouts, and stump sprouts) are also described.
• Oak reproductive biology. The production of acorns is an important topic in understanding the oak regeneration story. This section reviews the development, pollination, and fertilization of oak flowers and the development, dispersal, and germination of acorns.
• Juvenile growth: A physiological perspective. Oaks are generally viewed as being "inflexible", i.e., they do not acclimate well to changing environments, especially light. In this section, physiological explanations for this characteristic of oak juveniles are discussed by reviewing literature on the growth of stems, leaves, and roots as well as carbon fixing and allocation in oak seedlings.
• Juvenile growth: An ecological perspective. The following sections approach oaks inability to respond to release from an ecological perspective.
• Effects of fire on oaks. Most oak species have biological adaptations to fire that promote the accumulation and development of oak reproduction following fire. This section summarizes this and other benefits of fire for oak regeneration as well as discusses the negative consequences of fire suppression on oak forests.
• Threats to oak forest health. This section reviews eight of the major threats to oak forests, including gypsy moth, oak dieback and decline, and global warming.
• Knowledge gaps in oak regeneration ecology. Smith (1993) reviewed the regeneration-related silvical characteristics of 31 oak species and found significant regeneration gaps for at least 27 oak species. (Table: Summary of Regenration-Related Silvical Characteristics) This section concludes by summarizing eight important areas for future research.