Wildlife Damage Management, Internet Center for
Date of this Version
4-15-1991
Abstract
Hardwoods occupy about 25% of the total forest area in California (Bolsinger 1988). Predominant among the hardwoods are oaks (Table 1). Over the past 10 years, concerns have been raised about the ability of some oak woodland stands to replace themselves. These concerns have focused on 2 distinct management dilemmas. The first involves the gradual loss of oak woodland acreage due to human activities. These activities often involve some type of conversion, such as the clearing of trees for rangeland improvement, production agriculture, or residential development (Schmidt and Tietje 1987). The rapid increase in California's population means more pressure on oak woodlands and hardwood rangelands to convert them into housing developments. Over the past 15 years, 85% of the oak woodland acreage lost has been due to urbanization and road building (Bolsinger 1988). Over 50% of the woodland area converted since 1973 has been the blue oak type. There are 29 million people in California today. By the year 2000, the population is expected to reach 31 million, and by the year 2020, 37 million (Ewing 1987). Pressure on oak woodlands undoubtedly will increase, and policies for reducing or mitigating this loss need to be developed. In addition, utilization of oak biomass for fuelwood consumption is expected to follow a similar increasing trend. The second oak management dilemma involves the biological processes relating to regeneration. Three species, valley oak, blue oak, and Engelmann oak, have been recognized as suffering from poor regeneration on a statewide basis, although there are regional and site-specific concerns for other species. The actual mechanisms resulting in the poor regeneration of blue, valley, and Engelmann oaks are unknown, although a number of factors, acting in concert or alone, are presumed responsible (Holmes 1990). These factors include rodent, bird, pig (Sus scrofa), and deer (Odocoileus hemionus) predation on acorns; rodent, rabbit (Lepus and Sylvilagus spp.), and deer browsing on seedlings; livestock consuming acorns and seedlings; competition for water and nutrients with annual grasses; and modified soil and fire dynamics.