Sudden Oak Death in Redwood Forests: Vegetation Dynamics in the Wake of Tanoak Decline

Introduction Numerous lines of inquiry have concluded that tanoak (Lithocarpus densiflorus) will continue to experience drastic population declines and may even disappear entirely from redwood (Sequoia sempervirens) forests as a result of the exotic disease sudden oak death (SOD) (Maloney and others 2005, McPherson and others 2005, Meentemeyer and others 2004, Rizzo and others 2005). As the only species that can both compete for canopy space and tolerate the deep shade of redwood understories, tanoak is widespread and abundant in redwood forests, and is an integral component of the structure and function of these unique ecosystems. Tanoak is the most common hardwood species in conifer forests of California’s coastal mountains, and is associated with redwood throughout the majority of the redwood range (Burns and Honkala 1990, Hunter and others 1999, Noss 2000). As such, the loss of tanoak from redwood forests is likely to result in significant impacts. The primary objectives of this study were to: (1) examine the short-term compositional and regenerative effects of SOD in redwood forests; (2) determine which compositional and regenerative variables are correlated with tanoak abundance; and (3) consider the long-term structural and compositional effects of SOD-induced tanoak decline in redwood forests.