Landscape Dynamics of the Spread of Sudden Oak Death

Abstract

plant community structure (Ristaino and Gumpertz, 2000; Sudden Oak Death is caused by a newly discovered virulent Lundquist and Klopfenstein, 2001). pathogen (Phytophthora ramorum) that is killing thousands We present a landscape-scale study of the spatio-temporal of native oak trees in California. We present a landscape-scale dynamics of SuddenOak Death (SOD), analarming disease that study on the spatio-temporal dynamics of oak mortality. is killing thousands of native oak trees and tanoaks in the Coast Second-order spatial point-pattern analysis techniques Ranges of California and southwestern Oregon (McPherson et (Ripley’s K) were applied to the distribution of dead tree al., 2000; Garbelotto et al., 2001). Considerable progress has crowns (derived from high-resolution imagery) in Marin been made in the past year identifying host species and underCounty, California to determine the existence and scale of standing how this disease is related to other tree-killing dismortality clustering in two years (2000 and 2001). Both years showed clustering patterns between 100 and 300 m. A eases (Davidson et al., 2001; Davidson et al., 2002; Rizzo et al., classification tree model was developed to predict spatial 2002). However, we still do not know how the disease extends patterns of risk for oak mortality based on several landscape- its range across California’s landscape, and we have no ability scale variables. Proximity to forest edge was the most important to predictwhich stands of treesare at highrisk of infection.The explanatory factor, followed by topographic moisture index, objectives of this research are to proximity to trails, abundance of Umbellularia californica, and ● Determine the distribution and rate of oak mortality in the potential summer solar radiation. This research demonstrates study area; the utility of integrating remotely sensed imagery analysis with ● Determine the scale and extent to which the oak mortality is geographic information systems and spatial modeling for spatially clustered;