Estimating the Potential for Forest Degradation in the Eastern United States Woodlands from an Introduction of Sudden Oak Death

Dillon J Haller,Michael C Wimberly

doi:10.3390/f11121334

Abstract

Research Highlights: This research identified areas of the eastern United States forests that may be at particular risk from Sudden Oak Death (SOD) if it becomes established in the region. The highest suitability for SOD occurs where there are both species at risk of serious infection and species that could spread SOD to new hosts. Background and Objectives: SOD, caused by Phytophthora ramorum, can cause serious damage to forests. Although SOD is not believed to exist in the wild in the eastern United States, the presence of potential P. ramorum hosts in the area has led to questions about the potential for its establishment there. The present project expanded on previous efforts by examining both the possibility and potential consequences of P. ramorum establishment based on the presence of suitable hosts. Materials and Methods: We developed a map of the potential severity of tree loss that could result from a P. ramorum establishment in the eastern United States as well as a habitat suitability index based on the density of P. ramorum susceptible and spreader host species. We also implemented a connectivity analysis method for determining patches important to the spread of P. ramorum in the Great Smoky Mountains National Park. Results: The Ozarks and Appalachians both had a high potential severity of infection due to their high percentage of susceptible species, but the Appalachians had a higher overall level of risk due to the presence of more spreader tree species in the area. Connectivity analysis in the Great Smoky Mountains National Park identified patches likely to be particularly important to P. ramorum spread. Conclusions: Analysis of the presence of potential P. ramorum hosts in the eastern United States identified suitable conditions for SOD establishment there, particularly in the Appalachians. Techniques developed in this research can identify critical areas for SOD spread at both landscape and regional scales.

Highlights

IntroductionSudden Oak Death (SOD) is a recently established destructive tree disease that first appeared in the forests of California in 1995 and began rapidly spreading thereafter [1,2]
Sudden Oak Death (SOD) poses a serious threat to the forests of the eastern USA if the pathogen, Phytophthora ramorum, is able to establish and spread in this region
Previous research has found that large portions of the eastern USA are climatically suitable for P. ramorum, the predicted geographic range varies depending on the methods used [8,9,12,13]

Summary

Introduction

Sudden Oak Death (SOD) is a recently established destructive tree disease that first appeared in the forests of California in 1995 and began rapidly spreading thereafter [1,2]. The disease is caused by an oomycete called Phytophthora ramorum. SOD affects oaks (Quercus spp.) and tanoaks (Notholithocarpus densiflorus), though P. ramorum can infect a wide variety of botanical hosts and cause a wide range of conditions. Trees that develop SOD may not die for years after initial symptoms present themselves, though in some cases, SOD can kill more quickly. Seedlings and saplings are rarely affected by SOD [1]

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