LONG-TERM IMPACTS OF SUDDEN OAK DEATH AND INTERACTIONS WITH FIRE IN BIG SUR, CA USING COUPLED DYNAMIC SPATIAL TEMPORAL EPIDEMIOLOGICAL MODELING

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  • March 20, 2019
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  • Jones, Christopher
    • Affiliation: College of Arts and Sciences, Department of Geography
Abstract
  • Invasive forest pathogens are an increasing risk to forest ecosystems. One such invasive forest pathogen is Phytophthora ramorum, a generalist pathogen with asymmetries in host competency and susceptibility. Apparent competition, indirect competition between two or more species mediated by a common enemy (P. ramorum), can emerge when asymmetries in host response to a pathogen occur. Additionally, invasive pathogens can interact with natural disturbance regimes to alter forest ecosystems in unexpected ways due to non-linear dynamics. Coupled spatial temporal models provide the ability to examine how disease and interactions with fire alter forest composition over the course of a century. Epidemiological models typically treat forest composition as static and don’t account for disease related mortality. Here, I present the first dynamic spatial epidemiological model that can interact with a FLSM, LANDIS-II, to incorporate changes in forest composition due to disturbance, natural growth, mortality, and regeneration. The model incorporates asymmetries in host susceptibility and competency across species and age classes and changes in inoculum production based on temperature and precipitation. Average odds ratio of the model was 7.9 compared to 7.6 for the current P. ramorum spread model. This model was then coupled with a forest composition model and fire behavior model to analyze the effect of disturbance interaction and apparent competition. The model simulated from 1990-2090 using 10-year time steps for the FLSM and a 1-year time step for the disease and fire model in Big Sur, CA using daily projected climate data. The model was replicated 30 times to account for stochastic variability in climate, disease spread, fire ignition locations, and seedling establishment. Three disturbance scenarios were utilized: fire, disease, and fire and disease. Model results suggest overall disease decreased fire severity, however, when disease related mortality occurred 3 years prior to a fire then fire severity increased. The model results suggest that bay laurel increases relative to other host species due to apparent competition under the disease only scenario. This effect is mitigated in the disease and fire scenario due to individual species response to fire.
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  • In Copyright
Advisor
  • Song, Conghe
  • Meentemeyer, Ross
  • Moody, Aaron
  • Mitchell, Charles
  • Riveros-Iregui, Diego
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2017
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Date uploaded
  • March 15, 2018

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