Available at: https://digitalcommons.calpoly.edu/theses/3171
Date of Award
6-2025
Degree Name
MS in Forestry Sciences
Department/Program
Natural Resources Management
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Richard Cobb
Advisor Department
Natural Resources Management
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Invasive plant pathogens have killed an uncountable number of trees and disrupted ecosystem processes throughout the world. Newly introduced pathogens may interact with historically occurring disturbances in unexpected ways to cause amplified mortality and change to ecosystem processes. Here, I examine the a natural experiment created by three wildfires in Big Sur, a portion of the central coast of California impacted by the nonnative pathogen Phytophthora ramorum, to forecast the future of a species susceptible to the pathogen. Using a plot network which spans the length of Big Sur, I track the survival of individual tanoak (Notholithocarpus densiflorus) stems and trees over a 12-year period in areas with various fire and disease histories. Large, old tanoak stems are killed by P. ramorum infection, which causes a disease known as sudden oak death. Young stems are vulnerable to fire. My results indicate that the combination of this novel pathogen and fire results in high mortality of existing tanoak stems of all size classes followed by energetic sprouting of new stems, converting the tanoak from a large overstory tree to a multi-stemmed shrub. This new form alters the fuel quantity and distribution within affected stands and may influence future fire behavior in the central coast region of California.