Abstract
Bark beetle outbreaks and forest fires have imposed severe ecological damage and caused billions of dollars in lost resources in recent decades. The impact of such combined disturbances is projected to become more severe, especially as climate change takes its toll on forest ecosystems in the coming years. Here, we investigate the impact of multiple disturbances in a demographically heterogeneous tree population, using an age-structured difference equation model of bark beetle outbreaks and forest fires. We identify two dynamical regimes for beetle and fire dynamics. The model predicts that fire helps dampen beetle outbreaks not only by removing host trees but also by altering the demographic structure of forest stands. We show that a stand thinning protocol, which reduces the population size of the largest few juvenile classes by a small percentage, is able to significantly reduce beetle-induced tree mortality. Our research demonstrates one approach to capturing compound disturbances in a mathematical model.
Highlights
Ecosystems have long been characterized by resilience in the face of large disturbances such as fire, storms, pathogens, and drought, which are often interacting
We first characterize the dynamical regimes of the model as a function of the burning rates 1, 2, and the decay rate
In this paper we used a mathematical model of pest and fire dynamics in pine forests to show how fire can suppress beetle outbreaks
Summary
Ecosystems have long been characterized by resilience in the face of large disturbances such as fire, storms, pathogens, and drought, which are often interacting. The MPB is a small insect endemic to the pine forests of Ecological studies examining the relationship between MPB and wildfire damage are numerous, but have not reached a strong consensus in all aspects Axelson et al (2009); Lynch et al (2006); Simard et al (2011); Bradley and Tueller (2001); Kaufmann et al (2008); Meigs et al (2016); Agne et al (2016); Seidl et al (2016); Jenkins et al (2008). Lynch et al (2006) used remote sensing data associated with the 1988 Yellowstone National Park fires to investigate the link between fire prevalence and beetle attack. They found that beetle attack initially lowered the probability of crown fire in a patch, but bark beetle activity significantly increases fire risk 13-16 years in the future. To make things more complicated, some studies have found that measures
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