Development of a hierarchical Bayesian model to describe and predict the spread of blister rust in whitebark pine throughout the Greater Yellowstone Ecosystem

Jaclyn A Hatala, Harvard University, jhatala@post.harvard.edu (Presenting)
Robert L Crabtree, Yellowstone Ecological Research Center, crabtree@yellowstoneresearch.org
Paul R Moorcroft, Harvard University, paul_moorcroft@harvard.edu

Mortality due to pathogen outbreaks is recognized as a key process in the dynamics of Western forest ecosystems, yet the spatial patterns of stress and mortality in some systems are particularly complex and difficult to describe in an explicit spatial context. Stress and mortality in whitebark pine (Pinus albicaulis) caused by the invasive fungal pathogen blister rust (Cronartium ribicola) has been increasing in recent years at high altitudes in the Greater Yellowstone Ecosystem (GYE), an ecosystem formerly declared a “safe zone” from blister rust infection. The complex life history of blister rust includes a five-stage life cycle and spread through Ribes, an alternate host shrub. This has complicated former spatial understanding of blister rust population dynamics and its incipient distribution and spread through the GYE.



Here, we develop a hierarchical Bayesian model to describe the spatial spread of blister rust in the GYE from 1996 to present. Within the model, field survey data collected in 1996, 2001 and 2007 describing four stages of the disease, information regarding environmental covariates with transition rates between the four states and hyperspectral remotely sensed data are combined to inform a model of blister rust progression in whitebark pine through space and time. The dispersal kernel for blister rust is computed by an analytical wind dispersal model using data from the North American Regional Reanalysis. We’re currently parameterizing the model with ground and remote sensing observations to predict the future spread of the pathogen, to illuminate complex spatial interactions, and to serve as a tool for forest managers concerned about the spread of pathogens like blister rust in ecosystems.