Studying the probability of spruce beetle caused mortality in Colorado's spruce forests using Bayesian hierarchical models

The association between environmental factors and Engelmann spruce mortality in western Colorado was investigated using Bayesian hierarchical zero‐and‐one inflated beta regressive model. The results indicated that the probability of mortality occurrence rate was positively associated with moderate to warm temperature zones, moderate precipitation, and single canopy stands with the smaller size class of spruce within stands. The probability of full mortality rate was positively associated with warm and humid climate zones with spruce as subdominant species in the vertically complex stands. On the other hand, higher mortality rate was more associated with local stand characteristics than climate factors that low mortality rate associated with stands dominated by spruce of a large size classes. The correlation model offers an approach to create predicted risk map for probability and rate of spruce mortality that could help manager in precedent planning for the upcoming outbreak events. Recommendations for Resource Managers This study aims to investigate the environmental association of spruce bark beetle caused mortality in landscape context with binomial‐beta hierarchical framework. Both regional‐scale climate and stand‐level characteristics should be considered to assess the risk and severity of outbreak caused mortality at a large spatial scale. The mortality risk is higher and more severe in warmer zones, especially the stands with spruce as subdominant tree species should be more concerned. Predicted map could improve the ability to spatially assess the risk of spruce mortality assisting managers to be better prepared for the future outbreaks, particularly in the risky area.