Evaluating mortality dynamics during a spruce beetle epidemic in the southern Colorado Rocky Mountains
Date
2017
Authors
Woodward, Brian D., author
Ex, Seth, advisor
Evangelista, Paul, advisor
Davis, Thomas, committee member
Falkowski, Mike, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The onset of a decade-long spruce beetle (Dendroctonus rufipennis) epidemic in Southern Colorado has resulted in the death of thousands of acres of forests primarily dominated by Engelmann spruce (Picea engelmannii). To evaluate the ecological and economic impacts of this massive mortality event, researchers and land managers need the ability to actively track its progression, spread, and severity across large spatial extents. This study improves our understanding of this under researched spruce beetle epidemic in multiple ways. First, I mapped the progression and severity of this epidemic scale spruce beetle infestation using traditional remote sensing methods in new, unexplored scenarios. Working in a large (5000 km2), persistently cloud covered study area, I successfully fused data from multiple Landsat sensors in a decision tree based modelling framework to track the progression and severity of spruce beetle induced mortality throughout peak years of infestation (2011-2015). Next, I characterized spruce stand susceptibility to attack in this outbreak event and tracked how environmental characteristics of new spruce beetle attacks changed through time. I found that sites with new spruce beetle attack had higher canopy densities, were closer to disturbance events, and further from stream environments as compared to sites that had never been attacked. As the epidemic progressed, sites with new attacks occurred at higher elevations, on less steep slopes, were further from disturbances, and had less dense canopies. Findings from this study will support implementation of future landscape scale forest monitoring efforts using remote sensing, enable more directed on-the-ground management activities following beetle infestation, and highlight the dynamic nature of spruce beetle induced mortality across large spatial extents.