Western spruce budworm outbreak associated with wet periods in the Colorado Front Range: a multicentury reconstruction
Date
2022
Authors
Santiago, Olivia, author
Hart, Sarah, advisor
Redmond, Miranda, committee member
Bombaci, Sara, committee member
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Abstract
Western spruce budworms (WSB) are one of the most important native defoliators of coniferous forests in North America, causing widespread reductions in tree growth and elevated levels of tree mortality during outbreak. Like other eruptive insects, outbreaks of WSBs are thought to be influenced by a broad regional driver such as climate. Documentation of WSB outbreak is limited to the mid-20th century, constraining our understanding of how climate may influence outbreak. Previous research has linked periods of outbreak with both anomalously wet and dry periods in the Southwest and Pacific Northwest, respectively. To assess this relationship in the Colorado Front Range, I used tree ring methods to reconstruct periods of WSB outbreak over 437 years (1564-2001) at 15 sites. I detected 102 outbreak periods lasting on average 9.7 years (±1.0) with 27.7 years (±7.2) between outbreak periods. These outbreaks were regionally synchronous and were most common during wet periods that followed periods of average or low moisture. Considering the potential impacts of WSB defoliation on the provisioning of key ecosystem services, including carbon sequestration, provisioning of timber, and wildlife habitat, the findings provide valuable information for forest scientists and managers responsible for promoting forest health and resilience.
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Subject
dendrochronology
moisture availability
defoliator
western spruce budworm
drought