Drought and Moisture Availability and Recent Western Spruce Budworm Outbreaks in the Western United States
Xu B. 2018. Drought and Moisture Availability and Recent Western Spruce Budworm Outbreaks in the Western United States. University of Idaho (Moscow)
Western spruce budworm (WSBW) is a common defoliating insect that has caused extensive damage to a number of tree species across the western United States (US). Past studies have linked outbreaks of WSBW to increases of moisture stress of host trees in Northwest US and decreased moisture stress in Southwest US. This study analyzed seasonal drought stress metrics in multiple locations with WSBW outbreaks in the western US during 1997-2015 identified from aerial detection surveys. Superposed epoch analysis and insect population growth rates (as represented by defoliation area change) were assessed to quantify the drought condition associated with the initiation and continuation of outbreaks, respectively. We found that a few consecutive years of drought were associated with outbreak initiation in the Northwest US, but that outbreak initiation of the Southwest US was associated with only weak drought or neutral conditions. During outbreak continuation stage, there was a weak correlation between the increase of May moisture availability and insect population increase in the Southwest, and no apparent correlation in the Northwest. Given future climate change, the increase of summer drought frequency may increase WSBW outbreaks, and thus improved understanding of the role of drought, as presented here, will lead to improved predictions and management of future outbreaks of WSBW.
- Type
- Academic
- Authors
- Xu, Bingbing
- Date of Issue
- 2018-12
- Publisher
- University of Idaho (Moscow)
- Units
- CRCO , GLAC
- Keywords
- climate, defoliator, drought, forest pathogen, thesis, vegetation, western spruce budworm
- Subjects
- Ecological Framework: Landscapes | Landscape Dynamics | Land Cover and Use