Graduate Thesis Or Dissertation


Large Downed Wood as Post-fire Refugia for Terrestrial Salamanders in Pacific Northwest Forests Public Deposited

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  • Climate change, wildfire, timber harvest, and land conversion alter the availability of downed wood in forests of the western United States. Numerous taxa rely on downed wood for temperature and humidity refugia, and downed wood may play a key role in enabling the persistence of climate-sensitive, low-vagility species like terrestrial salamanders (family Plethidontidae) after high severity wildfire. However, few studies have quantified the relationship between the quantity, size, and quality of downed wood and terrestrial salamander occupancy—especially in harsh microclimate conditions following high severity fire. We quantified terrestrial salamander occupancy, abundance and diversity and relationships with downed wood in mesic mixed-conifer forests along three major latitudinal bands and three time-since-high-severity-fire categories in the western Cascades of Oregon. Ensatina (Ensatina eschscholtzii) were observed most frequently, but Dunn’s salamander (Plethodon dunni), western red-backed salamander (Plethodon vehiculum), and the at-risk Oregon slender salamander (Batrachoseps wrighti) and clouded salamander (Aneides ferreus) were also detected. Eighty-seven percent of salamander detections occurred in association with large downed wood, and the estimated odds of occupancy and estimated abundance increased by 0.027 (90% CRI: 0.012-0.038) and 0.094 (90% CRI: 0.021-0.262), respectively, for each 1,000 unit increase in large downed wood per hectare of forestland. Plethodontid salamanders selected for larger diameter (p < 0.001) and decayed wood (p < 0.001) on the landscape without preference for the presence or absence of fire-altered carbon (p > 0.10). Terrestrial salamander occupancy and abundance were greatest in sites with no fire on record (p < 0.001 and p < 0.001, respectively) while diversity (Shannon-Wiener diversity index = 0.94) was greatest in sites that recently burned (p < 0.001). These findings provide guidance on large downed wood conservation priorities to maintain persistence of terrestrial salamanders in the face of climate change, continued timber harvesting, and increasing climate-driven wildfire conditions.
  • Keywords: Habitat quality, Occupancy, Coarse woody debris, Forest succession, Fire effects, Abundance, Plethodontid salamanders, Fire Ecology
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  • The Northwest Climate Adaptation Science Center and Oregon State University Department of Fisheries, Wildlife, and Conservation Sciences funded this research.
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