We examined tree rings from Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) timbers in the Salt Lake Tabernacle, constructed from 1863–1867 in Salt Lake City, Utah. A seismic upgrade to the Tabernacle initiated in 2005 required the replacement of wooden timbers with steel beams. Our objectives were to 1) determine cutting dates for the timbers to identify logs that may have been salvaged from previous structures, and consequently would have greater historical significance, 2) identify the species and provenance of the timbers, and 3) develop a chronology that could extend or strengthen the existing tree-ring record for environmental and historical applications in northern Utah. We built a 162-year floating chronology from 13 cores and 15 cross-sections, crossdated visually using skeleton plots and verified statistically with COFECHA. Statistically significant (p , 0.0001) comparisons with established chronologies from northern Utah indicated that the Tabernacle chronology extends from 1702–1862. Cutting dates ranged from 1836–1863, with most in 1862 or 1863 and a smaller cluster around 1855. The broad range of cutting dates suggests that some of the timbers were used in previous structures, and that some trees were dead before they were cut. This study provides valuable information for the preservation of historical materials, and increases the sample depth of existing chronologies during the 18th and 19th Centuries.

The 1994 Beaver Mountain fire ignited the canopies of subalpine fir, Abies lasiocarpa, and spread ground fire into adjacent Douglas-fir forests, Pseudotsuga menziesii var. glauca. Despite shorter flight seasons due to lower annual temperatures and persistent snow, the Douglas-fir bark beetle, Dendroctonus pseudotsugae Hopkins, attacked a range of moderately fire-injured host conifers. Logistic regression models illustrated that in 1995 associated bark beetles selected large diameter Douglas-fir with 60-80% bole char, 60-80% crown volume scorch, and 50-70% probability of mortality due to fire. In 1996 beetle preference shifted to smaller diameter trees with lighter fire injury. Tree size was less significant for predicted attack in 1996 because most large fire-damaged conifers were colonized by beetles in 1995. Beetle populations did not reach outbreak proportions outside the fire boundary, but 53 green trees were also infested in 1997 along the burn perimeter. Log linear tests conducted to quantify beetle emergence supported conclusions that beetles were not only attracted to mature, moderately fire-weakened conifers, but also produced greater brood numbers with up to 60-80 emergence holes/ 1800 cm2. Fire-defoliated trees provided bark beetles with sufficient phloem and limited resistance, allowing beetles to aggregate on areas of viable stem tissue regardless of overall bole char extent.