Timbers from church speak of previously unknown drought during pioneers' arrival, study shows (2/22/2008)

BYU geography professor Matthew Bekker analyzed timbers from the Salt Lake Tabernacle and discovered that a severe drought began in the years before the first Mormon wagon trains rolled into the Salt Lake Valley.

A Brigham Young University geographer studying timbers from the Salt Lake Tabernacle concludes those old walls can talk, and they tell a new tale of pioneer hardship.

Analysis of the width of the rings in the wood shows that a severe drought began in the years before the first Mormon wagon trains rolled into the Salt Lake Valley the summer of 1847.

"The 1840s were drier than any other decade in this tree-ring history, which spans the years 1702 to 1863," said BYU professor Matthew Bekker, whose findings are published in the current issue of the academic journal Tree-ring Research. "It was a really rough time to establish a settlement based on irrigated agriculture."

During the recent renovation of the Tabernacle, Bekker sampled timbers on the building's west end underneath the stage that supports seating for the Mormon Tabernacle Choir and the widely-recognized organ. Tree rings that grew in 1846 were much narrower than would be expected with a normal year's rainfall, ranking as the sixth narrowest of the 162 years studied. The pioneers' first two years of settlement saw little relief with 1847 and 1848 ranked as the 10th and 16th driest seasons in the period.

"The Wasatch Front does not get a lot of rain during the summer, so the settlers depended on snowpack and stream flow," Bekker said. "After several dry years, the first good winter of snowfall may not have brought immediate relief because more of the snowmelt would have been absorbed by the dry soil before it could flow down to the valley where the settlers needed it."

Bekker determined that all 28 trees he sampled were Douglas-fir, which would have been called "red pine" by the pioneers because of the reddish hue in the heartwood.

By comparing the patterns of rings Bekker also established their relative age differences. Up to that point, however, he did not know the exact year any of the trees were cut. For a point of reference, Bekker turned to recently collected samples of very old live trees in northern Utah whose outer rings represented the year they were sampled. These old live trees overlapped the Tabernacle timbers' ring history, enabling Bekker to establish dates for the Tabernacle timbers by zeroing in on where they shared similar patterns.

The rings from one timber that supported the organ spanned from 1762 to 1862. The earliest ring goes back to 1702. The distinction of having the oldest ring was shared by seven trees with outer rings grown in 1863, the year the Tabernacle's foundation was completed.

Nailing down those dates yielded another surprise: five of the 28 trees died or were cut earlier than 1847, meaning the pioneers harvested trees both live and dead.

"In this desert environment, the settlers would not overlook the dead trees," Bekker said. "In fact there may be advantages to using post-mortem timber because you don't have to take bark or twigs off and it's already dried so it's not going to warp anymore after you cut it."

Two trees with terminal rings dating 1846 intrigued Bekker because of a possibility that they had been cut by the Donner-Reed party which was said to have cut timber while clearing a road in Emigration Canyon that the Mormon settlers followed one year later.

"There's an outside chance that the Mormon pioneers came across cut timbers in Emigration Canyon and hauled them down on their way, or perhaps the drought was severe enough that year to have killed some trees," Bekker said. "That's one thing the walls won't tell you."

Dead timber may also explain the rapid construction of an open-sided structure the Mormon settlers completed one week after their arrival. Several others were built before work on the Tabernacle began. Called "boweries" in the pioneer journals, these structures consisted of thatched roofs made of brush and willow boughs supported by wood beams. At least one pioneer journal documents a bowery on Temple Square being dismantled to so the lumber could be re-used, suggesting that the Tabernacle timbers could have been salvaged from these earlier structures.

"Taken as a whole, the study is an excellent example of the wide range of information that can be derived from structural wood," said University of Arizona professor Jeff S. Dean, an expert in the study of old buildings using tree-ring analysis. "The study shows how the interplay between tree-ring and historical data provides a much fuller range of information on past human behavior than can be achieved from either source by itself."

The renovation of the Tabernacle included the installation of modern support structures where these timbers once lay. Although hidden from view now by new walls and ceilings, some of the old timbers were bolted alongside the new steel beams to preserve a part of the building's historical context.

Note: This story has been adapted from a news release issued by Brigham Young University

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