Note: This article is a sidebar to this issue's feature story, "Written in the Rings."
Sure, counting tree rings might sound like a cushy job. But before you set out into the bristlecone pines, make sure you know what you’re in for. A few of the basic requirements:
Strong legs. Since the clearest records of climate are found in harsh environments such as mountain slopes and steep, rocky hillsides, the best field sites are usually a long haul from the nearest road. Lisa Graumlich, a former faculty member of the tree-ring lab and the current director of the Big Sky Institute in Bozeman, Mont., admits to "a bit of a reputation as a slave driver" earned during her research adventures in the highest peaks of the Great Basin. "But I never killed anybody!" she protests.
Patience, patience, patience. Though computers have sped up the process in recent decades, crossdating a set of tree-ring samples still takes a near-pathological love of detail. Crossdaters spend hours staring through microscopes at finely sanded pieces of wood, comparing multiple samples to pick out misleading false and missing rings. Though some researchers farm out the labor to graduate students, many dendrochronologists still find crossdating satisfying — even thrilling. "There’s a certain ‘aha!’ every time you date a piece of wood," says lab director and fire ecologist Tom Swetnam.
Love of statistical gymnastics. Making sense of the tree-ring record is no easy task, as botanist Hal Fritts discovered. Accurately isolating a single variable — say rainfall — from the multiple factors that influence tree growth requires a tolerance for big datasets, an affection for mind-bending statistics, and, last but not least, a very comfortable office chair.