Photos courtesy of Tiffany Curtis. These are the remains of an old trapper’s cabin discovered near a remote lake on the Kenai National Wildlife Refuge.
By Clark Fair
Redoubt Reporter
Many people enjoy a package of fresh cookies, and, in that way, researcher Tiffany Curtis is no different than most. But for Curtis, who is working on her master’s program in conjunction with the U.S. Fish and Wildlife Service, freshly wrapped cookies are slices of old cabin logs, and her method of enjoying them involves a power tool, a microscope and an electronic measuring device.
Curtis, a graduate student at the University of Alaska Anchorage, is working with Kenai National Wildlife Refuge ecologist Ed Berg and historian Gary Titus to determine the ages of historic cabins and cabin ruins throughout the refuge — and thereby help to determine the settlement patterns in the area.
Berg and Titus had been working with cabin tree rings for years, but the cookies from old cabin logs began to accumulate faster than they could get them analyzed, so they decided to try to hire a graduate student looking for a research project.
Titus learned of some funds that could be made available for the work, and he contacted the UAA Anthropology Department for a student recommendation. When Curtis learned of the opportunity, she thought, “Well, it’d be cool for the summer, you know,” she said. “First of all, I’d heard that the Kenai’s not the worst place to spend your summer. Turns out that’s true. It was awesome down there. And secondly, I was interested in that (subject).”
After a summer of training in data collection and the use of the instruments employed for analysis, Curtis is currently back in classes at UAA, while spending her “spare time” performing a practicum: re-analyzing old data compiled over the years by Titus and Berg, and double-checking it for accuracy.
Next summer, she will be back at the refuge to examine unanalyzed cookies and begin compiling enough data to allow her to draw data-supported conclusions for her master’s thesis, which she hopes to write in the winter of 2010-11 and to defend by May 2011.
This photo shows a cabin log “cookie,” which is a cross-section of the log. This cookie’s growth rings have been marked in 10-year increments.
Titus, in his years of researching historic cabins in and around the refuge, has discovered dozens of building sites, some with the cabins still intact and serviceable on them, and others containing little more than mossy indentations in the ground, surrounded by some decaying and equally mossy stumps.
Although his long experience gives him a general idea of the dates that many of these cabins were built, he has, in many cases, no hard data on which to base his assumptions. Curtis’ work should change all that.
Based on Berg’s 400-year, spruce-centered dendrochronology (tree-ring-based history) of the Kenai Peninsula, Curtis is using tree-ring data from refuge cabins to learn where they fit into the overall chronology.
Dendrochronology is a highly accurate scientific method for measuring the age of a tree or placing a log-based artifact into the time continuum. Studies of the growth rings of living and dead-but-preserved trees in a particular area help establish a pattern based on cold and warm years or wet and dry years.
Tiffany Curtis stands, in uniform, alongside a canoe in preparation for launching into Swanson River, seen behind her.
Cabin logs, which amount to growth records frozen in time, can be carefully measured and compared against the known patterns.
But a lot of work goes into determining a log’s age and then finding its place in the overall chronology.
Curtis begins with rough wooden cookies, which have been sawn in one- to two-inch segments from old cabin logs and then wrapped in plastic and labeled with a black marker. In order to get an accurate measurement, she must first smooth the coarse surface of the cookie. And to do that, she needs the right tool — in this case, an electric, five-inch rotary Craftsman sander from Sears, and plenty of sandpaper.
“The proper tool for the job makes all the difference in the world,” she said with a chuckle.
Beginning with 60-grain sandpaper, she works over the flat surface of the wooden disk, then typically moves on to coarseness values of 80-grain, then 100, 220, 320, 400, and even jeweler-grade 600-grain. In the end, she hopes, she has a perfectly smooth surface on which to perform her measurements.
The dendrochronology workstation for Tiffany Curtis in the lab at USFWS headquarters near Soldotna. Seen here are several wooden cookies and a stereo-visual microscope that is hooked electronically into a computer running software that uses tree-ring measurements to accurately determine the date when a log cabin was built.
To measure the distance between growth rings, she uses statistical-analysis software called COFECHA, then double-checks with a second software program called CDendro.
Viewing the cookie through a stereoscopic microscope, hooked to a VELMEX measuring device, she uses the instrument’s cross-hairs to specifically locate the edge of a growth ring along a radius beginning at the pith (the cookie’s center) and extending to its bark or outer edge. With a click of a button on the device, which is connected to her computer, she locks in the location of the ring on the software program. When she locates the next ring, the program automatically registers the distance between the two — up to one thousandth of a millimeter.
Because a cookie (virtually a circle) offers the possibility of multiple radii, she can take several measurements from a single sample, unlike the more restrictive process of taking measurements from core samples extracted with an increment bore.
Dozens of clicks — and some eye strain — later, she has a complete set of data for that cookie, and she can proceed to the next, and so forth.
When she first completed her training and was prepared to begin actual analysis, Curtis said, Berg and Titus decided to test her. They gave her the cookies for some cabins that they already had specific known dates for, and they asked her to date them.
“And I was right,” she said. “The dates I came up with were right on. And for me, that was awesome. That was the moment when everything pretty much came together.
“I wanted to make a good impression, you know, and I worked and worked and struggled and struggled, and I was left alone to ruminate and come up with my own dates. And when I was right, that was really the coolest moment for me.”
