Tom's Blog

Friday, November 15, 2013

Tree ring analysis at Pleasant Valley Conservancy

We are cooperating with the Tree-Ring, Earth, and Environmental Sciences Laboratory (TREES) of the University of Wisconsin-Platteville on their study on drought and climate change over the past 300 years in Wisconsin's Driftless Area. This project, under the direction of Professor Evan Larson and Chris Underwood of the UWP Geography Department, is funded by a grant from the U.S. Geological Survey and the UW Aquatic Sciences Center. Sara Allen is managing the project as a post-bachelor research fellow.

Yesterday the tree ring team cored a number of large bur and white oaks at Pleasant Valley Conservancy. These were mostly larger savanna trees along the ridge top.

The coring device is a precision increment borer 0.20" in diameter, with a sharp, steel, cutting end that penetrates the tree. The tube is fixed to a handle which provides leverage for the coring process.

Steve coring a fairly elderly bur oak on the ridge top in Unit 8.

Once the cutting edge reaches the center of the tree, the core is broken, an extractor inserted, and the core carefully removed from the tree. The photo below shows the core as it is being removed from the tree.

The core being extracted. The extractor is a curved metal strip.

At this stage the tree rings are not very well defined so I have added arrows to give an idea of the distribution of rings.
The arrows show a few of the rings. The palm of the hand provides the scale.

To protect the core, it is inserted into a long straw, and both ends sealed. In the laboratory the core is mounted on a wooden holder and sanded flat so that the tree rings stand out. Analysis is done under a dissecting microscope.


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