Laboratory Methods in Dendrochronology

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Laboratory Methods in Dendrochronology
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• Now, lets take our wood samples back to the
  laboratory
• Pre-process our cores
• Lay out all cores in their straws so they can
  air-dry.
• Once dry, select a core and write its ID on a
  core mount (both sides).
• Carefully remove the core from the straw
  theres a right way and a wrong way to do this.
• If the core is in pieces, ensure that all pieces
  are in their correct order and in their correct
  alignment!
• Lay the core alongside the core mount and place
  glue in the groove of the mount the length of the
  core.

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• Mount your core properly!
• The core must be mounted with its cells
  vertically aligned, i.e., straight up and down,
  similar to how they were positioned originally in
  the tree.
• If the core is mounted improperly, you may have
  ruined any chance of the sample being used,
  because
• if the core is mounted with the cells at an
  angle or horizontal, the ring boundaries will not
  be distinct.
• First, inspect the core and find the shiny
  sides. These are the sides of the core. Why does
  a core have shiny sides?

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Individual wood cells
Shiny side!
Shiny side!
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• Mount your core properly!
• Second, inspect the ends of the core to verify
  your evaluation. The ends of the core will
  clearly show the alignment of the cells.
• Press the core into the groove. Excess glue is no
  problem.
• Tape the core down onto the mount firmly at both
  ends and in the middle of the core.

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• What if your core is twisted?
• The sample must be mounted with the cells
  vertically aligned. Some samples, however, may be
  twisted. This is common.
• If the core is only slightly twisted, you can
  simply break the core into two or three pieces
  and mount these correctly.
• If the core is badly twisted (many turns), you
  have to steam the core while simultaneously
  untwisting it gently. Dont have to do this too
  often.

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• Measuring the ring widths
• Preferably should be done after you have
  crossdated your samples.
• If the rings are not problematic, you can measure
  your cores first and then crossdate them
  statistically.
• Total ring width is only one physical property of
  a tree ring we can measure. What others can we
  measure?

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• Measuring the ring widths
• Four parts to a measuring system
• Movable stage micrometer with trigger
• Digital display
• PC running measurement software
• Stereozoom boom-arm microscope with crosshair
  reticule and light source.
• This is NOT cheap. Basic system 3,000 2,000
  1,500 200 6,700.

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Advanced measuring system
CCD camera
Microscope
21 TV monitor
Light source
Movable stage
Digital display
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• Measuring the ring widths
• Crosshair guides you from one ring boundary to
  the next.
• Make sure you measure perpendicular to the ring
  boundary, always!
• Turn the handle on the stage from one boundary to
  the next.
• Hit the trigger to record the measurement.
• MeasureJ2X most popular software for measuring.
  Java based, requires Pentium PCs or Macs.
• Measures to the nearest 0.01 mm or 0.001 mm
  (preferred).

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• Sometimes you have to physically move or relocate
  the core to ensure that you measure the width of
  the ring perpendicular to the ring boundaries.

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• Imaging Systems the future of dendrochronology.

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• Finally

• Measurements must be archived in several
  locations.
• All tree-ring measurements are also archived at
  the International Tree-Ring Data Bank of the
  World Data Center for Paleoclimatology (part of
  the National Climatic Data Center) in Asheville,
  North Carolina.

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• Crossdating tree rings

• Consumes the majority of time learning about
  tree-ring dating.
• The more you do it, the better you become.
• Revolves around pattern recognition.
• Three basic techniques
• Graphical techniques then
• Statistical techniques, which lead to
• Memorization techniques

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• Crossdating tree rings

• Graphical techniques
• Two techniques
• Skeleton plots (favored in the U.S.)

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• Crossdating tree rings

• Graphical techniques
• Two techniques
• Alignment plots (favored in Europe)

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• Crossdating tree rings

• Remember the ultimate goal you must start
  memorizing which rings are particularly narrow or
  which have noteworthy properties.
• Other properties
• very wide rings
• frost rings
• thin latewood rings
• light rings
• rings with resin ducts
• false rings

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• Crossdating tree rings

• Lets try crossdating via skeleton plots by
  visiting Dr. Paul Sheppards excellent
  educational web site at the Laboratory of
  Tree-Ring Research, University of Arizona in
  Tucson