Laboratory Methods in Dendrochronology

Now, let’s take our wood samples back to the laboratory:Now, let’s take our wood samples back to the laboratory: Pre-process our cores: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 – there’s 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.

Mount your core properly!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?

“Shiny side”! Individual wood cells

Mount your core properly!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.

What if your core is twisted?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. Don’t have to do this too often.

Measuring the ring widths:Measuring the ring widths: Preferably should be done after you have crossdated your samples.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.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?Total ring width is only one physical property of a tree ring we can measure. What others can we measure?

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

Movable stage Digital display Microscope Light source 21” TV monitor CCD camera Advanced measuring system:

Measuring the ring widths:Measuring the ring widths: Crosshair guides you from one ring boundary to the next.Crosshair guides you from one ring boundary to the next. Make sure you measure perpendicular to the ring boundary, always!Make sure you measure perpendicular to the ring boundary, always! Turn the handle on the stage from one boundary to the next.Turn the handle on the stage from one boundary to the next. Hit the trigger to record the measurement.Hit the trigger to record the measurement. MeasureJ2X most popular software for measuring. Java based, requires Pentium PCs or Macs.MeasureJ2X most popular software for measuring. Java based, requires Pentium PCs or Macs. Measures to the nearest 0.01 mm or mm (preferred).Measures to the nearest 0.01 mm or mm (preferred).

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.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.

Imaging Systems = the future of dendrochronology.Imaging Systems = the future of dendrochronology.

Measurements must be archived in several locations.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.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. International Tree-Ring Data Bank International Tree-Ring Data Bank Finally…Finally…

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

Graphical techniquesGraphical techniques Two techniques:Two techniques: Skeleton plots (favored in the U.S.)Skeleton plots (favored in the U.S.) Crossdating tree ringsCrossdating tree rings

Graphical techniquesGraphical techniques Two techniques:Two techniques: Alignment plots (favored in Europe)Alignment plots (favored in Europe) Crossdating tree ringsCrossdating tree rings

Remember the ultimate goal: you must start memorizing which rings are particularly narrow or which have noteworthy properties.Remember the ultimate goal: you must start memorizing which rings are particularly narrow or which have noteworthy properties. Other properties:Other properties: very wide ringsvery wide rings frost ringsfrost rings thin latewood ringsthin latewood rings light ringslight rings rings with resin ductsrings with resin ducts false ringsfalse rings Crossdating tree ringsCrossdating tree rings

Let’s try crossdating via skeleton plots by visiting Dr. Paul Sheppard’s excellent educational web site at the Laboratory of Tree-Ring Research, University of Arizona in Tucson …Let’s try crossdating via skeleton plots by visiting Dr. Paul Sheppard’s excellent educational web site at the Laboratory of Tree-Ring Research, University of Arizona in Tucson … Crossdating tree ringsCrossdating tree rings