Laboratory Methods in DendrochronologyLaboratory Methods in Dendrochronology

• Now, let’s take our wood samples back to the Now, let’s take our wood samples back to the laboratory:laboratory:

• Pre-process our cores:Pre-process our cores:

1.1. Lay out all cores in their straws so they can air-Lay out all cores in their straws so they can air-dry.dry.

2.2. Once dry, select a core and write its ID on a Once dry, select a core and write its ID on a core mount (both sides).core mount (both sides).

3.3. Carefully remove the core from the straw – Carefully remove the core from the straw – there’s a right way and a wrong way to do this.there’s a right way and a wrong way to do this.

4.4. If the core is in pieces, ensure that all pieces If the core is in pieces, ensure that all pieces are in their correct order and in their correct are in their correct order and in their correct alignment!alignment!

5.5. Lay the core alongside the core mount and Lay the core alongside the core mount and place glue in the groove of the mount the place glue in the groove of the mount the length of the core.length of the core.

• Mount your core properly!Mount your core properly!

1.1. The core The core mustmust be mounted with its cells be mounted with its cells vertically aligned, i.e., straight up and down, vertically aligned, i.e., straight up and down, similar to how they were positioned originally in similar to how they were positioned originally in the tree.the tree.

2.2. If the core is mounted improperly, you may If the core is mounted improperly, you may have ruined any chance of the sample being have ruined any chance of the sample being used, because…used, because…

3.3. ……if the core is mounted with the cells at an if the core is mounted with the cells at an angle or horizontal, the ring boundaries will angle or horizontal, the ring boundaries will notnot be distinct.be distinct.

4.4. First, inspect the core and find the “shiny First, inspect the core and find the “shiny sides.” These are the sides of the core. Why sides.” These are the sides of the core. Why does a core have shiny sides?does a core have shiny sides?

“Shiny side”!

“Shiny side”!

Individual wood cells

• Mount your core properly!Mount your core properly!

5.5. Second, inspect the ends of the core to verify Second, inspect the ends of the core to verify your evaluation. The ends of the core will clearly your evaluation. The ends of the core will clearly show the alignment of the cells.show the alignment of the cells.

6.6. Press the core into the groove. Excess glue is no Press the core into the groove. Excess glue is no problem.problem.

7.7. Tape the core down onto the mount firmly at Tape the core down onto the mount firmly at both ends and in the middle of the core.both ends and in the middle of the core.

• What if your core is twisted?What if your core is twisted?

1.1. The sample must be mounted with the cells The sample must be mounted with the cells vertically aligned. Some samples, however, may vertically aligned. Some samples, however, may be twisted. This is common.be twisted. This is common.

2.2. If the core is only slightly twisted, you can If the core is only slightly twisted, you can simply break the core into two or three pieces simply break the core into two or three pieces and mount these correctly.and mount these correctly.

3.3. If the core is badly twisted (many turns), you If the core is badly twisted (many turns), you have to steam the core while simultaneously have to steam the core while simultaneously untwisting it gently. Don’t have to do this too untwisting it gently. Don’t have to do this too often.often.

• Measuring the ring widths:Measuring the ring widths:

• Preferably should be done Preferably should be done afterafter you have you have crossdated your samples.crossdated your samples.

• If the rings are not problematic, you can If the rings are not problematic, you can measure your cores first and then crossdate measure your cores first and then crossdate them statistically.them statistically.

• Total ring width is only one physical property of Total ring width is only one physical property of a tree ring we can measure. What others can we a tree ring we can measure. What others can we measure?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 Stereozoom boom-arm microscope with crosshair reticule and light source.crosshair reticule and light source.

• This is NOT cheap. Basic system = $3,000 + This is NOT cheap. Basic system = $3,000 + $2,000 + $1,500 + $200 = $6,700.$2,000 + $1,500 + $200 = $6,700.

Movable Movable stagestage

Digital Digital displadisplayy

MicroscopeMicroscope

Light sourceLight source

21” TV 21” TV monitormonitor

CCD CCD cameracamera

Advanced measuring system:Advanced measuring system:

• Measuring the ring widths:Measuring the ring widths:

• Crosshair guides you from one ring boundary to Crosshair guides you from one ring boundary to the next.the next.

• Make sure you measure perpendicular to the Make sure you measure perpendicular to the ring boundary, always!ring boundary, always!

• Turn the handle on the stage from one boundary Turn the handle on the stage from one boundary to the next.to the next.

• Hit the trigger to record the measurement.Hit the trigger to record the measurement.

• MeasureJ2X most popular software for MeasureJ2X most popular software for measuring. Java based, requires Pentium PCs or measuring. Java based, requires Pentium PCs or Macs.Macs.

• Measures to the nearest 0.01 mm or 0.001 mm Measures to the nearest 0.01 mm or 0.001 mm (preferred).(preferred).

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

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

• Measurements must be archived in several Measurements must be archived in several locations.locations.

• All tree-ring measurements are also All tree-ring measurements are also archived at the 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.

• Finally…Finally…

• Consumes the majority of time learning Consumes the majority of time learning about tree-ring dating.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 Alignment plots (favored in Europe)Europe)

Norris Dam and Swaggerty Blockhouse Chronologies

Swaggerty Norris

• Crossdating tree ringsCrossdating tree rings

• Remember the ultimate goal: you must Remember the ultimate goal: you must start memorizing which rings are start memorizing which rings are particularly narrow or which have particularly narrow or which have noteworthy properties.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 Let’s try crossdating via skeleton plots by visiting Dr. Paul Sheppard’s excellent visiting Dr. Paul Sheppard’s excellent educational web site at the Laboratory of educational web site at the Laboratory of Tree-Ring Research, University of Arizona in Tree-Ring Research, University of Arizona in Tucson …Tucson …

• Crossdating tree ringsCrossdating tree rings