Relative Scale of Skeleton Plots

Trees living within a homogeneous stand or forest:

Usually exhibit the same relative pattern of growth variation through time, BUT
Often have absolute growth rates that differ substantially due to living in different microsites:
- Difficult to compare the ring-growth variation of two or more specimens from actual wood samples
- For example, see figure:
  1. All three samples above have exactly the same pattern of variation
  2. Top sample has a growth rate less than that of the middle sample
  3. Middle sample has a growth rate less than that of the bottom sample

Problem: Because of different growth rates, it's impossible to align the common pattern of variation using the actual wood samples

Solution: Skeleton plots can standardize scales:

Represent growth variation of samples onto separate strips of graph paper
Equalize the absolute scales of ring growth
Easily compare growth variation of two or more specimens
Note the three skeleton plots of the figure above:

Have the same relative scale
Are easy to compare to one another
Clearly show the same pattern of variation of each sample:

When you try skeleton plotting for yourself, you can move the virtual core left and right:

Put the cursor anywhere on the core above
Click and hold the mouse button
Move the mouse left or right
Don't worry that the core goes off the edges – it always comes back!

Note: The virtual core comes with every 10^th ring prenumbered – which won't be true in real life, so number your wood carefully!

When you try skeleton plotting for yourself, you can change the scales of the graphics:

magnification options

There will be magnification circle buttons, as on the left
You may enlarge or reduce the virtual core to see rings better

Choose between 1x, 2x, or 3x
Hint for magnifying a ring:

There will be a vertical blue line marking the middle of your screen, as on the right
Put the ring that you wish to see better at the blue line
Then magnify – at 3x magnification, narrow rings are apparent

You may also enlarge or reduce the graphs

Choose between Large, Medium, and Small

zoom magnification

When you try skeleton plotting for yourself, you can move the virtual core left and right:

Put the cursor anywhere on the core above Click and hold the mouse button Move the mouse left or right Don't worry that the core goes off the edges – it always comes back!

When you try skeleton plotting for yourself, you can change the scales of the graphics:
	There will be magnification circle buttons, as on the left You may enlarge or reduce the virtual core to see rings better Choose between 1x, 2x, or 3x Hint for magnifying a ring: There will be a vertical blue line marking the middle of your screen, as on the right Put the ring that you wish to see better at the blue line Then magnify – at 3x magnification, narrow rings are apparent You may also enlarge or reduce the graphs Choose between Large, Medium, and Small

Paul R. Sheppard
Laboratory of Tree-Ring Research, The University of Arizona
Tucson, Arizona 85721 USA
office: (520) 621-6474, fax: (520) 621-8229
Comments to: sheppard@ltrr.arizona.edu