Principles of Dendrochronology

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Principles of Dendrochronology January 30
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1. Uniformitarianism Principle

• James Hutton, British geologist (published
  17851788)
• The present is the key to the past.
• Corollary to this principle The past is the key
  to the future.
• Illustrates the trajectory of science, past,
  present, and future

1. Study processes as they occur at present
2. Improved understanding comes from the past
3. Extrapolate/predict the future applied!

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1. Uniformitarianism Principle

Examples
A. Reconstructions of past climate
Dendroclimatology
Future?
Present
Assumes that climatic processes operating today
were operating similarly in the past.
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1. Uniformitarianism Principle

Examples
B. Reconstructions of past fire
Dendropyrochronology
Assumes that wildfires operate today as an
ecosystem process just as they did in the
past.
Future?
Present
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2. Principle of Limiting Factors

• Basic principle in biology
• Adaptation to dendrochronology
• Tree growth can proceed only as fast as allowed
  by the primary environmental and physiological
  mechanisms that restrict growth.
• Sometimes, more than one mechanism operates to
  restrict growth.
• We MUST have variable tree growth!

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2. Principle of Limiting Factors
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3. Ecological Amplitude

• A tree species will be more responsive and
  sensitive to changes in environmental conditions
  in the outer limits of its range.

• Latitudinally and longitudinally

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3. Ecological Amplitude Range map of sugar maple.
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3. Ecological Amplitude

• A tree species will be more responsive and
  sensitive to changes in environmental conditions
  in the outer limits of its range.

• Also, elevationally!

Not so good
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Red Spruce
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4. Principle of Site Selection

• Within any given area chosen for study, specific
  site characteristics should be sought that will
  enhance a trees responsiveness to environmental
  factors.
• Notice how this is related to the principle of
  limiting factors. We should select sites where
  factors are more limiting.
• Notice also that recognizing the growth forms of
  trees will provide clues where such sensitive
  sites exist.

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4. Principle of Site Selection
Notice vastly different growth forms of these
trees
Notice vastly different ring patterns
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5. Aggregate Tree Growth

• Tree growth can be decomposed into five basic
  parts

• R ring width, t the current year, and delta
  presence (1) or absence (0) indicator
• A age-related trend
• C climate
• D1 exogenous (external) disturbance processes
  (examples?)
• D2 endogenous (internal) disturbance processes
  (examples?)
• E random error

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5. Aggregate Tree Growth

• Tree growth can be decomposed into five basic
  parts

Only ONE can be the desired signal. All OTHERS
constitute noise. We wish to maximize the signal
to noise (S/N) ratio (concept borrowed from
engineering). For example, if climate is our
desired signal, we must (1) mathematically remove
the effects of other parts, and (2) sample to
ensure no other noise affects tree growth in our
study area.
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6. Principle of Replication

• The environmental signal being investigated can
  be maximized (and the amount of noise minimized)
  by sampling more than one stem radius per tree
  and more than one tree per site.
• Obtaining more than one increment core per tree
  reduces the amount of "intra-tree variability"
  the amount of undesirable environmental signal
  peculiar to only that tree.
• Obtaining numerous trees from one site (and
  perhaps several sites in a region) ensures that
  the amount of "noise" is minimized.

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6. Principle of Replication

• Follows the basic statistical rule INCREASE YOUR
  SAMPLE DEPTH !!! MORE IS BETTER !!!

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7. Principle of Crossdating

• Matching patterns in ring widths or other ring
  characteristics (such as ring density patterns)
  among several tree-ring series allows the
  identification of the exact year in which each
  tree ring was formed.
• Both a principle and a technique. Without either,
  dendrochronology is unscientific ring-counting.
• The Principle of Crossdating concerns why trees
  have the same ring patterns.
• The Technique of Crossdating concerns how we can
  use this property to (1) ensure we have precisely
  assigned the correct calendar year to each tree
  ring, and (2) at the same time, account for those
  problem rings, such as false or locally absent
  rings.

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• Why does crossdating work?
• Because trees within a region will be responding
  similarly to the overall climate regime in which
  they grow.
• Different rates of growth may occur due to local
  micro-environmental effects, but this does not
  matter!