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Principles of Dendrochronology

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Only ONE can be the desired signal. All OTHERS constitute noise. ... Different rates of growth may occur due to local micro-environmental effects, ... – PowerPoint PPT presentation

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Title: Principles of Dendrochronology


1
Principles of Dendrochronology
2
  • 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
  • Study processes as they occur at present
  • Improved understanding comes from the past
  • Extrapolate/predict the future applied!

3
  • Uniformitarianism Principle

Examples
A. Reconstructions of past climate
Dendroclimatology
Future?
Present
Assumes that climatic processes operating today
were operating similarly in the past.
4
  • 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
5
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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The basic model
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The low precip high temp model
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The high precip low temp model
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2. Principle of Limiting Factors
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2. Principle of Limiting Factors
13
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

14
3. Ecological Amplitude Range map of ponderosa
pine. Note different spatial scales will help us
isolate several locations where ponderosa pines
may be especially responsive.
15
3. Ecological Amplitude Range map of sugar maple.
16
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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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
21
What to look for in trees that indicate longevity
  • Dead spike top or broken top
  • Heavy, drooping lower limbs
  • Short stature, inverted carrots
  • Erratic growth forms
  • Stripbark
  • Sparse foliage in crown
  • Exposed roots
  • Isolated individuals

El Malpais National Monument, NM
22
El Malpais National Monument, NM
Five feet tall, broken top, inside ring AD 1406
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Alta Peak, Sierra Nevada, CA
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San Mateo Mountains, NM
25
Magdalena Mountains, NM
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El Malpais National Monument, NM
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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

28
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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5. Aggregate Tree Growth
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5. Aggregate Tree Growth
Stand dynamics
Death of nearby tree
Release after wildfire
31
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.

32
6. Principle of Replication
  • Follows the basic statistical rule INCREASE YOUR
    SAMPLE DEPTH !!! MORE IS BETTER !!!

33
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.
  • Well cover the Technique of Crossdating later.

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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!

35
Look at these five cores (taken from five
different trees) from Mt. Graham in southeastern
Arizona, and pick out the wide and narrow rings
they have in common.
36
Again, these three cores (taken from three trees
growing in El Malpais National Monument in New
Mexico) have ring patterns in common. For example
37
Notice that crossdating uses both wide rings and
narrow rings, although the narrow rings are (for
some reason) easier to visually key in on. These
narrow rings will be used later when we learn the
technique of crossdating.
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