Principles of Dendrochronology - PowerPoint PPT Presentation

About This Presentation
Title:

Principles of Dendrochronology

Description:

Title: PowerPoint Presentation Author: Henri D. Grissino-Mayer Last modified by: Georgina DeWeese Created Date: 8/20/2003 12:31:28 PM Document presentation format – PowerPoint PPT presentation

Number of Views:260
Avg rating:3.0/5.0
Slides: 20
Provided by: Henr1168
Learn more at: https://www.westga.edu
Category:

less

Transcript and Presenter's Notes

Title: Principles of Dendrochronology


1
Principles of Dendrochronology January 30
2
  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!

3
  1. Uniformitarianism Principle

Examples
A. Reconstructions of past climate
Dendroclimatology
Future?
Present
Assumes that climatic processes operating today
were operating similarly in the past.
4
  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
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!

6
(No Transcript)
7
2. Principle of Limiting Factors
8
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

9
3. Ecological Amplitude Range map of sugar maple.
10
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
11
Red Spruce
12
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.

13
4. Principle of Site Selection
Notice vastly different growth forms of these
trees
Notice vastly different ring patterns
14
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

15
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.
16
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.

17
6. Principle of Replication
  • Follows the basic statistical rule INCREASE YOUR
    SAMPLE DEPTH !!! MORE IS BETTER !!!

18
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.

19
-
  • 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!
Write a Comment
User Comments (0)
About PowerShow.com