Wood

1. PRINCIPLES OF
DENDROCHRONOLOGY
• Set of principles or “scientific rules”
• Some are specific to dendrochronology
– Tree selection
• Others are basic to many disciplines
– Replication

2. Crossdating
• Matching of ring patterns across trees
– Widths, density, other features
• Allows year date of formation to be
assigned to each ring
• Critical to
dendrochronology

3. Limiting Factors
• Liebig’s Law of the
Minimum
– Rate of a process is
limited by most limiting
factor
– Interactions between
nutrients
– Other factors: water?

4. Limiting Factors
• Tree Growth
– Cannot proceed faster than is allowed by
most limiting factor
– Degree and duration of a limiting factor
change from year to year  ring
variation
– Could be different limiting factors
relative to various frequencies of growth

5. Limiting Factors
• Sheep Mt bcp: moisture/temperature limited
at high-frequency
• Decadal ramp evidence of CO2 limitation?

6. Aggregate Tree Growth
• Ring variation is a function of
– Age or size
– Climate
– Endogenous disturbances
– Exogenous disturbances
– Leftover

7. Aggregate Tree Growth
• To focus on one of these factors,
others must be accounted for
– To study past climate:
– Sample trees without past disturbance
– Remove age effect

8. Aggregate Tree Growth
• Age or size effects removed by detrending
0
2
4
1800 1850 1900 1950 2000
Ring
W
idth
(mm)
RW = 2.68 • e
(-0.02 • tim e )
+ 0.26
(a)
0
1
2
1800 1850 1900 1950 2000
Y ear
Index
(b)

9. Site and Tree Selection
• Select a site to maximize effect of an
environmental factor on tree growth
• Eliminate or
equalize other
factors
• Isolate the single
factor of interest
• Edaphic variation
can be below surface

10. Site and Tree Selection
• Not random sampling in true ecological
sense
• Ramifications for inference
– Instead of saying: Climate affects tree
growth in such a way …
– We might say: Past climate at this site has
been such and such …

11. Replication
• Multiple radii to estimate tree growth
• Multiple trees to crossdate, estimate site
patterns
• Multiple sites
to estimate
regional
tendencies
• Multiple samples
to establish
building sequences

12. Ecological Amplitude
• Tree growth more sensitive to environmental
factors at edge of species range
• Altitudinal:
– Pine sensitive to
moisture at lower
elevational limit

13. Ecological Amplitude
• Latitudinal:
– Trees may occupy wide variety of
microsites in center of range, not limited by
single factor
– Trees may occupy narrow variety of
microsites along margins of range

14. Ecological Amplitude
• White oak is classic
– Enormous range
– Gentle topography
– Itrdbfor: “In the East …
tree sensitivity to climate
increases from the range
center out toward the
range edge.”

15. Ecological Amplitude
• Might affect age of trees:
– Schulman, Ferguson 1956 (Science 1954, v.
119, pg. 396, 883)
– “Young” bcp in
east
– Old bcp to west
– Corresponds to
average rainfall
totals

16. Ecological Amplitude
• Currey 1964:
– Found oldest bcp on Wheeler Peak, NV
– “The simple hypothesis of Schulman and
Ferguson
is … no
longer
tenable.”

17. Uniformitarianism
• Physical and biological processes that link
current environmental processes with
current patterns of tree growth operated
similarly in the past
• “Present is key to past” (Hutton 1785)

18. Uniformitarianism
• Tree rings from the 1900s calibrated with
rainfall records from 1900s
– Annual precipitation
• Past rings indicate past precipitation

19. Uniformitarianism
• Have current environmental conditions
existed in past?
• Do past environmental conditions exist
currently?
• Young trees vs. old trees?
– Szeicz and MacDonald 1994: Age-
dependent tree-ring growth responses of
subarctic white spruce to climate. CJFR
24:120-132.

20. Uniformitarianism
• Paleo twist: Past is key to future
– This is why we do what why do