PRINCIPLES OF DENDROCHRONOLOGY • Set of principles or “scientific rules” • Some are specific to dendrochronology – Tree selection • Others are basic to many disciplines – Replication
Dec 22, 2015
PRINCIPLES OF DENDROCHRONOLOGY
• Set of principles or “scientific rules”
• Some are specific to dendrochronology
– Tree selection
• Others are basic to many disciplines
– Replication
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
Limiting Factors
• Liebig’s Law of the Minimum
– Rate of a process is limited by most limiting factor
– Interactions between nutrients
– Other factors: water?
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
Limiting Factors
• Sheep Mt bcp: moisture/temperature limited at high-frequency
• Decadal ramp evidence of CO2 limitation?
Aggregate Tree Growth
• Ring variation is a function of
– Age or size
– Climate
– Endogenous disturbances
– Exogenous disturbances
– Leftover
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
Aggregate Tree Growth
• Age or size effects removed by detrending
0
2
4
1800 1850 1900 1950 2000
Rin
g W
idth
(m
m)
RW = 2.68 • e(-0.02 • time) + 0.26
(a)
0
1
2
1800 1850 1900 1950 2000
Year
Inde
x
(b)
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 variationcan be below surface
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 …
Replication
• Multiple radii to estimate tree growth
• Multiple trees to crossdate, estimate site patterns
• Multiple sites to estimate regional tendencies
• Multiple samplesto establish building sequences
Ecological Amplitude
• Tree growth more sensitive to environmental factors at edge of species range
• Altitudinal:
– Pine sensitive tomoisture at lowerelevational limit
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
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.”
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 rainfalltotals
Ecological Amplitude
• Currey 1964:
– Found oldest bcp on Wheeler Peak, NV
– “The simple hypothesis of Schulman and Ferguson is … no longer tenable.”
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)
Uniformitarianism
• Tree rings from the 1900s calibrated with rainfall records from 1900s
– Annual precipitation
• Past rings indicate past precipitation
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.