Introduction to Dendrochronology

produkte/glossare/dendro_glossary/ search_EN 351 terms in 7 different languages: English, German, French, Spanish, Italian, Portuguese and Russian Multilingual Glossary of Dendrochronology

The Ultimate tree-ring web page The Science of Tree Rings

Dendro-chrono-logy dendron (= “tree”) chronos (= “time”) - logy (= the study of) The science that uses tree rings, dated to their exact year of formation, to analyze temporal and spatial patterns of processes in the physical and cultural sciences. Dendrochronology

Natural Archives

6 The different archives

Tree is a recorder, a biological databank that records and stores the information from the environment. Knowing the growing processes and how trees react to the different ecological factors we should be able to read and understand these information. Tree rings are natural archives

Tree rings must be present Tree rings must be annual Basic condition

Limits and troubles using the tree rings

Wood types Picea abies Fagus sylvatica Quercus robur 15x60x 270x

Event Ring Ring with a conspicuous feature within a limited section of a visually assessed individual tree-ring sequence. It can be morphologically realized in various ways:

A tree ring which in a sample is absent due to the failure of cambial activity Missing Ring

Wedging Ring A tree ring which is simply discontinuous (partial, incomplete)

Apparentely complete growth zone with well-marked boundaries, formed within one growing season. It could be hard to distinguish from true rings. It is a layer of cells, within a tree ring, with different shape, size, wall thickness and colour, often with fuzzy boundaries. False Ring Intra-Annual-Density-Fluctuation (IADF)

Light and Dark Rings Latewood zone with thin-walled cells, usually in trees at high elevation or latitude.

Distorted xylem tissue damages by freezing in the growing season during which the cells were being formed. It could be found in the early- or latewood according to the timing of the frost event. Frost Ring

Frost Ring in 2005 at Dolomites

Frost Rings in common Juniper

These rings have many resin ducts and/or pockets mainly organized in regular files within the early- or latewood. They are often the results of mechanical stresses (wind), wounds or frost damages. Traumatic Resin Ducts

A visually conspicuous reduction of growth or recovery within an individual tree-ring sequence. The first year of an abrupt growth change is considered an event year Abrupt Growth Change

Having several synchronous (cross-dated) event years within a group of trees, we could define a pointer year, which identification and interpretation is fundamental in all dendrochronological and dendroclimatological analyses. A sequence of pointer years or pointer intervals used to be called a “signature”. Pointer Year

Principles of dendrochronology As with any science, dendrochronology is governed by a set of principles or "scientific rules.” Some are specific to dendro-chronology while others are basic to many disciplines. Some of them have their roots as far back as 1785 but others are quite recent (1987). All tree-ring research must adhere to these principles, or else the research could be flawed.

The Principle of Limiting Factors Basic principle in biology 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. The limiting factor(s) varies in space and time → variable tree growth! It/they must affect many trees together.

The Principle of Ecological Amplitude The growth of a tree species is more sensitive (more prone to annual variability) in the outer limit of its diffusion area. Diffusion area of stone pine (Pinus cembra) Sensitive versus Complacent

The Principle of Ecological Amplitude N N S S E E W W Optimal growth conditions, reduced sensitivity Stressful locations, increased sensitivity A tree species will be more responsive and sensitive to changes in environmental conditions in the outer limits of its range. This limit could be either latitudinal or longitudinal

T °C T (°C) The Principle of Ecological Amplitude A tree species will be more responsive and sensitive to changes in environmental conditions in the outer limits of its range. This limit could also be elevational

Principle of Site and Trees Selection Sites useful to dendrochronology can be identified and selected based on criteria that will produce tree-ring series sensitive to the environmental variable being examined. We must select sites and trees that will maximize the environmental signal being investigated trying to reduce the effects of other environmental factors. Careful sample and site selection Max signal – Min noise

The Uniformitarian Principle This principle states that physical and biological processes that link current environmental processes with current patterns of tree growth must have been in operation in the past. “The present is the key to the past” (Hutton 1785). Illustrates the “trajectory of science,” past, present, and future: A.Study processes as they occur at present B.Improved understanding comes from the past C.Extrapolate/predict the future = applied! James Hutton ( )

The 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, (2) at the same time, account for those problem rings, such as false or locally absent rings and (3) extend a tree-ring series back in time.

These three cores (taken from three trees growing in El Malpais National Monument in New Mexico) have ring patterns in common. For example… 1793 = wide ring with thick latewood 1806 = narrow ring (absent on bottom) 1816 Year Without a Summer wide ring 1840 = wide ring 1847 = very narrow ring

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! - The Principle of Crossdating

Crossdating can also be used to extend a chronology back in time by overlapping older and older samples. Crossdating to extend tree-ring series

Crossdating can also be used to extend a chronology back in time by overlapping older and older samples.

Notice that crossdating uses both wide rings and narrow rings, although the narrow rings are (for some reason) easier.

Datable series Complacent series Sensitive series Average tree-ring width Arboreal dominance Closed canopyTreeline Increasing effect of the limiting factors Percentage of partial rings Low High Tree rings and environmental factors

This principle states that any individual tree-growth series can be "decomposed" into an aggregate of environmental factors, both human and natural, that affected the patterns of tree growth over time. The Principle of Aggregate Tree Growth R t = A t + C t +  D1 t +  D2 t + E t

The Principle of Aggregate Tree Growth R t : observed ring parameter for year t (e.g. width, density, chemistry) A t : age (size) related growth trend C t : growth related to climate D1 t : endogenous (i.e. small scale) disturbance pulse (related to tree dynamics; e.g. branch loss, lightening) D2 t : exogenous (i.e. large scale) disturbance pulse (related to stand dynamics; e.g. fire, insect defoliation) E t : error variance (e.g. genetic variability) N t : annual variability in nutrient availability CA t : annual variability in carbon allocation within a tree (e.g. masting) EO t : errors made by the operator N t +CA t +EO t +E t

The Principle of Aggregate Tree Growth R t = A t + C t +  D1 t +  D2 t + E t 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. For example, if climate is our desired signal, we must (1) sample to ensure no other noise affects tree growth in our study area, and (2) mathematically remove the effects of other parts.

The 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.

The Principle of Replication

The different types of information derived from tree-ring series Trees as natural archives Site and trees selection Climate as the key factor Ecological interpretation Climate reconstruction Possible applications at different time-domains Time scale Short term (annual) Long term (centuries and more) Spatial scale Detailed (single-tree level) Wide (regional to global) R t = A t + C t +  D1 t +  D2 t + E t