Cross dating dendrochronology

cross dating dendrochronology

Crossdating in Dendrochronology. A. E. Douglass. Laboratory o! Tree-Ring Research, University o! •4rizona. This paper defines and illustrates crossdating. Dendrochronology, the study of the annual growth in trees, is the only method of The fundamental technique in dendrochronology is cross-dating, whereby. Request PDF on ResearchGate | Cross-dating methods in dendrochronology | Different cross-dating methods are compared. All methods considered are based .

The inner portion of a growth ring forms early in the growing season, when growth is comparatively rapid hence the wood is less dense and is known as "early wood" or "spring wood", or "late-spring wood" [17] ; the outer portion is the "late wood" sometimes termed "summer wood", often being produced in the summer, though sometimes in the autumn and is denser.

Many trees in temperate zones produce one growth-ring each year, with the newest adjacent to the bark. Hence, for the entire period of a tree's life, a year-by-year record or ring pattern builds up that reflects the age of the tree and the climatic conditions in which the tree grew.

cross dating dendrochronology

Adequate moisture and a long growing season result in a wide ring, while a drought year may result in a very narrow one. Direct reading of tree ring chronologies is a complex science, for several reasons.

First, contrary to the single-ring-per-year paradigm, alternating poor and favorable conditions, such as mid-summer droughts, can result in several rings forming in a given year.

Dendrochronology

In addition, particular tree-species may present "missing rings", and this influences the selection of trees for study of long time-spans. For instance, missing rings are rare in oak and elm trees. Researchers can compare and match these patterns ring-for-ring with patterns from trees which have grown at the same time in the same geographical zone and therefore under similar climatic conditions. When one can match these tree-ring patterns across successive trees in the same locale, in overlapping fashion, chronologies can be built up—both for entire geographical regions and for sub-regions.

Moreover, wood from ancient structures with known chronologies can be matched to the tree-ring data a technique called cross-datingand the age of the wood can thereby be determined precisely.

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Dendrochronologists originally carried out cross-dating by visual inspection; more recently, they have harnessed computers to do the task, applying statistical techniques to assess the matching. To eliminate individual variations in tree-ring growth, dendrochronologists take the smoothed average of the tree-ring widths of multiple tree-samples to build up a ring history, a process termed replication.

A tree-ring history whose beginning- and end-dates are not known is called a floating chronology. It can be anchored by cross-matching a section against another chronology tree-ring history whose dates are known. As soil water declines through the summer, the cells become thicker-walled and more dense. Thus each annual ring consists of early light and late dark wood. Tree-ring series can be classified as either complacent uniform ring widths where moisture and heat are sufficient throughout the growing season or sensitive pronounced year to year variation in ring width, where conditions are frequently near the limits of the trees tolerance, e.

The search for proxy climatic data was the original application of tree rings.

cross dating dendrochronology

Inhe noticed ring-width variations on a cut log and reasoned that these were controlled by the tree's environment Fritts, Douglass illustrated the relationship between climate and ring width by plotting both against time, and introduced the technique of cross dating by correlating ring-width signatures sequences of wide and narrow rings among trees distributed over large areas. In western Canada, dendrochronology has been largely confined to the montane and boreal forests Case and MacDonald, ; Luckman and Innes, An investigation of fire and insect infestation frequency in the jack pine forests of Manitoba Gill, was the first Canadian study to use ring-width data and cross-dating techniques to develop a tree-ring chronology.

cross dating dendrochronology

Shortly afterwards, Powell compared variation in wheat yields in Saskatchewan to ring-width variation in white spruce and some hardwood species. Much of the tree ring research in western Canada has at the Laboratory of Tree Ring research in Tucson, Arizona, including the first studies of Douglas Fir in Alberta Schulman,the first regional dendrochronological network for western North America Drew,regional climatic reconstructions Fritts, ; Fritts, et al. One major exception is the research group at the University of Western Ontario which has established long tree-ring chronologies for the Canadian Rockies, to reconstruct climatic and glacial history of the last millennium and evaluate tree growth - climate relationships at altitudinal treeline e.

Luckman,; Luckman and Colenutt, The general absence of trees has obviously discouraged the pursuit of dendrochronology in the southern Interior Plains. Although a belt of aspen parkland extends across the prairie provinces, much of the original aspen polar was removed for crop production and this tree species is much inferior to coniferous trees for tree ring research Fritts, Methods The cores and disks are processed using standard laboratory techniques Stokes and Smiley, Cores are glued to a grooved pieces of wood such that the tracheids were approximately 30o from their original vertical orientation, ensuring maximum visibility of the latewood to earlywood transition between successive years.

The wood is sanded with progressive finer paper to expose the growth rings for counting and measurement of ring width.

cross dating dendrochronology

The fundamental technique in dendrochronology is cross-dating, whereby distinctive series of narrow and wider tree rings are identified and matched among trees of different ages. Calendar years can then be assigned to rings from dead wood. This extends tree-ring chronologies beyond the life spans of living trees, and enables dating of pre-historic events e. Cross dating among tree ring series of about the same length and age enables the detection of missing and false rings. Annual growth rings can be missing in unusually cold or dry growing seasons.

cross dating dendrochronology

False rings represent renewed growth after a cold or dry weather causes the formation of late wood mid way through a growing season.