Dendrochronology

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Beam sample from the town hall of Gödenroth (oak wood)

The dendrochronology (. From the Greek δένδρον Dendron "tree" χρόνος chronos "time" λόγος lógos "teaching", "science", so "teaching / science of tree age," even tree-ring dating called) is a dating method of geoscience , the archeology , the art Science and dendroecology, in which the annual rings are associated with a particular, known growth time of trees according to their different width. The term dendrochronology goes back to the American astronomer Andrew Ellicott Douglass (1867–1962). Dendrochronology is related to dendrology (general wood science).

Basics and history of dendrochronology

Annual rings from years with good growing conditions are wider than those from years with poor growing conditions. Since the living conditions are almost the same for all trees of a species in a certain area, all trees of a species in this region have roughly the same characteristic sequence of narrow and wide annual rings.

First descriptions of tree rings are said to appear in Theophrastus . However, the first clear mention of tree rings comes from China in the 12th century in a story by Hong Mai . The first mentions of tree rings from Europe can be found in Leonardo da Vinci and Montaigne . Buffon and Duhamel were able to associate tree rings with a historical event for the first time in 1737, namely with the particularly severe winter of 1708/09. In his "The Ninth Bridgewater Treatise" (1837), Babbage carried out very detailed theoretical considerations on dendrochronology and already referred to "cross-dating". In the course of the 19th century there was an increasing number of attempts to actually "overlap" the succession of tree rings from different trees. B. by Arthur Freiherr von Seckendorff-Gudent .

The founder of dendrochronology, Andrew E. Douglass, wanted to use the annual rings to show a connection between the earth's climate and the eleven-year cycle of sunspots . Douglass was the first to take drill cores from trees in order to obtain information about the climatic growth conditions by means of the thickness of the annual rings. However, this is not entirely unproblematic, as other factors also play a role in the growth of the trees, such as B. the supply of nutrients, competition from neighboring trees, damage from forest fires and lightning strikes, diseases and pest infestation. For example, spruce trees are sensitive to temperature fluctuations, while fir trees are sensitive to water shortages. Andrew E. Douglass has never succeeded in providing recognized evidence of the connection between sunspot activities and tree ring thickness.

Douglass measured the thickness of the annual rings on long-lived trees and plotted the values ​​on a diagram . He created a collection of data by aligning the characteristic sequences of extremely narrow and wide annual rings (so-called event years) of trees of different ages, but temporally overlapping trees, on a time scale. Using this "overlapping technique" (cross-dating method), Douglass was also able to determine the age of dead and blocked tree samples. In 1929 he succeeded in establishing a 1229 year long tree ring chronology, which goes back uninterrupted from the present to the year 700 AD. Using this chronology, he was able to date Indian dwellings when he entered the annual ring pattern of the archaeological find wood in the older section of his chronology. Swedish, Irish and British sites could also be dated as early as the 1930s.

Inspired by the success of Douglass, the Austrian botanist Bruno Huber began researching tree rings at the Tharandt Forestry University in the 1930s . In 1941, he succeeded in providing sensational proof of the suitability of the process in Central Europe. The Bronze Age played Wasserburg -Palisaden in the Federsee region a central role, and their dating by Huber marks the beginning of the dendrochronological investigation method in Central Europe. After the Second World War he continued his research at Munich University, and he succeeded in dating three lakeside settlements in eastern Switzerland in this way and in demonstrating their temporal parallelism. Since they belonged to the Pfyner and the Cortaillod cultures , evidence was provided for the first time that both cultures had coexisted at the same time.

Dieter Eckstein achieved a decisive further development of dendrochronology in Germany in the mid-1960s through the first use of computer-aided evaluation methods. He dated the Viking settlement in Haithabu near Schleswig. As a result, he and other researchers succeeded in creating long chronologies for the wood species oak and pine . The longest time series go back to the early post-ice age .

Process of the analyzes

Hollow drill for dendrochronology sampling, two drill cores on the left

By overlaying the ring patterns of many trees (crossdating method), an averaged tree ring sequence (tree ring chronology) is created, which can cover many millennia due to the overlapping lifetimes of the trees. Until the introduction of electronic data processing in the middle of the 20th century, the determination of simultaneous growth sections of different trees and the creation of the resulting tree ring chronologies was a time-consuming affair. The samples (tree discs or drill cores) were smoothed and prepared with a contrast medium such as chalk. Then each individual annual ring was measured with a magnifying glass. All the measured values ​​were drawn as a time series on transparent film. The time series of all measured trees were finally shifted against each other on the light table and checked for visual correspondence.

A characteristic measure of the agreement was the synchronism value (this is the percentage of the curve intervals in the overlap area of ​​two curves that rise or fall synchronously). In the resulting tree-ring chronology, the common growth patterns of the trees become more prominent, while the individual patterns are suppressed. Intervals in which a high percentage of the individual trees involved showed the same tendency (rising or falling) were referred to as wise intervals, which were of great importance in further comparisons. With the increasing availability of electronic data processing, these comparisons are made virtually in the computer, with numerous statistical parameters of the time series analysis (such as the correlation coefficient ) being collected.

Such annual ring chronologies serve as reference patterns for further dating of tree samples in an area. If a tree ring chronology shows gaps in the present, only relative dating is possible (for example tree A was felled x years earlier than tree B). However, if a tree ring chronology extends from the past to the present without any gaps, then the annual rings of a tree sample can be dated absolutely and precisely for this period. A tree sample cannot be dated if, for example, it cannot be assigned to an area or a tree ring chronology or if it consists of too few annual rings, less than about 80.

While the taking of samples for dendrochronology in components such as B. roof trusses is usually possible without difficulty, complex and sensitive objects from which taking a sample would cause serious damage (e.g. musical instruments, colored altar structures, etc.) could not be dated for a long time. With the help of computed tomography , however, three-dimensional models of the wood structure can now be created, which enable non-destructive dendrochronological dating of such objects.

Important annual ring tables

In some areas it was possible to create complete annual ring tables for some tree species for the last 10,000 years (for example the Central European oak chronology). An error-free dendrochronology allows the year of its creation to be assigned to each tree ring.

Extent of the created curves:

Application examples of dendrochronology

In science

In natural science, dendrochronology goes far beyond the function of a pure instrument for determining the age of wood. Thus, for the modern age, climate-growth correlations can be derived from the connection of climate data with the tree-ring chronologies, which document the reaction of trees to environmental influences in one-year resolution. One of the tasks of this orientation of dendrochronology is to provide prognoses for the growth of trees and thus for the forest ecosystem under changing climatic conditions ( climate change ). Since the individual growth of trees depends on many other factors, such as age trend, anthropogenic influences, competition, autocorrelation, noise and other factors, in addition to climate influences, these must first be factored out. For this purpose, dendrochronology uses an extensive range of mathematical methods.

Before the time of scientific weather measurements (from 1850), from which hardly any reliable data are available, dendrochronology itself was used as an indirect climate archive.

Dendrochronologically, a climate catastrophe could also be documented for a ten-year period around the year 540 AD (see also plague under Justinian I , the so-called Justinian plague , and Michael the Syrian ). Comet impacts or volcanic eruptions are believed to be the cause of this global atmospheric cloudiness .

A supplement to dendrochronology is dendroanalysis , which enables the identification and quantification of substances such as heavy metals in the tree rings.

In building research and monument preservation

Weathered growth rings on a tree trunk felled around 1111 in the Aztec Ruins National Monument .

With the help of the tree ring analysis of built-in timber, construction times of buildings can be determined very precisely. It makes a very important contribution to building research and the cultural history of buildings ( monument preservation ). However, the accuracy of the dating depends on several factors; It is only precise if 1. the built-in wood still shows the so-called forest edge , if 2. the wood was used for the first time and 3. is still at the location of the first use (" in situ "). As a rule, the year the tree fell is identical to the year it was installed. If there are no annual rings (difference to the edge of the forest), only approximate values ​​are possible (e.g. “± 10 years”, “around / after 1786”).

If the timber shows traces of processing (e.g. grooves) that are not related to the last use ("second use"), i.e. if it has already been used in another building, the felling date (dendro date) is usually before the time of construction of the building now examined, which is then younger. While a wooden beam as a lintel is difficult to replace, it may have been inserted into a roof truss later as a repair measure. Particularly extensive experiences were made in Lower Lusatia with village churches threatened by open-cast lignite mining and their wooden predecessor buildings.

Since the annual ring tables are now being differentiated more and more according to tree species and regions (e.g. "North German oak curve"), statements about the origin of the construction timbers are possible, including conclusions. When examining the medieval city centers of the Hanseatic cities on the Baltic Sea, it was possible to determine when the surrounding forests were cleared, so that imports from the Scandinavian countries were necessary.

In art history research

In the meantime, dendrochronology achieved spectacular successes in investigations into late medieval panel painting . The analyzes of the oak panels , on which Hieronymus Bosch , for example, used to paint, led to the clear result that a whole series of works previously attributed to Bosch had to be removed from the overall oeuvre because the panels came from trees that were felled only after Bosch's death were. Dendrochronology is also important for Dutch panel painting of the 16th and 17th centuries.

Dendrochronology is also used for the temporal classification of the wood used in the construction of musical instruments (string, plucked and keyboard instruments). In addition to the exact dating of known places of manufacture, the reverse method can also provide information on the origin of the wood and the use of wood in various workshops, such as B. that of the violin maker Jakobus Stainer . A significant example is the tribe of the Messiah Stradivarius and a G. P. Rogeri violin. It has been proven that the tops of the two violins were made from the same tree trunk (spruce).

In scientific publications dendrochronologically determined dates are often indicated by the addition “(d)”, i.e. around 1497 (d).

See also

literature

To the method

  • MGL Baillie : A Slice through Time. Dendrochronology and precision dating. Batsford, London 1995, ISBN 0-7134-7654-0 .
  • Bernd Becker : Dendrochronology. In: Erwin Keefer (ed.): The search for the past. 120 years of archeology at the Federsee, catalog for the exhibition, Württembergisches Landesmuseum Stuttgart, 1992, ISBN 3-929055-22-8 , p. 60 f.
  • Grahame Clark : Archeology and Society. Methuen, London 1939, pp. 141-143.
  • ER Cook, LA Kairiukstis: Methods of Dendrochronology. Applications in the Environmental Sciences. Kluwer Academic Publishers, Dordrecht et al. 1990, ISBN 0-7923-0586-8 .
  • Wolfgang Gruhle and Burghart Schmidt: Climatic traces of the trees. Radiation fluctuations of the sun as a pulse generator. Nünnerich-Asmus, Mainz 2017, ISBN 978-3-961760-03-9 .
  • Erwin Keefer: Bruno Huber and the moated palisades. In: Erwin Keefer (ed.): The search for the past. 120 years of archeology at the Federsee, catalog for the exhibition, Württembergisches Landesmuseum Stuttgart, 1992, ISBN 3-929055-22-8 , p. 62.
  • Peter Klein , Dieter Eckstein: Dendrochronology and its application. In: Spectrum of Science . 1, 1988, ISSN  0170-2971 , pp. 56-68.
  • Fritz Hans Schweingruber: The tree ring. Location, methodology, time and climate in dendrochronology. Haupt, Bern et al. 1983, ISBN 3-258-03120-7 .

Extension of the curves

  • Sturt W. Manning, Bernd Kromer, Peter Ian Kuniholm, Maryanne W. Newton: Confirmation of near-absolute dating of east Mediterranean Bronze-Iron Dendrochronology. In: Antiquity. Oxford 77, 2003, ISSN  0003-598X , online .

Application examples

  • Mike Baillie: Exodus to Arthur. Catastrophic Encounters with Comets. Batsford, London 1999, ISBN 0-7134-8352-0 .
  • Peter Klein: Dendrochronological Analysis of Works by Hieronymus Bosch and his Followers. In: Jos Koldeweij, Bernard Vermet (ed.): Hieronymus Bosch. New Insights Into His Life and Work. NAi Publishers, Ghent et al. 2001, ISBN 90-5662-214-5 , pp. 121-131.
  • Micha Beuting, Peter Klein: Dendrochronological studies on string instruments by Jacob Stainer . In: Rudolf Hopfner: Jacob Stainer “… imperial servant and violin maker in Absom”. Edited by Wilfried Seipel . Skira, Milan 2003, pp. 167–171, ISBN 3-85497-060-9 (exhibition catalog, Kunsthistorisches Museum Wien, Ambras Castle, June 4 - October 31, 2003).
  • Micha Beuting: Wood history and dendrochronological investigations on resonance wood as a contribution to organology. Kessel-Verlag, Remagen-Oberwinter 2004, ISBN 3-935638-48-5 (also: Hamburg, Univ., Diss., 2003).
  • Micha Beuting: Dendrochronological dating of string instruments of the 15th and 16th centuries with special consideration of the violin makers Linarolo and Ciciliano. In: Technological Studies. 8, 2009, ZDB -ID 2180772-3 pp. 177-213.
  • Arjan Versteeg: Blood brothers, Messiah dendrochronology. In: The Strad. March, 2011. Online (PDF file; 2.28 MB)

Web links

Commons : Growth Rings  - Collection of images, videos and audio files
Wiktionary: Dendrochronology  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Franz Krojer: Chronologie der Dendrochronologie Differential-Verlag, Munich 2014, p. 24 ( PDF ).
  2. ↑ Keefer / Becker and Keefer, pp. 60 ff.
  3. ↑ Archived copy ( memento of the original from March 28, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot / botanik.uni-hohenheim.de
  4. ↑ Markus Agthe: Archaeological investigations and architectural historical observations on churches in Niederlausitz and the adjacent Elbe-Elster region. In: Insights. Archaeological contributions for the south of Brandenburg. 2002. Work reports on the preservation of monuments in Brandenburg. Vol. 12. Wünsdorf 2003, pp. 217–288. ISSN  1436-249X .
  5. ↑ Thorsten Westphal: Early urban development between the middle Elbe and the lower Oder between approx. 1150-1300 based on the dendrochronological data. Bonn 2002. ISBN 3-7749-3103-8 .
  6. ↑ Arjan Versteeg: Blood brothers, Messiah dendrochronology. In: The Strad , March 2011.