BECKER AND GERMAN DENDROCHRONOLOGY

            It is also during the early 1970’s that the German government began massive projects to further their autobahn system.  The standard foundation of the autobahn is a gravel layer on which the roadway is constructed.  The best sources of gravel in Germany are the extensive gravel beds of the River Main and Danube (Figure 2.12).  Associated with the excavation of the gravel for the purposes of autobahn construction and upkeep, was the problem of hitting fossil logs and jamming the mechanism costing the gravel miners time and money.  The problem was that the mines were using the treadmill-and-bucket method of removing the gravel and the logs would jam the mechanism (Figures 2.13 and 2.14).  These logs were presumed to be quite old due to their dark and weathered appearance (Figures 2.15 and 2.16). 

It was Bernd Becker who decided to use this wood for the purposes of dendrochronology because the ring-structure remained in tact even after several millennia in anaerobic environments under the gravel beds of these major rivers.  This was mutually advantageous to both the company and Becker, because the company usually just burnt the wood in large bonfires – which, of course, destroyed the samples.  By collecting the oak and pine from these gravel mines, the University of Höhenheim and Becker collected tens of thousands of samples, covering vast lengths of the ancient times.  The oldest piece of wood dated over 11,000 years before present.

These efforts were very beneficial when in 1993, Becker released a radiocarbon calibration curve using the long continuous chronology built upon the fossil wood, historic buildings, and recent trees (Becker, 1993) .  The data was withheld from private hands due to the profiteering of several individuals in medieval house dating companies.  The dating of historic buildings matured in the 1980’s and 1990’s and produced many untrained dendrochronologists in Europe and their desire to hold their data, for economic means, has contributed greatly to the difficulty in obtaining data from Europe sources.

Data that has been released, namely Hollstein’s Chronology in 1980, was and is still hindered by the 27-year discrepancy (Hollstein, 1980) .  This was brought to the attention of then retired Hollstein in a meeting with Frenzel and Becker.  Becker’s new project was to evaluate the past work of Huber and Hollstein. 

Becker decided to use a new method of evaluating homogeny of the cores from the fossil wood sources called gleichläufigkeit (GLK).  GLK, or a sign test that compares the similarities and intensities in dendrochronology curves for the entire tree, was different from Hollstein’s method of wuchswert (WS), or growing value measurement from only previous growth years.  The GLK coefficient is a comparison between two chronologies and is calculated as:

                                    Δi= (X_i+1 ^- X_i )            if Δi >0; G_ix = +1/2

                                                                        if Δi =0; G_ix = 0 (very rare)

                                                                        if Δi <0; G_ix = -1/2

for two curves G(x,y) = (1/n-1)  n-1∑i=1 |Gix + Giy|

Where G = the gleichläufigkeit coefficient, X and Y are chronologies, n = the series length in years, i = moment in time (Schweingruber, 1988).

This change in methodology to GLK from WS, aided by computer technology, allowed for a more reliable method of crossdating shorter segments.  This newer methodology allowed Becker to identify that there was indeed an error in Hollstein’s chronology that pushed his dating off by 27 years.  This information was not well received by Hollstein, but it was discovered that the sample wood of Hollstein had been destroyed due to lack of storage space.  However, the now computerized data was still in existence.

Frenzel called a meeting of all the regional dendrochronologists together to break the intellectual code-of-silence that had developed.  This was due mostly to the privateering of the non-academic dendrochronologists, but also due to the long processing hours needed to razor the wood samples for evaluation.  This meeting was the first of its type and eventually became the Eurodendro annual meeting of European dendrochronologists. 

The purpose of this meeting was to allow for freer communication between the laboratories and advance scientific endeavors.  The problem of little Roman Age wood was discussed in detail.  The oldest trees in this sampling were only 480 years old with the best samples being 200 - 400 years old.  This lack of sample depth in the individual laboratories contributed to a problem of interpretation, which is one of the reasons that this period had been overlooked in Germany.  It was decided that they should combine their information and begin to work together.

            They decided to split the work into three labs with Höhenheim as the main data storage area and all labs were require to store their samples indefinitely.  There were many laboratories, but only three associated with academia, Höhenheim, Heidelberg, and Hemmenhofen.   Their funding was all from governmental and private sources, but these did not require them to release or publish data, again adding to the difficulty of obtaining European data.

            From this meeting, Becker returned to Höhenheim and began evaluating the 27-year error with his assistant Michael Friedrick, which was soon realized to be a simple mistake (Friedrich and Greiner, 2001) .  This prompted the laboratory to reevaluate all of the data that had been processed before the modern computer analysis programs.  After the passing of Bernd Becker, Michael Friedrich and Marco Spurk have continued to update and correct Huber, Hollstein, and Beckers’ earlier chronologies (Spurk et al., 1998, Friedrich and Greiner, 2001, Becker, 1993, Becker, 1981) .