Bristle jaw chronology - Borstenkiefern-Chronologie

The bristlecone pines chronology (English Bristlecone pine chronology ) from the tree rings Durable pines (Engl. Pines Bristlecone ) has long been considered the most reliable time series dendrochronological investigations and for the calibration of the radiocarbon method used. It goes back around 9,000 years without any gaps. Since the 1980s, the Belfast Chronology has come by its side.

The long-lived pine (Pinus longaeva) was still considered a subspecies of the awn pine (also: bristle pine ) (Pinus aristata) until around 1970 . About 20 more than 4,000-year-old specimens growing at high altitude in the Schulman Grove in the White Mountains in California . The oldest known specimens include “ Methuselah ” with an age of around 4,767 years. A specimen called " Prometheus " felled in 1964 revealed an age of 4,950 years after counting the tree rings. In 2012, a new record holder was announced who was dated to an age of 5,062 years, converted to the year 2012. [1]

Researchers (Ferguson 1969, LaMarche 1974 and others) at the Laboratory of Tree-Ring Research at the University of Arizona created one of the longest and most reliable reference chronologies from tree samples of this tree species. The old age of the trees results in correspondingly long ring sequences and, due to the large overlap of the individual ring sequences that can be achieved, a very high level of reliability.

In addition, dendrochronology benefits from the fact that the wood of this type of pine is very resistant to rotting and can withstand thousands of years without consequences even after the tree has died. Another advantage is that in these pines the formation of double rings occurs only very rarely in a year and, if it does, this can be easily recognized by the experienced dendrochronologist. However, the trees sometimes suspend the formation of annual rings, which can account for up to 5%, in extreme locations even more than 10% of the rings.

The first calibration curves for radiocarbon dating were based on the bristle jaw chronology. The average ring width of the long-lived pine is only very thin (in the range of tenths of a millimeter), so that only little material per ring is available for radiocarbon dating. For this reason, today's radiocarbon calibration curves are based on chronologies of other tree species with wider rings, in particular the Hohenheim tree ring calendar .

The series have been used by a team of researchers (Michael Mann, Raymond Bradley and Malcolm Hughes) for the climate discussion, but the reasoning has been heavily criticized by other scientists (McIntyre and McKitrick) regarding data selection and interpretation.

See also


Individual evidence

  1. Rocky Mountain Tree Ring Research: Database of ancient trees (Stand: Januar 2013)