I.e. there were 90 stems retrieved from that excavation and it all confirmed Hollstein's dating of the bridge to AD336.

Technically and statistically, I do not understand exactly what the authors have done except for putting a lot of measurements together to form proper reference curves.

Though here are some citations of special interest:

• "The material comes from 9 laboratories based in France, Belgium, Switzerland and Germany.."
• "The oldest ring dates back to 546 BC, the latest ends the system at 1995 AD. The missing years are precisely between 194 AD and 671 AD."
• "Finally, thousands of wood chronologies were connected for a 2500 years period except for the late Roman and Merovingian times for which we got some chronologies, still floating though."
• Also especially see Figure 5 on page 249 of the report where the authors have plotted a gap approximately between AD170 and AD460 and state that chronologies of that time is "floating"!

There is apparently STILL a severe lack of samples from that time. Otherwise the authors would not state chronologies of that time as floating but instead indicate them as "correct dated elements but not sufficient global quality for starting extra interpretations".

Of course that could be because of no building activities in the period after the WEST Roman empire had closed down - so too few samples found afterwards. And no oak trees of that time found in the river valleys because of a long dry period?

Still another question related to this data: The 90 stems from "die erste Kölner Rheinbrücke" - were that data available before that TRACE report was written? The authors of the report claim that they have a gap starting at AD170. Though the "Rheinbrücke" ends at AD336. So if the "Rheinbrücke"-data was available to the French team then I had expected data of the time AD170-AD336 to be classified at least as "correct dated elements but not sufficient global quality for starting extra interpretations".

The whole story about dendro data of this period looks very puzzling to me.