The origin of the wood that the Romans used is exactly known

It must have happened towards the end of the year 124. Many oaks in forests between Venlo and Xanten were felled by Roman lumberjacks. They then dropped the Rhine to the Netherlands in a flat bottom, to end up there in various places as a pointed posts for the construction of the Limesweg along the northern border of the Roman Empire.

This entire process is now known thanks to interdisciplinary research by archaeologist Ronald Visser, promoted at the end of May at the VU University in Amsterdam.

Good storage conditions

Archaeologists have found plenty of wood in the Netherlands that was used as building materials in Roman times. Due to the good storage conditions, the remains of ships, watchtowers and roads have been found over time. They are also neatly dated on the basis of annual rings.

But where exactly the wood came from was never really well investigated. Thanks to Visser, specialized in annual ring research and data science, there is now a better understanding of the origin and production of the wood used. He gives another example: “For ships found at Zwammerdam and Woerden, not only used local wood, but also wood from what is now Germany.”

From historical sources it was already possible to conclude that the Romans were doing forestry. Visser, main teacher Archeology at Saxion University of Applied Sciences in Deventer, has read those sources in their original language, Latin and Greek. “With a translation next to it,” he adds modestly. In addition, there are inscriptions and archaeological finds at home and abroad that make it clear that the Romans had foresters (Saltuarii) and four forestry systems. Visser lists them: “Bare hood, selection, coppice and agricultural forest use.”

Visser used 7,665 already existing annual rings series for the determination of the wood. They come from 3,858 samples of 266 find locations, not only in the Netherlands, but also in parts of Belgium, France and Germany.

Network analysis

The big question in the beginning – Visser only completed his PhD research due to different circumstances after eighteen years – was how he could best discover in his large dataset patterns.

Eventually the book brought Linked From Albert-Laszlo Barbasi the solution: “network analysis,” says Visser. “There are annual ring patterns that are very similar in terms of successive thick and thin annual rings, even though they can come from wood that has been found in different places. These annual ring patterns are not only unique in time, they are also location, because the growing conditions of, for example, trees in the West Netherlands are different from the Dutch sandy areas or, for example, there are directions.

“The networks are a representation of this: very corresponding annual ring patterns indicate corresponding growing conditions and so they end up close to each other in the network. The locations in networks thus give an indication of the origin.”

In one effort also a new statistical measure of comparing annual ring series, the SGC. “That stands for Synchronous Growth Changes. The statistical size that has been used since the 1940s, the Gleichläufigkeitskoeffiezienentalso describes the simultaneous growth changes in different annual ring series, but counts years in which the annual ring width remains the same as that of the previous year as half a Gleichläufigkeit. With large data series, a greater degree of agreement can therefore come out than there is actually. “

Growth

The network analysis showed that the vast majority of the wood came from the immediate vicinity of the locations. “About twenty percent came from elsewhere,” says Visser. An example of this is the wood that was used in 125 AD for the road laid out by the Roman army along the Limes, the Roman border along the Rhine. “The wood found at different locations shows a strong statistical agreement. It was cut down in the autumn of 124 or the following winter, and part of it shows growth prints with a cycle of three to five years. That is a strong indication of the periodic outbreak of Meikevers, which seems to be clear that the wood was made of the wood and xanten analysis made it to the wood. The Roman army as the wood was removed from further road, it was possible to be inferior to Germania inferior. ”

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Forum Hadriani

In exceptional cases, the wood also came from outside the province. That is the case with the oak wood that was used around 160 and 205 for the construction of the port of Hadriani forum, the Roman city at the current Voorburg. “Part of the wood came from the Moselle/Neckar region,” says Visser. “I call it ‘use at the government level’. That may have to do with Prestige – Keizer Hadrian has visited the city named after him – but also with the simple fact that the place was part of the Roman infrastructure that made it possible to get wood from distant. As we now want to buy Scandinavian wood, but because we per se.”

The wood was probably supplied by flat bottoms suitable for transport. “Freshly cut oak sinks in water and no traces of softwood for rafts have been found.”

The same tree

Several flat -bottomed bottoms have been found in the Netherlands. In two, respectively, the Zwammerdam 6 and De Woerden 7 baptized, Visser with fellow wood specialist Yardeni Vorst discovered a striking agreement. “The wood in both ships is partly from Gallia Belgica and Germania Superior, and it is also from the same tree. That indicates that they have been made by the same shipyard. However, that yard has not yet been found.”

According to Visser, his network analysis has also proven itself as a means of control. “Other researchers believed that the wood for the Limesweg, which I would like to call Hadrian’s way, also came from the Ardennes. Apart from the fact that it is not logical to first transport wood over land or a bit upstream across the Rhine, the analysis shows that it is not correct either.”

Who wants can check it for themselves: the entire investigation, Including software developed by Visseris open access.

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