Long-distance oak supply in mid-2nd century AD revealed: the case of a Roman harbour (Voorburg-Arentsburg) in the Netherlands

We present dendrochronological evidence of long-distance oak timber supply for the harbour of the Roman town Forum Hadriani, an important market place and point for military supplies located at the watershed of the Rhine and Meuse rivers, near the North Sea in the west of the current Netherlands. During excavations at Voorburg-Arentsburg (site Forum Hadriani) in 2007-2008, the wooden quay from the Roman harbour was revealed and 60 oak (Quercus sp.) piles were sampled and analysed by dendrochronology. Hierarchical cluster analysis was employed to group the tree-ring series from the piles according to their affinity, and three object chronologies representing different provenances were obtained. These were compared to a spatial network of archaeological and palaeo-ecological site chronologies from the Netherlands and Germany covering the Roman period. Our research revealed two construction phases in the harbour, which were built with wood from different geographical sources. The oldest phase, dating to ca. AD 160, consists of oak from the southeast of the Netherlands and southern Germany, whereas the second, more recent one, was built in or shortly after AD 205 with oak grown in the catchment basin of the river Mosel. Our results further suggest that scarcity of local timber resources was the reason for the import of wood for the quay at Forum Hadriani, and evidence that the Romans had established a well organised timber distribution network to supply wood over large distances already in the mid-2nd century AD.