Relating Roman Rings: An interdisciplinary study using archaeology, data science and tree rings to understand timber provision in the German Provinces of the Roman Empire

This study examines wood and dendrochronological data from the Lower Rhine region during the Roman period. The Roman period brought many changes to the region, including its integration into a large-scale economy with long-distance transport of goods. Wood was a critical resource in the Roman economy, yet its production and distribution remain poorly understood. Based on the development of dendroprovenance research, three understudied aspects are distinguished: 1) the focus on single objects rather than multiple objects from large regions; 2) methods, measures and visualisations for a big data approach are lacking and; 3) dendroprovenance studies for the Roman period are lacking. This research is mainly based on legacy data. The analyses of data is as open and reproducible as possible, following the Open Science principles. The data used consist mainly of archaeological, dendrochronological and spatial data, in combination with historial, epigraphical and other data. The large volume of data in combination with varying temporal and spatial distributions defines the data as sparse big data. In this study the possible applications of silvicultural systems in the Roman period are discussed. Sufficient knowledge and skills were available in the Roman period for the application of silviculture. Evidence was found for four silvicultural systems: clear cutting, selection, coppice and agroforestry. Based on dendroarchaeological data various patterns are discerned. The study of the dendrochronological material from wood that was used to build a road along the limes in the Netherlands leads to new insight. The wood was felled in a single season (in 124-125 AD) and obtained from a woodland in the region between Rhine and Meuse and transported over 100 kilometres. This road can seen as Hadrians’ Road. Other cases include wood used in several regions in the Netherlands in different periods. A model is presented showing three spheres of wood procurement. Local wood procurement seems to have been most common. For large-scale military infrastructural works wood was procured within the province. For special purposes, wood was obtained beyond the boundaries of a province (imperial sphere). Various new methods were developed for dendroprovenance. The Gleichläufigkeitskoeffizient (GLK) is an often used non-parametric similarity measure and based on growth changes of subsequent tree rings. This measure has some issues, which are solved with the newly developed synchronous (SGC) and semi-synchronous growth changes (SSGC) to replace the GLK. A novel method is presented for the analysis of large datasets of dendrochronological material in relation to the provenance. Networks of tree-ring material are created using relations determined by statistical similarity. A combination of archaeological, network and spatial arguments is used to estimate the provenance of wood, leading to new insights. The network approach is also applied on the dendrochronological measurements from several Roman barges, combining dendrochronology with network science and spatial analysis to determine the provenance of wood from river barges. This made it possible to estimate provenance and to understand building practices. A strong relation between shape and function was attested, probably related to attributes of wood with certain growth conditions. Two barges were probably built in the same shipyard. Wood was locally obtained for shipbuilding, but also in Gallia Belgica and Germania Superior. Complete trees were most likely loaded on barges and transported over the Rhine and Meuse. Wood is only preserved if the right conditions are met. The exceptional conditions in the research region, makes wood the archaeological ‘gold’. Local wood procurement was the rule and long-distance transport the exception in the Roman period. The open science approach by combining network science, data science dendrochronology and archaeology is a powerful way to understand patterns in the Roman timber economy.