8.1 Research Recommendations

Site-based Recommendations

Isotope dating provides a means for dating fast-grown wide ringed samples and non-oak species that may not normally be considered suitable for ring-width dendrochronology (Alcock and Miles 2013, Suggett 2005). As a consequence, they may not be sampled during a standard building assessment. It is important therefore that archaeologists and dendrochronologists consider these new dating opportunities and are trained how to best select samples when conducting initial surveys and assessments. Equally important for the understanding and conservation of Scotland’s cultural heritage is that historical wood samples are not discarded post excavation, but archived or offered for the development of isotopic reference chronologies given the challenges of dendrochronology in Scotland and the rapidly diminishing nature of this important resource. 

Isotope dendrochronology is commonly applied in cases where a sample returns multiple ring-width dates, or where timber samples have been dendrochronologically cross-matched into a site assemblage, but where this cannot be anchored in time. Similar applications have helped to refine construction phasing, and in certain cases, it has been possible to isotopically date samples that have been heavily pollarded or managed. As with ring-width dendrochronology, more informative results are obtained from multiple samples rather than from the analysis of a single timber alone.  

Research recommendation: Educate archaeological consultants, practitioners and heritage managers through production of a user guide and workshop on dendrochronology and (wiggle match) radiocarbon dating of wood (eg English Heritage 1998). 

Research recommendation: Ensure that valuable material is not thrown away, but archived. Where this may not be possible then it should be offered to the research community prior to disposal. Archival of and access to the diminishing supply of historic wood is essential to the future sustainable development of new dating methods and to an improved understanding of Scotland’s built and cultural heritage. 

Research recommendation: Include a requirement for dendrochronology and timber retention (pre-disposal) within all projects associated with national heritage bodies and embed this as a contractual requirement when tendering as appropriate.  

Place-based Recommendations 

Stable isotope dendrochronology, like ring-width dendrochronology, benefits from the analysis and combination of multiple timbers if the aim is to refine the construction phasing of a building or the evolution and development of site. This approach is exemplified at Llwyn Celyn, a Welsh medieval hall house, undateable through ring-width dendrochronology, but through isotope dendrochronology it was possible to reveal its origins, subsequent modifications and the addition of multiple phases of agricultural outbuildings (McCarroll et al 2019). Analysis of multiple samples has also been shown to provide confidence when working with non-oak samples and cross-dating short sequences (<50 rings) (Loader et al 2020b). 

Regional Recommendations 

Isotopic reference curves have demonstrated that they can date over a wider geographic range than ring-widths. In this way, it is possible to isotopically date samples for which there are no “local” ring-width data. Dating samples in this way can support the identification of a native from non-native timber and help support ring-width dendrochronology by fixing the dates of new sections of native ring-width reference chronologies for regions where a continuous chronology is lacking (Davies et al 2024). This approach is currently in use across southern Britain where a reference curve for the 1st millennium AD is being developed with support from dendro-dated samples from Ireland and Belgium. Here the “exotic” timbers provide a temporary framework for chronology development for a period and location where timbers are scarce and ring-width dating more challenging due to the limited number of well-replicated reference chronologies. 

Where a well replicated reference curve is not yet available then isotope dendrochronology can still be used successfully to securely date timbers from within a structure and study region. Whilst the statistical framework differs slightly when working in this way, it can prove an effective approach to dating that can also provide proof of concept to underpin future development of a regional reference chronology. This has recently been successfully applied to samples from the Basque region (Northern Spain) to provide the first precise felling dates for oak and beech timbers used to construct the Newport Medieval Ship (Nayling et al 2023, 2024).   

Research Recommendation: Establish the isotopic coherence of dated native oak sampled from dendrochronologically-dated buildings and sites across Scotland. This is most easily evaluated using dendrochronologically-dated timbers that overlap in time. Where isotopic coherence is strong, these may then be combined to form a local chronology and feed directly into an evolving regional reference chronology. In doing so these initial data would also help to advance community awareness of dating historic buildings with a view to its wider application in less-represented parts of Scotland. 

Strategic and Overarching recommendations

Key to the sustainable development of stable isotope dendrochronology and its extension into Scotland is the development of well-replicated reference chronologies. With support from the heritage sector and dendrochronology community, an initial reference chronology (10 tree replication 1200-present) could be developed rapidly and efficiently with the first dates within about a year. Such an undertaking could initially take the form of a regional “Northern UK” chronology in partnership with bodies such as Historic England to enable initial applications in Scotland that will ultimately lead to a more regionalised approach. There are collaborative funding opportunities to enable this work through UK Research and Innovation (UKRI), but funding through these sources is highly competitive and chances of success would be greatly enhanced through meaningful partnership with the heritage and university sectors.

Research requirement: Develop a well-replicated reference chronology for Scotland and Northern England AD 1200-2000. This can best be achieved in partnership with local stakeholders providing access to samples and in collaboration with existing isotope dating laboratories. The priority should be oak as this is where need is greatest.  

Research recommendation: Conduct an audit of dated and undated samples, buildings and structures with a view to reviewing their potential for stable isotope dating. Revisit sites and samples to rapidly evaluate the application of isotope dating in Scotland and to gain new insight and information on Scotland’s heritage and timber use through time.  

Research recommendation: Establish a national database comprising dendrochronological data, structural assessments, scanned images of samples and reports.  

Research recommendation: Establish a national resource (timber library) through National Museums of Scotland where the collection is overseen by a working committee and National Lead on historic dendrochronology. Initial funding could be sought through UKRI but it would need the long-term backing and support of the Scottish Heritage sector. 


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