Branch age and diameter: useful criteria for recognising woodland management in the present and past?

Abstract

When prehistoric archaeological sites yield non-carbonised wood, one of the ways to test for management practices consisting of pollarding and coppicing is analysis of branch diameter and age. However, the interpretation of such data is often based on assumptions. To test whether it is in fact possible to identify past woodland management on the basis of age/diameter analysis in archaeological wood assemblages, this paper presents models that predict the expected age and diameter distribution of branches from unmanaged and managed trees. The models have been tested using data on modern-day Alnus glutinosa, Fraxinus excelsior and species of the genus Salix. Branches of modern-day unmanaged and managed trees with a diameter up to approx. 2 cm (not an absolute limit) have a comparable age. Branches with a diameter of approx. 2–6 cm from unmanaged trees are older than similar branches from managed trees. The age distribution in the latter also ends abruptly. The age/diameter data from the modern-day trees indicate that the models can be used to discern management in the past, if branches up to approx. 2 cm in diameter are avoided and if, critically, taxon, sample size, growing conditions, natural disturbance/opportunistic wood collection and the possibility of diameter selection are taken into account. Archaeological datasets mainly from prehistoric sites are then reinterpreted by means of comparison with the models. Indications of management in prehistory as demonstrated by age/diameter are scarce but available. There is thus a clear need for further research in this field. Practical suggestions are provided for improving the quality of future research on woodland management practices by means of branch age/diameter analysis