Four levels of patterns in tree-rings: an archaeological approach to dendroecology

This paper introduces a method detailing how tree-ring data from subfossil and archaeological wood can be interpreted in palaeoecological terms. On the basis of a literature review concerning the effects of known impacts on tree growth, an attempt is undertaken to provide a general theoretical framework for structuring and interpreting non-recent data where the ecological context is usually missing. The most important tools are dendrotypology and the systematic analysis of tree-ring patterns on four levels. These levels are: (1) ring-anatomical patterns; (2) impact patterns in ring width series at the single-tree level; (3) stand-dynamic patterns, i.e. patterns in ring width series on a stand-wide level; (4) complex patterns that are made up of consistent combinations of the other three pattern levels with each other or additional information. The distinction of these patterns allows the disentangling of different sources of influence on tree growth, which can also potentially be applied to archaeological wood. Several types of reaction to different categories of impact are defined. On a stand-wide scale, the phases of stand development can be reconstructed by identifying characteristic combinations of events. Thus, the range of possible interpretations can be narrowed down to a few possibilities, and sometimes only one. While the general concept is thought to be applicable to a wider range of regions and ecological settings, the presented discussion focuses on gap-phase dominated lowland forests and anthropogenic stands derived from such, which form the focus of central European dendroarchaeological research.