Tree rings are a key terrestrial archive providing insight into past climate conditions at annual and intra-annual resolution and from local to hemispheric scales. Tree ring proxies are also important indicators of plant physiological responses to changing environments and of long-term ecological processes. In this broad context we welcome contributions using one or more of the following approaches to either study the impact of environmental change on growth and physiology of trees and forest ecosystems or to assess and reconstruct past environmental change: (i) traditional dendrochronological methods including studies based on tree ring width and density, (ii) stable isotopes in tree rings and related plant compounds, (iii) dendrochemistry, (iv) quantitative wood anatomy, (v) sap flow, dendrometer and related monitoring data analyses, and (vi) mechanistic modelling, all at different temporal and spatial scales.