Tree rings are a key terrestrial archive providing insight into past climatic conditions at annual resolution and from local to hemispheric scales. Tree ring proxies are also important indicators of plant physiological responses to changing environmental conditions and further our understanding 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 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 (CSIA), (iii) quantitative wood anatomy, (iv) sapflow, dendrometer and related monitoring data analyses, and (v) mechanistic modeling, all at different temporal and spatial scales.