Which environmental factors can be analyzed using tree rings?
Long-living trees can archive long-term climate changes, but also short-term weather extremes by their growth responses and adjustment in wood anatomical structure. The variations in the width of tree rings and other wood parameters react differently to various environmental factors, depending on species and location. At cold-humid high-elevation sites, tree-ring width is often correlated with temperatures during the winter months before the growth phase, or with the mean temperature during the vegetation period. In contrast, tree growth in semi-arid mountainous environments is mainly limited by the available moisture conditions during the growing season. The maximum late wood density is a good indicator to reconstruct summer temperatures, while the isotopic variations of oxygen and carbon in tree-ring cellulose are sensitive to hydroclimatic climate parameters and evaporation. Quantitative analyses of the wood anatomical structure allow an extremely high temporal resolution of the stored climate information down to a few days. By combining several wood parameters with different seasonal sensitivities, a comprehensive reconstruction of the climate during the course of the year can be accomplished. Thus, tree-ring data can also be compared with other climate proxies, such as ice cores, lake sediments or runoff data, but additionally offer the advantage of an exact, year-accurate dating. In high mountain areas, this offers the opportunity to analyze landscape dynamic processes such as glacier fluctuations and geomorphological events using tree-ring data. With the help of long-living shrub species, tree-ring analyses can be extended into the alpine region above the tree-line