Tree-ring studies on conifers along ecological gradients and the potential of single-year analyses

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Abstract
Cores from conifers growing in four different climatic regions were analyzed using radiodensitometric methods. All the sites are located along altitudinal gradients between the subalpine timberline and low elevations, in some regions the arid tree line. At each of the elevation levels considered, the soil conditions range from as shallow and dry as possible to deep and moist. Various dendroecological methods were applied to determine the relationships between tree-ring growth, climatic conditions, site elevation, and site characteristics. The dominant mode of linear response between ring growth and the monthly temperature and precipitation variables was identified using response functions. A new graphical method permitted a year for year description of the complex and often nonlinear responses of tree-ring growth to the limiting factors. This is a departure from different statistical approaches that measure the most dominant relationships for a population of many years. The described single-year method is suited to analyze time-dependent growth phenomena. Typical cases of single-year responses are illustrated and the dynamics of the overlapping environmental influences are discussed. The broad spectrum of sites was used to identify ring parameters and site types most suitable for reconstructions of temperature or precipitation records.