VS oscilloscope: A new tool to parameterize tree radial growth based on climate conditions
It is generally assumed in dendroecological studies that annual tree ring growth is adequately determined by a linear function of local or regional precipitation and temperature with a set of coefficients that are temporally invariant. However, various researchers have maintained that tree ring records are the result of multivariate, often nonlinear biological and physical processes. To describe critical processes linking climate variables with tree ring formation, the process based tree ring Vaganov Shashkin model (VS model) was successfully used. However, the VS model is a complex tool requiring a considerable number of model parameters that should be re estimated for each forest stand. Here we present a new visual approach of process based tree ring model parameterization (the so called VS oscilloscope) which allows the simulation of tree ring growth and can be easily used by researchers and students. The VS oscilloscope was tested on tree ring data for two species (Larix gmeliniiand Picea obovata) growing in the permafrost zone of Central Siberia. The parameterization of the VS model provided highly significant positive correlations (p 0.0001) between simulated growth curves and original tree ring chronologies for the period 1950 2009. The model outputs have shown differences in seasonal tree ring growth between species that were well supported by the field observations. To better understand seasonal tree ring growth and to verify the VS model findings, a multi year natural field study is needed, including seasonal observation of the thermo hydrological regime of the soil, duration and rate of tracheid development, as well as measurements of their anatomical features.