Ecological interpretation of tree-ring width and intraannual density fluctuations inPinus sylvestrison dry sites in the central Alps and Siberia

The radial growth of Pinus sylvestris L. from nine sites at the semiarid lower forest border of the central Alps (Switzerland) and central Siberia (Russia) has been investigated using dendroecological methods. Tree growth differed according to soil substrate, with trees on dune sites showing lower mean ring widths, lower mean sensitivities, and higher autocorrelation. The relationships between climate and tree-ring width were studied using response function analysis. Independent of the climatic zone and the soil substrate, precipitation just before and at the beginning of the growing season is positively correlated with radial growth. The climatic response of dune sites is low, possibly because of the poor water-holding capacity and the high permeability of the sandy soils. Intraannual density fluctuations (IADFs) were observed at all the sites. Most IADFs were found in latewood. On dunes, fewer cores contain IADFs, and their frequency is lower. All stands showed significant relationships between IADF frequency and tree-ring width (positive) and ring age (negative). For Swiss sites, moist-cool conditions in the middle of the growing season are demonstrated as the triggering factor for IADFs. For the Russian sites, inadequate climatic data made it impossible to demonstrate any climate dependence of IADFs.