Multiproxy dendroclimatology: a pilot study in northern Finland

Ten potential proxy measures of past climate were recovered from Scots pine ( Pinus sylvestris) at three sites on a latitudinal transect close to the pine limit in northern Finland (earlywood, latewood and annual ring width; earlywood, latewood and maximum density; stable carbon isotope ratio; height increment; needle production; pollen deposition). Cambium dynamics were also monitored. The aim was to determine how climate influences each potential proxy and to decide which proxies are potentially useful for reconstructing climate. Height increment, needle and pollen production are strongly influenced by the temperature of the previous July, which is when the bud forms, but needle and particularly flower development may also be influenced by spring frosts. Maximum and latewood densities provide proxies of net photosynthesis. delta(13)C is controlled mainly by summer sunshine, reflecting the influence of photon flux on photosynthetic rate, and moisture stress which reduces stomatal conductance. By combining proxies, the strength of climate correlations is increased and the range of extractable parameters extended. The multiproxy approach provides a powerful means of extracting climatic information from long tree-ring chronologies.