The paper concerns relationship between climatic factors and annual ring indices mainly in Southern Finland. The studied index series were from papers of different authors and from different localities. The monthly mean temperatures and precipitation sums were derived from the measurements of meteorological stations. Effective temperature sums for different periods of the year were calculated from the monthly mean temperatures.

The autocorrelation functions were estimated for each index series. The autocorrelations at lag I were significant except for one series. Altogether the differences in the structures of the index series were noticeable, especially between the Scots pine (*Pinus sylvestris* L.) index series. The influence of climatic factors on the annual ring index variation was studied using cross correlation analysis, simple distributed lag models and transfer function-noise models.

The decisive factor for the annual ring index variation of Norway spruce (*Picea abies* (L.) H. Karst.) appears to be the effective temperature sum of the growing season. Warm periods during latter parts of previous summer had a negative effect on indices. For the variation of the Scots pine indices the most important climatic factors were the effective temperature sum of the latter part of the growing season and, especially on the arid sites, the precipitation sum during May-July.

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