Influence of Climate and Age on Annual Shoot Increment in Salix Herbacea

(1) Shoots of the dwarf shrub Salix herbacea were collected from three alpine snow-bed sites in northern Sweden. Multiple regression analysis was used to examine the importance of shoot age, mean monthly temperature and precipitation in determining annual shoot increment. (2) Shoot age accounted for 39-48% of the within-shoot variation in length of the annual stem segments, which showed a logarithmic decline throughout the life-span of the shoot. (3) Climatic variables contributed little to the total variation in annual increment. However, temperatures during the intense snow-melt period (May and June) during the year before growth, accounted for about 80% of the between-year variation in two of the three samples. This suggests that growing season length limits the carbohydrate stores available for the following year's shoot increment.