GROWTH AND PHOTOSYNTHESIS OF PINUS-SYLVESTRIS AT ITS ALTITUDINAL LIMIT IN SCOTLAND

1 The work examines the growth and photosynthesis of saplings and mature trees of Pinus sylvestris L. along an altitudinal gradient in the Cairngorm Mountains of Scotland. 2 Meristem temperatures of seedlings declined with altitude, but an especially sharp decline was sometimes observed at the tree-line. 3 Growth, measured as shoot length, needle length and needle (fascicle) number, declined with altitude. 4 Extension growth could be related to temperature using regression analysis. However, the number of fascicles formed in a given year was related to the temperature of the previous summer. 5 Substantial losses of first-year needles were observed over the winter. 6 In the early part of the year, photosynthetic performance in the valley population was superior to the tree-line population, both in the current- and previous-year's needles. 7 The results are discussed in relation to the likely impact of increasing temperatures on the productivity of the species.