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

1 The work examines the growth and photosynthesis of saplings and matu re trees of Pinus sylvestris L. along an altitudinal gradient in the C airngorm Mountains of Scotland. 2 Meristem temperatures of seedlings d eclined with altitude, but an especially sharp decline was sometimes o bserved at the tree-line. 3 Growth, measured as shoot length, needle l ength and needle (fascicle) number, declined with altitude. 4 Extensio n growth could be related to temperature using regression analysis. Ho wever, the number of fascicles formed in a given year was related to t he temperature of the previous summer. 5 Substantial losses of first-y ear 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.