NEEDLE RETENTION AND NEEDLE LOSS OF SCOTS PINE IN RECENT DECADES AT THETFORD AND ALICE-HOLT, ENGLAND

Fourteen Scots pines (Pinus sylvestris L.) were felled in Thetford and Alice Holt forests, southern England, for needle retention studies. I n the field, the main stem of each tree was divided into annual sectio ns, with each section being reduced to 30 cm long bolts or less, omitt ing branch whorls and using the internodal part of each annual shoot. The bolts were then planed one annual ring at a time to reveal the loc ation of needle traces. In the summers of 1950-1990, the average needl e retention was 2.6. Average needle retention varied annually from 1.5 to 3.3. There was a slight reduction in needle retention following hi gh values at the end of the 1960s, and this accelerated during the 198 0s. Needle retention history was similar at both Thetford and Alice Ho lt. The amount of annual needle loss varied between 0.3 and 1.6 needle sets, and the 40-year average of 1.02 sets indicated a long-term redu ction in the number of needle sets during the lifetime of the trees.