Effects of early and late season defoliation on growth and carbohydrate dynamics in Scots pine.
Abstract
In a Swedish experiment, 18-yr-old Scots pine were defoliated by hand in early and late summer, simulating different degrees of insect grazing on the youngest or the two youngest needle year-classes on each occasion. Significant negative effects were found on stem annual ring width, shoot length, needle biomass and number of buds. More severe effects were found when two needle-year classes were removed compared to one, and when current-year and 1-yr-old needles were removed in late season compared to 1-yr-old and 2-yr-old needles in early season. The build-up of starch reserves in the needles of defoliated trees was less than normal and the reserves more rapidly drained, especially in trees defoliated in late season. From authors' summary.