Effects on growth of simulated and induced shoot pruning by Tomicus piniperda as related to carbohydrate and nitrogen dynamics in Scots pine.
In a field experiment in central Sweden, shoots of 20-year-old Scots pine (Pinus sylvestris) were hand-pruned in 2 series, 1 with non-fertilized trees and another with fertilized trees, and in a 3rd series, by inducing Tomicus piniperda attacks on non-fertilized trees. The prunings, in 4 degrees of severity, were made in late summer; pruning by hand simulated attacks of the beetles. Starch and nitrogen concentrations in remaining and new needles were monitored. The small and transient effect on stem growth 2 and 4 years later of even severe pruning is discussed in terms of compensatory mechanisms. These may be the result of an improvement in nitrogen status and an increased photosynthetic capacity of remaining and new needles, making possible a rapid restoration of needle biomass and, hence, growth.