EFFECTS OF CROWN REDUCTION ON NEEDLE NUTRIENT STATUS OF SCLERODERRIS-CANKER-DISEASED AND GREEN-PRUNED SCOTS PINE

The effects of green crown reduction (needle loss) on the nutrient sta tus of needles were studied in Scots pine (Pinus sylvestris L.) in Fin land. Trees were either diseased with scleroderris canker (Gremmeniell a abietina (Lagerb.) Morelet) or had been green pruned. The concentrat ions of 15 different elements were determined in needles collected in March 1987 from 120 trees in six young Scots pine stands. Four of the stands had suffered from scleroderris canker over the last 10 years, w hereas the other two stands were healthy and had been pruned about 2 y ears before sampling. To eliminate the effects of soil and environment al factors, sample trees were chosen in pairs. Each pair contained one tree with a severely reduced crown (about a 50% reduction in crown le ngth as a result of disease or pruning) and an adjacent tree (control) with an unaffected crown. Compared with the control trees, concentrat ions of foliar B, Ca, N, and S were significantly higher in both disea sed and pruned trees, while Mn was higher only in diseased trees and N a and Cu, only in pruned trees. Foliar Fe and Mg concentrations were l ower in diseased trees than in control trees. In many stands there was a significant correlation between needle element concentrations and s everity of crown reduction, suggesting that differences in foliar elem ental concentration in Scots pine needles depend on the extent of crow n reduction. This phenomenon should be considered when interpreting fo liar analyses of recently defoliated conifers, particularly before con clusions are made about the need for fertilization, nutritional distur bances, or the effects of air pollution.