Nutrient availability in Corsican pine stands in the Netherlands and the occurrence of Sphaeropsis sapinea: a field study.
Soil and foliage samples were collected in spring and early summer 1986 in 13 Corsican pine (Pinus nigra subsp. laricio) stands heavily affected by Sphaeropsis sapinea [Diplodia pinea] (trees displayed severe shoot blight, with dead branches and crown wilt also observed) and in 16 stands slightly affected by the fungus in the Peel area, southern Netherlands. Infected trees contained significantly more foliar nitrogen and phosphorus than healthy trees. Soil samples from infected and healthy stands displayed many significant differences in extractable nutrients; ammonium and phosphorus contents were both greater in infected stands. Most of the additional foliar nitrogen in infected stands was stored in free amino acids, especially asparagine, glutamine, lysine, histidine, arginine and proline. Glutamic acid was the only amino acid with reduced contents in infected trees. Results are discussed in relation to other studies on D. pinea.