ACUTE AND LONG-TERM EFFECTS OF IRRADIATION ON PINE (PINUS-SILVESTRIS)STANDS POST-CHERNOBYL

The effect of ionizing irradiation on the viability of pine stands aft er the fallout from the damaged nuclear energy plant at Chernobyl (ChN PP) was shown within the territory of the 10-km zone. During the perio d 1986-1991, irradiated and damaged forest stands, so-called 'red fore st', located in this area were systematically classified by observatio n. Mortality rate, re-establishment, development of tree canopies, rep roduction anomalies and stand viability were shown to be dependent on absorbed irradiation dose, on the age of the stand and on forest compo sition. For pine stands in the acutely affected zone, doses of more th an 60 Gy resulted in a massive mortality and no regeneration of pine t rees since 1987. The injured trees had burned or had dried-up. The dry ing process was accelerated by a massive production of pathogenic inse cts invading the dying trees. Specifically, irradiation doses of 10-60 Gy, 1-10 Gy and 0.1-1 Gy caused high, medium and low injury to the fo rest stands, respectively. Doses of less than 0.1 Gy did not cause any visible damage to the trees. In 1987, repair processes were displayed by the tree canopies and practically the entire viability of the fore st stands had recovered except for trees in the acute and highly affec ted zones. The young forest was reestablished in the same place as the perished trees and new pine saplings were planted on the reclaimed ar eas.