Abstracts

In 1991 core samples of wood (213 trees) were collected at 15 localities of the 1908 Tunguska Event to investigate the tree radial growth. Six localities were situated in the central area of forest levelling within 6-14 km of the epicentre of explosion, three localities within 22-26 km to the east of the epicentre and the other one within 17 km to the south-west of the epicentre. In addition, samples were taken for comparison purposes at five localities outside the area of tree levelling within 35-60 km to the south of the epicentre of explosion. This paper gives the results of the investigation on the radial growth pattern in trees of the Chekanovsky larch (Larix × czekanowskii Szag.) (Kropachinsky, Votovskaya, 2002) and common pine (Pinus sylvestris L.). In the central part of the region of the Tunguska Event, samples of the pre-explosive generation show the reduced growth duration between 2 and 20 years, beginning in 1909. For the majority of the trees the reduced growth continued over a period of 3 to 5 years. As seen from the radial growth site chronologies constructed for each locality, the depth and duration of the post-event growth depression are reduced away from the epicentre. Immediately after the event the growth even increased over three areas under investigation along the eastern boundary of tree levelling. This is obviously related to better growing conditions owing to partial tree levelling and the fact that the trees were not scorched with fire. The first investigators noted a significant increase in the radial growth rate of trees in the central part of the region of the Tunguska Event occurred just after the growth depression (Emelianov, Nekrasov, 1960). Our comparison between the maximum growths in survived trees and those which came to being after the event does not revealed any abnormal growth in trees of the post-explosive generation. Thus, for example, the maximum radial growth in larches found within 6 km to the south and south-west of the epicentre during the first years of their life early in the 18th century was quite the same as in larches of the post-explosive generation during the first years of their life early in the 20th century. At another locality situated within 10.5 km to the south-east of the epicentre, a single survived larch displayed a three to fourfold increase in its growth by 1920 after a minimum growth in 1909-1915 associated with the damage of the tree. Another larch of the post-explosive generation found at the same locality also displayed a three to fourfold radial growth after all the adjacent trees being cut in 1986. In other words, the increased growth effect owing to forest stand thinning after the explosion coincided with the same effect owing to forest cutting. A similar conclusion about the absence of the abnormally great growth in the central zone of tree levelling was also made by Nesvetailo (1990, 1993).

Note. Abstracts are published in author's edition

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© 1996-2000, Siberian Branch of Russian Academy of Science, Novosibirsk