Рубрики:
LIGHT RINGS
WOOD STRUCTURE
CATASTROPHE
EXPLOSION
QUEBEC
CANADA
Кл.слова (ненормированные):
Tunguska event, June 1908 -- tree rings -- deformed tracheids -- pressure on trees
LIGHT RINGS
WOOD STRUCTURE
CATASTROPHE
EXPLOSION
QUEBEC
CANADA
Кл.слова (ненормированные):
Tunguska event, June 1908 -- tree rings -- deformed tracheids -- pressure on trees
Аннотация: We analyzed tree rings in wood samples collected from some of the few surviving trees found close to the epicenter (within 4-5 km) of the Tunguska event that occurred on the last day of June 1908. Tree-ring growth shows a depression starting in the year after the event and continuing during a 4-5-year period. The most remarkable traces of the event were found in the rings' anatomical structure: (1) formation of "light" rings and a reduction of maximum density in 1908; (2) non-thickened tracheids (the cells that make up most of the wood volume) in the transition and latewood zones (the middle and last-formed parts of the ring, respectively); and (3) deformed tracheids, which are located on the 1908 annual ring outer boundary. In the majority of samples, normal earlywood and latewood tracheids were formed in all annual rings after 1908. The observed anomalies in wood anatomy suggest two main impacts of the Tunguska event on surviving trees-M defoliation and (2) direct mechanical stress on active xylem tissue. The mechanical stress needed to fell trees is less than the stress needed to cause the deformation of differentiating tracheids observed in trees close to the epicenter. In order to resolve this apparent contradiction, work is suggested on possible topographic modification of the overpressure experienced by these trees, as is an experimental test of the effects of such stresses on precisely analogous growing trees.
WOS,
Scopus
Держатели документа:
Univ Arizona, Tree Ring Res Lab, Tucson, AZ 85721 USA
Russian Acad Sci, Siberian Branch, VN Sukachev Inst Forest, Krasnoyarsk, Russia
Russian Acad Sci, Inst Monitoring Climat & Ecol Syst, Siberian Branch, Tomsk, Russia
Доп.точки доступа:
Vaganov, E.A.; Hughes, M.K.; Silkin, P.P.; Nesvetailo, V.D.