Survival Response of Larix Sibirica to the Tunguska Explosion

Abstract The disastrous Tunguska explosion (TE) in 1908 uprooted trees in a radial pattern. Several trees in this area survived and kept growing in the post-Tunguska environment. We collected samples from surviving trees (14 and 131 years old at the time of the TE) that lived until collection in 2008 and another sample from a control tree farther from the blast epicenter (germination in 1928), which were analyzed by x-ray fluorescence (XRF) and prompt gamma neutron activation analysis. Chemical composition of xylem tracheids of the surviving trees revealed several patterns potentially related to the TE. A calcium peak is associated with the 1908 ring in both of the exposed trees, but additional high concentrations in adjacent rings could represent enhanced translocation of Ca over the whole sapwood as a response to defoliation from the TE. Sr and Mn anomalies near 1908 appeared in one exposed tree but not in the other. High-resolution XRF indicates Ca as well as Zn anomalies are primarily located in the earlywood of the rings, whereas peaks in Mn, Zn and Cu are more associated with the latewood. A directional response was evidenced by a wider zone of elevated Ca in the rings on the southern side toward the airblast, which might have experienced the greatest defoliation and perhaps enhanced root damage as the tree was rocked by the pressure wave. The TE event in the middle of the 1908 growing season must have triggered tree responses to deliver more nutritive resources to the crown in order to hasten restoring new leaves in the crown and to aid in structural repair.