New results have been obtained in the study of the so-called light, clear or friable rings in the wood of surviving conifers. We have shown that the rings with anomalously clear autumnal wood are present on a greater territory than previously thought and that, contrarily to what written by some authors, they are found not only in larches, but at least in all the kind of conifers present in the Tunguska explosion site: larches, spruces, pines (see paper pdf and Figure).
The reduced lignification in the months following the catastrophe is seen here on the 1908 tree ring of a Siberian spruce (third ring from the bottom of the figure). Defoliation, as a consequence of the explosion damage and heat, is responsible for the thinnest 1909 growth ring. From 1910 the accelerated tree-ring growth is observed (see also Figure).