These types of injuries result in an abrupt reduction of tree growth. Tree-ring analysis may reveal significant growth loss as an atypical series of narrow rings. Avalanche impact can tilt or uproot trees causing them to produce reaction wood to retain upright growth. In conifers, the reaction wood is produced on the downhill side of the stem. The reaction wood differs from normal wood by its thick, dense cells and dark, reddish-brown color.
Deciduous trees produce reaction wood on the uphill side of the tree.
The cells are long, and dense with a grey or yellowish color. Reaction wood formation also causes eccentric ring growth resulting in wider than normal rings. Counting rings from the bark inward to the year of initial reaction wood formation provides a reliable date for the avalanche event. New vertical stems may develop from release of lateral branches or dormant buds on the upper surface in response to tilting or stem breakage. Approximate avalanche dates can be determined from ages obtained from these new stems by counting the annual rings.