PP21B-1977: Widespread locally-absent rings in tree-ring records across the Northern Hemisphere during the last millennium
Authors: Scott St George1, Toby Ault2, Max Torbenson1
Author Institutions: 1. Department of Geograpy, University of Minnesota, Minneapolis, MN, USA; 2. Advance Study Program, National Center for Atmospheric Research, Boulder, CO, USA
Under environmental stress, boreal and temperate trees will occasionally form an discontinuous layer of wood about their stem, a condition known as a locally-absent (or ‘missing’) growth ring. Here we present a synthesis of locally-absent rings across the Northern Hemisphere during the last millennium based on more than 2,300 tree ring-width records. Over the entire dataset, the ratio of absent rings to visible rings is 1:240, and more than half of all records do not contain a single absent ring. Absent rings form frequently in Pinus and Psuedotsuga, occasionally in Larix, and very rarely in Quercus and Picea. They are extremely uncommon in high-latitude records (poleward of 50 °N), where the absent:visible ratio is 1:2,500. Missing rings were not either intensive (present within a majority of specimens from a single record) or widespread (cases where a large fraction of available tree-ring records included one or more specimens without a ring) during the growing seasons that followed major volcanic eruptions, including AD 1259 and 1816. During the last millennium, widespread absent rings have been observed only in the southwestern United States and were associated with severe drought rather than low growing-season temperatures or other stressors.