Use of false rings in Austrian pine to reconstruct early growing season precipitation

As a consequence of dry conditions, coniferous trees may produce radially s maller diameter tracheids within their tree rings before regular latewood f ormation starts. The resulting structures, which are commonly called false rings, have demonstrated utility as an environmental indicator. However, th e climatic patterns behind false rings and their potential use in climate r econstruction models have been barely explored. The study is based on 313 A ustrian pines (Pinus nigra Arn.) sampled at 29 sites in the Viennese basin, an area with low annual rainfall, extended dry periods during the growing season and usually severely cold winters. False rings relate significantly to May precipitation, and in years with higher false-ring proportions, a re lationships with the combination of wet April, dry May, and wet June is oft en seen. In linear regressions, the presence-absence of false rings was use d as a "dummy" variable and, together with earlywood width, explained 31% o f variation in May precipitation. Years with high false-ring proportions we re found when May precipitation was less than half its long-term average. F alse-ring trends during the past 100 years were closely associated with cha nging May rainfall pattern. Overall, false rings are shown to be a useful t ree-ring feature and may be applied successfully in dendroclimatic studies, i.e., in the reconstruction of very low rainfall months in early growing s easons during pre-instrumental periods.