Tree-ring blue intensity measurements from treeline sites in the Ural Mountains exhibit a strong summer temperature signal

Abstract

The high northern latitudes offer an ideal environment to analyze tree growth responses to unprecedented recent warming. In this study, for the first time, we explore the dendroclimatological potential of latewood blue intensity (LWBI) and delta blue intensity (DBI) at two Siberian larch (Larix sibirica Ledeb.) sites in the upper treeline ecotone of the Ural Mountains, northern Russia. To assess the climate signals encoded in LWBI and DBI, as well as tree-ring width (TRW) and maximum latewood density (MXD), we correlated these parameter-specific chronologies against monthly temperature means, precipitation totals, and the SPEI index. LWBI and BDI exhibit robust and stable positive correlations with summer temperature, higher than TRW but slightly lower than MXD at both sites, with marginal negative effects from precipitation and strong negative correlations with SPEI. As direct surrogates for MXD, LWBI and DBI from larch trees offer reasonable alternatives as proxies for temperatures in northern latitudes.