Blue rings in trees and shrubs as indicators of early and late summer cooling events at the northern treeline

Agata Buchwal, Pawel Matulewski, Ylva Sjöberg, Alma Piermattei, Alan Crivellaro, Angela Balzano, Maks Merela, Luka Krže, Katarina Cufar, Alexander V Kirdyanov, Tatiana Bebchuk, Tito Arosio, Ulf Büntgen