Frequency and factors of earlywood frost ring formation in jack pine (Pinus banksiana) across northern lower Michigan

Late spring frost disturbances have significant ecological and physiological impacts on forests. Frost-induced cambial damage that occurs when cells are actively dividing can result in the formation of frost rings, abnormal modifications to wood anatomy within the annual growth rings of an injured tree. Frost rings are indicators of growing season frost damage to the cambium and therefore have potential to be used both as a proxy in the reconstruction of extreme climatic events and to identify frost-prone environmental conditions. In this study, we measured the occurrence of earlywood frost rings across cambial age and diameter class in 11 jack pine (Pinus banksiana) populations of northern lower Michigan. Earlywood frost ring formation was greater in younger trees and in trees with smaller diameters. Biotic (cambial age, diameter, and ring width) and abiotic (elevation, initial site-related growth rate, and minimum temperature) factors demonstrated significant influence on the probability of earlywood frost ring formation. When using frost rings as a proxy of historical climate, susceptibility to abrupt freezing temperatures during the growing season and thus the ability of an individual tree to record a frost disturbance should be considered.