Frost hollows of the boreal forest: a spatiotemporal perspective

1. Frost hollows (FH) are small, confined lichen-dominated ecosystems surrounded by lichen woodlands. FH are impacted by repetitive frosts occurring during the growing season. We evaluated the dynamics of FH across the boreal forest in eastern Canada and assessed the influence of latitude as the main geoclimatic factor controlling their development. 2. The distribution and abundance of FH along 39 longitudinal transects were based on aerial photographs and field validation. Black spruce (Picea mariana) in FH and adjacent woodlands were sampled for age determination, year of tree establishment, height growth rate of spruce, and intensity and frequency of frost rings. 3. Most FH are located in the southern part of the boreal forest, in depressions bordered by dry, open, lichen woodlands. The inception and development of FH are not dependent on latitude but rather on the presence of lichen woodlands. Frost-induced thúfurs and frost rings were more frequent and abundant in the southernmos...