n. The layer above the soil and below the snowpack that serves as a winter refuge for many species.
The small area between the snowpack and the ground, called the subnivium (from the Latin nivis for snow, and sub for below), might be the most important ecosystem that you have never heard of.
— Kimberly Thompson, “Beneath the snowpack lies a secret ecosystem: the subnivium,” Aeon, May 31, 2016
With the heavy snow starting in mid-January, I predicted the critters of the subnivium would have an easy time of munching on the garden shrubbery, and that certainly came true, at least in our area.
—Fred Gralenski, “Quoddy Nature Notes (4/20/15),” The Middleton Stream Team, April 20, 2015
Two key features help the subnivium support its tenants: temperature stability and air pockets that give animals a little breathing room.
—Eleanor Nelson, “A Hidden World Thrives Below the Snow,” Quest, April 03, 2014
2013 (earliest)
Previous authors have described the “subnivean space" or "subnivean environment" as the interface between the soil and snow (Halfpenny and Ozanne 1989) and the environment under snowpack (Marchand 1996); here, we coin the term "subnivium" to describe the "below snow" seasonal refugium because it provides environmental stability and serves as a habitat to which species can retreat to during changing environmental conditions.
—Jonathan N Pauli, et al., “The subnivium: a deteriorating seasonal refugium,” Frontiers in Ecology and the Environment, June 01, 2013
The subnivium: "nature's igloo". Source: National Science Foundation