Winter seems to have come early to the Adirondacks, as below zero temperatures and periodic bouts of measureable snowfall have been a part of our weather pattern since the last few weeks of November. The arctic air that has regularly swept across the region has made a sizeable dent in everyone’s wood pile, placed a strain on car batteries and forced many to wear Christmas sweaters on a daily basis.
The intense cold has also pushed the frost line down in numerous spots, which greatly impacts the existence of those creatures that attempt to survive this season by burrowing into the soil. It is difficult to determine how deep the frost line has advanced, as this critical feature of the winter environment varies greatly from one spot to another.
The frost line is the depth at which water molecules suspended in the soil freeze, creating a solid, impenetrable layer of material that is fatal to many lower forms of life. This is why many organisms sensitive to freezing conditions try to get as far down into the dirt as possible during the autumn so as to remain below this hardened zone of ice, sand and other soil components.
Unlike the layer of ice that forms on a body of water, the frost line is not uniformly thick. Rather, the thickness of this surface barrier varies greatly, depending on the localized surface features in the area and on the amount of snow that has accumulated at that site. In wind swept locations, such as along the windward shore of a lake or pond, the top of a mountain ridge, or an open meadow regularly buffeted by strong breezes, snow depth is often substantially less than in sheltered spots, thereby allowing the cold to more easily penetrate the ground. In places where snow frequently drifts, the insulating effect of this powdery material can prevent the soil’s heat from radiating to the atmosphere, which helps maintain only a shallow layer of frost in the ground.
While fluffy snow is ideal insulation, this light weight crystalline precipitation may fail to reach the ground in dense stands of conifers. At this time of year, evergreen trees, with their boughs laden with a thick white coating, are the picture of a winter wonderland, however a hike through a softwood forest reveals that the amount of snow on the ground is substantially less than in a close by stand of open hardwoods. Also, because many evergreen woodlands develop in lowland locations where cold air settles, the frost line can be much deeper in these snow covered woods compared to other areas.
It is believed by some naturalists that creatures sensitive to freezing temperatures instinctively seek out settings in which the frost line is not likely to develop very deep as they prepare for the coming winter. Most wasps, ants, and native species of bees, along with many types of beetles and grubs, worms and other invertebrates, some forms of salamanders and a few types of snakes have not evolved the cold hardy body chemistry capable of surviving freezing temperatures, like the snow flea, the wood frog, spring peeper and garter snake.
Animals intolerant of freezing conditions can sometimes survive in the Adirondacks by burrowing into south facing slopes where snow often drifts, causing the frost line to remain close to the surface. Depressions in the ground where dead leaves accumulate in autumn create an insulating layer of organic debris that can limit the frost from penetrating too far, as can the soil beneath a massive, decomposing log. In residential settings, the soil around the foundation of a house often remains just above freezing throughout the winter regardless of snow and temperature conditions. This is why there is always mole activity during the winter near my house, as this small subterranean mammal inevitably feasts on the collection of bugs lured to the thawed dirt just outside my basement.
Just as there is a world of activity beneath the surface of the snow in winter, there is a similar zone of life under the frost line throughout the winter. Because of the extreme difficulty in gaining information on the abundance of the life forms that occupy this area, their movements during this season, and the dynamics that occurs between these organisms, not much is known about life below the frost line. It is often a challenge to gain information on the daily habits of many creatures that live above ground, especially those that shy away from human presence. Gathering data on the interactions that routinely occur below the soil’s surface is even more difficult, and when the top layer of soil develops a concrete hardness, that challenge becomes even more impossible. Yet there are a few researchers that are gaining some insight into the working of nature below ground at this time of year.
The soil is an integral part of our natural world and understanding what occurs within it and below it, even during winter, is important in getting a more complete picture of nature here in the Adirondacks.