One is an icon of the holiday season. Another releases a sticky sap that was used to make America's first chewing gum. Still another spreads majestically throughout the Appalachian mountains as far south as Alabama, and due to its common name, is sometimes confused with a classical poison. These "usual suspects" of our winter landscape here in the White Mountains (Balsam fir, red spruce and eastern hemlock, respectively) are all tree species that are members of a fascinating plant group: the evergreen conifers. Among many other defining characteristics, these trees are easily identified by green to dark-green needles protruding from slender branches that are not dropped in winter. Because of this, evergreen conifers are the poster children for a northern New Hampshire forest; when you conjure up an image in your mind of the north woods in winter, what do you see?
What is most fascinating about trees such as the Balsam fir and red spruce is simply their puzzling presence in the winter landscape. What makes these trees so hardy? And why on earth would they keep their leaves in winter, when it is almost always too cold to photosynthesize? And wait....why are they not covered in several inches of snow following a storm?
The answers to these questions can be found in a wide array of peculiar and subtle adaptions of the evergreen conifers. Remember those slender, flexible branches to which the needles are attached? When a significant weight of snow builds on top of them, they will eventually bend downward enough to shed nearly all of the snow! This adaptation helps to reduce snow and ice damage to the branches through a rough winter. Another crucial adaptation of these trees to winter survival is their expansive growth range; evergreen conifers can live and thrive in very nutrient-poor soils, such as those on the higher slopes of the Presidentials.
Ultimately, their most important adaptation of all, and the explanation for retaining their needles, comes down to a basic lesson in plant economics. During an average winter in New Hampshire, the temperatures stay well below those needed for effective photosynthesis. Because of this, the tree must use stored energy to keep the needles alive, even though they are producing nothing! It seems like a recipe for disaster, right? The true evergreen advantage comes in the late fall and early spring: after deciduous trees have dropped their leaves, and before deciduous trees have had time to develop new leaves, the evergreen conifers will have already been photosynthesizing for quite a while. And after a few years, the amount of extra energy created in those late fall and early spring times will balance out and exceed the energy lost during the winter.
So while you are outside this winter, enjoying all that it has to offer, take a moment to stop at one of these fascinating evergreen specimens and appreciate it for it's genius. The great north woods would be quite barren without them!
- R. Rives, AMC Pinkham Notch Winter Naturalist
Photo credits: AMC Photo File; Mount Washington Observatory Photo Journal (J. Gemmiti)