Larry Weber: Trees with leaves are coping with arid winter air
After the recent snow and cold, the landscape is truly one of a northern winter. The snowpack is deep enough to deter many critters. Those that are moving about tend to go over the surface or tunnel below, if small enough, while the larger ones f...
After the recent snow and cold, the landscape is truly one of a northern winter. The snowpack is deep enough to deter many critters. Those that are moving about tend to go over the surface or tunnel below, if small enough, while the larger ones form trails of their own. Well-travelled deer routes abound in the region's deciduous forests.
Now is the time when these trees stand bare and bland in the woods. Scattered with them are several kinds of conifers that continue to wear their green foliage attire. Seeing spruces, balsams and pines that are not only green but also these needles hold boughs of snow adds a touch of beauty to the already-scenic display. But there is more.
Anyone going out in the mixed forests on these winter days will see the occasional deciduous trees still holding onto their brown leaves. The annual leaf drop of such trees takes place in mid-October and, though some trees linger for a few weeks later, we don't expect to see any with leaves now in January. But, as often happens in nature, a few trees prove to be the exception to the normal falling leaves.
While walking, snowshoeing, cross-country skiing or just driving by these woods, I see a few still with leaves. When getting closer for an inspection, I determine three kinds of deciduous trees still holding leaves: sugar maples, red oaks and ironwoods. In each case, such foliated trees are the minority. Some of these trees are with leaves, but most are not.
I have noticed that these brown foliated trees tend to be farther into the woods and not along the edge. They also appear more with younger trees, not older and larger ones, and some will repeat this wintering each year.
Sugar maples with leaves are quite uncommon, but I do see some every winter. Red oaks and ironwoods are more common and, along some well-traveled routes, I expect to see them as the cold season moves in. Instead of a leaf drop in fall, they shed them in spring. Why do they keep leaves all winter?
Though we observe the leaf color and defoliation each October, most of us do not know why it happens. Flat, broad leaves, like those on most of our deciduous trees, are a source of much evaporation of water from trees (transpiration). Such transpiration, when happening in the warm and moist times of year, is rather easily replaced and the trees will not dry out. This works well in summer -- not in winter.
Besides snowy and cold, winter is our driest time of year. We experience this on our bodies as our skin often dries and cracks. If trees kept their leaves alive on their branches during winter, they would lose so much moisture to the dry air that the trees would not survive the cold. And so, deciduous trees drop the flat leaves. A few, especially the young red oaks and ironwoods, keep the leaves (though not alive) as a deterrent to dehydration. The curled and dead brown leaves hold onto branches at sites that will help to block more drying out. And so we see these trees are coping with the arid air of winter in a way of their own.
Retired teacher Larry Weber is author of several books that are available now. Contact him with questions or comments c/o email@example.com .