The temperature hovered around 10 degrees Fahrenheit as I drove down the canyon between Creede and South Fork. The top half of the mountains to the west were bathed in golden morning light while the Rio Grande flowed below in deep shade. Sheets of ice clung onto the downstream sides of boulders while slushy frazil ice was carried along in the current. It was the first week of November and winter seemed to be knocking on the door.
The light colored trunks of leafless aspen trees created strong vertical lines contrasting against the green, Douglas fir and blue spruce. The bare crowns of the cottonwood trees exposed sometimes simple, sometimes complex tangles of limbs.
Deciduous trees and shrubs in our area drop their leaves and become dormant as the days get shorter and the temperatures dip below freezing. Dropping leaves in the autumn reduces water loss and prevents injury from freezing temperatures in the winter. This seemingly smart strategy comes with consequences though, as the trees then have to tap into carbohydrates stored in their roots to put out new leaves every spring.
That doesn’t seem like a big deal, as we see the aspen and cottonwoods leaf out every spring without any issues. A few years ago, though, some of our stands of aspen experienced large tent caterpillar outbreaks. The caterpillars ate all the leaves off the trees in June causing the trees to have to tap more carbohydrates from their roots to grow new leaves. If the caterpillar outbreak continued for several years, the carbohydrate reserves could have been reduced to the point that the aspen couldn’t leaf out in the spring. Luckily, the tent caterpillar outbreak mostly subsided before that became an issue.
All of the coniferous trees (cone-bearing trees) in our area are evergreens, that is, they keep their needles all year. Some coniferous trees, such as the western larch, found in the northwestern United States and southern British Columbia, drop their needles every year.
Coniferous evergreens save energy by not dropping their needles, but can lose moisture that is not replenished in the winter when everything is frozen. The needles are covered with a waxy coating and their stomata (i.e., pores) close during the winter providing protection from water loss. But, the waxy coating often gets pitted and scratched by blowing snow crystals on windy days. On calm, sunny, cold days, the dark needles warm up, which increases the humidity inside the needles as interior ice crystals melt. The difference in humidity between the inside of the needles and the dry outside air causes water vapor to move out of the needles and into the air.
Just as our trees are adapted for the frigid days of winter, so are the various types of bark beetles that infest them. Spruce beetles and their larvae begin producing various forms of sugar alcohols as temperatures begin to drop. These sugar alcohols act like antifreeze protecting the beetle larvae down to thirty below zero. Additionally, the adult beetles are more mobile than the larvae so they move down to the lower part of spruce trees where snow will pile up providing extra insulation.
As I looked down at the slushy Rio Grande below me, it was hard not to notice how low the river appeared. The Rio Grande was only running at about 60 percent of average for this time of year. Soon the frazil will freeze solid forming a sheet of ice over much of the river.
A few miles further down the road, the canyon opened up allowing for a good view of Beaver Mountain. Much of the north facing slope of the mountain was white with snow. We’ve had a decent start on snow this year and Wolf Creek Ski Area was the first ski area in the nation to open. As autumn moves into winter, I’m hoping the snow keeps coming for I am well adapted to the cold and snow with warm clothes, skis and snowshoes.
Mike Blakeman is the public affairs officer for the Rio Grande National Forest. He spends much of his free time scrambling around the mountains with a camera in his hand.