The recent windstorms have left new widowmakers in the trees. I spoke with a young neighbor who was hit by one, and left with a gash in the back of his head – and was reminded that they aren’t all that easy to see when you are dropping a tree. It is a reminder of the blessings of wearing a hard hat – but even that isn’t a perfect solution.
Not all widowmakers are new. As I clean up blowdowns, thin crowded trees, and so on, I encounter one widowmaker that Dad warned me about when I was in my early teens. Nearly sixty years later, it is still wedged into the tree, dried and seasoned, but still large enough to provide a fatal headache. I can see how to drop the tree safely – but as the tree falls, I can also see where you don’t want to be when the widowmaker finally falls free.
As it starts to get colder, animals have several options. “Leave for warmer places” is the primary strategy of migratory birds. Many animals take the “Find somewhere warm and stay there” strategy that is my personal approach to winter. Many animals find warm dens for the winter and hibernate, avoiding the cold and snow altogether. Finally, there is the “Bundle up real warm and live with it” strategy of of some of the fluffier varieties of wildlife. Of course, some mix and match of strategies is common; Venturing out for food and returning to a warm den is common enough.
But plants have one major handicap to their potential strategies. Unlike animals, which can move, plants are rather stuck. This means that a tree has no choice but to go with the “Live with it” strategy for coping with cold. Consequently, the trees we have in the area tend to be rather well equipped for that strategy.
We’re dominated by evergreens, or conifers. Conifers do not generally shed their leaves in the fall. The reason for this is that they don’t generally need to. The needles of a conifer are shaped very differently then the leaves of a broad-leafed tree (such as a maple), despite having pretty much the exact same purpose. Not losing all the leaves (they will lose some to wear and tear) is a huge advantage; it means that conifers can keep doing photosynthesis as long as there’s enough warmth and light to do so.
Why the needle shape? Snow load. Everything about the shape of a conifer helps with snow load. A tree is a lot like a roof, in that it can be damaged by the weight of accumulating snow. Conifer needles are shaped to avoid accumulating snow, and each needle will hold far less snow than the leaf of a deciduous tree. The tree itself is shaped to shed snow, with branches that tend to be fairly flexible. While branches may break from a particularly wet (and thus heavy) accumulation of snow, for the most part they bend and shed snow.
Freezing is, for most living things, a pretty serious problem. Water expands as it freezes, and at the cellular level this is quite destructive. Conifers avoid serious damage from this by allowing water outside of the cells to freeze, and by having cell walls that are harder, hard enough to generally withstand the pressure of expanding ice.
The final challenge of winter is not drying out. For conifers, that especially thick waxy coating on the needles is a way of preventing that.
Lessons to be learned from conifers?
Too much snow piled atop one is a bad thing. Being cone shaped helps
The dense smoke currently hanging over our part of the country has had me thinking about beetles. Why beetles, you say? Pine bark beetles and relatives (genus Dendroctonus) are notorious for killing large stands of coniferous trees (Fir, Larch, Pine, etc.) – even their scientific name translates to “tree killer”.
The most effective way we can control pine bark beetles on our own is by good management of our forest resources. Keep tree stands resistant to pine bark beetles by thinning trees to a healthy density – beetles are most likely to become a problem in over-crowded woods. Beetle damage will become evident by “boring dust” – spots of reddish sawdusty powder along the trunk, and “pitch tubes” – globs of resin the tree has pushed out, trying to stop a beetle’s tunneling (red pitch tubes likely indicate infestation, while yellow ones often indicate successful defense).
Remove stressed, fire-damaged, and wind-thrown trees. Promptly clean up fallen timber. Damaged and downed trees are excellent places for pine bark beetles to reproduce, and should be removed before new beetles emerge! Where one beetle feeds and reproduces, there will soon be more – pine bark beetles attract each other to damaged trees by releasing aggregation pheromones.
My favorite method of control involves removing the pine bark beetles’ symbiotic fungi. Without these fungi, most of the beetles can’t reproduce well. Because it’s not practical to directly remove fungi from beetles in the wild, scientists have raised pine bark beetles in captivity. These captive-raised beetles can be inoculated with special aggressive fungi which can outcompete and kill the fungi that wild pine bark beetles carry. The thought is that captive beetles could be released and will interact with wild beetles, spreading their different fungi like a disease. The new fungus will prevent beetle reproduction and thus stop small infestations from becoming large and economically devastating ones.
Unfortunately, beetle-delivered fungal control treatments aren’t ready for public use yet – ask your Forest Service folks what beetle controls they are researching and testing! If you’re particularly concerned about pine bark beetle infestation, they may be able to use chemical measures like anti-aggregation MCH pheromone to lessen the risk.