This picture, taken at timberline, shows several mountain hemlocks. By focusing on several trees in the proper sequence of growth, one can learn of the fascinating interaction between these trees and the windblown, scouring snow--an interaction that happens during severe storms when few humans are around to see their shaping influence.
The trees in the three pictures below are all visible in the photo above. The first picture below is taken at a different angle of the very inconspicuous tree in the lower right corner of the above photo. This is a "young" tree. One sees full bushy growth suddenly reduced to a stub of a trunk. This change is where the trunk sticks out of the winter's protecting snow. The foliage below the snow is protected from the ice crystals blowing over the surface. Anything sticking above gets sanded down. This sanding is most intense right above the snow's surface. Some plants can't survive this abuse and grow no higher.
In the picture below are a series of "middle-aged" trees which are growing higher and higher above the snow level. Notice that there comes a height where the abrasion drops off drastically. Because most of the abrading blowing snow bounces along the snow level, a tree that survives long enough to grow above this abrasion level enters a new zone of growth opportunity. These trees are at different stages of exploiting this newly-entered opportunity.
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Finally we see the majesty of the "old trees". These trees have fully filled the area high above the snow level. A combination of shade in the summer and abrading snow in the winter have smoothed the lower trunk. |