“All that is gold does not glitter” is the beginning of a poem by Bilbo Baggins about Aragorn in J.R.R. Tolkien’s Fellowship of the Rings but here the poem may be used to describe the autumn glory that is the Larix. The Larix is commonly known as larch, but larch is such an inelegant word for this elegant tree. It is tall and narrow, graced by moss in part of its range, and in October the needles turn gold prior to dropping off. Yes, this genus of pine tree is deciduous, or to put it another way, it is not an evergreen tree, like most pines. In fact, the needles do not grow again until the spring.
Why do many trees lose their leaves in autumn? Trees slow down their metabolism and rid much of their tissue of water to keep from freezing and losing energy during winter. Dropping leaves helps with this and the trees are quiescent during the cold months, so do not need the energy from photosynthesis. Pine trees in the northern or alpine regions of the world have small needles for leaves. These small, narrow, pointy leaves are modified to help regulate water loss and so they do not need to drop them all at once during winter. Pines do drop their needles, but they do so throughout the year. Well, with the exception of some trees like the Larix. This annual change in needle color may create a golden forest, not too different from another one of Tolkien’s creations. If the Larix are dropping their leaves in a forest with mixed age strands of younger Larix, then the combined gold infuses the floor, under story, and the sky of the forest all at once.
Water and the Larix are part of a cycle, a miniature Tethysphere. Water, in the form of precipitation and groundwater is used by the trees to carry their nutrients and sugars through a kind of circulatory system. Leaves help trees regulate this flow of water, an important function as the water carries energy in the form of sugars from their needles or leaves throughout the rest of the tree and carries nutrients up from the roots. Water is also necessary to convert sunshine into energy in the needles. In turn, the needles of the Larix return to soil and water, carrying this energy. The needles are broken down by insects, fungi, and bacteria in both the water and the soil, making the nutrients and energy available for the ecosystem to use again.
So, as the Larix seems to stand still on the side of the mountain, during the warm months it is busy creating energy and the by-product of this creation, oxygen. As a cold-adapted, north temperate genus of pine, it may face many trials in the decades to come as the climate warms. Most cold adapted species will need to move north, if they are mobile. The Larix will simply decrease in numbers in the southern reach of its range. Or, perhaps if we stopped biggering everything we would have a chance to keep the Larix here and continue to see this autumn blaze of gold.