Luck of the Larch

In Northwest Montana, hillsides burn gold as stands of larches delight

By Tristan Scott
Coram experimental forest, Nov. 1, 2013. Greg Lindstrom | Flathead Beacon

Despite the Flathead Valley’s brief winter prelude earlier this week, a spray of gold still dapples Northwest Montana’s hillsides, radiating an urgency to hikers and bikers eager for a final romp in the mountains before the snow arrives in earnest.

Others are taking the opportunity to enjoy scenic drives, soaking in a visual feast that is unrivaled by autumn’s other arboreal variations in the heart of western larch country, where the “leaf peeping” pastime popular in more deciduously dominated regions of the United States during fall’s peak colors is supplanted with “larch looking,” or something catchier.

Indeed, anyone who has visited the region in autumn hears a familiar refrain this time of year — some variation of “the larch are popping!” or “the larch are going off!”

They’re referring to the deciduous trees that stand out in a sea of evergreen because they turn golden in the autumn chill, glowing like fire as the transformation takes place. For those fortunate to catch the stunning display, the luck of the larch is on their side.

Western larch have captured imaginations for centuries; a deciduous conifer that looks like an evergreen, a larch tree’s needles lose their chlorophyll in the fall, showing bursts of yellow and orange before the needles drop for the winter.

It’s a highly anticipated event that should be enjoyed for the simple, eye-popping pleasure of watching broad swaths of forested mountainsides crackle like fireworks, but the scientific explanation of the phenomenon is equally absorbing.

Western larch, found in western Montana and in northern Idaho, is the largest of the American larches — the U.S. Forest Service notes has discovered 700-year-old trees with a girth eight feet in diameter towering 150 feet high.

Often referred to as tamaracks, in Northwest Montana they’re more likely to be western larch, according to Montana Fish, Wildlife and Parks.

They’re the same genus, larix, but different species. Western larch is larix occidentalis, while tamarack is larix laricina.

As close relatives, it doesn’t really matter what you call them, and most people use the terms interchangeably — the word “tamarack” is found all through the Flathead Valley, from businesses to events.

Western larch needles take on their golden luminescence as the days grow shorter and temperatures drop. Conducting photosynthesis becomes more difficult, so the tree conserves nutrients by ceasing the process. The needles’ color changes because chlorophyll (the light-absorbing pigment that provides energy for photosynthesis) is absorbed back into the tree, leaving behind a yellow pigment, xanthophyll.

Eventually the needles will drop off the tree, glittering across the forest floor until a blanket of snow dims their light. The trees, meanwhile, remain bare-limbed until spring.

Beyond the stunning fall colors, western larch trees are unique for other reasons. Boreal and subalpine forests in the northern U.S. are typically distinguished by evergreen trees, such as Douglas fir and lodgepole pine. They use nutrients conservatively, allowing them to survive long, cold winters and short summers with needles intact. So, how does a deciduous conifer like the western larch thrive in harsh conditions so suited to evergreens?

Larches may have learned to mimic evergreen conifers in order to survive, according to research.

Their conical canopy structure, needle shape and water transport systems closely resemble those of evergreen conifers. Larches, however, save energy and avoid winter damage to their foliage by dropping their needles. This helps them grow tall and compete with other conifers.

Larches have also evolved to succeed amid wildfire and its effects on forests. They have thick bark that is low in resin content, helping them resist ground fires. They shed their bottom branches as they grow and have high canopies to stave off crown fires. Their winged seedlings spread easily in the wind and grow quickly in the mineral-rich soils of scorched ground. Mature larches are often the only trees left standing after a wildfire.

The western larch provides important food and shelter for wildlife. Several studies have documented its importance to pileated woodpeckers, which prefer it to other trees for nesting and foraging. Many other birds, rodents and small mammals will feed on and nest in both living and dead larch trees.

The larches in the region are nearing their golden peak, treating us to a brilliant display before winter sets in with a beauty all its own.

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