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An island of fir trees surrounded by bare ground that’s formed in Wyoming’s Bighorn Mountains. (Wendy Johnson)All In The Family<\/p>\nWendy Johnson was driving through Granite Pass in the Bighorn Mountains when she noticed something beautiful and inexplicable.<\/p>\n
\u201cThey were clusters of conifers, like an island in a sea of grass,\u201d the Billings, Montana, woman told Cowboy State Daily. \u201cI’ve been up there plenty of times, and I’d never noticed them before.\u201d<\/p>\n
The \u201cclusters\u201d were sitting in the middle of fields and meadows, far from the expansive forests beyond. They consisted of several tall, mature trees in the middle, standing close together and densely packed, encircled by much smaller saplings.<\/p>\n
\u201cThey looked like little fortresses,\u201d Johnson said. \u201cI didn’t pay attention to how many I saw, but there were definitely other ones. I found them fascinating.\u201d<\/p>\n
With all the high-elevation forests in the Bighorns, why do these trees stand out in a crowd, and how did they get there?<\/p>\n
F Is For Fir<\/p>\n
Shane Smith, former director of the Cheyenne Botanic Gardens, saw Johnson\u2019s photos of the conifer clusters and knew exactly what trees were growing there.<\/p>\n
\u201cIt\u2019s subalpine fir,\u201d he said. \u201cThey look a lot like spruces, but they’re different, and this is normal behavior for them.\u201d<\/p>\n
Abies lasiocarpa, the subalpine or Rocky Mountain fir, is an evergreen conifer that grows throughout the western United States and Canada. They\u2019re most commonly found at high altitudes, which explains why they\u2019re growing in the Bighorn Mountains.<\/p>\n
According to Smith, it\u2019s easy to determine the difference between firs and spruces. Just remember that fir starts with an \u201cF.\u201d<\/p>\n
\u201cIf you think fir, you think flat, because fir needles are flat if you touch them,\u201d he said. \u201cThe other F-word is flexible, because if you were to reach out and grab a fir branch, you could easily bend it 90 degrees, and it would happily bend with you.\u201d<\/p>\n
The flexibility of subalpine firs is an adaptation for windy environments. That\u2019s why the firs have winged seeds, using the wind to propagate themselves in their high-altitude ecosystems.<\/p>\n
Spruce, on the other hand, starts with \u201cS.\u201d Smith said that, in this context, \u201cS\u201d stands for sharp, square needles and stiff branches.<\/p>\n
Now you know.<\/p>\n
An island of fir trees surrounded by bare ground that’s formed in Wyoming’s Bighorn Mountains. (Wendy Johnson)All In The Family<\/p>\n
Johnson called the clusters of subalpine firs \u201cislands\u201d in the Bighorns. The scientific term for these clusters of trees is \u201catolls,\u201d so she wasn\u2019t far off.<\/p>\n
Fir atolls are formed by a process known as layering. It\u2019s a well-known botanical phenomenon in which stems or branches can promote root development while remaining attached to the main plant.<\/p>\n
\u201cIt’s a way the old trees can help the seedlings get established,\u201d Smith said. \u201cSome brave tree, that could be long gone or still in the middle of the cluster, germinated there and grew very slowly to a ripe old age, then started dropping pinecones and seedlings that took off in the sweet spot.\u201d<\/p>\n
Smith said subalpine firs struggle to grow in the granitic, rocky soil covering most of the Bighorns. When they find an optimal spot to grow, they make the most of it.<\/p>\n
A telltale sign of a thriving atoll is where the seedlings are growing.<\/p>\n
\u201cYou would think the seedlings would be like inside the (atoll) in total protection, but they’re actually outside because they need more moisture and light,\u201d Smith said. \u201cThey do get beat up by wind, but this is one species of evergreen that is really good with the wind.\u201d<\/p>\n
Over time, the atoll will slowly expand outward as more trees mature and saplings sprout. The firs will keep expanding until they\u2019ve covered the entire patch of optimal soil.<\/p>\n
\u201cWith the soils in Granite Pass, I don’t think they’re going to expand into full-fledged forests, but they’re going to get bigger,\u201d Smith said.<\/p>\n
Fir Fungus<\/p>\n
When Johnson first saw the subalpine fir atolls, she called them \u201ccolonies.\u201d She stopped when she realized the atolls were probably different from the truly colonial aspens.<\/p>\n
\u201cI know aspen groves are produced because the parent tree sends up suckers that turn into other aspens that are all identical,\u201d she said. \u201cI don’t believe all the conifers are growing from the parent’s roots.\u201d<\/p>\n
The subalpine fir atolls aren\u2019t colonies or clones of the same tree, but there actually is some communal sharing that helps them stay healthy. It\u2019s all related to a fungus growing among all the roots in the atoll, called mycelium.<\/p>\n
\u201cIf you’ve ever dug into some rich organic soils and saw some white material that almost looks like white ash, that’s mycelium,\u201d Smith said. \u201cThrough that fungal mycelium thread connection, trees can actually share nutrients. Even crazier, they can share information. They can communicate.\u201d<\/p>\n
When a subalpine fir is under threat from a browsing herbivore, usually a moose, they can exude substances that can deter the animals. Through a mycelial thread connection, that same defense mechanism can be triggered in every connected tree.<\/p>\n
Smith called these subterranean fungal networks \u201cthe World Wide Web for trees,\u201d which botanists are still trying to understand.<\/p>\n
\u201cWe know how important these fungal networks are to our forests and trees,\u201d he said. \u201cWhy would the fungal network want to become the fiber network? They might be taking some of the sugar and nutrients passing between the trees, which would be a fair trade.\u201d<\/p>\n
So, referring to these atolls as colonies isn\u2019t that far off.<\/p>\n
\u201cI’d bet the house that the mother trees are connected to the baby trees and connected to each other,\u201d he said. “It\u2019s an amazing symbiotic relationship.\u201d<\/p>\n
Networking For Success<\/p>\n
With the inherent adaptability of subalpine firs and the important mycelial thread, the atolls in the Bighorns can be extremely resilient. According to Smith, each atoll provides an ideal environment for all current and future trees to thrive.<\/p>\n
\u201cThey create their own microclimates,\u201d he said. \u201cWith these dense little islands, they can slow down the wind and catch the snow. That\u2019s how they survive in areas where hardly any other conifers grow.\u201d<\/p>\n
The main threat to these subalpine fir atolls is the same one that could devastate flora and fauna throughout the Rocky Mountains: climate change. For Smith, it\u2019s a serious concern.<\/p>\n
\u201cI’m seeing many forests right now that are changing in my lifetime, and that’s just in the last 10 years, 15 years at most,\u201d he said. \u201cLower-altitude spruces are more susceptible to disease and bugs. Pines are more susceptible to drought. Some lower-altitude aspen forests I’m seeing are 50% dead.\u201d<\/p>\n
Right now, the high-altitude forests are the least susceptible to these climate-related changes, but they won\u2019t be immune forever. Their habitable range could shrink over time as the climate gets warmer and water becomes scarcer.<\/p>\n
That\u2019s why Smith is happy to see these subalpine fir atolls enduring.<\/p>\n
\u201cLet’s hope these subalpine firs keep expanding and making new islands,\u201d he said. \u201cIt’s really fun when you come across them.\u201d<\/p>\n