Subalpine Life Zone

It’s useful to know a little bit about a few of the more common alpine landforms when learning to understand and identify its plants. The complex topography includes ridge tops, exposed saddles, talus and scree slopes, fell field, dry turf, and several types of wetter areas which can be ephemeral or permanent. Meadows and marshes occur on the more level and lower areas.

Dry turf with deeper, more developed soils can become established on gentler slopes, flat ridges, valleys, and basins where the soil has become relatively stabilized and the water supply is more-or-less constant. It should be noted, though, that it can take many hundreds of years to develop an inch of soil in this place. Areas bordering streams, or springs and pockets under melting snow banks, are places where the more water-dependent plants congregate.

Fell fields are those open rocky spaces scoured by fierce winds that keep them free of snow in winter and usually found on the upper slopes. The word itself is derived from from the Gaelic word fell, meaning stone; thus we have a field of stone. Often the effect of frost shattering the rock will cause recognizable patterns to form here. What grows in these stony exposed places with shallow, poorly developed soil? Cushion plants, mosses, and lichens do. Vegetation is sparse in the fell field, typically covering only between 15 and 50% of the area.

Cushion plants are common throughout the alpine and have a special role as facilitators. As their name implies, cushion plants hug the ground in protective mounds, avoiding winds and trapping heat and moisture, essentially forming their own microclimates. Their strong, thick, perennial tap-roots poke down into soil pockets or insert themselves into the clefts and crannies been rocks, where they can descend as much as two feet or more to obtain water. Cushion plants are considered a foundation species because they provide a habitat for other plants, ones that might not be able to come in and inhabit bare soil.

Heading downslope from the fell fields where the dry turf and meadows form, taller plants can survive, and the height of the blooming season is closer to midsummer instead of the earlier blooms of the fell field. And at the lowest borders of the alpine dense thickets of willows (Salix species), the tallest of the alpine plants reign supreme; some individuals among these specimens are many of thousands of years old.

The alpine is unique in so many ways. Although it may seem counter-intuitive, alpine areas host a much higher diversity of plant species than the forested areas below them. They also are home to a high percentage of endemic plants, meaning plants that can grow there and nowhere else. And in a classical paradox, the extremely harsh conditions of the alpine have created one of the most delicate of ecosystems, small disruptions have big impacts. Human interactions, footsteps, tire tracks, litter, and all the associated et ceteras cause damage that take decades to repair, if it can be repaired at all.

The collective alpine zones in Colorado also provide twenty percent of our stream flow. Acting like a sponge, it absorbs snow and melt water, releasing it downslope to a thirsty land below throughout the summer. Native plants are the ‘enablers’ here, without them, the soil would loose its ability to retain moisture. The alpine provides benefits of many kinds, we certainly want to enjoy it, but also to recognize its value and to enjoy it with appropriate caution.

~Sue Dingwell

Selected Bibliography
Ackerfield, Jennifer, Flora of Colorado, Botanical Research Institute of Texas Press, 2015

Bowman, W., Alpine Vegetation: Patterns of Biodiversity and Response to Environmental Change. Retrieved March 2, 2021, from: https://slideplayer.com/slide/4951209/

Griggs, Robert F. “Competition and Succession on a Rocky Mountain Fellfield.” Ecology, vol. 37, no. 1, 1956, pp. 8–20. JSTOR, www.jstor.org/stable/1929664. Accessed 2 Apr. 2021.

NatureServe Explorer 2.0, NatureServe, explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.722857/Rocky_Mountain_Alpine_Turf.

Zwinger, Ann, and Beatrice E. Willard. Land above the Trees: a Guide to American Alpine Tundra. Johnson Books, 1996.