Sunday, September 20, 2020

Alpine Tundra Wildflowers in Rocky Mountain National Park

Life is hard for plants of the alpine tundra (previous post link). Alpine tundra is the ecosystem above treeline, in the United States from about 10,000' elevation up. The growing season is short, about three months. Frosts occur most nights all year and snow can fall any day. 

                     alpine tundra in July

The soil is unstable as the water in it freezes (expanding) and thaws (contracting). The soil shifts and the rocks steadily move around. Plant roots are displaced, making them sprawl. There is little cover, thin atmosphere, and less distance to the sun, so sunlight is very strong, despite cool temperatures, making sun damage to tissues much more common than better-protected places.

High mountains are windy, often brutally so. Photos don't do it justice, here is a video.

Plants have many adaptations to survive these conditions, documented by generations of botanists who loved climbing to the heights to see what was there

Alpine tundra plants are low, taking advantage of the cover produced by even small rocks.

alpine tundra

miniature plants of tundra
Miniature alpine tundra plants.
The pink fitbit is 1 1/4 inches (3 cm) across 

Often their flowers are bright. That makes them visible from a distance, despite being short.  Many flowers form a shallow bowl which faces the sun, creating a warm spot. The air in the bowl warms in the sun and, protected by the petals, stays warm to warm more. Pollinators love this. Where air temperatures are marginal for insects to fly, these little warm spots attract pollinating bees, flies and butterflies, like the sunspot below the window attracts housecats. Here are alpine cinquefoils (Potentilla, rose family, Rosaceae, there are four species common in the Colorado alpine), with insects in their flowers.

yellow tundra flowers with insects

Other flowers are blue because it appeals to bumblebees. Bumblebees are capable of flying at cooler temperatures than most insects and will walk, staying low in the warmer, less windy air close to the ground, to visit flowers. 
Mertensia in the alpine
Bluebells, likely alpine bluebells, Mertensia alpina,
under 6" tall
Growing in clumps (mats, cushions) also warms the plant, because heat from the sun or reflected from rocks is trapped and warmed between the clustered leaves.

clumps of plants in the alpine tundra
Plants in clumps. The white flowers are a
native phlox, probably alpine phlox, Phlox condensata
Some tundra plants have red foliage. They have filled their leaves with compounds that look red to us (anthocyanins), that block the tissue-damaging ultraviolet rays of the intense sunlight. 

red, uv-blocking foliage

You will also find fuzzy leaves and succulent leaves. The hairs of fuzzy leaves trap a still air layer, protecting the leaf surface. Succulent leaves hold water. Periods of drought in the Colorado alpine make water conservation important. 

Not all the alpine plants have showy flowers that attract pollinators. Grasses and sedges are abundant and wind-pollinated.

sedges and grasses in the alpine
The plants with dark heads are sedges,
there are grasses behind them.

Many of the alpine tundra plants are relatives of familiar, lower elevation plants. They have adapted to the tundra, by miniaturizing, adding hairs, flowering despite low temperatures and a short growing season, and more. 

purple alpine aster
alpine aster, leafy alpine aster Symphyotrichium foliaceum 

Norton's St. John's wort, Hypericum scouleri
a tiny St. John's wort, Norton's St. John's wort, Hypericum scouleri

And finally, another clump of phlox, this one growing out of a rock wall near the Alpine Visitor Center in Rocky Mountain National Park. 


Take the time to bend down and look at the alpine wildflowers. They are beautiful and thrive in a very harsh environment.

All of these pictures are from readily accessible places in Rocky Mountain National Park. 

Comments and corrections welcome. 

Kathy Keeler, A Wandering Botanist
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1 comment:

  1. The thought of a bumblebee walking from flower to flower amused me no end. I don't know why that should seem to funny, but it does. I've enjoyed both this and your previous post very much.