The harsh environment of the true alpine zone (about 5,500 feet and above) reduces most vegetation to "dwarf" status. The interaction of snow and wind shapes the habitat. Temperatures range from well below freezing in any month to 90 degrees in August. Water is scarce on exposed alpine ridges which are blown free of winter snow and frequently besieged by drought in the summer. Soil cover is sparse, generally lacking in nutrients, and is unstable and prone to erosion. Plants in the alpine ecosystem have developed a number of strategies to survive:
Krummholz Abies Lasiocarpa and Pinus Albicaulis photographed by Walter Lockwood. Copyright 2004. All rights reserved.
- At or above timberline, trees become gnarled and twisted, shrinking into stunted "krummholtz" forms. Typically, one small tree is flanked by a skirt of prostrate limbs and shoots; the height of the skirt is limited by its blanket of snow cover, as protruding branches are pruned by wind and blowing ice. Subalpine fir and mountain hemlock have adopted this strategy.
- Most alpine plants are perennials, since it is extremely difficult for annual seed production to function efficiently in low temperatures and high winds. Many rely on well developed root systems to extract nutrients from poor soil. A few, such as glacier lily and false hellebore, generate growth from stored energy while still beneath the snow.
- Many wildflowers grow in low mats, or cushions, which provide protection from wind and desiccation, as well as absorbing solar warmth at ground level. Most are covered in silky hairs which provide insulation from rapid temperature changes, and reduces water loss. Thick, waxy leaves provide added protection.
- Since pollination is hampered under high wind and low temperature conditions., alpine species produce lovely blossoms, the better to attract insects.
Alpine forget-me-not (Eritrichum nanum) photographed by Dana Visalli. Copyright 2004. All rights reserved.
There are pockets of more stable and developed soil in the North Cascades’ alpine zone. Vegetation in these areas can be widespread and meadow-like, typically with various grasses, sedges, and dwarf (up to a few inches) varieties of alpine willow, heather and huckleberries. However, the alpine ecosystem consists mainly of rocky or talus slopes, gravelly ridgetops, rock formations and outcrops, and snowfields/glaciers. Some common species in the North Cascades include saxifrages (rock breakers), penstemon, alpine daisies, moss campion, spreading phlox, stonecrops, silky phacelia, buckwheats, cliff paintbrush, shrubby cinquefoil, elegant Jacob’s ladder, and members of the mustard, pea and pink family. There are, of course, many others. Perhaps the sweetest of all, though rare, is the alpine forget-me-not.
Add to this mix numerous and colorful lichens which occur throughout the area, and one readily appreciates the diversity and beauty of the flora of this fragile ecosystem.
The North Cascades, including the National Park, plays host to a range of habitats and a wealth of native plant diversity, much of it protected in near to pristine surroundings. The tree communities alone amply illustrate:
- On the western side lush forests and valleys are dominated by red cedar and western hemlock, with Douglas fir, big-leaf maple and red alder common in more open, sunny areas. At 4,000 feet and above Pacific silver fir, mountain hemlock and subalpine fir appear, and eventually take over.
- On the eastern side the progression is from Douglas fir and ponderosa pine at lower elevations (black cottonwood and willows line the rivers), through western larch, lodgepole pine, and Engelmann spruce communities, to stands of subalpine larch, white-bark pine and subalpine fir at higher elevations.