Climb into the high mountains of the Cascades, and you will reach a point where the forest thins, where the trees are nolonger tall and upright; instead they are short and often spreading in dense clumps. This is timberline: a broad transition zone between forest and alpine communities in which high wind, heavy snow, and summer freezes create a difficult environment for trees. Timberline is the upper limit for the growth of trees.

Like the wind trees of coastal forests, those at timberline are often pruned by the high winds of winter storms, resulting in branches only on the leeward side of the tree. These oddly shaped trees are known by their German language name: krummholz, which means literally 'crooked timber.' Near our transect, we can visit Mt. Rainier National Park to explore timberline. Trailheads at the Sunrise Visitor's Center begin at timberline and pass through krummholz of whitebark pine (Pinus albicaulis) and subalpine fir (Abies lasiocarpa). On the rocky slopes among the krummholz trees are low, spreading plants with woody stems, such as the mountain heathers (Phyllodoce empetriformis and P. glandulosa), which have delicate bell-like flowers, and partridge foot (Luetkea pectinata).

The view of Mt. Rainier from treeline near the Sunrise Visitor's Center.	A clump of low, spreading conifers at treeline.

A subalpine fir with a short, twisted trunk and branches shaped by the wind that is typical of krummholz.	Mountain heather	Partridge foot

Biologists use the term alpine for high mountain environments above timberline. It is a short walk to the alpine from the Sunrise Visitor's Center in Mt. Rainier National Park. Above the Visitor's Center, there are broad alpine meadows on ridges that face Mt. Rainier. The plants of this environment are distinctive. Most have woody stems, but they do not stand erect like trees; instead they generally stand only inches above the soil. Alpine plants tend to be very compact, forming mound-like cushions or mats that creep along the soil surface. Close to the soil, they are protected somewhat from the chill, drying wind that sweeps the alpine landscape. To further protect themselves, many alpine plants are covered by hairs that create a boundary between the plant surface and the drying wind. These hairs are light colored, and this serves to reflect much of the harsh sunlight present at high elevations. Most plants of the alpine grow and flower for more than one year. These alpine perennials store nutrients during the growing season in underground structures, especially in thick roots that extend deep into the soil and in swollen underground stems. The nutrients stored over winter are used in the early spring to produce quickly flowers and new leaves. The quick production of flowers and leaves is important for survival in an environment where the growing season is very short.

Alpine meadow at Mt. Rainier	Arctic sandwort
Prairie lupine	Variable leaf cinquefoil

Flowers in alpine environments are especially showy and colorful, perhaps in response to competition among different kinds of plants for insect pollinators. The bright colors in the alpine include phlox (Phlox diffusa) with lavender flowers, golden fleabane (Erigeron aureus) with bright yellow heads of flowers, and the cliff paintbrush (Castilleja rupicola) with flowers clustered among brilliant red leaves.

Phlox	Golden fleabane
Cliff paintbrush