Our transect follows closely the corridor of Interstate 90 from Seattle to Snoqualmie Pass in the Cascade Mountains. We can see a transition in the forest on the western slope of the mountains as we drive from sea level to the pass. At the lower elevations, the forest consists largely of western hemlock (Tsuga heterophylla), western red cedar (Thuja plicata), and Douglas fir (Pseudotsuga menziesii). As we rise in elevation, silver fir (Abies amabilis) becomes more common. If we were to leave Interstate 90 to hike to elevations above Snoqualmie Pass, we would find western hemlock and western red cedar becoming less common, but different trees, such as mountain hemlock (Tsuga mertensiana) would be prevalent.

Western hemlock and Douglas fir in old growth forest of the Cascade Mountains.	Young western hemlock on mountain slopes near Mt. Rainier.

Along the short trail to Talapus Lake, which is northeast of North Bend in the Alpine Lakes Wilderness of Mt. Baker-Snoqualmie National Forest, we can examine features of forests common from sea level up to mid elevations on the western slope of the Cascade Mountains. This is a forested zone that has been highly disturbed by fires and logging. Much of the trail to Talapus Lake is surrounded by second growth forest, which means that it is in the process of succession following clearing (e.g., by fire or logging). Near the trailhead this is evident in the prevalence of Douglas fir (Pseudotsuga menziesii) and red alder (Alnus rubra). Red alder is common especially in the early stages of succession. There is evidence, too, of the old forest that once was here: broad stumps-some four to five feet in diameter-of logged trees are common and large downed trunks now serving as old nurse logs are scattered among the standing young forest. As we walk up the trail, the forest shifts to consist largely of western hemlock (Tsuga heterophylla) and western red cedar (Thuja plicata), the trees that dominate undisturbed old forests of the western slope of the Cascades. In the swampy lowland we enter near Talapus Lake, western red cedar is found to the exclusion of other trees.

Large stumps are evidence of logging disturbance along the trail to Talapus Lake.	A forest of western red cedar lines the moist margin of Talapus Lake.

On the western slopes of the Cascade Mountains, the forest communities are not very different from those we examined on the Olympic Peninsula. Many common understory plants of the coastal forest and Olympic temperate rainforest are also frequently encountered in the forests of the western slope of the Cascade Mountains. For example, sword ferns (Polystichum munitum) and deer ferns (Blechnum spicant) along with Oregon wood-sorrel (Oxalis oregana) are prominent. Along the trail to Talapus Lake, we can also find bunchberry (Cornus canadensis), foamflower (Tiarella trifoliata), pipsissewa (Chimaphila umbellata), rattlesnake plantain (Goodyera oblongifolia), and vanillaleaf (Achlys triphylla).

Bunchberry	Foamflower
Pipissewa	Vanillaleaf