"It's a forest!" Well, strictly speaking Cedar Butte is a topographic feature, a "minor out-lying knob", but of the experience of hiking Cedar Butte that is most succinct characterization I can make.
While this might seem quite ho-hum if you have driven too many miles past second-growth Douglas fir "log farms" with their fringe of salal along the road, "forest" actually implies a great richness of diversity and complexity. Adequately describing that richness is beyond my abilities; for a much more comprehensive treatment I highly recommend Arthur Kruckeberg's excellent book "The Natural History of the Puget Sound Country". For now I would like to point out just a few of the diverse aspects of the forest that can be glimpsed here by even a casual observer, and perhaps hone your awareness, and thereby enhance your appreciation, of those aspects. I will focus mainly on the defining elements of the forest, the trees.
The characteristic lowland forest of the Puget Sound country is that of the Western Hemlock. This may be surprising to long-time residents accustomed to the ubiquity of the Douglas fir. But that is mainly due to human perturbation: nearly all of the forest in Western Washington is "second growth", less than eighty years old, as the original, natural forest was logged in the past century. (And often less than twenty years old, due to repeated harvesting.) In the lifetime of a forest this is mere infancy. This is the first observation to note: nearly all of the forest we see in western Washington is a greatly perturbed ecosystem that is still at the early stages of restablishment.
While the forest here is still quite young, it already illustrates many differences, and much of the process of how the lowland forest grows and matures. For instance, you might notice that along the Fence Line trail (the old trail past Christmas Lake) and the John Wayne trail are many alder trees, and quite a few big-leaf maple trees (some of them immense). On Cedar Butte itself the trees are mostly Douglas fir and western hemlock, but towards the top more fir can be found. These patterns are not at all random; the forest reflects the influence of definite factors.
Alder, for instance, (alnus rubra) is perhaps the most successful colonizer in this region, and does well in sandy or even gravelly ground. Bulldoze the vegetation off a patch of ground in this area, and early next spring there will be little shoots of alder springing up. However, it does better in wetter areas than dry, well drained areas. So you see it in the wetter areas (often with salmonberry bushes) where the forest has been disturbed, where it grows rapidly and crowds out some of the competition.
However, big-leaf maple (acer macrophyllum), though not quite so fast-growing, is also a good colonizer, and is not so easily crowded it out as the young maples are more tolerant of shade. Eventually the maples will start dominating the alder.
Douglas fir (pseudotsuga menziessi) and western hemlock (tsuga heterophylla) both favor the slightly drier and better drained conditions found higher up on the slopes of Cedar Butte. Both are also excellent colonizers, as can be seen by the many, many saplings along side the trail in the logged area. (The hemlocks are the ones with the more supple shape.) However, Douglas fir grows faster, and within several decades they will have not only overtopped the other trees, but shut out the sunlight to the forest floor. This can be seen in the area just above the logged area. Instead of nearly impenetrable brush, there is so little brush that one can wander freely between the trees. One might not even suspect that when the trail up from the Blowout was built it had to be hacked through thick stands of salal where today there are only wispy remnants.
(While I am mostly focusing on the trees, I would like to mention Indian Pipe (monotropa uniflora). This plant is a type of "saprophyte" that derives its energy from organic material. It doesn't use photosynthesis, therefore doesn't need sunlight, and grows well in the deep shade. Watch for its little clumps of white stems and bent-over flowers, or other saprophytes, several days following a rain.)
You might wonder why, if Douglas fir can so successfully suppress other trees, it has not taken over all of the forests in its habitat range. Well, it is not shade tolerant itself, so it also suppresses new Douglas fir. As the shorter, weaker members of the colonizing generation succumb the remaining trees get bigger. (Sort of like our economy.) Eventually a tree falls that leaves a big enough gap in the canopy to let in just enough light for a hemlock or cedar tree to grow. And eventually they take over.
So why hasn't hemlock or even cedar completely suppressed Douglas fir in the lowland forests? It seems that even forests have a natural life-span, and eventually die. Eventually the decadal variation of climate results in an extended dry spell, a forest fire burns off a section, and every thing starts over again. (Just like history!)
The immense stands of Douglas fir that greeted the first European explorers along our shores came about, according to the forestry scientists, because of a large number of forest fires about three hundred years before European colonization. According to the Watershed, one such fire on Mount Washington has been dated to around 1634. (However, the many snags to be seen on Mount Washington, and even on Cedar Butte, are from fires in the past century subsequent to logging operations.)
Unfortunately, we can see only the early stages around here, as it generally takes a forest 200 to 300 years to reach maturity, and nearly every spot within sight of Cedar Butte has been logged within the last century. To see some old-growth forest you need to visit the Ashael Curtis Nature Trail (next to the Annette Lake trailhead at exit 47), where the loggers missed a little spot. (And it is a very nice place to visit.) (Or visit Schmitz Park in West Seattle. Or see Kruckeberg's list of old-growth sites on pages 134-136.) But scattered around Cedar Butte--indeed, around the entire region, and even in quite a few suburban yards--you can see the large stumps left when the old-growth forest here was logged a century ago.
Towards the top of Cedar Butte the profusion of Pacific silver fir (abies amabilis) shows a transition from the lowland western hemlock forest to the midmontane (middle mountain) zone. This usually happens at a slightly higher elevation, and just across on Mount Washington you can see that the lowland forest is still going strong at the same elevaton. The difference here ie due to environmental stress: the summit of Cedar Butte is more exposed, and, on the western side, where the trail comes up, a little drier because the rain tends to come in from the east. Curiously, just east of the summit can be seen the tip of a cedar. This is not really anomalous: the eastern side of Cedar Butte, as well as the northern face of Mount Washington, catches more rain, and favors hemlocks and sword ferns rather than Douglas fir and salal.
So the composition of a forest varies not only across topgography, but also across a progression or succession of stages in its life: at any one spot it reflects not only the physical characteristics of that spot, but also how far it has matured since it was last cleared. Careful observation reveals that the tapestry of a forest is not a uniform, boring green, but a complex pattern of influences.
There is, of course, more to forests than trees; what I've described here is just the slightest of glimpes into the nature of a forest. Do read Kruckeberg's "The Natural History of the Puget Sound Country", or any of the many other good books he recommends.