You are looking at a prototypical plantation forest.

There are similarly-sized, evenly-spaced trees in recognizable rows. Under natural circumstances, fir trees do not regenerate so that all of the trees are identical in age and nearly identical in size and spacing. With the rapid growth of the planted Douglas-fir trees, and their even spacing, a monoculture is almost sure to prevail here. The Alder and other deciduous trees will begin to disappear over the next five to ten years as they struggle (unsuccessfully) with the tall firs for light.