Young Douglas–fir forests, even those regenerating naturally after wildfire, have simply structured canopies consisting of similar–aged trees with mostly model–conforming crowns.
Old–growth Douglas–fir forests are far more interesting structurally and support a great variety of arboreal life. This 400–year–old forest near the Wind River Canopy Crane has trees up to 200 feet tall.
Epiphytic chlorolichens, especially Alectoria and Usnea, drape the branches of this 400–year–old forest.
Trees in this 550–year–old forest near Mount Rainier approach 300 feet in height but rarely exceed this. Winds rushing through the Carbon River valley below the glacier sculpt the tops of the trees. The 271–foot–tall dead–topped tree on the right has no reiterated trunks, but now that its top is dead, we suspect it will reiterate soon.
The canopy of the Carbon River forest is among the most spectacular on Earth, not least because, in addition to Douglas–fir, there are hemlock (Tsuga heterophylla) and redcedar (Thuja plicata) approaching 250 feet.
Many of the tall Douglas-fir in the Carbon River forest have dead and dying tops and are succumbing to attacks by wood decay fungi.
Mist rising through the Carbon River forest reveals a deep canopy with great structural complexity.
There are few Douglas–fir forests left to truly remind us of the great forests logged in the 19th and 20th centuries. This Carbon River forest is perhaps the finest.
Another great example is this 650–year–old forest of the Cedar Flats Research Natural Area near Mount St. Helens. The tallest trees reach nearly 300 feet. Almost all of them have dead and dying tops.
Many of the Douglas–fir trees in the Cedar Flats forest are dead, dying, or on the verge of being killed by wood decay fungi, but quite a few trees continue the battle to protect their wood and are still thriving. The biggest tree we measured in this forest has 95 million leaves that cover an area over 31 thousand square feet.
Like coast redwood and giant sequoia, Douglas–fir responds to injury by producing reiterated trunks. This tree´s main trunk broke late in life, however, and wood decay fungi will likely hinder recovery of its crown.
Trees that have succeeded in rebuilding severely damaged crowns become the most structurally complex individuals in a forest. Three–quarters of the leaves on this 550–year–old Douglas–fir are from reiterated trunks.
Douglas–fir achieves less than redwood or giant sequoia, but some individuals are truly gnarly. Here is a fusion between a reiterated trunk and a limb 200 feet above the ground in a 550–year–old tree.
Douglas–fir bark is less toxic and more stable than that of redwood or giant sequoia, so its limbs and branches support lots of epiphytes, such as these thick mats of the moss Antitrichia gigantea 195 feet high in a 234–foot–tall tree.
Big Douglas–firs can have impressive limbs, such as this one supporting an epiphytic hemlock sapling 190 feet above the ground. A branch could never withstand such a cavity of decaying wood and soil on its upper surface, but a limb can, because living wood is being produced in the buttress extending along its lower surface from the reiterated trunk.
The tallest living Douglas–firs occur in the old–growth forests of northwestern California, where they compete with redwoods. This 305–foot–tall Douglas–fir (red arrow) is taller than any of the redwoods within 50 feet of it and is probably no more than 250 years old.
Here is a view looking up along the reiterated trunk near the top of the tallest live–topped Douglas–fir, a 317.7–foot–tall tree in Prairie Creek Redwoods State Park. No known non–redwood on Earth has a higher leaf than this tree.
Here is a view looking down from the same position 289 feet above the ground.
A rich community of lichens and bryophytes inhabits the crowns of Douglas–firs in old–growth redwood forests. Unlike the neighboring redwoods, Douglas–firs are home to large quantities of nitrogen–fixing lichens, such as this Lobaria oregana.
Lobaria and other nitrogen–fixing lichens accumulate slowly in tree crowns primarily because they are dispersal–limited. Their propagules have difficulty traveling long distances between trees. In redwood forests, the situation must be exacerbated by the fact that most of the trees in the forest have bark that is relatively inhospitable to these lichens.
Two species of Lobaria are particularly abundant on Douglas–firs in Prairie Creek Redwoods State Park. The pale green thalli are L. oregana, and the brown–green thalli are L. pulmonaria.
A wide variety of nitrogen–fixing species inhabit Douglas–fir crowns, such as this assemblage of Lobaria oregana (pale green lichen), L. scrobiculata (bluish gray lichen), and Sticta limbata (brown lichen). The reddish liverwort is Frullania nisquallensis.
My favorite liverwort inhabiting Douglas–fir crowns is Douinia ovata, shown here growing on the lower surface of a large branch with other epiphytes. Note the liverwort’s sporophytes.
Branches in the lower crowns of tall Douglas–firs are home to many bryophytes, such as this one covered by the mosses Neckera and Isothecium as well as the liverwort Porella.
Organic soil develops beneath bryophytes on Douglas–fir limbs and branches. This soil–covered limb 161 feet high in a 303–foot–tall Douglas–fir carries a well–developed mat of bryophytes and the fern Polypodium glycyrrhiza.
The evergreen fern Polypodium scouleri, which is abundant on redwoods, also does well on Douglas–fir. Here is a young fern mat on an epicormic branch next to a Douglas squirrel’s cone–feeding perch.
Epiphyte mats on Douglas–firs are home to many creatures. Here is a nest of the Sonoma tree vole (Arborimus pomo) amidst a moss– and fern–covered branch 180 feet above the ground.
Tree voles feed exclusively on Douglas–fir leaves, which they dutifully gather and devour every day. Here is fresh feces of a vole whose meal we accidentally interrupted.
Some vole nests must be decades old, such as this one 165 feet above the ground. Note the thick layers of vole feces beneath a mat of resin ducts and fresh leaves.
Many arboreal animals inhabit Douglas–fir crowns in old–growth redwood forests. I was somewhat startled by this pool of water inside a cavity beneath a dead and broken reiterated trunk 261 feet above the ground. Note the nematode worms, mosquito larvae, and other aquatic creatures.
