Sitka Spruce, Picea sitchensis
Extending from Alaska to California, Sitka spruce takes over as the dominant coastal tree where the geographic range of redwood ends in extreme southwestern Oregon. Heavily persecuted for its wood, whose strength to weight ratio is among the highest on Earth, very little old–growth Sitka spruce forest remains. Today there are only a few individuals over 91.4 meters (300 feet) remaining in British Columbia and Washington, and we know of none in Oregon. As with Douglas–fir, the highest concentration of Sitka spruce over 300 feet now resides in northwestern California amidst the redwoods, where the tallest live–topped individual stands 316.8 feet. Here are some images I collected recently while studying Sitka spruce in Washington and California.
Olympic National Park protects some of the finest remaining Sitka spruce forests. Here is a canopy view of 330–year–old forest along the Queets River.
The rain forests of the Queets River flood plain are so wet that lichens are only abundant near the treetop, such as on this 269–foot–tall spruce. Note the moss mats on branches close to the top.
Most of the bryophytes you see on the branches of this 330–year–old tree is the moss Antitrichia gigantea. Our calculations indicate that individual spruce trees along the Queets River can carry more than one ton (dry) of epiphytic material, about twice the mass of all the tree´s leaves.
Canopy soils develop beneath epiphytes on spruce branches, such as this one supporting the moss Antitrichia gigantea and the fern Polypodium glycyrrhiza. Unlike the situation further south in California, Sitka spruce crowns along the Queets River support very few nitrogen–fixing lichens, perhaps because relatively warm and wet summers cause excessively high rates of cellular respiration in the lichens.
The tallest remaining Sitka spruce grow in Prairie Creek Redwoods State Park, which is now the only forest on Earth with three tree species over 300 feet tall standing side–by–side in the same grove. Here is a view of a 316.8–foot–tall Sitka spruce (red arrow on left) standing next to a 304–foot–tall Douglas–fir (red arrow on right) from near the top of a 303–foot–tall Douglas–fir. Several of the redwoods visible are also over 300 feet, and the Sitka spruce in between the two highlighted trees is actually 311 feet (It grows lower on the slope.).
Sitka spruce are less shade tolerant than redwood, but they manage to dominate some valley bottoms in redwood forests and become progressively more abundant near the ocean. Several Sitka spruce are visible in this view of the forest along Prairie Creek.
Compared to redwood, Sitka spruce bark is very attractive to epiphytes. Several species of nitrogen-fixing lichens as well as mosses, liverworts, and a fern are visible in this photograph taken near the top of a 259–foot–tall tree.
Lichens are pushed to the outer crown as bryophytes aggressively cover the older portions of branches. Most of the lichens visible in this photograph are thalli of the nitrogen–fixing species Lobaria pulmonaria.
Few lichens can withstand the bryophyte onslaught. The whitish thalli near the middle of the upper branch in this photograph are of the chlorolichen Cladonia. Note that the rest of this branch and the visible portions of other branches have no such lichens.
Moving down from the treetop, bryophytes quickly dominate Sitka spruce crowns. This limb in the upper crown is thickly covered with bryophytes (and ferns) but has relatively few lichens. Note that bryophytes cover nearly all of the limb and much of the reiterated trunk.
The deciduous fern Polypodium glycyrrhiza thrives amidst bryophytes on Sitka spruce branches. With its rhizomes embedded in the soil developing beneath bryophytes, the fern unfurls its fronds below the branch, capturing light unavailable to other epiphytes.
Main trunks of Sitka spruce can be good substrates for epiphytes, too, especially if they are leaning slightly, such as this fern– and bryophyte–covered trunk 125 feet above the ground.
The lower canopy of old–growth redwood forests is often too shady for Sitka spruce. The leaves of this plunging spruce branch are dying, but the epiphytes are still getting enough light to flourish here..
Soil that develops beneath epiphytes on Sitka spruce branches may benefit the tree. In this branch 161 feet above the ground, a large spruce root is visible traversing a portion of the branch cleared of epiphytes for an experiment. Adventitious tree roots are common in the thick epiphyte mats on Sitka spruce and other rain forest trees.
