Sequoia sempervirens
Sequoia sempervirens is the sole living species of the genus Sequoia in the cypress family Cupressaceae. Common names include coast redwood, coastal redwood and California redwood. It is an evergreen, long-lived, monoecious tree living 1,200–2,200 years or more. This species includes the tallest living trees on Earth, reaching up to in height and up to in diameter at breast height. These trees are also among the longest-living trees on Earth. Before commercial logging and clearing began by the 1850s, this massive tree occurred naturally in an estimated along much of coastal California and the southwestern corner of coastal Oregon within the United States. Being the tallest tree species, with a small range and an extremely long lifespan, many redwoods are preserved in various state and national parks; many of the largest specimens have their own official names.
The name sequoia sometimes refers to the subfamily Sequoioideae, which includes S. sempervirens along with Sequoiadendron and Metasequoia. Here, the term redwood on its own refers to the species covered in this article but not to the other two species.
Description
The coast redwood normally reaches a height of, but can be more than in some cases, with a trunk diameter of. Historically, the American naturalist, physician and founder member of the California Academy of Sciences, William P. Gibbons described in 1893 the hollow shell of a coast redwood in the Oakland Hills of Alameda County with diameter of at breast height. This tree's girth is rivalled by the "Fieldbrook Stump" of Humboldt County with a diameter of at from the ground. This stump is still intact, with numerous healthy stump shoots encircling it.Coast redwoods have a conical crown, with horizontal to slightly drooping branches. The trunk is remarkably straight. The bark can be very thick, up to, and quite soft and fibrous, with a bright red-brown color when freshly exposed, weathering darker. The root system is composed of shallow, wide-spreading lateral roots.
The leaves are variable, being long and flat on young trees and shaded lower branches in older trees. The leaves are scalelike, long on shoots in full sun in the upper crown of older trees, with a full range of transition between the two extremes. They are dark green above and have two blue-white stomatal bands below. Leaf arrangement is spiral, but the larger shade leaves are twisted at the base to lie in a flat plane for maximum light capture.
The species is monoecious, with pollen and seed cones on the same plant. The seed cones are ovoid, long, with 15–25 spirally arranged scales; pollination is in late winter with maturation about 8–9 months after. Each cone scale bears three to seven seeds, each seed long and broad, with two wings wide. The seeds are released when the cone scales dry and open at maturity. The pollen cones are ovular and long.
Genetics
Its genetic makeup is unusual among conifers, being a hexaploid and possibly allopolyploid. Both the mitochondrial and chloroplast genomes of the redwood are paternally inherited. According to Guinness the Coast Redwood has the largest known genome of any plant examined up to the year 2020, totaling 26.5 gigabases.Taxonomy
Scottish botanist David Don described the redwood as Taxodium sempervirens, the "evergreen Taxodium", in his colleague Aylmer Bourke Lambert's 1824 work A description of the genus Pinus. Austrian botanist Stephan Endlicher erected the genus Sequoia in his 1847 work Synopsis coniferarum, giving the redwood its current binomial name of Sequoia sempervirens. It is unknown how Endlicher derived the name Sequoia. See Sequoia Etymology.The redwood is one of three living species, each in its own genus, in the subfamily Sequoioideae. Molecular studies have shown that the three are each other's closest relatives, generally with the redwood and giant sequoia as each other's closest relatives.
However, Yang and colleagues in 2010 queried the polyploid state of the redwood and speculate that it may have arisen as an ancient hybrid between ancestors of the giant sequoia and dawn redwood. Using two different single copy nuclear genes, LFY and NLY, to generate phylogenetic trees, they found that Sequoia was clustered with Metasequoia in the tree generated using the LFY gene, but with Sequoiadendron in the tree generated with the NLY gene. Further analysis strongly supported the hypothesis that Sequoia was the result of a hybridization event involving Metasequoia and Sequoiadendron. Thus, Yang and colleagues hypothesize that the inconsistent relationships among Metasequoia, Sequoia, and Sequoiadendron could be a sign of reticulate evolution among the three genera. However, the long evolutionary history of the three genera make resolving the specifics of when and how Sequoia originated once and for all a difficult matter—especially since it in part depends on an incomplete fossil record.
Names
The species name "sempervirens" means "evergreen", thought to be because of its previous placement in the same genus as Taxodium distichum of the southeastern USA. Unlike coast redwood, baldcypress loses its leaves in winter. The common name "redwood", applied to both the coast redwood and the giant redwood, is a reference to the red heartwood of the trees. Common names that refer to Sequoia sempervirens alone include "California redwood", "coastal redwood", "coastal sequoia", and "coast redwood".Distribution and habitat
Coast redwoods occupy a narrow strip of land approximately in length and in width along the Pacific coast of North America; the most southerly native grove is in Monterey County, California, and the most northerly groves are in extreme southwestern Oregon. The aforementioned qualification of "native" is because the species was introduced to various locations in Victoria, Australia, in the 1930s for experimental reasons and have since flourished. The prevailing native elevation range is above sea level, occasionally down to 0 and up to about. They usually grow in the mountains where precipitation from the incoming moisture off the ocean is greater. The tallest and oldest trees are found in deep valleys and gullies, where year-round streams can flow, and fog drip is regular. The terrain also made it harder for loggers to get to the trees and to get them out after felling. The trees above the fog layer, above about, are shorter and smaller due to the drier, windier, and colder conditions. In addition, Douglas-fir, pine, and tanoak often crowd out redwoods at these elevations. Few redwoods grow close to the ocean, due to intense salt spray, sand, and wind. Coalescence of coastal fog accounts for a considerable part of the trees' water needs. Fog in the 21st century is, however, reduced from what it was in the prior century, which is a problem that may be compounded by climate change.The northern boundary of its range is marked by two groves on mountain slopes along the north side of the Chetco River, which is on the western fringe of the Klamath Mountains, near the California–Oregon border. The northernmost grove is located within Alfred A. Loeb State Park and Siskiyou National Forest at the approximate coordinates 42°07'36"N 124°12'17"W. The southern boundary of its range is the Los Padres National Forest's Silver Peak Wilderness in the Santa Lucia Mountains of the Big Sur area of Monterey County, California. The southernmost grove is in the Southern Redwood Botanical Area, just north of the national forest's Salmon Creek trailhead and near the San Luis Obispo County line.
The largest and tallest populations are in California's Redwood National and State Parks and Humboldt Redwoods State Park, with the overall majority located in the large Humboldt County.
The ancient range of the genus is considerably greater, with relatives of the coast redwood living in Europe and Asia prior to the Quaternary geologic period. In recent geologic time there have been considerable shifts in the coast redwood's range in North America. Coast redwood bark has been found in the La Brea Tar Pits, showing that 25,000–40,000 years before the present redwood trees grew as far south as the Los Angeles during the last ice age. The authors of a 2022 paper suggest, "Were it not for the remarkable ability to sprout after fire, many southern forests may have lost their Sequoia component long ago." As to previous redwood range to the north, an upright fossil stump of a coast redwood on a beach in central Oregon was documented north of the current range.
Assisted migration
The ability of Coast Redwood to live for more than a thousand years, along with its unusual capacity to resprout from its root crown when felled by natural or human causes, have earned this species the label of "carbon-sequestration champion." Its potential to contribute toward climate change mitigation, as well as its demonstrated ability to thrive in coastal regions of the Pacific Northwest, led to the formation of a citizen group in Seattle, Washington undertaking assisted migration of this species hundreds of miles north of its native range.In contrast to cautionary statements made by forestry professionals assessing other tree species for assisted migration, the citizens involved with the group known as PropagationNation had met with little controversy until in 2023 a national news outlet published a lengthy article that cast a favorable light on their efforts. The New York Times Magazine wrote:
Not wanting to cause ecological problems by planting the trees across the Pacific Northwest, Stielstra would eventually contact one of the foremost experts on the coast redwood, a botanist and forest ecologist named Stephen Sillett, at Cal Poly Humboldt, and ask if moving redwoods north was safe. Sillett thought planting redwoods around Seattle was a fantastic idea. Another factor encouraged Stielstra too: Millions of years ago, redwoods — or their close relatives — grew across the Pacific Northwest. By moving them, Stielstra reasoned, he was helping the magnificent trees regain lost territory.
In December 2023, the Associated Press exclusively reported criticism from professionals in the region and nationally: While beginning to favor experiments in assisted population migration of more southerly genetics of the main native timber tree, Douglas fir, professionals were united against large-scale plantings of California redwoods into the Pacific Northwest. The next month, January 2024, carried a regional news article that, once again, showed strong support as well as bold statements by the group's founder.
Even before the controversy developed in Washington state, professionals in Canada were documenting horticultural plantings of the California species already in place in southwestern British Columbia. In 2022 a Canadian Forestry Service publication used northward horticultural plantings, along with a review of research detailing redwood's paleobiogeography and current range conditions, as grounds for proposing that Canada's Vancouver Island already offered "narrow strips of optimal habitat" for extending the range of coast redwood. The authors point to a topographical "bottleneck" north of the California border that could have impeded northward migration during the Holocene. The bottleneck entails a lack of lowland passages through the Oregon Coast Range north of the Chetco River, coupled with the absence of coastal landscapes beyond storm salt-spray and tsunami inundation — for which this conifer species is highly intolerant.