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You are here >1Up Info > Wildlife, Animals, and Plants > Plant Species > Tree > Species: Sequoia sempervirens | Redwood
 

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BOTANICAL AND ECOLOGICAL CHARACTERISTICS

SPECIES: Sequoia sempervirens | Redwood
GENERAL BOTANICAL CHARACTERISTICS : Redwood is a native, evergreen, long-lived (greater than 2,200 years), monoecious tree [38,40]. Redwoods are among the world's tallest trees; trees over 200 feet (61 m) are common, and many are over 300 feet (91 m) [40]. The largest tree thus far was measured at 364 feet (110.3 m) in height and 20 feet (6.1 m) in d.b.h. [44]. The root system is composed of deep, widespreading lateral roots with no taproot [40,44]. The bark is up to 12 inches (30 cm) thick and quite fibrous [44]. Redwood self-prunes well in dense stands [40]; the base of the bole is strongly buttressed [38]. RAUNKIAER LIFE FORM : Phanerophyte (megaphanerophyte) REGENERATION PROCESSES : Redwood reproduces both sexually and asexually. The male and female strobili are borne separately on different branches. Redwood begins producing seeds at 5 to 15 years of age. Large seed crops occur frequently, but viability of the seed is low [8]. A dry period during pollination allows better pollen dispersal and improves seed viability. The seeds are small and light, averaging 120,000 seeds per pound (265,000 seeds/kg). The wings are not effective for wide dispersal [19], and seeds are dispersed by wind an average of only 200 to 400 feet (61-122 m) from the parent tree [40]. Redwood seeds do not require pretreatment to germinate. Germination is epigeal [40]; the best seedbed is moist mineral soil with some shade [17,36]. Germination rates are generally low due to low viability rather than to dormancy. Germination rates with a mean of 10 percent are the norm [8]. Seedlings require adequate moisture to survive. The roots of redwood seedlings do not have root hairs and are thus inefficient at extracting soil moisture. Once established seedlings can obtain remarkable growth rates in the first season. Growth of 18 inches (46 cm) is not uncommon. Older saplings (4 to 10 years old) can grow 6.5 feet (2.0 m) in one growing season [40]. Redwoods can reproduce asexually by layering or sprouting from the root crown or stump. Sprouts from the root crown are generally favored for tree crops [10]; sprouts originating from the stump are generally not as vigorous as root-crown sprouts, and are very susceptible to wind throw [40]. Sprouts orginate from dormant or adventitious buds at or under the surface of the bark [17,40]. The formation of these buds occurs at a young age, as even seedlings have been observed to sprout after top-kill [30]. The sprouting capacity of redwood decreases with size and age [17]. Sprouting appears to be the greatest on the downhill side of the tree [14]. Within a short period after sprouting each sprout will develop its own root system, with the dominant sprouts forming a ring of trees around the parent root crown [40]. The mean crop tree sprouting potential per root crown is five, which adds many crop trees to a given site [10]. Sprouts can achieve heights of 7 feet (2.1 m) in a single growing season. Shading does not decrease sprout height, but it does reduce the number and weight of sprouts [14]. Density of sprouts also affects sprout vigor; the higher the density, the less vigorous the sprouts [40]. SITE CHARACTERISTICS : Redwood occurs in a maritime Mediterranean climate, where the winters are cool and rainy, and the summers are dry. The mean precipitation is 70 inches (180 cm), with 90 percent falling between October and May. The dry summers are mitigated by a heavy fog belt [30]. The fog reduces the drought stress of this hydrophilic plant by reducing evapotranspiration and adding soil moisture. Redwoods beyond the fog belt appear to be limited to areas of high moisture. Currently there is considerable debate over the link between the fog belt and redwood distribution [11]. Preferred sites for redwood stands are alluvial fans, coastal plains, and benches along large streams [40]. The size of a redwood can be site dependent: a 400-year-old specimen on a hillside had a d.b.h. of 2 feet (0.6 m), while a 600-year-old specimen on an alluvial fan had a d.b.h. of 12 feet (3.6 m) [4]. Elevation: Redwood occurs at elevations ranging from sea level to 3,000 feet (0-915 m), but most stands occur from 100 to 2,320 feet (100-703 m) [11,40]. Redwoods are sensitive to salt spray [40], and are usually separated from the coast by intervening grassland [22] Soils: Redwood has a strong affinity for deep, moist soils in the Inceptisol and Ultisol soil orders [40]. The common parent materials are graywacke sandstones, shales, and conglomerates [30]. Associates: In addition to those previously listed under Distribution and Occurrence, overstory associates include Sitka spruce (Picea sitchensis), Pacific yew (Taxus brevifolia), California torreya (Torreya californica), Gowen cypress (Cupressus goveniana), bishop pine (Pinus muricata), Montery pine (P. radiata), bigleaf maple (Acer macrophyllum), Oregon white oak (Quercus garryana), and Oregon ash (Fraxinus latifolia) [40]. Understory associates include vine maple (Acer circenatum), chittam bark (Rhamnus purshiana), evergreen huckleberry (Vaccinium ovatum), Pacific rhododendron (Rhododendron macrophyllum), salmon berry (Rubus spectabilis), and evergreen ceanothus (Ceanothus velutinus) [40]. SUCCESSIONAL STATUS : Faculative Seral Species Obligate Climax Species Redwood is classified as a shade-tolerant to very shade-tolerant species due to its high photosynthetic capacity at low light levels [40]. Redwood releases well even at quite an old age. One specimen after 1,000 years released from 30 to 6 rings per inch (12-2.4 rings/cm) [19]. There is some debate over the classification of redwood as a climax species. Some consider redwood a climax species, while others consider it a fire-dependent seral species [15,41,54,55]. Osburn and Lowell [41] reported that if fire is excluded from Redwood National Park over the next 2,000 years redwood will disappear, and Sitka spruce, western hemlock (Tsuga heterphylla), and western redcedar (Thuja plicata) will dominate. Viers [55] on the other hand reported that redwood is a climax species in the vicinity of Redwood National Park because it maintains uneven age distributions with or without fire. After disturbance redwood dominates in early seres due to its ability to sprout [27,58]. In the floodplain environment redwood deploys what has been called "the endurer strategy." After flooding and stem burial, redwood will develop a new and higher lateral root system from buried buds on the bole of the tree. While the repeated flooding and deposition of soil (often to depths of 30 inches [76 cm]) kills competing vegetation, redwood endures [3,40,58]. SEASONAL DEVELOPMENT : Redwood female strobili become receptive and pollen is shed from late November to early March. Female strobili start ripening in September of the first year. Mature female strobili can be identified when their color changes from green to greenish yellow. Seed dispersal begins in late October, with most of the seeds being dispersed from November to February [8].

Related categories for Species: Sequoia sempervirens | Redwood

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Information Courtesy: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Fire Effects Information System

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