Pinus radiata (syn. Pinus insignis), the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast of California, and the Guadalupe and Cedros islands of Mexico. It is an evergreen conifer in the family Pinaceae. Pinus radiata is a versatile, fast-growing, medium-density softwood, suitable for a wide range of uses and valued for rapid growth (up to two meters (6.5 feet) in one year), as well as desirable lumber and pulp qualities. Its silviculture reflects a century of research, observation and practice. It is often considered a model for growers of other plantation species. Although P. radiata is extensively cultivated as a plantation timber in many temperate parts of the world, it faces serious threats in its natural range, due to the introduction of a fungal parasite, the pine pitch canker (Fusarium circinatum). The pine shoot moth Rhyacionia buoliana is another serious problem. In cultivation in New Zealand, Pinus radiata has grown as much as 61 m (200 ft) in 41 years, an average of 1.5 m (4 ft 11 in) per year.
Description
Pinus radiata is a coniferous evergreen tree growing to 15–30 m (50–100 ft) tall in the wild, but up to 60 m (200 ft) in cultivation in optimum conditions, with upward pointing branches and a rounded top. The leaves ("needles") are bright green, in clusters of three (two in var. binata), slender, 8–15 cm (3–6 in) long and with a blunt tip. The ovulate cones are 7–17 cm (3–6+1⁄2 in) long, brown, ovoid (egg-shaped), and usually set asymmetrically on a branch, attached at an oblique angle. The bark is fissured and dark gray to brown. When not cut short by disease or harvesting, it has a lifespan of 80 to 90 years. The specific epithet radiata refers to the cracks which radiate from the umbo of the cone scales. It is closely related to bishop pine and knobcone pine, hybridizing readily with both species; it is distinguished from the former by needles in threes (not pairs), and from both by the cones not having a sharp spine on the scales. The modern plantation tree is vastly different from the native tree of Monterey. In plantations the tree is commonly planted at 4 square meter spacing on a wide variety of landscapes from flat to moderately steep hills. Because of selective breeding and more recently the extensive use of growth factor seedlings, forests planted since the 1990s have very straight tall trunks without the problem of twin leaders. The trees are pruned in three lifts so that the lower two-thirds of a mature tree is free of branches and hence of knots.
Distribution and habitat In the United States, it is native to three very limited areas located in Santa Cruz, Monterey, and San Luis Obispo Counties of California. In Mexico, it is found on two islands in the Pacific Ocean, Guadalupe Island and Cedros Island. On Guadalupe Island, located 280 km (150 nmi) off the mainland coast, the pines are found on the steep northern end of the island, at elevations of around 500 to 1,200 m (1,600 to 3,900 ft), where they follow the ridgetops and steep slopes. Edward Palmer and Francescho Franceschi were the first to discover the pines on Guadalupe Island. When Franceschi visited in 1892, he noted that they extended all over the northern and northwestern part of the island, comprising a very thick forest, with some of the finest trees growing with the Guadalupe palm. On Cedros Island, the pines are more abundant, being found in far greater numbers partly due to the lack of feral goats. (Goats were exterminated on Guadalupe island by 2007.) They are found at lower elevations than on Guadalupe, at around 285 to 690 m (935 to 2,264 ft), on the windward ridges and canyons of the north and central parts of the island. In both cases, the pines seem to be heavily dependent on locations with a high frequency of fog. In Australia, New Zealand, and Spain it is the leading introduced tree and in Argentina, Chile, Uruguay, Kenya, and South Africa it is a major plantation species. It is also an introduced tree on the world's most remote inhabited island, Tristan da Cunha.
Taxonomy
Subdivisions Two varieties of this species have been recognized, each corresponding to the island they are endemic to in Baja California. Some authors lump these taxa and do not recognize infraspecies. On both islands it is the only pine species, and one of the few tree species. Compared to the mainland species, which are mostly three-needled, the insular varieties have their needles in bundles of two. Their cones are also smaller, and they show greater wind resistance in regards to wind-induced toppling. John Thomas Howell found that in some examples of the pines on Guadalupe Island, vigorous shoots often had needles in threes, similar to typical Pinus radiata. Howell treated the pines on Guadalupe as three separate forms rather than the endemic variety, with forma radiata having very asymmetrical cones, forma guadalupensis with nearly symmetrical cones, and forma binata with intermediate cones, similar to those of the type collection of var. binata collected by Edward Palmer. The pines of Cedros Island were previously referred to as Pinus muricata, or a variety of that species described by Howell, P. muricata var. cedrosensis. Other botanists, like Herbert L. Mason, instead identified it as Pinus remorata. Later studies, like those conducted by Daniel Axelrod, instead suggested that the pines of Cedros Island belonged to Pinus radiata. The two island varieties have two to several resin canals on their needles, while the mainland species has zero to two.
Pinus radiata var. binata (Engelm.) Lemmon — Commonly known as the Guadalupe Island pine. Endemic to Guadalupe Island. The Guadalupe pines are larger than the mainland pines, with example noted by Howell having a 2.71 m (8.9 ft) diameter trunk, greater than the largest diameter trunk recorded on the mainland of 1.83 m (6.0 ft). The mean length of the Guadalupe Island pine's cones is 8.2 cm (3.2 in), which is shorter than the mainland plants (measuring between 9.6 cm (3.8 in) and 13.9 cm (5.5 in), depending on population), but longer than the Cedros Island pine's cones. Pinus radiata var. cedrosensis (J.T. Howell) Silba — Commonly known as the Cedros Island pine. Endemic to Cedros Island. The mean length of Cedros Island pine's cones is 6.5 cm (2.6 in), the smallest among all populations.
Ecology
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