Pinus radiata
Pinus radiata, the Monterey pine, insignis pine or radiata pine, is a species of pine native to the Central Coast of California and 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, 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. The pine shoot moth Rhyacionia buoliana is another serious problem. In cultivation in New Zealand, Pinus radiata has grown as much as in 41 years, an average of per year.
Description
Pinus radiata is a coniferous evergreen tree growing to tall in the wild, but up to in cultivation in optimum conditions, with upward pointing branches and a rounded top. The leaves are bright green, in clusters of three, slender, long and with a blunt tip. The ovulate cones are long, brown, ovoid, 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, 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 off the mainland coast, the pines are found on the steep northern end of the island, at elevations of around, where they follow the ridgetops and steep slopes. On Cedros Island, the pines are more abundant, being found in far greater numbers partly due to the lack of feral goats. They are found at lower elevations than on Guadalupe, at around, 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.
- Pinus radiata var. binata Lemmon — Commonly known as the Guadalupe Island pine. Endemic to Guadalupe Island.
- Pinus radiata var. cedrosensis Silba — Commonly known as the Cedros Island pine. Endemic to Cedros Island.
Ecology
In its native range, P. radiata is associated with characteristic flora and fauna. It is the co-dominant canopy tree, together with Cupressus macrocarpa, which also naturally occurs only in coastal Monterey County. Furthermore, one of the pine forests in Monterey, California, was the discovery site for Hickman's potentilla, an endangered species. Piperia yadonii, a rare species of orchid, is endemic to the same pine forest adjacent to Pebble Beach. In its native range, P. radiata is a principal host for the dwarf mistletoe Arceuthobium littorum.
The habitat of the pines on Cedros Island contrasts greatly with the desert scrub on other parts of the island, forming zones of abrupt transition. The numerous groves form a mostly-monotypic forest of the species, with very few other plants besides seedlings emerging in the understory. In some areas, the edges of the forest form a zone that supports chaparral species, including Malosma laurina, Diplacus ''stellatus, and the endemic Eriogonum molle. With their large surfaces to condense fog, the pines create irrigation for themselves and their associates. Towards the far northern end of the island, a succulent community mostly consisting of Dudleya is found, and the endemic Dudleya pachyphytum can sometimes be found growing under the pines in the ecotone.
A remnant P. radiata'' stand in Pacific Grove, the Monarch Grove Sanctuary, is a prime wintering habitat of the monarch butterfly.
In South Africa, the tree is a threat to already scarce water resources. The tree has remarkable roots. Monterey pine roots will reach downward as far as physically permitted by subterranean conditions. Roots have been discovered up to long. Efforts to remove large quantities of the non-native tree in areas of South Africa have resulted in significant increases in accessible water.
Conservation status
Fungal disease
The three remaining wild stands of var. radiata are infected and under threat of extirpation from pine pitch canker caused by Fusarium circinatum, a fungal disease native to the southeast United States and found to have been introduced to California. When trees decay due to the disease, they attract bark beetles which provide a pathway for infection of other trees. In some stands, 80–90% of trees are infected. If the disease is introduced in agroforestry areas dependent upon P. radiata, such as New Zealand, it could have catastrophic effects in those countries as well.Sphaeropsis blight infects P. radiata in California and causes serious damage to plantations of the species in New Zealand, Australia and South Africa, especially after hail damage to growing tips.
Baja California
On Guadalupe Island, var. binata is critically endangered. Most of the population was destroyed as tens of thousands of feral goats ate binata seedlings and caused soil erosion from the mid-19th century until just a few years ago. The older trees gradually died off until by 2001–2002 the population stood at only one hundred. With a program to remove the goats essentially complete by 2005, hundreds of young Guadalupe pines have started to grow up in habitat fenced after 2001, the first significant new growth in about 150 years. Possible accidental introduction of pine pitch canker is considered the biggest threat at present to the survival of the Guadalupe Island pine population. The University of California's Russell Reservation forestry research station hosts an orchard planted with 73 P. radiata seedlings from Guadalupe Island and plays an important role in conserving the binata variety.Cultivation
Australia
Pinus radiata was introduced to Australia in the 1870s. It is "the dominant tree species in the Australian plantation estate" – so much so that many Australians are concerned by the resulting loss of native wildlife habitat. The species is widely regarded as an environmental weed across southeastern and southwestern Australia and the removal of individual plants beyond plantations is encouraged. The Kuitpo Forest, south-east of the Adelaide city centre, is a planted forest of Monterey Pine trees. west of the Sydney city centre, there is a forest of introduced Monterey Pine trees in Prospect Hill, in the suburb of Pemulwuy.Chile
Pinus radiata has greatly replaced the Valdivian temperate rain forests, where vast plantations have been planted for timber, again displacing the native forests. In 2001, this species produced 5,580,724 cubic meters of lumber, or 95% of Chile's total lumber production. In 2021 1.3 million of Chile's 2.3 million ha of forest plantations were planted with Pinus radiata.New Zealand
The Monterey pine was first introduced into New Zealand in 1859 and today 89% of the country's plantation forests are of this species. This includes the Kaingaroa Forest, which is one of the largest planted forests in the world. Mass plantings became common from 1900 in the Rotorua area where prison labour was used. In some areas it is considered an invasive species where it has escaped from plantations. It is the most extensively used wood in New Zealand.Use of pine in construction did not become widespread until forced by wartime shortages. It had been used in Southland from about 1920, but doubts were being expressed about it as late as 1945, when at least one MP considered it only suitable for interior studding. Experiments in pressure treatment with water-soluble preservatives were made from 1943.