Pine
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 Maritime Pine (Pinus pinaster)
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See Pinus classification for complete taxonomy to species level. See list of pines by region for list of species by geographical distribution. |
A pine is a coniferous tree of the genus Pinus, in the family Pinaceae. There are about 115 species of pine, although different authors accept anything from 105 to 125 species.
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[edit] Classification
Pines are divided into three subgenera, based on cone, seed and leaf characters:
- Subgenus Strobus (white or soft pines). Cone scale without a sealing band. Umbo terminal. Seedwings adnate. One fibrovascular bundle per leaf.
- Subgenus Ducampopinus (pinyon, lacebark and bristlecone pines). Cone scale without a sealing band. Umbo dorsal. Seedwings articulate. One fibrovascular bundle per leaf.
- Subgenus Pinus (yellow or hard pines). Cone scale with a sealing band. Umbo dorsal. Seedwings articulate. Two fibrovascular bundles per leaf.
[edit] Distribution
Pines are native to most of the Northern Hemisphere. In North America, they range from the Arctic south to Nicaragua and Hispaniola, with the highest diversity in Mexico and California. In Eurasia, they range from Portugal and Scotland east to the Russian Far East, Japan, and the Philippines, and south to northernmost Africa, the Himalaya and Southeast Asia, with one species (Sumatran Pine) just crossing the Equator in Sumatra. Pines are also extensively planted in many parts of the Southern Hemisphere.
[edit] Morphology
Pines are evergreen and resinous. The bark of most pines is thick and scaly, but some species have thin, flaking bark. The branches are produced in regular "pseudowhorls", actually a very tight spiral but appearing like a ring of branches arising from the same point. Many pines are uninodal, producing just one such whorl of branches each year, from buds at the tip of the year's new shoot, but others are multinodal, producing two or more whorls of branches per year. The spiral growth of branches, needles and cone scales are arranged in Fibonacci number ratios. The new spring shoots are sometimes called "candles"; they are light-colored and point upward at first, then later darken and spread outward. These "candles" offer foresters a means to evaluate fertility of the soil and vigour of the trees.
[edit] Foliage
Pines have four types of leaves. Seedlings begin with
- a whorl of 4-20 seed leaves (cotyledons), followed immediately by
- juvenile leaves on young plants, 2-6 cm long, single, green or often blue-green, and arranged spirally on the shoot. These are replaced after six months to five years by
- scale leaves, similar to bud scales, small, brown and non-photosynthetic, and arranged like the juvenile leaves; and
- the adult leaves or needles, green (photosynthetic), bundled in clusters (fascicles) of (1-) 2-5 (-6) needles together, each fascicle produced from a small bud on a dwarf shoot in the axil of a scale leaf. These bud scales often remain on the fascicle as a basal sheath. The needles persist for 1.5-40 years, depending on species. If a shoot is damaged (e.g. eaten by an animal), the needle fascicles just below the damage will generate a bud which can then replace the lost growth.
[edit] Cones
Pines are mostly monoecious, having the male and female cones on the same tree, though a few species are sub-dioecious with individuals predominantly, but not wholly, single-sex. The male cones are small, typically 1-5 cm long, and only present for a short period (usually in spring, though autumn in a few pines), falling as soon as they have shed their pollen. The female cones take 1.5-3 years (depending on species) to mature after pollination, with actual fertilization delayed one year. At maturity the cones are 3-60 cm long. Each cone has numerous spirally arranged scales, with two seeds on each fertile scale; the scales at the base and tip of the cone are small and sterile, without seeds. The seeds are mostly small and winged, and are anemophilous (wind-dispersed), but some are larger and have only a vestigial wing, and are bird-dispersed (see below). At maturity, the cones usually open to release the seeds, but in some of the bird-dispersed species (e.g. Whitebark Pine), the seeds are only released by the bird breaking the cones open. In others, the fire climax pines (e.g. Monterey Pine, Pond Pine), the seeds are stored in closed ("serotinous") cones for many years until a forest fire kills the parent tree; the cones are also opened by the heat and the stored seeds are then released in huge numbers to re-populate the burnt ground.
[edit] Ecology
Pines grow well in acid soils, some also on calcareous soils; most require good soil drainage, preferring sandy soils, but a few, e.g. Lodgepole Pine, will tolerate poorly drained wet soils. A few are able to sprout after forest fires, e.g. Canary Island Pine. Some species of pines, e.g. Bishop Pine, need fire to regenerate and their populations slowly decline under fire suppression regimes. Several species are adapted to extreme conditions imposed by elevation and latitude; see e.g. Siberian Dwarf Pine, Mountain Pine, Whitebark Pine and the bristlecone pines. The pinyon pines and a number of others, notably Turkish Pine, are particularly well adapted to growth in hot, dry semi-desert climates.
The seeds are commonly eaten by birds and squirrels. Some birds, notably the Spotted Nutcracker, Clark's Nutcracker and Pinyon Jay, are of importance in distributing pine seeds to new areas where they can grow. Pine needles are sometimes eaten by some Lepidoptera species (see list of Lepidoptera which feed on Pines) and also the Symphytan species Pine Sawfly.
[edit] Name origins
[edit] Uses
Pines are commercially among the most important of species used for timber and wood pulp in temperate and tropical regions of the world. This is because they are fast-growing softwoods that can be planted in relatively dense stands, and because their acidic decaying needles may inhibit the growth of other competing plants in the cropping areas. Commercial pine crops are grown in plantations.
The resin of some species is important as the source of turpentine. See also pitch.
Some species have large seeds, called pine nuts, that are harvested and sold for cooking and baking.
Some pines are used for Christmas trees, and pine cones are also widely used for Christmas decorations.
Many pines are also very attractive ornamental trees planted in parks and large gardens. A large number of dwarf cultivars have been selected, suitable for planting in smaller gardens.
Pine trees are also famous for their pleasant smell, while some people find the smell overbearing. A very small number of people are allergic to pine resin and its scent has been known to trigger an asthma attack. What makes this particularly unusual is that it is also a treatment for asthma in some forms of alternative medicine[citation needed].
[edit] Nutritional use
Pines are well-known survival food plants. The soft, moist, white inner bark, or cambium, found clinging to the dead, woody outer bark is edible and very high in vitamins A and C. It can be eaten in slices raw as a snack or dried and ground up into a powder for use as a thickener/flavoring in stews, soups, and other foods. The bunches of young green cones found at the ends of branches make a healthy hiking snack. A tea made by steeping young, green pine needles in boiling water (known as "strunt" in Sweden) is high in vitamins A and C.
[edit] References
- Farjon, A. 1984, 2nd edition 2005. Pines. E. J. Brill, Leiden. ISBN 90-04-13916-8
- Little, E. L., Jr., and Critchfield, W. B. 1969. Subdivisions of the Genus Pinus (Pines). US Department of Agriculture Misc. Publ. 1144 (Superintendent of Documents Number: A 1.38:1144).
- Richardson, D. M. (ed.). 1998. Ecology and Biogeography of Pinus. Cambridge University Press, Cambridge. 530 p. ISBN 0-521-55176-5
- Mirov, N. T. 1968. The Genus Pinus. Ronald Press, New York (out of print).
[edit] External links
- Classification of pines
- Arboretum de Villardebelle Images of cones of selected species
- Gymnosperm Database - Pinus
- Gymnosperm families - scroll down to the Pinaceae
| Genera of the Pinaceae family |
| Pinus | Picea | Cathaya | Larix | Pseudotsuga | Abies | Cedrus | Keteleeria | Pseudolarix | Nothotsuga | Tsuga |
