Pine tree

A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae.

''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as current, with additional synonyms, and ''Plants of the World Online'' 126 species-rank taxa (113 species and 13 nothospecies), making it the largest genus among the conifers. The highest species diversity of pines is found in Mexico. Pines are widely distributed in the Northern Hemisphere; they occupy large areas of boreal forest, but are found in many habitats, including the Mediterranean Basin, and dry tropical forests in southeast Asia and Central America.

Wood from pine trees is one of the most extensively used types of timber, and some pines are widely used as Christmas trees.

Description

Pine trees are evergreen, coniferous resinous trees (or, rarely, shrubs) growing tall, with the majority of species reaching tall. The smallest are Siberian dwarf pine and Potosi pinyon, and the tallest is an tall sugar pine located in Yosemite National Park.

Pines are long lived and typically reach ages of 100–1,000 years, some even more. The longest-lived is the Great Basin bristlecone pine (''P. longaeva''). One individual of this species, dubbed " Methuselah", is one of the world's oldest living organisms at around 4,800-years old. This tree can be found in the White Mountains of California. An older tree, now cut down, was dated at 4,900-years old. It was discovered in a grove beneath Wheeler Peak and it is now known as "Prometheus" after the Greek immortal.

The spiral growth of branches, needles, and cones scales are arranged in Fibonacci number ratios.

File:Big bristlecone pine Pinus longaeva.jpg, Ancient ''Pinus longaeva'', California
File:Tree Types and Barks 004.jpg, '' Pinus taeda'' bark
File:Pine needles.png, Pine needles
File:Pinus radiata cone.jpg, '' Pinus radiata'' female cone

Bark

The bark of most pines is thick and scaly, but some species have thin, flaky bark. The branches are produced in "pseudo-whorls", 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.

Foliage

Pines have four types of leaf:

* Seed leaves ( cotyledons) on seedlings are borne in a whorl of 4–24.
* Juvenile leaves, which follow immediately on seedlings and young plants, are long, single, green or often blue-green, and arranged spirally on the shoot. These are produced for six months to five years, rarely longer.
* Scale leaves, similar to bud scales, are small, brown and not photosynthetic, and arranged spirally like the juvenile leaves.
* Needles, the adult leaves, are green (photosynthetic) and bundled in clusters called fascicles. The needles can number from one to seven per fascicle, but generally number from two to five. Each fascicle is 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's growing tip is damaged (e.g. eaten by an animal), the needle fascicles just below the damage will generate a stem-producing bud, which can then replace the lost growth tip.

Cones

Pines are monoecious, having the male and female cones on the same tree. 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 fertilisation delayed one year. At maturity the female 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 anemochorous (wind-dispersed), but some are larger and have only a vestigial wing, and are bird-dispersed. Female cones are woody and sometimes armed to protect developing seeds from foragers. At maturity, the cones usually open to release the seeds. In some of the bird-dispersed species, for example whitebark pine, the seeds are only released by the bird breaking the cones open. In others, the seeds are stored in closed cones for many years until an environmental cue triggers the cones to open, releasing the seeds. This is called serotiny. The most common form of serotiny is pyriscence, in which resin binds the cones shut until melted by a forest fire, for example in '' P. radiata'' and '' P. muricata''; the seeds are then released after the fire to colonise the burnt ground with minimal competition from other plants.

Naming

Etymology

The modern English name "pine" derives from Latin ''pinus'', traced to the Indo-European base ''*pīt-'' 'resin'. Before the 19th century, pines were often called firs, a name now applied to another genus, '' Abies''. In some European languages, Germanic cognates of the Old Norse name are still in use for pines, as in Danish ''fyr'', Swedish ''fura/furu'', and German ''Föhre''.

Taxonomic history

The genus ''Pinus'' was named by Carl Linnaeus in 1753. ''Pinus sylvestris'', the Scots pine, was later chosen as the type species.

Evolution

Taxonomy

Pines are gymnosperms. The genus is divided into two subgenera based on the number of fibrovascular bundles in the needle, and the presence or absence of a resin seal on the scales of the mature cones before opening. The subgenera can be distinguished by cone, seed, and leaf characters:
* ''Pinus'' subg. ''Pinus'', the yellow, or hard pine group, with cones with a resin seal on the scales, and generally with harder wood; the needle fascicles mostly have a persistent sheath (two exceptions, '' Pinus leiophylla'' and '' Pinus lumholtzii'', have deciduous sheaths). The subgenus has also been called ''diploxylon'', on account of its two fibrovascular bundles.
* ''Pinus'' subg. ''Strobus'', syn. ''Pinus'' subg. ''Ducampopinus'', the white, or soft pine, and pinyon pine groups, with cones without a resin seal on the scales, and usually have softer wood; the needle fascicles mostly have a deciduous sheath (one exception, '' Pinus nelsonii'', has a persistent sheath). The subgenus has also been called ''haploxylon'', on account of its single fibrovascular bundle.

Phylogenetic evidence indicates that both subgenera have a very ancient divergence from one another. Each subgenus is further divided into sections and subsections.

Many of the smaller groups of ''Pinus'' are composed of closely related species with recent divergence and history of hybridisation. This results in low morphological and genetic differences. This, coupled with low sampling and underdeveloped genetic techniques, has made taxonomy difficult to determine. Recent research using large genetic datasets has clarified these relationships into the groupings often accepted today.

Phylogeny

''Pinus'' is the largest genus of the Pinaceae, the pine family, which first appeared in the Jurassic period. Based on recent transcriptome analysis, ''Pinus'' is most closely related to the genus '' Cathaya'', which in turn is closely related to the genus '' Picea'', the spruces. These genera, with firs and larches, form the pinoid clade of the Pinaceae. Pines first appeared during the Early Cretaceous, with the oldest verified fossil of the genus being '' Pinus yorkshirensis'' from the Hauterivian- Barremian boundary (~130-125 million years ago) from the Speeton Clay, England. However, there are possible records from the Jurassic.

The evolutionary history of the genus ''Pinus'' has been complicated by hybridisation. Pines are prone to inter-specific breeding. Wind pollination, long life spans, overlapping generations, large population size, and weak reproductive isolation make breeding across species more likely. As the pines have diversified, gene transfer between different species has created a complex history of genetic relatedness.

Two recent phylogenies are given below; the differences between them, and other published phylogenies, demonstrate these complications:

Distribution and habitat

Pines are native to the Northern Hemisphere, and to a few parts from the tropics to temperate regions in the Southern Hemisphere. Most regions of the Northern Hemisphere host some native species of pines; they occupy large areas of Boreal forest, and are found all around the Mediterranean Basin. The northernmost is Scots pine, reaching just north of 70° N in Stabbursdalen National Park in Norway; Google Maps shows geolocated images with pines at 70° 09' N. One species ( Sumatran pine) crosses the equator in Sumatra to 2°S. In North America, various species occur in regions at latitudes from as far north as 66° N to as far south as 12°N.

Pines may be found in a very large variety of environments, ranging from semi-arid desert to rainforests, from sea level up to , from the coldest to the hottest environments on Earth. They often occur in mountainous areas with favourable soils and at least some water.

Various species have been introduced to temperate and subtropical regions of both hemispheres, where they are grown as timber or cultivated as ornamental plants in parks and gardens. A number of such introduced species have become naturalised, and some species are considered invasive in some areas and threaten native ecosystems.

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) can 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 regimens.

Pine trees are beneficial to the environment since they can remove carbon dioxide from the atmosphere. Although several studies have indicated that after the establishment of pine plantations in grasslands, there is an alteration of carbon pools including a decrease of the soil organic carbon pool.

Several species are adapted to extreme conditions imposed by elevation and latitude (e.g. Siberian dwarf pine, mountain pine, whitebark pine, and the bristlecone pines). The pinyon pines and a number of others, notably Turkish pine and gray pine, are particularly well adapted to growth in hot, dry semidesert climates.

Pine pollen may play an important role in the functioning of detrital food webs. Nutrients from pollen aid detritivores in development, growth, and maturation, and may enable fungi to decompose nutritionally scarce litter. Pine pollen is also involved in moving plant matter between terrestrial and aquatic ecosystems.

Wildlife

Pine needles serve as food for various Lepidoptera (butterfly and moth) species. Several species of pine are attacked by nematodes, causing pine wilt disease, which can kill some quickly. Some of these Lepidoptera species, many of them moths, specialise in feeding on only one or sometimes several species of pine. Beside that many species of birds and mammals shelter in pine habitat or feed on pine nuts. The seeds are commonly eaten by birds, such as grouse, crossbills, jays, nuthatches, siskins, and woodpeckers, and by squirrels. Some birds, notably nutcrackers and pinyon jays, are of major importance in distributing pine seeds to new areas. Pine needles are sometimes eaten by the Symphytan species pine sawfly, and goats.

Uses

Timber and construction

Pines are among the most commercially important tree species, valued for their timber and wood pulp throughout the world.
In temperate and tropical regions, they are fast-growing softwoods that grow in relatively dense stands. Commercial pines are grown in plantations for timber that is denser and therefore more durable than spruce (''Picea''). Pine wood is widely used in high-value carpentry items such as furniture, window frames, panelling, floors, and roofing due to its abundance and low-cost.Turpentine is extracted from the wood of some species of pine.

As pine wood has no insect- or decay-resistant qualities after logging, in its untreated state it is generally recommended for indoor construction purposes only (indoor drywall framing, for example). It is commonly used in Canadian Lumber Standard graded wood. For outside use, pine needs to be treated with copper azole, chromated copper arsenate or other suitable chemical preservative.

Ornamental uses

Many pine species make attractive ornamental plantings for parks and larger gardens with a variety of dwarf cultivars being suitable for smaller spaces. There are currently 818 named cultivars (or trinomials) recognised by the American Conifer Society ACS. Pines are also commercially grown and harvested for Christmas trees. Pine cones, among the largest and most durable of all conifer cones, are craft favourites. Pine boughs, appreciated especially in wintertime for their pleasant smell and greenery, are popularly cut for decorations. Pine needles are also used for making decorative articles such as baskets, trays, pots, etc., and during the U.S. Civil War, the needles of the longleaf pine "Georgia pine" were widely employed in this. This originally Native American skill is now being replicated across the world. Pine needle handicrafts are made in the US, Canada, Mexico, Nicaragua, and India. Pine needles are also versatile and have been used by Latvian designer Tamara Orjola to create different biodegradable products including paper, furniture, textiles and dye.

Forestry

When grown for sawlogs, pine plantations can be harvested after 25 years, with some stands being allowed to grow up to 50 or more years (the wood value increases more quickly as the trees age). In colder and drier climates, growth is slower, and harvesting can be at much older ages. Imperfect trees (such as those with bent trunks or forks, smaller trees, or diseased trees) are removed in a "thinning" operation every 5–10 years. Thinning allows the best trees to grow faster, because it prevents weaker trees from competing for sunlight, water, and nutrients. Young trees removed during thinning are used for pulpwood or are left in the forest, while most older ones are good enough for saw timber.

A 30-year-old commercial pine tree grown in good conditions in Arkansas will be about in diameter and about high. After 50 years, the same tree will be about in diameter and high, and its wood will be worth about seven times as much as the 30-year-old tree.
This however depends on the region, species and silvicultural techniques. In New Zealand, a plantation's maximum value is reached after around 28 years with height being as high as and diameter , with maximum wood production after around 35 years (again depending on factors such as site, stocking and genetics). Trees are normally planted 3–4 m apart, or about 1,000 per hectare (100,000 per square kilometre).

Food and nutrients

The seeds ( pine nuts) are generally edible; the young male cones can be cooked and eaten, as can the bark of young twigs. Some species have large pine nuts, which are harvested and sold for cooking and baking. They are an ingredient of '' pesto alla genovese''.

The soft, moist, white inner bark (cambium) beneath the woody outer bark is edible and very high in vitamins A and C. It can be eaten raw in slices as a snack or dried and ground up into a powder for use as an ersatz flour or thickener in stews, soups, and other foods, such as bark bread. Adirondack Indians got their name from the Mohawk Indian word ''atirú:taks'', meaning "tree eaters".

A tea is made by steeping young, green pine needles in boiling water (known as ''tallstrunt'' in Sweden). In eastern Asia, pine and other conifers are accepted among consumers as a beverage product, and used in teas, as well as wine. In Greece, the wine retsina is flavoured with Aleppo pine resin.

Pine needles from '' Pinus densiflora'' were found to contain 30.54 milligram/gram of proanthocyanidins when extracted with hot water.

In traditional Chinese medicine, pine resin is used for burns, wounds and skin complaints.

Culture

Pines have been a frequently mentioned tree throughout history, including in literature, art, and in religious texts.

The pine is a particular motif in Chinese art and literature, which sometimes combines painting and poetry in the same work. Some of the main symbolic attributes of pines in Chinese art and literature are longevity and steadfastness: the pine retains its green needles through all the seasons. Sometimes the pine and cypress are paired. At other times the pine, plum, and bamboo are considered as the " Three Friends of Winter".

Literature

Writers of various nationalities and ethnicities have written of pines. Among them, John Muir, Dora Sigerson Shorter, Eugene Field, Bai Juyi, Theodore Winthrop, and Rev. George Allan D.D.

Art

Pines are often featured in art, whether painting and fine art, drawing, photography, or folk art.

Religious texts

Trees which may be pines or other conifers are mentioned in some verses of the Bible. In the Book of Nehemiah 8:15, the King James Version translates Hebrew "עץ שמן" (etz shman), 'oil tree', as pine, and the unknown type of tree of Hebrew "תדהר" in Isaiah 60:13 similarly. Some botanical authorities believe that the Hebrew word "ברוש" (bərōsh), "cypress", which is used many times in the Bible, properly designates '' Pinus halepensis'', the Aleppo or Jerusalem pine, or in Hosea 14:8 which refers to fruit, '' Pinus pinea'', the stone pine.
The word used in modern Hebrew for pine is "אֹ֖רֶן" (oren), which occurs only in Isaiah 44:14, but two manuscripts have "ארז" ( cedar), a much more common word. Biblia Hebraica Stuttgartensia ad loc.

See also

* El Pino (The Pine Tree)
* Pine barrens
* Pine-cypress forest
* Pine Tree Flag
* Tree of Peace

References

Bibliography

*
*
*
*
*
*
*
*
*

External links

40 Species of Pine Trees You Can Grow
by The Spruce
* , covers Californian species

Pinus in Flora of North America

Pinus in the USDA Plants Database

Conifer Database

{{Authority control

Pinaceae
Pinus