Pine

A pine is a coniferous tree in the genus Pinus, in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.

Distribution

Pines are native to most of the Northern Hemisphere. In Eurasia, they range from the Canary Islands and Scotland east to the Russian Far East, and the Philippines, north to just over 70°N in Norway ( Scots Pine) and eastern Siberia ( Siberian Dwarf Pine), and south to northernmost Africa, the Himalaya and Southeast Asia, with one species ( Sumatran Pine) just crossing the Equator in Sumatra to 2°S. In North America, they range from 66°N in Canada ( Jack Pine) south to 12°N in Nicaragua ( Caribbean Pine). The highest diversity in the genus occurs in Mexico and California.

Pines have been introduced in subtropical and temperate portions of the Southern Hemisphere, including Chile, Brazil, South Africa, Australia, and New Zealand, where they are grown widely as a source of timber, and some species are becoming invasive.

Morphology

Pines are evergreen and resinous trees (rarely shrubs) growing to 3–80 m tall, with the majority of species reaching between 15-45 m tall. The smallest are Siberian Dwarf Pine and Potosi Pinyon, and the tallest, Sugar Pine. Pines are long-lived, typically reaching ages of 100–1,000 years, some even more. The longest-lived is the Great Basin Bristlecone Pine Pinus longaeva, one individual of which at 4,840 years 2008 is the oldest living organism in the world.

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 covered in brown or whitish bud scales and point upward at first, then later turn green and spread outward. These "candles" offer foresters a means to evaluate fertility of the soil and vigour of the trees.

Foliage

Pines have four types of leaves:

1. Seed leaves ( cotyledons) on seedlings, borne in a whorl of 4-24.
2. Juvenile leaves, which follow immediately on seedlings and young plants, 2-6 cm long, single, green or often blue-green, and arranged spirally on the shoot. These are produced for six months to five years, rarely longer (and also produced later in life after injury in some pines).
3. Scale leaves, similar to bud scales, small, brown and non-photosynthetic, and arranged spirally like the juvenile leaves.
4. Needles, the adult leaves, which are 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.

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.

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.

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 that feed on pines) and also the Symphytan species Pine Sawfly.

Uses

Pines are among the most commercially important of tree species, valued for their timber and wood pulp throughout the world. In temperate and tropical regions, they are fast-growing softwoods that will grow in relatively dense stands, their acidic decaying needles inhibiting the sprouting of competing hardwoods. Commercial pines are grown in plantations for timber that is denser, more resinous, and therefore more durable than spruce (Picea). Pine wood is widely used in high-value carpentry items such as furniture, window frames, paneling and floors.

The resin of some species is an important source of turpentine. See also pitch.

Many pine species make attractive ornamental plantings for parks and larger gardens, with a variety of dwarf cultivars being suitable for smaller spaces. Pines are also commercially grown and harvested for Christmas trees. Pine cones, the largest and most durable of all conifer cones are craft favorites. Pines boughs, always appreciated, especially in wintertime for their pleasant smell and greenery, are popularly cut for decorations.

Pine needles serve as food for various Lepidoptera. See List of Lepidoptera which feed on Pines.

Food uses

Some species have large seeds, called pine nuts, that are harvested and sold for cooking and baking.

The soft, moist, white inner bark ( cambium) found clinging to 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 a thickener in stews, soups, and other foods. A tea made by steeping young, green pine needles in boiling water (known as "tallstrunt" in Sweden) is high in vitamins A and C as well.

Etymology

The modern English name pine derives from Latin Pinus by way of French pin; similar names are used in other Romance languages. In the past (pre-19th century) they were often known as fir, from Old Norse fyrre, by way of Middle English firre. The Old Norse name is still used for pines in some modern north European languages, in Danish, fyr, in Norwegian and Swedish, furu, and Föhre in German, but in modern English, "fir" is now restricted to Fir (Abies) and Douglas-fir (Pseudotsuga).