Beech family (Fagaceae)

views updated

Beech family (Fagaceae)

The beech family is an important group of flowering plants that includes the beeches, oaks, and sweet chestnuts. Most members of the family are deciduous or evergreen trees or shrubs. The leaves, arranged alternately along branches, are leathery in texture, often strongly ribbed, and have margins that are entire, toothed, or deeply lobed. The flowers are unisexual. Male flowers are usually arranged in catkins, whereas female flowers are in few-flowered clusters. The fruit is a one-seeded nut that is partially or completely covered by a cupule of scales or a spiny bur.

The family includes eight genera and about 1,000 species. The Fagaceae are widely distributed and most abundant in temperate and subtropical regions of the Northern Hemisphere, although there is one tropical and one south temperate (Nothofagus ) genus. Beech (Fagus ) and sweet chestnut are, or were, in the case of American chestnut (Castanea dentata ), prominent components of mature deciduous and mixed forests of North America and Eurasia. Much of central Europe was covered by forests of beech and oak until cleared by people for agriculture. Similar forests in the Southern Hemisphere are dominated by southern beeches in the southern Andes, eastern Australia, and New Zealand.

Oaks (Quercus ) are also important in rich temperate deciduous forests as well as on droughty soils such as the sand plains of the eastern North American seaboard, where oaks grow abundantly with pines. Evergreen oaks are especially important in the arid regions of the Gulf of Mexico, southern China, and southern Japan. Evergreen species of both oaks and southern beeches are prominent in the mixed mountain forests of Southeast Asia. Given their prominence as the producers of deciduous and mixed forests, the Fagaceae are extremely important ecologically. Their

nuts are also important food sources for a variety of insects, birds, and mammals.

The beech family is among the most valuable sources of hardwood timber in the world. There are over 300 species of oak worldwide and the characteristics of their wood varies. Nevertheless, most produce strongly grained durable wood that polishes well. The white oaks of North America, in particular, produce fine wood that is commonly used for furniture, paneling, and flooring. Oak bark is often rich in tannin, used to tan leather. Oak wood is to make barrels for the storage of whiskey, wine, and sherry, and is also valued as firewood and for making charcoal. Tropical members of the family, such as Castanopsis and Lithocarpus (called chinkapin and tanoak respectively in North America), also produce high-quality wood, but they have not as yet been heavily exploited.

The bark of the Mediterranean cork oak (Quercus suber ) is the principle source of commercial cork. Cork bark is stripped in summer by making a circular cut at the base of the trunk and another just below the first branches. A lengthwise slit is then made between the two circular cuts and the bark is carefully removed with special hatchets so as not to damage the conducting tissue of the inner bark. The stripped bark is stacked and allowed to season for a few weeks, then boiled in tanks of water, followed by the removal of the rough outer bark. The cork is then dried and ready for use. The bark is stripped from trees once every 8-10 years. Aside from its role in stoppering bottles, cork is

used for gaskets, floats, nonslip walkways, corkboard, and flooring. The main cork-producing areas are Portugal and southwest Spain.

Chestnuts are especially prized for their large, sweet, edible nuts. Although there are about 10 species of sweet chestnuts, the most widely grown is Castanea sativa, commonly called the Italian, Spanish, or European sweet chestnut, a native of southern Europe. The nuts can be roasted, used whole or sliced in stews and stuffings, or pureed into the exquisite French dessert called marrons glac´s. The American chestnut was once an important timber and nut tree, and it is said that its nuts were sweeter and tastier than those of European species. Unfortunately, this once-dominant member of the deciduous forest of eastern North America is now a rarity, struck down by chestnut blight.

Chestnut blight was introduced into eastern North America from abroad in about 1904. By 1940, the American chestnut had disappeared from most of its range, clinging in places as sprouts from the root collars of trees whose trunks had died, but although these sprouts may grow for 40 years, they do not produce fruit, and so the tree is condemned to die without leaving offspring. The disease is caused by the fungus Endothia parasitica, which produces spores that stick onto the beaks and feet of bark-feeding birds and on the bodies of bark beetles. The spores are carried by the birds and insects to healthy trees that become infected when spores are accidentally deposited into wounds caused by the feeding of the birds and beetles. The spores germinate and the growing fungal threads enter vital cells of the inner bark, killing them.

KEY TERMS

Catkin— An elongate, spikelike cluster of unisexual flowers, often drooping at maturity.

Evergreen— Plants whose leaves persist and function for two or more years.

There are no adequate control measures for chestnut blight.

Beeches (Fagus and Nothofagus ) both produce valuable wood. European beeches have proved to be extremely useful in bentwood furniture, which is made by steaming laminated pieces of wood and then pressing them against forms until dry. Beech nuts were once commonly eaten by people, but now the nuts, along with acorns, are mostly fed to pigs, especially in Europe. In many parts of eastern North America, the American beech has been afflicted by a canker disease that disfigures the lovely, smooth, gray bark and obstructs the conducting tissue causing reduced rates of growth.