Forest classification

Forests to a non-specialist seem to be nothing but a collection of trees. The closer they are examined, the more they differ. Furthermore, their difference may be expressed in a number of ways. Some scientists write: “A plant association mainly of trees or other woody vegetation occupying an area of land is a forest”. Others they that a collection of trees becomes a forest only when it has sufficient density and covers a large enough area to develop local climatic and ecological conditions that are different from those outside. There must be some changes in temperature, moisture, light and wind as well as in the character of upper soil layer. With these changes comes a different vegetation under the trees and different animal life in the forest. In technical language a specialist says that a forest “biocenoze” has been set up. Originally “forest” meant simply wild or uncultivated land. Today the term "forest" is sometimes applied to an economic unit of operating area. A forest of trees of similar age and composition is called a “stand”. Every stand has a more or less regular upper layer of green crowns, called “the forest canopy” under which there may be an open space except for the stems of the forest trees or more or less occupied with lower canopies. They are called understories and are typical of tropical forests but may be in the forests of the temperate zone too.

Very often a single understorey consists of saplings which are coming in to replace the falling stand of veterans above. Where the forest is open or thin there may be ground cover of grass. The nature of this cover is very different. In dense forests the ground under the trees – the forest floor – may have no living vegetation and be covered with dead leaves and branches.

The species composition of the forest is one of the most important features. The stand may be composed of a single species making a pure forest or several species are associated to form a mixed forest. Perfectly pure forests over large areas occur not often however. It was observed that species do not do well when planted in pure stands, especially upon usual forest soils. The reason is that they make very heavy demands upon soil plant food (nutrients). Such pure stands may do well in youth, but as they become older, their growth becomes very slow and the trees die.

Stands are classified according to age classes of which they are composed. Even-aged stand is one in which all the trees are of one age. Uneven-age stand, on the other hand, theoretically has trees of every age, from seedlings to old veterans. Forests are found in almost every part of the world. Only the north and south poles, the tops of some mountains, the deserts, and some prairies are bare of forests. Forests can be grouped by location, climate, or the types of trees common to them. Forests can also be described in terms of the uses made of them. Commercial forests, for example, are lands used for growing successive crops of trees for products. Wilderness preserves, on the other hand, are areas where no harvesting is allowed.

Trees in the forest are of two basic kinds. Hardwoods (figure1.1) have broad leaves and bear their seeds in dry clusters or in fruits; examples are oak, maple, hickory, and apple. Most of the North American hardwoods are deciduous, which means they lose their leaves each fall. Softwoods (figure 1.2) have needle-shaped leaves and bear their seeds in cones, for which reason they are often called conifers; examples are pine, spruce, fir, and larch. Most softwoods are evergreen, which means they lose only some of their needles each year, and so remain green year-round. This description can be misleading, however, because several hardwoods, including the American holly and the magnolia, are also evergreen.

1.3 Find the answers to the following questions in the text 1:

1.What does the term” forest” mean?

2. What is a stand?

3. In what case does a single understorey consist of saplings?

4. How do pure and mixed forests differ?

1.4 Divide the text into the main paragraphs and name each of them.

What is it?

1. … is a cold-temperate forest dominated mostly by conifers (spruce, fir, etc.). It may also contain some broad-leaved deciduous trees such as birch. This type of forest is circumpolar-it stretches around the globe. It is located between the northern tundra and the southern temperate mixed forests or steppe. Winters are long and cold here, lasting from 6 to 9 months.

2. … is a forest type with widely spaced trees and an understory of grasses and other forbs that require high levels of light.

3. … is large, dry, level, grassland having few or no trees.

4. …occur in the lowlands around the equator. They are characterized by many vines and epiphytes (plants that live on other plants), and trees that flower, fruit, and have leaves all year.

5. … is a grassy plain in the arctic and antarctic dominated by sedges, rushes, and wood rushes, perennial herbs, small woody shrubs, mosses, and lichens.

6. … – a place of dense, shorter plants, including shrubs and grasses. Because hardly any trees grow in a field, plants that need a lot of sunlight are able to grow. A farmer’s field has only the plants that the farmer wants to grow; a wild field, such as a meadow, has many different plants and animals.