Text 8 tree size and type classification

Tree age and size can be described in a general and approximate way by use of such words as seedling, sapling, pole-size, mature, and veteran. A stand of trees can be even-aged or all-aged. A forest made up principally of one species is a pure stand, while one composed of several species is a mixed stand. Trees are also classified by the positions of their crowns relative to the general level of the forest canopy, the covering created by the crowns interweaving each other.

Dominant: A tree having a well-developed crown that extends above the general level of the other crowns and is exposed to full light from above and partial light from the sides.

Co-dominant: A tree with smaller crown than the dominants that helps form the general level of the canopy and receives full light from above but limited amount from the sides.

Intermediate: A small-crowned tree crowded into the general level of the forest canopy, receiving some light from above and virtually none from the sides.

Suppressed: A tree with poorly developed crown, beneath the level of the canopy (overtopped), receiving very little light from above or the sides.

Foresters refer to a measure of the number and size of trees in a given area as stand density. It indicates whether the forest is under stocked, medium stocked, or well stocked. For example, if the canopy of a tract of timber is closed over as much as 40 to 70 percent, it is medium- stocked.

Words to remember:

1. sapling – молодое деревце

2. mature – зрелый

3. pure stand – однородное лесонасаждение

4. canopy – полог

5. level – уровень

6. beneath – внизу

7. measure – мера

Exercise 2. True or false?

a. A pure stand is made up of different species.

b. Trees can not be classified by the positions of their crowns.

c. In a forest, each crown of each tree stays away from each other.

d. A dominant tree receives some light from the sides.

e. A co-dominant tree gets no sunlight from the sides.

f. A suppressed tree receives no light at all.

g. An intermediate tree does not have any light from the sides.

h. Stand density is the number and sizes of trees in a given area.

i. Basing on the crowns of trees that are relative to the general level of the forest canopy, trees can be classified into four types.

j. If the canopy of a tract of timber is closed as much as 55%, it is medium-stocked

Text 9 what a forest is

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 great 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 say 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.

Originally “forest” meant simply wild or uncultivated land. Today the term “forest” is applied to an economic unit of operating area.

A forest of trees of similar age and composition is called “a stand”. Every stand has 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 temperature zones 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 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. Species do not do well when planted in pure stands. 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 slow and the trees die.

Words to remember:

1. to seem – казаться

2. to examine – изучать

3. sufficient – достаточный

4. forest canopy – лесной полог

5. stand – лесонасаждение

6. understorey – второй ярус насаждения

7. branch – ветвь

8. demand – требование

9. except for – кроме

10. pure – чистый

Exercise 1. Answer the questions

1. What definitions of forest are given in the text?

2. What is “a stand”?

3. What can we see on the ground in a dense forest?

4. What makes a pure forest?

5. Do species in pure stands grow well?