Essentials of Ecology

216 CHAPTER 10 Sustaining Terrestrial Biodiversity: The Ecosystem Approach

200 years or more (Figure 10-2). Old-growth or pri-

mary forests are reservoirs of biodiversity because they

provide ecological niches for a multitude of wildlife spe-

cies (Figure 7-16, p. 155, and Figure 7-17, p. 156).

The second type is a second-growth forest: a

stand of trees resulting from secondary ecological suc-

cession (Figure 5-17, p. 117, and Figure 7-15, center

photo, p. 154). These forests develop after the trees in

an area have been removed by human activities, such

as clear-cutting for timber or cropland, or by natural

forces, such as fire, hurricanes, or volcanic eruption.

A tree plantation, also called a tree farm or com-

mercial forest (Figure 10-3), is a managed tract with

uniformly aged trees of one or two genetically uniform

species that usually are harvested by clear-cutting as

soon as they become commercially valuable. The land

Figure 10-2 Natural capital: an old-growth forest in the U.S. state of Washington’s Olympic National Forest (left)

and an old-growth tropical rain forest in Queensland, Australia (right).

Weak trees

removed

Seedlings
planted

Clear cut

30 yrs

5 yrs 10 yrs

Years of growth

15 yrs

25 yrs

SuperStock

Kevin Schafer/Peter Arnold, Inc. Mark Taylor/Warren Photographic/Bruce Coleman USA

Figure 10-3 Short (25- to 30-year) rotation cycle of cutting and re-
growth of a monoculture tree plantation used in modern industrial
forestry. In tropical countries, where trees can grow more rapidly year-
round, the rotation cycle can be 6–10 years. Old-growth or second-
growth forests are clear-cut to provide land for growing most tree plan-
tations (see photo, right). Question: What are two ways in which this
process can degrade an ecosystem?