4 The root system

The root system is important to the eucalyptus primarily because its rapid growth and size demands large quantities of water. It needs a strong taproot to secure it and lateral roots to support its size. The taproot needs to sink down into the soil at least six feet for good anchorage. Lateral roots will spread out to one hundred feet which can be a problem when planted near buildings and other types of facilities. The roots and rootlets can disrupt ditches, crack cisterns, clog water pipes and damage septic tanks. Eucalyptus roots are aggressive.

Aspen has an extensive root system, and ramets have been recorded growing up to 40 metres from a parent tree. Because of their access to nutrients through the parent tree’s root system, aspen ramets can grow very quickly – up to a metre per year for the first few years. As the ramets grow, they remain joined through their roots, and all the interconnected trees are called a clone. They are all the same individual organism and are therefore all single-sexed, either male or female. Each clone exhibits synchronous behaviour, with, for example, all the component trees coming into leaf at the same time in the spring. A clone can also sometimes be identified by the specific colour its leaves change to in the autumn. Aspen roots also have the unusual ability of staying alive underground for many years after the death of the parent tree. This leads to the appearance of aspen ramets in areas where there are no mature trees.

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5 Hardwood Forests

One major type of hardwood forest is the steamy, tropical rain forest that grows in the tropics and subtropics. These forests are typically composed of big, old evergreen hardwood trees that grow in several layers, or groups according to height. The tallest layer may reach heights of 150 feet (45 meters) or more. Other layers, composed of shade-tolerant trees, reach to about 100 feet (30 meters). Smaller trees and vines cover the ground in the shade in a dense tropical rain forest. These forests are often called jungles, though true jungles are dense thickets of brush and vines that may not have any tall trees.

One of the largest and most important tropical rain forests is in South America. It extends from the mouth of the Amazon River, in Brazil, to the mouth of the Orinoco River, in Venezuela, and covers millions of acres. Another great rain forest girdles the waist of Africa, and much of Southeast Asia is covered with rain forests. In the United States, only the southern tip of Florida and a bit of the coast of Texas have tropical forests.

Beautiful woods such as rosewood, mahogany, ebony, and teak are commercially important products of these forests. They are prized for fine furniture, cabinetry, and artistic uses.

Hardwood forests other than tropical ones cover much of the United States, most of Northern Europe, areas of northern Russia, eastern China, and the east coast of Australia. These forests include broad-leaved trees adapted to higher elevations with more moderate climates.

The largest forest area in the United States is the Central Hardwood Forest. It covers about 130 million acres (52.6 million hectares), from the edge of the central plains, across the lower edge of the Great Lakes states, to the coasts of New Jersey and New York. It straddles the Appalachian Mountains as far south as northern Georgia and spreads westward and covers large parts of eastern Texas. Because this area is blessed with rich soil and a moderate climate, it has been cleared in many places for farming.

Much of the wood for America’s furniture industry comes from this forest. Hardwoods such as black walnut, red oak, white oak, yellow poplar (also called tulip tree), sweet gum, and sycamore are among the most valu­able trees. A few softwoods are also found, including the shortleaf and white pines.

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