Martin Horst, age 13, of Monroe, La., for his question:
WHAT ARE SAVANNAS?
Savannas are areas of widely spaced trees. In some savannas, the trees grow in clumps. In others, individual trees grow throughout the area, forming an uneven, wide open canopy. In either case, most of the ground is covered by shrubs, especially grasses.
Savannas are found in regions where low rainfall, poor soil, frequent fires or other environmental features limit tree growth.
Scientists have divided the world's forests into six main formations, and the savanna is one type. The other five types of forest include the tropical rain forest, the tropical seasonal forest, the temperate deciduous forest, the temperate evergreen forest and the boreal forest.
The largest savannas lie in the tropics between heavy forests and grasslands. Tropical savannas grow throughout much of Central America, Brazil, Africa, India, southeast Asia and Australia.
Most temperate savannas, which are also called woodlands, grow between forests and grasslands and between forests and deserts.
Temperate savannas are found in areas of Canada and the United States that have fairly light annual rainfall and a long season of dryness. Most of these areas lie between heavily wooded forests and open areas.
Temperate savannas dominated by aspen grow in North Dakota, Manitoba, Saskatchewan and Alberta. Outside this region,.oak, pine or both oak and pine dominate the temperate savannas of North America.
Savannas of bur oak, mixed in some areas with other oaks or hickory, extend in a belt from Manitoba through Texas. Coniferous savannas of juniper and pinion pine cover the dry foothills of the Rocky Mountains from Idaho to northern Mexico. In California, the foothills of the Sierra Nevada have savannas of blue oak and digger pine.
Along the coast of Southern California, the climate supports a broadleaf savannah of various species of oaks.
All life in a savanna and in every other forest in the world is part of an extremely complex ecosystem.
An ecosystem consists of all the living and nonliving things in a particular area and the relationships among them.
The forest ecosystem is highly complicated. The trees and other green plants use sunlight to make their own food from the air and from water and minerals in the soil. The plants themselves then serve as food for certain animals while these animals, in turn, are eaten by other animals.
After plants and animals die, their remains are broken down by bacteria or tiny soil dwelling animals, as well as by plants called fungi. This process returns minerals to the soil, where they can again be used by green plants to make food.