The Thorntree and Tropical Scrub is characterized by short, thorny trees and shrubs. Trees The vegetation may form a continuous cover eliminating grasses. This vegetation formation is a response to a longer, and more intense drought period.
Figure 13.17 Livestock grazing severely damages the thorntree savanna leading to problems of desertification. Burkina Faso* (Picture credit: Carolyn Redenius, United Nations)
The thorntree and tropical scrub has suffered
under the misuse of human activity. Overgrazing has reduced the
capacity of the system to withstand the erosive forces of wind,
and to a lesser extent water. Without the protective restraint
plants, soil and sand, along with valuable soil nutrients, can
blow free from the surface. Deserts are rapidly encroaching and
replacing the savannas and steppe grasslands. Many years of
prolonged drought combined with human pressures on the biome
increases the likelihood for desertification of these areas.
Figure 13.18 Bald Top Oak Savanna, Oregon.
A Midlatitude savanna is sometimes called a parkland. Here, grasses are broken by patches or ribbons of broadleaf trees. The midlatitude savanna is located in a transitional area between the humid continental and midlatitude steppe climates. Parkland often is a step in the successional evolution of plant communities on abandoned farm fields of the eastern United States. For more see "Prairie Parkland (Temperate) Province ".