Page 690 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

654 part IV Soils, Ecosystems, and Biomes
(a) Trumpet trees (Tabebuia caraiba) are dry-season deciduous trees that are common in the seasonal forest and scrub of Paraguay.
better drained, thereby providing a strong base for agriculture and grazing. Sorghums, wheat, and groundnuts (peanuts) are common crops of this biome.
Africa has the largest area of tropical savanna on Earth, including the famous Serengeti Plains of Tanzania and Kenya, and the Sahel region, south of the Sahara. Portions of Australia, India, and South America also are part of the savanna biome. Local names for tropical savannas include the Llanos in Venezuela, stretching along the coast and inland east of Lake Maracaibo and the Andes; the Campo Cerrado of Brazil and Guiana; and the Pantanal of southwestern Brazil.
Particularly in Africa, savannas are the home of large land mammals—zebra, giraffe, buffalo, gazelle, wildebeest, antelope, rhinoceros, and el- ephant. These animals graze on savanna grasses, while others (lion, cheetah) feed upon the graz- ers themselves. Birds include the ostrich, Martial Eagle (largest of all eagles), and Secretary Bird. Many species of venomous snakes, as well as the crocodile, are present in this biome.
Midlatitude Broadleaf
and Mixed Forest
Moist continental climates support a mixed for- est in areas of warm to hot summers and cool to cold winters. This midlatitude broadleaf and mixed forest biome includes several distinct com- munities in North America, Europe, and Asia. In the United States, relatively lush evergreen broad- leaf forests occur along the Gulf of Mexico. To the north are the mixed deciduous broadleaf and
needleleaf trees associated with sandy soils and frequent fires—pines (longleaf, shortleaf, pitch, loblolly) predomi- nate in the southeastern and Atlantic coastal plains. In
(b) Cattle ranching is common in the Gran Chaco region.
▲Figure 20.8 Tropical seasonal forest and scrub, Gran Chaco, Paraguay. [(a) Imagebroker/Alamy. (b) Universal Images/DeAgostini/Alamy.]
Savanna vegetation is maintained by fire, both a natural and a human-caused disturbance in this biome. During the wet season, grasses flour- ish, and as rainfall diminishes, this thick growth provides fuel for fires, which are often intention- ally set to maintain the open grasslands and sup- press the growth of trees. Hot-burning dry-season fires kill trees and seedlings and deposit a layer of nutrient-rich ash over the landscape. These condi- tions foster the regrowth of grasses, which again grow vigourously as the wet season returns, sprout- ing from extensive underground root systems that are an adaptation for surviving fire disturbance. In northern Australia, the aboriginal people are cred- ited with creating and maintaining many of the re- gion’s tropical savannas; as the traditional practice of setting annual fires declines, many savannas are reverting to forest.
Tropical savanna soils are much richer in humus than the soils of the wetter tropics and
▲Figure 20.9 Savanna landscape of the Serengeti Plains, east Africa. Wildebeest, zebras, and acacia trees. [EastVillage Images/ Shutterstock.]