Most of South America lies within the tropics, and lowland tropical ecosystems make up the majority of its landscapes. Although there is great concern for the Amazon ecosystem, the largest of the world’s tropical forests, there are many other fascinating and in some cases more endangered types of lowland forest. Such forests may be defined as lying below 1,000 m above sea level, although it is difficult to set arbitrary limits (Hartshorn, 2001). The two main lowland moist evergreen forests are the Hylea (a term coined by Alexander von Humboldt to denote rain forests of the Amazon Basin) and the much smaller Chocó forest on the Pacific coast between Panama and Ecuador. Two related yet distinctive types of forest are the Mata Atlântica or Atlantic moist evergreen forest and the Mata Decidua or dry deciduous forest, including the caatinga woodland, which is both deciduous and xerophytic (Rizzini et al., 1988). The latter two formations are among the most threatened of all South American forests. Lowland forests vary from dense and multilayered to open and single-layered, from evergreen to deciduous, and from flooded or semi-aquatic to near-arid. Tree heights range from 30 to 40 m with emergent trees reaching over 50 m, to forests where the tallest trees barely attain 20 m (Harcourt and Sayer, 1996; Solorzano, 2001). However, because of its extent and importance, Amazonia will form the principal focus of this chapter. Amazonia covers a vast area (>6 × 106 km2) and contains some 60% of the world’s remaining tropical forest. The Amazon and Orinoco basins influence not only regional climates and air masses, but also atmospheric circulation patterns both north and south of the Equator. The sheer size and diversity of Amazonia exhausts a normal repertoire of grandiose adjectives. The Amazon may or may not be the longest river in the world but it is by far the greatest in terms of discharge, sending around one fifth of the world’s fresh water carried by rivers to the oceans(see
chapter 5; Eden, 1990; Sioli, 1984). The drainage basin is twice as large as any other of the world’s catchments.
Human Threat On Phenological Cycle Of Selected Dry Deciduous Tree Species In North Gujarat Region (Ngr), Gujarat, India
