Data/hora: 14/06/2024 19:18:26

Biblioteca(s): 	Embrapa Pantanal.	
Data corrente: 	28/02/1996	
Data da última atualização: 	28/02/1996	
Autoria: 	BEARD, J. S.	
Título: 	The savanna vegetation of northern tropical America.	
Ano de publicação: 	1953	
Fonte/Imprenta: 	Ecological Monographs, v.23, n.2, p.149-215, Apr. 1953.	
Idioma: 	Inglês	
Conteúdo: 	1. The savanna is a plant-formation of tropical America comprising a virtually continuous, ecologically dominant stratum of more or less xeromorphic herbs, of which grasses and sedges are the principal components, with seattered shrubs, trees or palms sometimes present.
2. Three sub-formations can be recognized: Tall bunch-grass savanna, short bunch-grass savanna and sedge savanna. The tall bunch-grass savanna can be further subdivised into four phases-open, orchard, palm and pine savannas.
3. Tall bunch-grass savanna is composed of perennial, xeromorphic grasses up to 3 ft. in height, disposed in clumps and associated with many sedges and other herbs. Open sa- vanna is treeless; orchard savanna includes scattered gnarled trees and shrubs; palm savanna, palms; and pine savanna, pine trees.
4.Short bunch-grass savanna is composed of xeromorphic grasses up to only 1 ft. in hei- ght, disposed in clumps. Thorny trees may be present. 
5. Sedge savanna is composed of relatively xeromorphic sedges up to 18 in. in height, not tufted, and associated with many small moisture loving ground plants such as bladder- worts, ferns and mosses. Small evergreen trees and shrubs may be present.
6. Savannas occur under a great variety of climatic conditions from annual rainfall of 20 in. with seven or more drought months up to over 100 in. with negligible drought periods. Short bunch-grass savanna tends to predominate where there are less than 35 in. annua- lly and sedge savanna with over 80 in.
7. All types of climate in lowland tropical America, given favorable site conditions, are ade- quate to support woody growth of some kind. A tropical grassland climate does not exist.
8. Savannas occur upon ill-drained country of little relief, most generally a senile landsca- pe such as an old alluvial plain or a reduced upland.
9. All types of savanna may be swept by regular fires and the vegetation is so adapted as to be fire resistant. The herbaceous vegetation does not, however, depend upon fire for its maintenance and the savanna is an edaphic climax, i.e., it is determined by soil and site conditions.
10. Natural drainage is the most important characteristic of tropical soils affecting distribu- tion of vegetation and chemical status is of little account. 
11. The natural drainage of savanna soils is affected unfavorably by the lack of relief and the internal physical structure. Usually savanna soils exhibit the superposition of a permea- ble horizon upon an impermeable, or are extremely compact and impermeable throughout the profile, so that no true water table exists.
12. Savanna may be characterized as the vegetation of the higly mature soils of senile land-forms (or, in some cases, of very juvenile sites) which are subject to unfavorable drainage conditions in the form of intermittent perched water tables, with alternating seve- re periods of waterlogging and desiccation. 
13. The soils of upland forests are well-drained, by virtue either of porosity or relief or both.
14. Specialized swamp forests occur on ground subject to flooding, but the site differs from savanna in that a normal water table must be present.
15. Temperate grassland, for which the term "steppe" should be used, also represent a habitat almost perpetually adverse to growth, but the causes are climatic.	
Palavras-Chave: 	America tropical; Northern tropical America; savana; Savanna vegetation.	
Thesagro: 	Cerrado; Vegetação.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (31018-1) - ADD - SP - -- - SP2035 -  - 2035 - DIS