Data/hora: 20/06/2024 21:42:31

Biblioteca(s): 	Embrapa Amazônia Ocidental; Embrapa Pantanal.	
Data corrente: 	16/05/1996	
Data da última atualização: 	16/05/1996	
Autoria: 	JONES, M. B.; WOODMANSEE, R. G.	
Título: 	Biogeochemical cycling in annual grassland ecosystems.	
Ano de publicação: 	1979	
Fonte/Imprenta: 	Botanical Review, v.45, n.2, p.111-144, Apr./June, 1979.	
Idioma: 	Inglês	
Conteúdo: 	We have discussed the cycling of N, P, and S. These elements are essential nutrients for the maintenance of annual grassland ecosystems because they are important elements in the synthesis of organic matter. Many other  elements are also essential, but were not in- cluded in the discussion, because little information about the characteristics of their cycling is available. Nitrogen occurs principally in organic forms in ecosystems, but most of it is bound in very slowly cycling forms. Most N used by organisms is mineralized from plant residues of the previous growing season. The N cycle is open, meaning that significant amounts of the element may be added to the ecosystem from natural external sources: as NH4+ and NO3- from the atmosphere and as N2 from fixation by plants. However, signifi- cant amounts of N may be lost from the system by leaching, volatilization of NH3, and de- nitrification. Nitrogen plays a very important role in ecosystem functioning and can be ma- nipulated by fertilization or legume management. Phosphorus occurs in both organic and inorganic forms. As with N, organic forms occur in both slowly cycling and fast-cycling forms. The fast-cycling forms are very important sources of P for organisms, especcially in ecosystems where it is short supply. In addition to the organic forms of P, a labile inorganic pool can be very important. In some ecosystems this pool is sufficiently large to supply adequate amounts of P for plant growth, while in other systems it is small and P can limit vegetation production. In some systems P can stimulate legume development, thereby im- proving the N status of the community. The P cycle is relatively closed, compared to the N cycle, and natural additions and losses are very small. Where P is in limited supply, fertili- zation can be beneficial. As with N, sulfur occurs principally in organic forms and its cy- cling properties are generally similar to those of N. The "opennes" of the S cycle is proba- bly intermediate between N and P. Plant production responds to addition of S in many ecosystems. The response may be caused by amelioration of S deficiencies in many types of plants of the ecosystem, or the S may stimulate legume production, resulting in increa- sed N production.	
Palavras-Chave: 	Biogeochemical cycling in annual; Ciclo anual; Grassland ecosystems.	
Thesagro: 	Ecossistema; Pastagem.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (31792-1) - ADC - SP - -- - SP2291 -  - 2291 - DIS
CPAA - (33561-1) - ADD - SP - PP - S6147 -  - S6147 - DIS