Fitossociologia de comunidades de plantas daninhas em agroecossistema cana-crua
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Data
2007-09-01
Autores
Kuva, M.A.
Pitelli, R.A. [UNESP]
Salgado, T.P.
Alves, P.L.C.A. [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Sociedade Brasileira da Ciência das Plantas Daninhas
Resumo
Objetivou-se neste trabalho estudar a fitossociologia de comunidades de plantas daninhas de canaviais colhidos no sistema mecanizado, sem queima prévia da palha, e a similaridade entre talhões quanto à composição de espécies. Os levantamentos foram realizados em 28 talhões comerciais na região de Ribeirão Preto-SP. em cada talhão foram demarcadas áreas de coleta e avaliação, na proporção de duas por hectare, mantidas sem controle, e que serviram de local para as amostragens de plantas daninhas. As amostragens foram feitas com quadrados vazados (0,5 x 0,5 m), lançados aleatoriamente duas vezes em cada uma das áreas. Essas amostragens foram realizadas determinando-se a densidade e a biomassa específica aos 120 dias após o corte da cana. Cyperus rotundus foi a principal espécie, destacando-se quanto aos valores de importância relativa (IR). As plantas dicotiledôneas anuais de propagação por sementes também se destacaram, dentre as quais diversas espécies das famílias Euphorbiaceae e Convolvulaceae. em contrapartida, as gramíneas tradicionais de áreas de cana colhida queimada tiveram pouco destaque. O índice de Shannon (H) de diversidade de espécies das comunidades variou de 0 a 1,61, e o índice de similaridade entre os talhões (S) foi muito variável. A maioria das espécies ou grupo de espécies apresentou padrão agregado (V/m > 1,00), com valores relativamente altos de índice de agregação (V/m). Entretanto, na maioria dos casos, Cyperus rotundus e as Convolvulaceas apresentaram os maiores índices.
A study was carried out in northeastern São Paulo, Brazil to evaluate the similarity between species composition and phytosociological index in weed communities of no-burn sugar cane crop harvest at different times and number of cut-cycles. Assessments were carried out in twenty-eight sugar cane plots in the Ribeirao Preto-SP region. In each plot, collection and evaluation areas were established, two per hectare, kept without control and used as weed sampling sites. The samplings were made using squares (0.5 x 0.5 m), randomly cast twice in each area. Weed density and biomass were evaluated per species 120 days after sugar cane harvesting. The phytosociological studies showed that Cyperus rotundus presented the highest values of relative density, dominance, frequency and relative importance index. The seed-propagated dycot plants also presented high values for phytosociological index, mainly the species belonging to the families Euphorbiaceae and Convolvulaceae. on the other hand, the grass weeds, traditionally found in burned sugar cane areas, had very little relevance under the no-burn system. The diversity index (Shannon - H) varied from 0 to 1.61 and the similarity index(S) was low, except when groups of weeds were compared. The majority of the weed populations showed geographic distribution in match pattern. Areas with high infestation of C. rotundus and/or Convolvulaceae species showed the highest aggregation index.
A study was carried out in northeastern São Paulo, Brazil to evaluate the similarity between species composition and phytosociological index in weed communities of no-burn sugar cane crop harvest at different times and number of cut-cycles. Assessments were carried out in twenty-eight sugar cane plots in the Ribeirao Preto-SP region. In each plot, collection and evaluation areas were established, two per hectare, kept without control and used as weed sampling sites. The samplings were made using squares (0.5 x 0.5 m), randomly cast twice in each area. Weed density and biomass were evaluated per species 120 days after sugar cane harvesting. The phytosociological studies showed that Cyperus rotundus presented the highest values of relative density, dominance, frequency and relative importance index. The seed-propagated dycot plants also presented high values for phytosociological index, mainly the species belonging to the families Euphorbiaceae and Convolvulaceae. on the other hand, the grass weeds, traditionally found in burned sugar cane areas, had very little relevance under the no-burn system. The diversity index (Shannon - H) varied from 0 to 1.61 and the similarity index(S) was low, except when groups of weeds were compared. The majority of the weed populations showed geographic distribution in match pattern. Areas with high infestation of C. rotundus and/or Convolvulaceae species showed the highest aggregation index.
Descrição
Palavras-chave
Cyperus rotundus, Ipomoea spp., aggregation index, similarity index, Cyperus rotundus, Ipomoea spp., índice de agregação, Índice de similaridade
Como citar
Planta Daninha. Sociedade Brasileira da Ciência das Plantas Daninhas , v. 25, n. 3, p. 501-511, 2007.