Evaluation of weed flora changes in Portugal in a 10 year basis

• Autor(a) principal: Ramôa, Sofia
• Data de Publicação: 2017
• Outros Autores: Silva, Pedro Oliveira e, Travlos, Ilias, Vasconcelos, Teresa, Forte, Paulo, Portugal, João
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/13723
• topic: agroecosystems; weed infestation degree; Lolium rigidum; Mediterranean climate; plant biodiversity; multivariate analysis

The aim of this study was to assess the composition of weed communities starting from a rainfed farming system (1997), to the early period of transformation in agricultural systems with the adoption of irrigation (2007). The assessments were made within a 10-year interval and the floristic surveys were conducted in the same georeferenced plots. In 1997, the surveys were mostly performed in winter cereals (wheat, oat, barley), while in 2007, considering the same georeferenced plots, there were winter cereals and also irrigated olive groves, parcels of fallow, pasture and pine forest. Weed flora was determined by means of relative frequency, abundance and weed infestation degree. The effect of time was also evaluated by applying the methodology of variance analysis on the values of Shannon-Wiener Index. Canonical Correspondence Analysis was used to complement this information only for 2007 to know how the flora was distributed by the different cultures. Our results revealed that in both cases weed flora was of high diversity (229 and 264 species in 1997 and 2007, respectively), with the most representative families being always the same, namely Asteraceae, Poaceae and Fabaceae. The number of weeds that could be of concern for the farmers revealed to be relatively low. Our study confirmed that despite of the intensification of the agricultural production system, biodiversity increased over time. In both years, Lolium rigidum was present at high densities