Phytosociological surveys: tools for weed science?

Abstract

-In simple terms, a phytosociological survey is a group of ecological evaluation methods whose aim is to provide a comprehensive overview of both the composition and distribution of plant species in a given plant community. To understand the applicability of phytosociological surveys for weed science, as well as their validity, their ecological basis should be understood and the most suitable ones need to be chosen, because cultivated fields present a relatively distinct group of selecting factors when compared to natural plant communities. For weed science, the following sequence of steps is proposed as the most suitable: (1) overall infestation; (2) phytosociological tables/graphs; (3) intra-characterization by diversity; (4) inter-characterization and grouping by cluster analysis. A summary of methods is established in order to assist Weed Science researchers through their steps into the realm of phytosociology.Keywords: weed community; density; frequency; dominance; diversity; similarity.RESUMO -Levantamento fitossociológico, em termos simples, é um grupo de métodos de avaliação ecológica com o objetivo de fornecer uma visão compreensiva tanto da composição como da distribuição de espécies vegetais em uma certa comunidade. Para compreender a aplicabilidade desses levantamentos para a ciência das plantas daninhas, bem como sua validade, devem-se escolher os métodos mais adequados e com base ecológica, uma vez que áreas cultivadas apresentam um grupo relativamente distinto de fatores de seleção, em comparação com os ambientes naturais. Para estudos fitossociológicos de plantas daninhas, a seguinte sequência de passos é proposta como a mais adequada: (1) infestação geral; (2) tabelas ou gráficos fitossociológicos; (3) intracaracterização por diversidade; e (4) intercaracterização e agrupamento por similaridade. Um apanhado dos métodos é apresentado, visando apoiar pesquisadores e estudantes da área de Plantas Daninhas em seus passos no reino da fitossociologia.

Interferência de plantas daninhas na cultura do sorgo sacarino

“…According to Correia et al (2010), sourgrass has slow initial growth until 45 days after emergence, so even presenting high rDe (%) and rFr (%) in the initial stages, this weed was eventually suppressed at the end of the cycle by more dominant species, such as, tropical spiderwort and guinea grass. A dominant plant is characterized by large area of ground cover, great accumulation of mass and great distribution across the area (Concenço et al, 2013a).…”

“…Plants were cut at ground level, oven-dried at 70 °C to constant mass. Besides counting the species and total individuals per sampled area, the following phytosociological parameters were calculated: relative frequency (rFr), relative density (rDe), relative dominance (rDo) and index of importance value (IV), as proposed by Concenço et al (2013a) and Silva et al (2005).…”

Weed Phytosociological and Floristic Survey in Agricultural Areas of Southwestern Goiás Region

“…Assessing five treatments in the Brazilian city of Dourados, MS, Concenço et al (2013) have found Shannon-Wiener and Simpson indexes in the areas of maize succeeding soybeans of 3.11 and 0.83, respectively. The diversity data for the maize + signalgrass treatment recorded by these authors and the RR soybean + maize treatment of this study showed similar values for Simpson index (0.79).…”

“…This information provides important elements for the understanding of the occurrence of species interactions according to the selection of the management system and the practices in the areas (Concenço et al, 2013).…”

Phytosociological Survey of Weeds in Carpet Grass in Distinct Periods of the Year

“…According to Concenço et al (2013), the phytosociological survey is defined by a group of ecological assessment methods in order to provide a comprehensive view of both the composition and the distribution of plant species in a certain community. To be valid, one must choose the most suitable and ecologically based methods, since cultured environments have a relatively distinct group of selection factors compared to natural environments.…”