scholarly journals Weed Vegetation Structure in an Area of Organic Acerola Cultivation, Parnaíba, Piauí, Brazil

2020 ◽  
Vol 38 ◽  
Author(s):  
P.H.S. SOUSA ◽  
M.R.A. MENDES ◽  
A.D.B. VAL ◽  
M.C.S.A. TEIXEIRA
Keyword(s):  
Diversity Index ◽  
Panicum Maximum ◽  
Weed Species ◽  
Commelina Benghalensis ◽  
Amaranthus Spinosus ◽  
Organic Cultivation ◽  
Poaceae Family ◽  
Management Techniques ◽  
The Absolute ◽  
Shannon’S Diversity Index

ABSTRACT: This study aimed to identify and quantify the weed species in an area of organic acerola cultivation in the Distrito de Irrigação dos Tabuleiros Litorâneos do Piauí (DITALPI) in Parnaíba, Piauí, Brazil. Phytosociological sampling was completed in the rainy season, before the farmers adopted management techniques for the plants. Thirty plots of 0.25 m2 were sampled. The plots were located between crop rows, which consisted of herbaceous-subshrub plants. The absolute and relative covers and the absolute and relative frequencies of each species were calculated based on the occurrence and cover of each species. In total, 25 species comprising 13 families were registered, among which the Poaceae family that presented the largest number of species. Commelina benghalensis occurred the most frequently overall. Shannon’s diversity index (H’) and evenness were calculated as 2.30 nats ind-1 and 0.69, respectively. Five species accounted for 79.33% of absolute cover at DITALPI. The species were distributed heterogeneously within the field, and Commelina benghalensis, Urochloa plantaginea, Panicum maximum, Amaranthus spinosus, Cynodonsp., and Cyperus aggregatus were the species most likely to infest the acerola crop. As DITALPI is an area of organic cultivation, understanding these species is essential to help farmers select the best form of control.

scholarly journals Competitiveness of alexandergrass or Bengal dayflower with soybean

2010 ◽  
Vol 28 (3) ◽  
pp. 515-522 ◽  
Author(s):  
A.C.R. Dias ◽  
S.J.P. Carvalho ◽  
L.W. Marcolini ◽  
M.S.C. Melo ◽  
P.J. Christoffoleti
Keyword(s):  
Competitive Ability ◽  
Dry Mass ◽  
Total Density ◽  
Weed Species ◽  
Replacement Series ◽  
Commelina Benghalensis ◽  
Randomized Design ◽  
Full Flowering ◽  
Completely Randomized Design ◽  
Soybean Plants

Weeds compete with field crops mainly for water, light and nutrients, and the degree of competition is affected by the weed density and the intrinsic competitive ability of each plant species in coexistence. The objective of this research was to compare the competitiveness of alexandergrass (Brachiaria plantaginea) or Bengal dayflower (Commelina benghalensis) in coexistence with soybean, cv. M-Soy 8045. A factorial experiment (2 x 5) with two weed species and five competition proportions was carried out in a completely randomized design with four replicates. Proportions were based on a replacement series competition design, always maintaining the total density of four plants per 10 L plastic pots, which corresponded to 60 plants m ². The weed-crop proportions were: 0:4; 1:3; 2:2; 3:1; 4:0; that corresponded to the proportion of 100, 75, 50, 25 and 0% of soybean plants and the opposite for weeds, B. plantaginea or C. benghalensis plants. Leaf area, shoot dry mass of the weeds and soybean and number of soybean trifoliate leaves were evaluated when the soybean reached the phenologic stage of full flowering. B. plantaginea was a better competitor than soybean plants. Otherwise, C. benghalensis revealed a similar competitive ability that of the soybean. In both cases, there were evidences that intraspecific competition was more important.

scholarly journals Produção e partição de matéria seca de cultivares de feijão em competição com plantas daninhas

2011 ◽  
Vol 29 (1) ◽  
pp. 149-158 ◽  
Author(s):  
J.P. Cury ◽  
J.B. Santos ◽  
D. Valadão Silva ◽  
F.P. Carvalho ◽  
R.R. Braga ◽  
...  
Keyword(s):  
Bidens Pilosa ◽  
Commelina Benghalensis ◽  
Amaranthus Spinosus

Objetivou-se com este trabalho avaliar os efeitos da competição entre três cultivares de feijão e seis espécies de plantas daninhas no crescimento inicial e na alocação de matéria seca pelas plantas. Adotou-se arranjo fatorial em esquema 3 x 6 + 9, constituído pela combinação de três genótipos de feijão (IPR Colibri, IPR Eldorado e Pérola) em competição com seis espécies de plantas daninhas (Euphorbia heterophylla, Bidens pilosa, Cenchrus echinatus, Amaranthus spinosus, Commelina benghalensis e Brachiaria plantaginea), além de nove tratamentos adicionais, correspondentes aos cultivares de feijão e às espécies daninhas ausentes de competição. O delineamento foi em blocos casualizados com quatro repetições, e cada vaso contendo 5 L de substrato representou uma unidade experimental. O período de convivência entre os cultivares de feijão e as plantas daninhas foi de 45 dias após emergência da cultura; depois disso, coletou-se o material vegetal para avaliação da matéria seca e distribuição entre os diferentes órgãos (raízes, folhas e caule). Os cultivares de feijão apresentaram menor acúmulo de matéria seca quando estavam em competição com as espécies de plantas daninhas. A raiz foi o principal órgão afetado negativamente pela competição. De forma contrária, as folhas e o caule das espécies daninhas foram os órgãos mais prejudicados. De maneira geral, o cultivar Pérola foi o genótipo que mais tolerou a competição com plantas daninhas, e E. heterophylla foi a espécie daninha menos competitiva. A. spinosus e B. plantaginea foram as espécies com maior capacidade de competição com a cultura do feijão.

Comparison of weed communities in Manitoba ecoregions and crops

2000 ◽  
Vol 80 (4) ◽  
pp. 963-972 ◽  
Author(s):  
R. C. Van Acker ◽  
A. G. Thomas ◽  
J. Y. Leeson ◽  
S. Z. Knezevic ◽  
B. L. Frick
Keyword(s):  
Weed Management ◽  
Amaranthus Retroflexus ◽  
Weed Species ◽  
Canada Thistle ◽  
Wild Mustard ◽  
Polygonum Convolvulus ◽  
Weed Communities ◽  
Green Foxtail ◽  
Poaceae Family ◽  
Weed Survey

In 1997, a weed survey was conducted during July and August in fields of wheat, barley, oat, canola and flax in Manitoba. Field selection was based on a stratified-random sampling methodology using ecodistricts as strata. Species in the Poaceae family were most commonly observed in the survey, followed by species in the Polygonaceae, Asteraceae and Brassicaceae families. The six most abundant weed species were green foxtail [Setaria viridis (L.) Beauv.], wild oats (Avena fatua L.), wild buckwheat (Polygonum convolvulus L.), Canada thistle (Cirsium arvense L.), redroot pigweed (Amaranthus retroflexus L.) and wild mustard (Sinapis arvensis L.). The survey highlighted significant differences between ecoregions and between crops in residual weed infestations. The weed community in the Boreal Transition ecoregion was dominated by seven species, whereas fields in the Aspen Parkland and Lake Manitoba Plain ecoregions were dominated by two species and the Interlake Plain ecoregion was dominated by only one species. Although significant differences were found between the weed communities in crops, they were not as great as differences between ecoregions. The Manitoba residual weed community in 1997 was very similar to that reported for 1978–1981 and 1986, suggesting that the same species should remain a focus for weed management. Key words: Weed survey, weed relative abundance, weed distributions, Manitoba ecoregions

scholarly journals WEEDS AS POTENTIAL HOSTS FOR FUNGAL ROOT PATHOGENS OF WATERMELON

2019 ◽  
Vol 32 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Rui Sales Júnior ◽  
Ana Paula Medeiros dos Santos Rodrigues ◽  
Andreia Mitsa Paiva Negreiros ◽  
Márcia Michelle de Queiroz Ambrósio ◽  
Hailton da Silva Barboza ◽  
...  
Keyword(s):  
Root Rot ◽  
Citrullus Lanatus ◽  
Phytopathogenic Fungi ◽  
Soilborne Pathogens ◽  
Weed Species ◽  
Amaranthus Spinosus ◽  
Trianthema Portulacastrum ◽  
Different Types ◽  
Vine Decline ◽  
Boerhavia Diffusa

ABSTRACT Many watermelon (Citrullus lanatus) diseases are caused by soilborne pathogens in Brazil and worldwide. The goal of this study was to identify and quantify the frequency of phytopathogenic fungi associated with watermelon root rot and vine decline that were also present in the roots of weeds in the major watermelon production regions in the state of Rio Grande do Norte, Brazil. We collected root samples from 10 of the most prevalent weed species in 16 watermelon producing areas. The plants were identified and their frequencies in the fields were calculated. The fungi found in the weed roots were isolated and the main genera associated with watermelon vine decline were identified. We identified 13 weed species belonging to nine botanical families. The weed species with the highest frequencies found in the field were Amaranthus spinosus (25.0%), Trianthema portulacastrum (18.8%), Commelina sp. (18.8%), and Boerhavia diffusa (12.5%). The fungi Macrophomina, Rhizoctonia, and Monosporascus were isolated from the roots of the weed plants. While Macrophomina was isolated from 12 different types of plants, Rhizoctonia and Monosporascus were isolated from four and two different plant species, respectively.

scholarly journals Biodiversity and distribution of arbuscular mycorrhizal fungi in Araucaria angustifolia forest

2007 ◽  
Vol 64 (4) ◽  
pp. 393-399 ◽  
Author(s):  
Milene Moreira ◽  
Dilmar Baretta ◽  
Siu Mui Tsai ◽  
Sandra Maria Gomes-da-Costa ◽  
Elke Jurandy Bran Nogueira Cardoso
Keyword(s):  
Arbuscular Mycorrhizal Fungi ◽  
Mycorrhizal Fungi ◽  
Root Colonization ◽  
Biological Diversity ◽  
Diversity Index ◽  
Arbuscular Mycorrhizal ◽  
Am Fungi ◽  
Araucaria Angustifolia ◽  
Forest Sustainability ◽  
Shannon’S Diversity Index

Araucaria angustifolia (Bert.) O. Ktze. is an endangered Brazilian coniferous tree that has been almost exterminated in the native areas because of uncontrolled wood exploitation. This tree has been shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) and, therefore, AMF may be essential for forest sustainability and biological diversity. Root colonization, density and diversity of AMF spores were assessed in two Araucaria forest stands at the State Park of Alto Ribeira (PETAR), at two sampling dates: May and October. A comparison was made between a mature native stand composed of Araucaria trees mixed into a variety of tropical trees and shrubs, without any sign of anthropogenic interference (FN) and an Araucaria stand planted in 1987 (R), which has been used as a pasture. Assessments included percent root colonization, AMF spore numbers and species richness, Simpson's dominance index (Is), and Shannon's diversity index (H). Mycorrhizal root colonization did not differ between ecosystems in May. In October, however, the native stand (FN) presented a higher colonization than the planted forest (R), and the root colonization was more intense than in May. When considering both sampling periods and forests, 27 species of AM fungi, with higher numbers of spores in FN than in R were found. Canonical discriminant analysis (CDA) indicated Shannon's diversity index as the ecological attribute that contributed the most to distinguish between forest ecosystems, with higher value of H in FN in relation to R. CDA showed to be a useful tool for the study of ecological attributes.

Economic trade-offs of managing forests for timber production and vegetative diversity

1994 ◽  
Vol 24 (6) ◽  
pp. 1260-1265 ◽  
Author(s):  
David N. Holland ◽  
Robert J. Lilieholm ◽  
David W. Roberts ◽  
J. Keith Gilless
Keyword(s):  
Diversity Index ◽  
Basal Area ◽  
Timber Harvest ◽  
Forest Stand ◽  
Timber Production ◽  
Harvest Scheduling ◽  
Scheduling Model ◽  
Trade Offs ◽  
Compositional Diversity ◽  
Shannon’S Diversity Index

Three indices of forest stand structural and compositional diversity were incorporated into a linear programming timber harvest scheduling model to examine the trade-offs between managing stands for timber production and biodiversity objectives. The indices, based on Shannon's diversity index, characterized stand species diversity, basal area diversity, and vertical crown diversity. While harvest-level objectives were often compatible with the maintenance of vegetative diversity, the maximization of present net value was accompanied by substantial reductions in all three measures of diversity.

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

2016 ◽  
Vol 34 (1) ◽  
pp. 65-80 ◽  
Author(s):  
SANTOS W.F. ◽  
PROCÓPIO S.O. ◽  
SILVA A.G. ◽  
FERNANDES M.F. ◽  
BARROSO A.L.L.
Keyword(s):  
Cropping Systems ◽  
Floristic Composition ◽  
Sampling Period ◽  
Weed Species ◽  
Floristic Survey ◽  
Commelina Benghalensis ◽  
Number Of Species ◽  
West Region ◽  
Weed Communities ◽  
Agricultural Areas

The use of the Roundup Ready(r) technology and the cultivation of a second crop influence the floristic composition of weed communities in Brazilian Central-West region cropping systems. This study has aimed to diagnose the dominant weed species in southwestern Goiás in areas of genetically-modified and conventional soybeans, using phytosociological and floristic surveys. Weed sampling was obtained by collecting all the plants present within a 0.5 m hollow frame, randomly thrown 20 times in each of thirty-five agricultural areas in the 2012/2013 harvest. Field survey was carried out in three periods: before desiccation for soybean sowing, before postemergence herbicide in soybean first application and before postemergence herbicide application in late harvest. A total of 525 m2 was inventoried and 3,219 weeds were collected, which included 79 species, 58 genera and 28 families. Families Poaceae, Asteraceae, Euphorbiaceae, Fabaceae, Amaranthaceae, were the most representative in the survey. Species Cenchrus echinatus, Glycine max, Chamaesyce hirta, Commelina benghalensis, and Alternanthera tenella stood out in importance. The RR+millet soybean treatment had the highest number of species (44), while the conventional soybean + sorghum treatment had the lowest number of species (18). The highest number of species was recorded in first sampling period. Treatments conventional soybean + maize and conventional soybean + millet showed higher similarity (70%), while treatments RR soybean + millet and conventional soybean + sorghum showed the least (51%). Species of difficult control were recorded in all cultivation systems analyzed.

scholarly journals Influence of Spartina alterniflora invasion stages on macrobenthic communities on a tidal flat in Wenzhou Bay, China

2012 ◽  
Vol 60 (3) ◽  
pp. 441-448 ◽  
Author(s):  
Bao-Ming Ge ◽  
Yi-Xin Bao ◽  
Hong-Yi Cheng ◽  
Dai-Zhen Zhang ◽  
Zhi-Yuan Hu
Keyword(s):  
Species Richness ◽  
Spartina Alterniflora ◽  
Tidal Flat ◽  
Diversity Index ◽  
Eastern China ◽  
Macrobenthic Communities ◽  
Initial Stage ◽  
Invasion Stage ◽  
Shannon’S Diversity Index ◽  
Spartina Alterniflora Invasion

Many coastal habitats in eastern China are being substantially altered by the invasion of Spartina alterniflora. The species richness, density, Margalef's diversity index (R) and Shannon's diversity index (H') of macrobenthic communities on a tidal flat in Wenzhou Bay, China, were analyzed with the factors of invasion stage and season, in 2007. A significant effect of invasion stage, season, and the interaction between them on communities was detected. The macrobenthic community was more complex in the patch of initial S. alterniflora invasion than in the patches of some other invasion stages. Macrobenthic communities were classified by cluster and ordination in accordance with the habitat character of the S. alterniflora invasion stage. Our research demonstrated that the S. alterniflora invasion stage affected the macrobenthic communities significantly. The results indicated that biodiversity increased in the initial stage of invasion (invasion age 1-2 years) and then decreased in the stage of invasion underway (invasion age 3-4 years) and in the stage of invasion completed (invasion age 5-6 years); this phenomenon was related to the change in the S. alterniflora canopy which accompanied the invasion stages.

scholarly journals A Polyethylenetherephthalate (PET) device for sampling freshwater benthic macroinvertebrates

2004 ◽  
Vol 64 (3a) ◽  
pp. 531-541 ◽  
Author(s):  
C. Volkmer-Ribeiro ◽  
D. L. Guadagnin ◽  
R. De Rosa-Barbosa ◽  
M. M. Silva ◽  
S. Drügg-Hahn ◽  
...  
Keyword(s):  
Benthic Macroinvertebrates ◽  
Diversity Index ◽  
Macroinvertebrate Communities ◽  
Total Abundance ◽  
Tropical River ◽  
New Device ◽  
Four Seasons ◽  
Spatial Differences ◽  
Shannon’S Diversity Index ◽  
Similarity Matrices

A new device to sample freshwater benthic macroinvertebrates was used in a low and sandy stretch of a Brazilian sub-tropical river (the River Caí, Triunfo, RS) and in one of its small tributaries, Bom Jardim brook (Arroio Bom Jardim). In this study, the effectiveness of this device, a PET sampler, was tested at different sites in the river and the brook throughout the four seasons between 2001-2002. Comparisons were made by PCA and ANOVA, both employing a bootstrap procedure based on similarity matrices. The PET sampler proved to be a reliable tool for detection of seasonal and spatial differences in richness, total abundance of organisms, and Shannon's diversity index in both river and brook and is therefore recommended for use in the monitoring of macroinvertebrate communities in this system.

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