Species Composition Of Weed Communities Research Articles

The influence of tillage and chemical plant protection on weed infestation of winter spelt wheat cultivars (Triticum aestivum ssp. spelta) growing in continuous crop

The aim of the studies carried out over the period 2009–2011 on mixed medium heavy rendzina was to evaluate the weed infestation of winter cultivars of spelt wheat (‘Ceralio’, ‘Ostro’, ‘Schwabenkorn’ and ‘Spelt I.N.Z.’) depending on the tillage system (conventional and reduced) and chemical plant protection (Mustang 306 SE, Attribut 70 WG, Alert 375 SC, Stabilan 750 SL). Over a three-year study period, the highest dry weight of weeds was found in the crop of cv. ‘Spelt I.N.Z.’, whereas the level of weed infestation for the other cultivars was similar. Replacing ploughing with cultivating resulted in an increase in the numbers of Apera spica-venti, Echinochloa crus-galli, Matricaria maritima and Papaver rhoeas. As a result, the total number of weeds increased by 50.1% compared to conventional tillage, while their dry weight by 17.4% after the use of cultivator instead the plough. The dry weight of weeds decreased nearly 5 times under the applied crop protection treatments, but the species composition of weed communities did not change significantly compared to the control treatment without chemical protection.

Weed Communities in Semiarid Rainfed Croplands of Central Argentina: Comparison between Corn (Zea mays) and Soybean (Glycine max) Crops

AbstractThe semiarid Espinal in central Argentina, being recently transformed from natural semiarid grasslands into agriculture, represents an interesting scenario to understand the early stages of weed community assembly and its relationship with crop identity and management. Our aim was to characterize the weed communities in corn (Zea maysL.) and soybean [Glycine max(L.) Merr.], the main crops of the Espinal region, under the dominant rainfed conditions. Weed surveys were carried out in 53 fields, and farmers were interviewed to collect information about crop management. Floristic composition was compared within and between crops by calculating the additive partition of the abundance-based Bray-Curtis dissimilarity. We compared the frequency and mean cover of functional groups between crops through generalized linear models. Finally, canonical correspondence analysis was carried out to analyze the associations between floristic composition and agronomic variables. Mean alpha and gamma diversity was greater in corn (10.0 and 80 species, respectively) than in soybean (7.6 and 46 species, respectively). Furthermore, species composition of weed communities was more similar among soybean fields than among either cornfields or fields of both crops. Hence, floristic differences between crops are potentially the result of different microenvironmental heterogeneity above- and belowground, with corn likely to be more permissive to weed establishment compared with soybean. The higher frequency of annual, dicotyledonous, and native species, and the high proportion of rare species, mostly native, suggest a strong legacy of the original vegetation that thrived in these recently cultivated systems. The functional composition was also affected by agronomic management, with sulfur, nitrogen, and grass herbicide application being the most important factors related to the floristic composition of weed communities. This early description can be used as a starting point for studies concerning trajectories, mechanisms, and processes of weed communities related to environment and management.

Possibilities and limitations of weed management in fruit crops of the temperate climate zone

Abstract This manuscript contains information on the species composition of weed communities in orchards in Poland and other countries of the temperate climate zone. The manuscript deals with the influence of weeds on crops and the interaction between the weeds and other living organisms. The main methods of weed regulation are described. Characteristics of the particular crops – fruit trees and small fruits – and solutions that are either objects of study or have already been introduced into practice, are presented. Advantages and disadvantages of different methods of weed control are discussed, such as soil cultivation and tillage, cover crops, mulches, herbicide use, and flame burning.

Factors shaping the spatial variation of weed communities across a landscape mosaic

Alignier A & Petit S (2012). Factors shaping the spatial variation of weed communities across a landscape mosaic. Weed Research.52, 402–410.SummaryThe spatial pattern of weeds within field is widely accepted to be aggregated, but few studies have assessed the spatial structure of weed communities at the landscape scale. Using a combination of aggregation measures and similarity indices, this study aimed at inferring the processes behind the spatial patterning of weed communities. We analysed spatial variation in the species composition of weed communities to understand how similarity in weed composition varies with field and spatial effects. Weeds were surveyed in a regular grid sampling a 110 ha landscape mosaic made up of 24 fields. We showed that weed composition similarity among samples exhibited an aggregated pattern at the mosaic scale, of up to 400 m. Similarity in weed composition varied mainly among fields, but also within field according to the distance from the field border. The decay in species similarity was influenced both by field and spatial effects. Spatial effect remains signifi‐cant after controlling for field effect. These findings provide support for the hypothesis that niche relationships and dispersal processes are both involved in the spatial patterning of weed species composition at the mosaic scale.

Can conversion to organic farming restore the species composition of arable weed communities?

Benefits of organic cropping for biodiversity have usually been demonstrated in relation to modern conventional cropping. In this study, the ability of organic cropping to restore species composition of weed communities was explored by comparing weed communities of present day organic cropping with weed communities at the beginning of the application of modern cropping measures in the 1960s. The data of two weed surveys of spring cereals (conducted in 1961–1964 and 1997–1999) in Finland were utilized for a comparison. Frequency of occurrence and density (plants m −2) of 41 weed species were compared between decades. Partial canonical correspondence analysis (pCCA) was applied to explore the relationship between species composition, management and non-management variables. Eight species had lower and 30 species higher or similar frequency of occurrence in the 1990s’ organically cropped fields than in the fields of the 1960s. However, 18 species had lower and 20 species had higher or similar density in the organically cropped fields than in the fields of the 1960s. Three species were not detected at all in the organically cropped fields. Crop and under-sown grass explained more of the variation in species composition in the 1990s than in the 1960s. The role of drainage and pre-crop was more important in the 1960s than in the 1990s. The most immediate benefit was gained by nitrophilous species that had suffered from herbicide application. The recovery of perennials and non-nitrophilous species will take a longer time. The results suggest that despite some benefits for biodiversity, organic farming at early phase cannot recover weed populations to the same level as before application of intensive cropping measures.

Weed species diversity and community composition in organic and conventional cropping of spring cereals

Interest in organic farming is growing rapidly in Europe. The resulting expansion of the organic farming area has been expected to enhance the biodiversity of agricultural habitats. Organic cropping practices can be hypothesized to support a higher number of weed species than conventional cropping and also to favor herbicide-susceptible and less-nitrophilous species. The diversity and species composition of weed communities were compared in spring cereal fields cultivated by organic, conventional cereal and conventional dairy cropping methods in southern Finland between 1997 and 1999. Samples were taken before (May–June) and after (July–August) the treatment of conventional fields with herbicides. The number of species was used as a measure of species diversity. The total and mean numbers of species between cropping practices were compared by applying rarefaction and ANCOVA, respectively. In organically cultivated, fields the adjusted mean number of species per field exceeded that in conventionally cultivated fields by about two species in both May–June and July–August. The total number of species was higher in organically cultivated fields only in July–August. The species composition of organically cultivated fields was closer to that of conventional dairy than to that of conventional cereal fields. Species susceptible to herbicides (e.g. Chenopodium album) were abundant in organically cultivated fields in both sampling periods whereas the relative abundance of some of them declined in conventional fields from May–June to July–August. In conventional fields, the relative abundances of Viola arvensis, Stellaria media and Elymus repens increased from May–June to July–August. Only weak support was found for the hypothesis that organic cropping favors less-nitrophilous weed species. It is concluded that organic cropping promotes weed species diversity at an early phase of cropping history but that a change in species composition would require a longer period of organic cropping.

Weed species diversity and community composition in cropping practices at two intensity levels - a six-year experiment

Alternative cropping practices can be expected to increase the diversity and change the species composition of weed communities. In a six-year field experiment we compared species diversity and species composition in the weed community of cereal fields cultivated by conventional and by low-input cropping methods. In the conventional cropping both mineral fertilizers and herbicides were applied but in the low-input cropping the fertlizer was manure and herbicides were avoided altogether. The level of nitrogen fertilization was higher in conventional cropping. A five-year crop rotation comprising rye, oat-pea, barley and two-year grasslands was used in both cropping methods. We found that the species pool was larger (42 vs 35 species) and the average number of species higher (20.2 vs 13.1 species) in low-input than in conventional cropping. This was the case both in the data pooled across crops and in each crop separately. Herbicides affected species diversity and species composition more than did nitrogen fertilization. Species susceptible to the herbicides applied declined in abundance, which resulted in more skewed dominance patterns in the communities of conventional fields than in those of low-input fields. The crop affected the species composition of weed communities more than did the cropping method. Our results suggest that weed species diversity could be promoted by using low-intensity cropping practices.