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Non‐crop (segetal) plants in arable systems are commonly perceived simply as ‘weeds’, that is, harmful at worst and undesirable at best. The increase in management intensity in European arable systems has vastly reduced the populations of all but the most disturbance‐tolerant plant species, negatively impacting the whole agricultural food web. In recent years, efforts have been made to promote agricultural biodiversity through measures such as flower strips and unsprayed field margins. However, studies of their impacts on the arable flora have rarely considered their spatial variation within the crop field. We investigated the spatial distribution of vascular plant species richness and their contribution to the food web via biomass and flower units in conventional and agri‐environment cereal fields in six regions of Germany. We studied two types of in‐crop measures (extensive cereals without pesticides or fertiliser, and with or without intercropping with flowering species) and one adjacent measure (neighbouring flower strip), recording at 1‐m intervals from the field edge to the interior. These results were then extrapolated to illustrate the effects of these measures on resource provision at the field scale. Species richness and plant biomass dropped off sharply after the first metre in the conventional treatments, regardless of the adjacent habitat. The ‘extensive’ treatments maintained a much higher level of diversity and resource provision in the field interior. At the field level, this can mean more than a 60‐fold difference in the provision of flowering resources between conventional management (1900 flower units/ha) and agri‐environment measures (AEMs) (127,000 units/ha for extensive cereals). Synthesis and applications. The strong edge effects we found in conventional cultivation support the premise that reducing field sizes could play a role in promoting in‐crop biodiversity. However, incorporating extensive field margins as an AEM would be more efficient at maximising the diversity of generalists whilst maintaining high yields. [ABSTRACT FROM AUTHOR]

Enhancing diversity within crop systems can have benefits including increased resource use efficiency and productivity, and increased control of weeds, pests and diseases. Some benefits are expected to operate through biodiversity-driven insurance effects, whereby enhanced diversity increases the chance that a system component can compensate for the impacts of adverse environmental conditions. Studies of insurance effects in natural and agricultural systems have provided equivocal results. As insurance effects are expected to play a key role in helping to maintain crop production in more variable future climates (for example under periodic drought), it is essential to know when and how they operate and interact with other potentially beneficial biodiversity-function effects. Using barley as a model crop, and pot-based plant communities, we studied the interactive effects of barley cultivar diversity and drought stress on plant productivity and the response of agricultural weeds, fungal disease, and aphids. Drought reduced barley and weed biomass, but there were no interactive effects of drought and cultivar diversity on plant productivity. Increased cultivar diversity enhanced weed suppression, potentially as a result of reduced functional space availability, and reduced disease severity on a susceptible cultivar; these effects were consistent irrespective of drought. Aphid responses were more complex, with idiosyncratic response patterns on individual cultivars. Overall, we found no evidence of an insurance effect of enhanced cultivar diversity for the negative impact of drought on crop productivity, but our results indicate that other positive biodiversity effects (weed and disease suppression) are maintained under drought. However, it is clear that not all potentially-beneficial biodiversity effects respond in the same manner. Field trials are now needed to explore whether a range of responses also occur in crop field settings, whether these can be expected to occur predictably under a range of environmental conditions, and how these then impact on crop production. [ABSTRACT FROM AUTHOR]

Agricultural intensification has led to drastic population declines in Europe's arable plant vegetation, and continuous monitoring is a prerequisite for assessing measures to increase and conserve remnant populations of endangered arable plant species. Unfortunately, strong variation in plot sizes and in-field locations makes comparison of current arable plant monitoring approaches difficult. This study compares different relevé approaches in conventionally managed arable fields in Northwest German farmland with respect to plant species detection success and time expenditure. We compared species detection rate and expenditure of time of six different relevé types in 45 conventionally managed arable fields (each 15 fields of wheat, maize, and rapeseed): field "Interior" plots (50 × 2 m); field edge plots: "Edge_30" (30 × 2 m), "Edge_50" (50 × 2 m), and "Edge_500" (500 × 1 m); "Subplots" (four dispersed plots of 5 × 1 m); and "Corner" plots (50 × 2 m). To determine species detection rate, the species richness recorded with a survey method was related to the field's total plant species number as estimated from a survey of the entire field edge zone. With a species detection rate of 8.3% (median), interior plots were inadequate for characterizing the field's arable plant vegetation. Edge_500 plots yielded the highest proportion of the field's arable plant species pool (75.6%, including taxa of conservation value), followed by "Corner" plots (45.8%) and "Sublots" (32.6%). Edge_50 and Edge_30 plots detected less than 25% of the field's species pool. The average time needed for a relevé was 20 min in Edge500 plots and 5–11 min in the other plot types. We suggest implementing Edge_500 plots as a standard monitoring approach in conventionally managed farmland due to its favorable ratio of detection success to expenditure of time. Our findings should be compared to methodological studies conducted in other regions, in different farmland management systems, and in landscapes of variable complexities. [ABSTRACT FROM AUTHOR]

Organic farming not only increases plant diversity, but also simultaneously promotes biological weed control through provisioning of ample resources to seed predators., Harpalus affinis (Schrank, 1781) was collected from organically or conventionally managed winter-wheat fields with high or low surrounding shares of organic fields, aiming to test the impact of agricultural management on its activity density, body size and nutritional condition. Body size and nutritional condition were then related to the arable weed seed predation of this granivorous carabid beetle., Activity density of H. affinis was 3.5-fold higher in organically compared with conventionally managed fields, if these were primarily surrounded by conventional fields. Body size was larger in fields surrounded by large proportions of organically managed land, independent of local management. The nutritional condition of beetles was unaffected by local or landscape scale farming. Per capita seed predation significantly increased with body size, whereas nutritional condition had no effect., The results of the present study suggest that organic farming at local and landscape scales enhances the potential of species to control arable weeds by increasing activity densities and intraspecific body size. Seed predation therefore not only depends on local and landscape effects on the community composition of local guilds of granivores, but also on the contribution of individual species to this important ecosystem service. [ABSTRACT FROM AUTHOR]

This study examines plant and soil microbial diversity in a cereal–fallow rotation scheme in the cereal steppes of Castro Verde, Southern Portugal, which have an important conservation value as they provide habitat for many steppic birds with unfavorable conservation status. For that we monitored plant and soil microbial diversity during 4 years including all stages of the rotation cycle. The structure and composition of plant and soil communities during wheat crop were different from those found in the fallow years, although the effect of wheat crop on soil bacteria was still noticeable in the 1 st year of fallow. The main changes in the structure of microbial communities happened between the first and second year of fallow, probably due to changes in the quality and quantity of litter inputs. As expected, we observed an overall decrease in plant diversity in the wheat stage. Fallows had a positive effect on plant species diversity by allowing the maintenance of a seed bank and controlling the simplification of weed communities. However, the impact of fallow on microbial communities is more complex: bacterial diversity was higher during the wheat stage while fungal diversity was either higher or unchanged. These results suggest that the rotation stage is the main driver of the diversity and composition of soil microbial communities, probably through changes in the plant community that deserve further examination. Inter-annual fluctuations in rainfall had a stronger impact on plant communities than on microbial communities indicating that the later are likely adapted to the characteristic fluctuation of annual rainfall in areas under Mediterranean climate. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms of community assembly may provide evidence to improve crop management, and in particular how weeds impact on crop yields. Focussing on plant functional traits and their diversity, we analysed a crop–weed interaction study with different levels of weed species and barley cultivar diversity to assess how weed species and barley cultivars respond to competition. Pre-emption of light resources by the taller barley did not impact on the weeds, with both weeds and barley showing similar order of magnitude shifts in height, specific leaf area and leaf dry matter content in response to crop–weed competition. These shifts were to a more conservative growth pattern, and suggest in this study a greater importance of below- than above-ground interactions in driving trait responses. The mixture of barley cultivars shifted the weeds to a more conservative growth pattern compared to the cultivar monocultures. The results indicate that cultivar mixtures could result in less need for weed control in arable fields, and possibly that the development of complementary cultivar mixtures could reinforce this effect. This confirms the results of other studies which show that mixtures either improve yields or make yields less variable in response to weed competition. [ABSTRACT FROM AUTHOR]

Abstract: Many threatened plant species have genetic structures indicating effects of fragmentation, and in Central Europe arable plants are among the most threatened taxa. Although this threat has developed only recently in the course of agricultural intensification, their annual life form makes arable plants relatively sensitive to increasing fragmentation and decreasing population sizes. One of Central Europe''s rarest arable plant species is Bupleurum rotundifolium (Apiaceae). To analyze the genetic structure and diversity of this species we sampled 27 populations of B. rotundifolium in Central Europe, and assessed genetic structure by amplified fragment length polymorphism (AFLP) fingerprinting. Ordination, clustering and also Bayesian analysis suggested that most of the populations of the Eastern part of Germany formed one cluster, and most of the Western German populations as well as populations from outside Germany built another group. The two clusters accounted for 24% of differences in genetic structure of B. rotundifolium populations, while there was relatively strong differentiation among (41% variance) and within populations of a given group (35% variance). The overall ϕ ST-value was very high (0.65) and there was evidence for isolation-by-distance. Values of genetic diversity were very low for B. rotundifolium. The proportion of polymorphic loci per population varied between 9.4% and 38.7%, with those from eastern Germany being significantly less diverse (mean 19.1% vs. 25.5%). [Copyright &y& Elsevier]

Floristic composition and conservation value of the weed vegetation of winter cereal fields on base-rich soils in western Hungary was compared among three management systems: (i) small, extensively managed fields; (ii) small, intensively managed fields and (iii) large, intensively managed fields. Data were analysed by principal components analysis (PCA) and redundancy analysis (RDA). Most variation in species composition was explained by the differences between the three field types, particularly by the difference between the extensively managed fields and the two types of intensively managed fields and by crop cover. There were several species positively associated with small extensively managed fields, but no species associated with either of the two types of intensively managed fields. Logistic regression was made of the occurrence of species groups important for nature conservation on the first RDA axis, representing the distinction between the extensively and intensively managed fields. This showed that Red List and insect-pollinated plant species occurred more frequently in small extensively managed fields, but there was no difference between fields in the frequency of bird seed-food species. [ABSTRACT FROM AUTHOR]

1. Organic farming is thought to lead to increased biodiversity and greater sustainability than higher-yielding conventional farming systems. It is usually assumed that organic farms have both larger and higher quality areas of semi-natural habitats, although this assumption has not been unequivocally tested. 2. Here we test the hypothesis that in comparison to conventional farms, organic farms have larger areas of semi-natural and boundary vegetation, and organic farms support higher levels of plant abundance, richness and diversity within cropped and semi-natural areas. 3. Our study compared whole-farms: 10 organic farms were paired with 10 conventional farms in a complex landscape in the south-west of England. On average, organic farms were 7·3 years post conversion. Plant abundance, species richness and diversity were measured in all crop and non-crop landscape elements on each farm. 4. Organic farms had greater total areas of semi-natural habitat (woodland, field margins and hedgerows combined). Woodland area on it's own was also significantly greater. Organic farms had more continuous blocks of woodland (with simpler perimeters than similarly sized patches on conventional farms), whereas woodland on conventional farms often consisted of more linear patches. 5. Semi-natural habitats on organic farms did not have higher plant abundance, richness or diversity than their conventional counterparts. The only landscape element that showed a significant increase in plant abundance, richness or diversity was arable fields. 6. Synthesis and applications. Even within a complex agricultural landscape differences do exist between organic and conventional farms, these differences being larger areas of semi-natural habitats on organic farms. However, with the exception of arable fields, no habitats on organic farms were yet of a better quality than their conventional counterparts in terms of plant abundance and diversity. Conventional farmers may be able to achieve an increase in plant diversity within arable fields by adopting some organic management practices at the field scale (e.g. exclusion of synthetic herbicides), and whole-farm conversion to organic practice might not be required. However, further work is needed to determine any biodiversity benefits of larger areas of semi-natural habitat on conventional farmland. [ABSTRACT FROM AUTHOR]

• Four agri-environment measures increased arable plant diversity and cover. • Adapted management is crucial to maintain the positive effects over time. • Weather conditions strongly influence species richness and cover. • Long-term monitoring is necessary to reliably validate the success of measures. Agri-environment measures to support biodiversity in intensively used agricultural landscapes have been implemented in many European countries, but the large-scale downward trend in many species groups continues. The arable flora is one of the species groups that suffered the steepest declines in European cultural landscapes. Despite their fundamental importance in agroecosystems as the basis of the food web, few studies have tested the effectiveness of different agri-environment measures on the arable flora in replicated field trials over several consecutive years. In a four-year participative project with the farmers, we recorded the effects of four agri-environment measures, namely conservation field margins (CFM), annual fallow strips (fallows), alternately managed biennial flower strips (AFS), and perennial flower strips (PFS), on the species richness, plant cover and composition of the non-crop vegetation in 67 intensively managed arable fields in Northwest Germany. Compared to conventionally managed field edges, all measures led to a large increase in total plant cover (median values across measures and years: 68.5 vs. 9.5 %) and doubling of species richness (21 vs. 9 species per plot), promoting not only generalist species but also the typical arable flora (17 vs. 7 species, 56.5 vs. 8 % cover). Of the 207 plant species recorded during sampling, 43 (including 16 typical arable species) were solely found in measures. All measures promoted forbs more than graminoids, while annual species benefited especially from CFM and fallows. The overall effects on diversity and cover remained stable over the 3-yr implementation period but were significantly influenced by interannual weather fluctuation. Spillover effects of the measures into adjacent conventionally managed crops were not detectable. We conclude that, if well-managed, all tested measures can have a positive effect on the native arable flora even in long-term intensively farmed landscapes. However, especially CFM and the annual fallows are particularly effective in naturally restoring and maintaining arable plant diversity. The limited occurrence of 1/4 of typical arable plant species on less than four fields indicates severely impoverished soil seed banks in intensive farmland. Therefore, the re-introduction of native, rare arable plant species through seed mixtures should be considered in order to promote local diversity and save local populations of these species. [ABSTRACT FROM AUTHOR]

Detecting patterns of species co-occurrence is among the main tasks of plant community ecology. Arable plant communities are important elements of agroecosystems, because they support plant and animal biodiversity and provide ecosystem services. These plant communities are shaped by both agricultural and environmental drivers. The pressure of intensive agriculture worldwide has caused the decline of many characteristic arable species and communities. Italy is the European country where arable plant biodiversity is the best preserved. In this study, we assessed the patterns of co-occurrence of rare and threatened arable plants in 106 plots of winter arable vegetation located from Piedmont to Calabria, in the mainland part of the country. For this purpose, we based our investigation on the analysis of a recently acquired dataset and on the European list of rare and threatened arable plants. We highlight how different species of conservation interest tend to occur in the same community. On the other hand, generalist and more competitive taxa show similar patterns of co-occurrence. We suggest that single species of conservation value could be suitable indicators of a well-preserved community. On the other hand, to be effective, conservation strategies should target the whole community, rather than single species. [ABSTRACT FROM AUTHOR]