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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]

Although New Zealand is developing an increasing number of herbicide-resistant weed populations, it has a much lower incidence of herbicide resistance than Australia. Understanding the reasons for these differences may help with future management of herbicide resistance in both countries. Australia is much larger than New Zealand so greater areas of weeds are exposed to herbicides annually in Australia. Another difference is the high frequency of Lolium rigidum in Australian agricultural systems, a species almost absent in New Zealand, and many of the cases of resistance in Australia involve this species. However, species closely related to L. rigidum are increasingly being found resistant to herbicides in New Zealand. Higher rainfall in most parts of New Zealand allows much more crop rotation than is possible in Australia, and greater crop yields give New Zealand farmers more flexibility to use higher application rates and more expensive herbicides in rotation than is feasible in Australia. Dry conditions result in more use of summer fallows in Australia using glyphosate which has caused some of the problems. Selection pressure for resistance still occurs in New Zealand, so herbicide and crop rotation may just be delaying the appearance of resistance in this country. [ABSTRACT FROM AUTHOR]

Questions: Due to their high ecological and agronomical variability, borderland regions offer an excellent opportunity to study assembly patterns. In this study we compared the influence of various factors on summer annual weed communities consisting of both native and introduced species. Location: The borderland region of Austria and Hungary. Methods: We assessed the abundance of weed species in 300 fields of six summer annual crops, and collected information on 26 background variables for each plot. We applied redundancy analysis (RDA) to estimate multivariate species responses and variation partitioning to compare the relative importance of three groups of variables (environmental variables, management variables, and country as a singleton group), and we also checked for statistical association between country and the predictors of the other two groups. Results: The full RDA model explained 22.02% of the variance in weed species composition. Variation partitioning showed that environment and management had similarly high (~8%) influence on weeds, while country had a modest yet substantial (~1%) effect, and there was relatively little overlap between the variance attributable to the three groups. Comparing the individual variables, country ranked third (after preceding crop, and actual crop). The effects of 15 further variables were also significant, including seven management, and seven environmental variables, as well as the location of the sampling plots within the fields. Comparisons between the countries showed that farming type, preceding crops, tillage system, tillage depth and field size were significantly different between the countries. Conclusions: Country exhibited a small but significant influence on weed community composition, which could not be explained with easily accessible management and environmental variables. This suggests that the distinct historical agronomical background of the two countries, possibly involving some legacies of the former Iron Curtain period, still has an impact on the weed species composition of arable fields. [ABSTRACT FROM AUTHOR]

Reconstructing the origins of plant cultivation in southwest Asia is crucial for understanding associated processes such as the emergence of sedentary communities and domesticated crops. Among the criteria archaeobotanists developed for identifying the earliest plant cultivation, the presence of potential arable weeds found in association with wild cereal and legume remains has been used as a basis for supporting models of prolonged wild plant cultivation before domesticated crops appear. However, the proposed weed floras mainly consist of genus-level identifications that do not differentiate between arable weeds and related species that characterise non-arable habitats. Here we test, for the first time, whether the potential arable weed taxa widely used to identify wild plant cultivation also occur in non-cultivated wild cereal populations. Based on modern survey data from the southern Levant we show that the proposed weed taxa characterise both grasslands and fields. Our findings, therefore, do not support the use of these taxa for reconstructing early cultivation. Instead, for future studies we suggest an approach based on the analysis of plant functional traits related to major agroecological variables such as fertility and disturbance, which has the potential to overcome some of the methodological problems. [ABSTRACT FROM AUTHOR]

Agricultural intensification has caused once diverse arable fields to become species-poor. Their seed banks, which are fundamental for re-establishment and maintenance of plant communities in such repeatedly disturbed environments, are now largely depleted. In order to advise farmers on the successful implementation of agri-environmental measures, as well as reduce potential subsequent costs of continued weed control, understanding seed bank dynamics in relation to aboveground vegetation is essential. We (1) investigated the change in seed bank composition in the field edge and the interior, and (2) analyzed the seed bank in flower strips and adjacent fields in relation to the aboveground vegetation on intensively managed arable farms across Germany. Low-tillage systems contained more plant species and higher seed densities in the seed bank than regularly ploughed fields. Species diversity at the field edge was higher than in the field interior, with a continuous decrease in the number of species and seed density within the first 2 m from the edge. Flower strips can lead to an enrichment of the seed bank, but it is driven by the strong rise in a few common species such as Chenopodium album. To cultivate successful flower strips, we recommend close onsite monitoring, as well as rapid intervention in the case of weed infestation. [ABSTRACT FROM AUTHOR]

Fungi colonizing the surface and endosphere of two widespread Poaceae weed species, Avena fatua and Echinochloa crus-galli, were isolated to compare the taxonomic composition between the plant species, location, and year of the seed collection. The seed-degrading potential of Fusarium isolated from the seeds was tested by inoculating seeds of E. crus-galli with spore suspension. Molecular identification of epiphytic and endophytic fungal genera was performed by sequencing the ITS region of rDNA. Endophytes comprised of significantly lower fungal richness compared to epiphytes. A significant taxonomic overlap was observed between the endosphere and seed surface. The most abundant genera were Alternaria, Fusarium, Cladosporium, and Sarocladium. Analysis of similarities and hierarchical clustering showed that microbial communities were more dissimilar between the two plant species than between the years. Fusarium isolates with a high potential to infect and degrade E. crus-galli seeds in laboratory conditions belong to F. sporotrichioides and F. culmorum. [ABSTRACT FROM AUTHOR]

Seit 1950 sind sowohl die Artenvielfalt von Ackerunkräutern als auch die Arthropoden und Vögel in Deutschland und darüber hinaus stark zurückgegangen. Es stellt sich die Frage, welche Rolle Ackerunkräuter bei der Unterstützung der Artenvielfalt, insbesondere von Arthropoden und Vögeln, spielen. In einer Literaturrecherche wurden 51 Ackerunkrautarten und 3 Unkrautgattungen, welche in Deutschland häufig vorkommen, auf ihre Rolle als Nahrung und Lebensraum für die Fauna untersucht. Direkte und indirekte Verbindungen zwischen Ackerunkräutern und Vögeln sowie Arthropoden wurden anhand von Daten aus der veröffentlichten Literatur gezählt. Es wurden 5180 Verbindungen zwischen den Ackerunkräutern und Arthropoden bzw. Vögeln gefunden. Die Daten weisen darauf hin, dass Ackerunkräuter nicht nur die landwirtschaftliche Erzeugung behindern, sondern auch eine Vielzahl von Ökosystemleistungen unterstützen.

Abstract Semi‐natural habitats (SNHs) are becoming increasingly scarce in modern agricultural landscapes. This may reduce natural ecosystem services such as pest control with its putatively positive effect on crop production. In agreement with other studies, we recently reported wheat yield reductions at field borders which were linked to the type of SNH and the distance to the border. In this experimental landscape‐wide study, we asked whether these yield losses have a biotic origin while analyzing fungal seed and fungal leaf pathogens, herbivory of cereal leaf beetles, and weed cover as hypothesized mediators between SNHs and yield. We established experimental winter wheat plots of a single variety within conventionally managed wheat fields at fixed distances either to a hedgerow or to an in‐field kettle hole. For each plot, we recorded the fungal infection rate on seeds, fungal infection and herbivory rates on leaves, and weed cover. Using several generalized linear mixed‐effects models as well as a structural equation model, we tested the effects of SNHs at a field scale (SNH type and distance to SNH) and at a landscape scale (percentage and diversity of SNHs within a 1000‐m radius). In the dry year of 2016, we detected one putative biotic culprit: Weed cover was negatively associated with yield values at a 1‐m and 5‐m distance from the field border with a SNH. None of the fungal and insect pests, however, significantly affected yield, neither solely nor depending on type of or distance to a SNH. However, the pest groups themselves responded differently to SNH at the field scale and at the landscape scale. Our findings highlight that crop losses at field borders may be caused by biotic culprits; however, their negative impact seems weak and is putatively reduced by conventional farming practices.

Agricultural intensification has caused once diverse arable fields to become species-poor. Their seed banks, which are fundamental for re-establishment and maintenance of plant communities in such repeatedly disturbed environments, are now largely depleted. In order to advise farmers on the successful implementation of agri-environmental measures, as well as reduce potential subsequent costs of continued weed control, understanding seed bank dynamics in relation to aboveground vegetation is essential. We (1) investigated the change in seed bank composition in the field edge and the interior, and (2) analyzed the seed bank in flower strips and adjacent fields in relation to the aboveground vegetation on intensively managed arable farms across Germany. Low-tillage systems contained more plant species and higher seed densities in the seed bank than regularly ploughed fields. Species diversity at the field edge was higher than in the field interior, with a continuous decrease in the number of species and seed density within the first 2 m from the edge. Flower strips can lead to an enrichment of the seed bank, but it is driven by the strong rise in a few common species such as Chenopodium album. To cultivate successful flower strips, we recommend close onsite monitoring, as well as rapid intervention in the case of weed infestation.

Weeds in agricultural landscapes can serve as alternate hosts for phytopathogenic fungi and promote the spatial and long-term distribution of these fungi. Especially, semi-natural habitats such as kettle holes are considered as a source of fungal pathogens because they are a permanent habitat for various weed species in arable lands. In our study, we investigated the suitability of nine different weed species and families at the edges of 18 kettle holes in two consecutive autumn/winter seasons as alternate hosts for Fusarium and Alternaria. We detected a fungal infestation with both genera on every weed species investigated with significantly higher abundances of these fungi in the second, notably wetter season. Eight weed species were described as non-host plants for Fusarium and Alternaria in agricultural landscapes in Brandenburg, Germany for the first time. In both autumn/winter periods, weeds harbored more Alternaria than Fusarium. The study revealed a high Fusarium species diversity in weeds and a community structure of up to 12 Fusarium species at the edges of kettle holes. Grasses showed the highest diversity and often the highest fungal abundances compared to herbaceous plants. Therefore, these habitats in arable lands can act as ecosystem disservice and promote the spread of fungal diseases in the surrounding crop fields. [ABSTRACT FROM AUTHOR]

Questions: Two scientific disciplines, vegetation science and weed science, study arable weed vegetation, which has seen a strong diversity decrease in Europe over the last decades. We compared two collections of plot‐based vegetation records originating from these two disciplines. The aim was to check the suitability of the collections for joint analysis and for addressing research questions from the opposing domains. We asked: are these collections complementary? If so, how can they be used for joint analysis? Location: Europe. Methods: We compared 13 311 phytosociological relevés and 13 328 records from weed science, concerning both data collection properties and the recorded species richness. To deal with bias in the data, we also analysed different subsets (i.e., crops, geographical regions, organic vs conventional fields, center vs edge plots). Results: Records from vegetation science have an average species number of 19.0 ± 10.4. Metadata on survey methodology or agronomic practices are rare in this collection. Records from weed science have an average species number of 8.5 ± 6.4. They are accompanied by extensive methodological information. Vegetation science records and the weed science records taken at field edges or from organic fields have similar species numbers. The collections cover different parts of Europe but the results are consistent in six geographical subsets and the overall data set. The difference in species numbers may be caused by differences in methodology between the disciplines, i.e., plot positioning within fields, plot sizes, or survey timing. Conclusion: This comparison of arable weed data that were originally sampled with a different purpose represents a new effort in connecting research between vegetation scientists and weed scientists. Both collections show different aspects of weed vegetation, which means the joint use of the data is valuable as it can contribute to a more complete picture of weed species diversity in European arable landscapes. [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]

Semi‐natural habitats (SNHs) are becoming increasingly scarce in modern agricultural landscapes. This may reduce natural ecosystem services such as pest control with its putatively positive effect on crop production. In agreement with other studies, we recently reported wheat yield reductions at field borders which were linked to the type of SNH and the distance to the border. In this experimental landscape‐wide study, we asked whether these yield losses have a biotic origin while analyzing fungal seed and fungal leaf pathogens, herbivory of cereal leaf beetles, and weed cover as hypothesized mediators between SNHs and yield. We established experimental winter wheat plots of a single variety within conventionally managed wheat fields at fixed distances either to a hedgerow or to an in‐field kettle hole. For each plot, we recorded the fungal infection rate on seeds, fungal infection and herbivory rates on leaves, and weed cover. Using several generalized linear mixed‐effects models as well as a structural equation model, we tested the effects of SNHs at a field scale (SNH type and distance to SNH) and at a landscape scale (percentage and diversity of SNHs within a 1000‐m radius). In the dry year of 2016, we detected one putative biotic culprit: Weed cover was negatively associated with yield values at a 1‐m and 5‐m distance from the field border with a SNH. None of the fungal and insect pests, however, significantly affected yield, neither solely nor depending on type of or distance to a SNH. However, the pest groups themselves responded differently to SNH at the field scale and at the landscape scale. Our findings highlight that crop losses at field borders may be caused by biotic culprits; however, their negative impact seems weak and is putatively reduced by conventional farming practices. [ABSTRACT FROM AUTHOR]

ABSTRACT Vegetation history of southwestern Nigerian forest during the past ~1,416 cal yr BP (534 - 644 AD) is reconstructed based on palynological data from a core from Awerele, wetland in Orile-Owu. Six palynological zones were stablished. Zone I (195-175 cm; ~1,416 cal yr BP) was a period marked by low value of charcoal particles associated with low frequency of Elaeis guineensis pollen. In Zone II (175-135 cm), the environment experienced wet conditions depicted by high percentage mainly of Cyperaceae and fern spores. Further, the arable weeds and E. guineensis increased values, showing the higher frequency of Margaritaria discoidea pollen grains, coupled with a low charcoal amount. Zone III (135-105 cm) to Zone VI (50-0 cm) were characterised by the increase of E. guineensis and raising of charcoal particles, followed by the presence of plants exploited for food and medicinal purposes, which may indicate enlarged local landscape disturbance, probably associated with humans’ activities. Archaeological evidence suggest that humans occupied the Orile-Owu area from ~ 412 cal yr BP (AD 1,538 - 1,635). The pollen data displayed the persistence of a forest-savanna mosaic, associated with ecological perturbations, which were also noticed in other parts of sub-saharan Africa on the same period.

Questions: Studies in functional biogeography have mostly focused on unmanaged ecosystems, and neglected testing how management intensity affects communitylevel response of plant traits to bioclimatic gradients. We hypothesize that trait– climate relationships for arable weeds spontaneously establishing in croplands subject to intensive management should differ from the relationships characterizing less intensively managed grassland ecosystems. Location: France. Methods: We computed community-weighted means (CWM) and variances (CWV) of 954 and 5,619 cropland and grassland plant assemblages, respectively, for three fundamental leaf traits (specific leaf area, SLA; leaf dry matter content, LDMC; leaf nitrogen content, LNC). Based on growing season length accounting for both temperature and soil water limitations (GSLtw), we compared trait–climate relationships between herbicide-free croplands and grasslands, and between herbicide-free and herbicidesprayed cropland assemblages. The contribution of beta-diversity to the trait–climate relationships was then evaluated using multiple regression on distance matrices. Results: Distinct trait–climate relationships characterized herbicide-free cropland and grassland plant assemblages. CWM of all traits showed weaker relations with GSLtw in cropland relative to grassland assemblages. CWV of LDMC and LNC responded more sharply in croplands. Furthermore, no herbicide effect on trait–climate relationships was detected within cropland assemblages. These results seem to be explained by a greater taxonomic beta-diversity along the GSLtw gradient for grasslands. Conclusions: Specific trait–environment relationships characterize croplands, underlining that management intensity greatly affects trait–climate relationships for plant assemblages. Deciphering the interplay between land use intensification and climate is critical to accurately forecast functional vegetation changes in response to global changes, and hence to foster actions enhancing ecosystem resilience. [ABSTRACT FROM AUTHOR]

There is global concern that invertebrate populations are declining rapidly, particularly in agricultural habitats. Declines have been attributed to the intensification of farming systems, with many studies focussing on a lack of semi-natural habitat in the landscape and the use of insecticides. However, within-field arable weeds are also an important driver of invertebrate abundance and the ecosystem services to which they contribute. This study focuses on the role of arable weeds in supporting invertebrate populations and selected ecosystem services they deliver., using winter wheat as a case study. Weed-invertebrate relationships were investigated across seven studies of winter-sown wheat spanning 18 years. Both phytophagous and predatory invertebrates responded to weed cover but to different degrees. Phytophages showed a stronger positive relationship with weed cover than the predators, because they rely on the resources provided by the weeds whereas predatory species response is likely to be mediated by their prey. Farmland bird chick-food indices were positively related to both broadleaf and grass cover in cropped fields, indicating that increased weed cover can provide increased invertebrate food for birds in winter wheat. Despite this potential, there were insufficient invertebrate food resources for birds in the majority of wheat fields sampled. Weed diversity did not play a significant role in moderating the relationships between weeds and invertebrate abundance, however this may be a function of the low weed diversity in modern winter wheat fields. In this study the weed species most frequently shown to predict the invertebrate community were: Poa annua, Stellaria media, Fumaria officinalis, Sinapis arvensis, Senecio vulgaris, Persicaria lapathifolia, Sonchus spp., Matricaria discoidea, Persicaria maculosa, Agrostis spp., Lamium purpureum, Lamium album, Veronica spp., Atriplex spp., Myosotis spp. and Anagallis arvensis. We conclude that even in an intensively grown cereal, arable weeds can play an important role in maintaining and restoring invertebrate populations, that 10% weed cover is needed to fulfill the potential and that a successful outcome will be driven by the presence of weed species that support invertebrates that provide ecosystem services.

Weeds in agricultural landscapes can serve as alternate hosts for phytopathogenic fungi and promote the spatial and long-term distribution of these fungi. Especially, semi-natural habitats such as kettle holes are considered as a source of fungal pathogens because they are a permanent habitat for various weed species in arable lands. In our study, we investigated the suitability of nine different weed species and families at the edges of 18 kettle holes in two consecutive autumn/winter seasons as alternate hosts for Fusarium and Alternaria. We detected a fungal infestation with both genera on every weed species investigated with significantly higher abundances of these fungi in the second, notably wetter season. Eight weed species were described as non-host plants for Fusarium and Alternaria in agricultural landscapes in Brandenburg, Germany for the first time. In both autumn/winter periods, weeds harbored more Alternaria than Fusarium. The study revealed a high Fusarium species diversity in weeds and a community structure of up to 12 Fusarium species at the edges of kettle holes. Grasses showed the highest diversity and often the highest fungal abundances compared to herbaceous plants. Therefore, these habitats in arable lands can act as ecosystem disservice and promote the spread of fungal diseases in the surrounding crop fields.

Predicting the response of biological communities to changes in the environment or management is a fundamental pursuit of community ecology. Meeting this challenge requires the integration of multiple processes: habitat filtering, niche differentiation, biotic interactions, competitive exclusion, and stochastic demographic events. Most approaches to this long‐standing problem focus either on the role of the environment, using trait‐based filtering approaches, or on quantifying biotic interactions with process‐based community dynamics models. We introduce a novel approach that uses functional traits to parameterize a process‐based model. By combining the two approaches we make use of the extensive literature on traits and community filtering as a convenient means of reducing the parameterization requirements of a complex population dynamics model whilst retaining the power to capture the processes underlying community assembly. Using arable weed communities as a case study, we demonstrate that this approach results in predictions that show realistic distributions of traits and that trait selection predicted by our simulations is consistent with in‐field observations. We demonstrate that trait‐based filtering approaches can be combined with process‐based models to derive the emergent distribution of traits. While initially developed to predict the impact of crop management on functional shifts in weed communities, our approach has the potential to be applied to other annual plant communities if the generality of relationships between traits and model parameters can be confirmed. [ABSTRACT FROM AUTHOR]

• We established field boundaries with late mowing and high mowing heights. • This practice increased the numbers of inflorescences and pollinators. • The mowing regime did not influence the average weed cover in wheat fields. • The mowing regime did not influence the number of ground beetles. Herbaceous boundaries adjacent to arable fields can deliver ecosystem services not sufficiently provided at the field scale, as well as disservices such as increased weed pressure. The levels of services and disservices depend on the management regime implemented in these boundaries. Our study was conducted in Western France, where herbaceous boundaries of many arable fields constitute the road verge, and various mowing regimes were tested for conservation purposes. Until now, most studies of the influence of mowing regimes focused on one taxonomic group and documented contrasting results depending on the environmental context. This study aimed to compare the influence of two mowing regimes on road verges by evaluating different taxonomic groups that could potentially deliver services or disservices to adjacent arable fields. The mowing regimes used were a standard and an agro-environmental regime, the latter being characterized by one late mowing, a high mowing height and biomass removal. We monitored, during two consecutive years, seven road verges and their adjacent arable fields. Each road verge was divided into two zones of equal length, characterized by a different mowing regime. Communities of plants, flower-visiting insects and ground beetles were sampled in herbaceous boundaries and/or arable fields in the period between the mass-flowering of oilseed rape and sunflower crops. In zones where the agro-environmental mowing regime had been implemented, the average number of inflorescences and flower-visiting insects within boundaries were higher than under the standard mowing regime. However, between the two mowing regimes, no differences in weed cover within arable fields and the average number of ground beetles within boundaries and arable fields were observed. To conclude, our study suggests that in our particular environmental context, an agro-environmental mowing regime could promote pollination in adjacent arable fields without increasing weed pressure within the field. [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]

A “cultivation prior to domestication”, or a “pre-domestication cultivation” phase features in many reconstructions of Near Eastern plant domestication. Archaeobotanists who accept this notion search for evidence to support the assumption regarding a wild plant’s cultivation phase, which in their view, preceded and eventually led to plant domestication. The presence of non-crop plant remains in the archaeobotanical record interpreted as arable weeds, i.e., weeds of cultivation, is viewed as a strong argument in support of the pre-domestication cultivation phase. Herein, we show that the simple practice of harvest by hand-pulling (uprooting) has the potential to secure an almost weed-free harvest. Indeed, rather clean (weed-free) Neolithic seed caches from a range of relevant sites were documented in archaeobotanical reports. These reports, alongside ethnographic observations suggest that (in certain cases) ancient harvest may have been carried out by selective hand-pulling. Hence, one has no reason to view archaeobotanical assemblages from occupation sites as fully representative of cultivated fields. Therefore, the concept of “arable—pre-domestication weeds”, its logic, and its potential contribution to the prevailing reconstructions of Near Eastern plant domestication need be reconsidered.

A number of small middle-Neolithic (3300–2800 BC) settlements flourished in the Oldenburger Graben area of northern Germany. The excavations yielded large amounts of crop remains, suggesting that agrarian production was a cornerstone of subsistence economy. Until about 3000 BC, Oldenburger Graben was a fjord, which over time was separated from the Baltic Sea and became a lagoon. The location of the settlement in the wetlands would have been highly favourable, offering a range of terrestrial and aquatic resources. Nonetheless, it may have been challenging to the Neolithic farmers, as perhaps not much dry land was available for crop growing. The success of agrarian production likely depended on the methods employed. This is an initial attempt at reconstructing strategies of agricultural land use during the middle-Neolithic occupation of the Oldenburger Graben lowland. We combine information on the habitat preferences and life history of arable weeds, and the recently obtained carbon and nitrogen stable isotope values on crop grains from one of the sites. The evidence allows us to glean practices that crop cultivation may have entailed, including potential strategies aimed at improving productivity of arable land such as tillage, weeding and manuring. Although preliminary, the observations point at potentially different management of emmer and barley, perhaps due to their variable importance to the Neolithic residents. This is the first time that stable isotope analysis on crops from northern Germany is used to elucidate agricultural practices of the Funnelbeaker communities of the middle-Neolithic. [ABSTRACT FROM AUTHOR]

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Socio-economic factors often determine the extent to which different global regions have been invaded by non-native plant species, yet few studies examine whether such variables are similarly important for native species richness. In contrast to previous studies that have assembled regional floras for comparison, we examine global patterns of non-native and native plant species richness within a single, globally distributed ecosystem: cultivated wheat fields. Native species richness increased with the historic length of wheat cultivation, total wheat harvested area and arable land area in a country. In contrast, non-native weed species richness declined with increasing length of wheat cultivation, higher fertilizer inputs, and lower absolute latitude. The low percentage of native species in countries with a short history of wheat cultivation suggests that the invasion of crop fields by native plants takes longer than the migration of non-native weed species pre-adapted to crop fields in other parts of the world. Seed contaminants in grain imports are probably one of the main sources of non-native weeds, especially for regions with more recent wheat cultivation histories. To date there has been a tendency for research on agricultural weeds to be dissociated from that of plant invasions, yet we show how cultivation history has shaped the weed flora and why non-native weeds are perceived as such a problem in New World agriculture, as well as confirming at a global scale the role of crop husbandry and agricultural extent on weed floras. [ABSTRACT FROM AUTHOR]

The field experiments were conducted in 2008, 2009 and 2010 on a Gleyic Cambisol near Goettingen, Lower Saxony, Germany. A crop sequence of summer barley, winter cover crops (intercropped oat and sunflower) and summer faba bean was examined under organic farming conditions. Emphasis was given to the studying of arable weeds in faba beans. However, enhancing symbiotic nitrogen fixation of summer faba beans by accumulation of soil-nitrogen by winter cover crops was a second objective in these experiments. The faba bean field plots had been cultivated with three different tillage systems: 1. zero tillage, sowing with cross-slottechnique, 2. conservation tillage (wing share cultivator, rotary harrow) sowing with cross-slot-technique and 3. conventional tillage with mouldboard plough followed by rotary harrow, sowing with precision monoseeder. In plots with zero tillage preceding cover crops were left as mulch on the soil surface. Cover crops accumulated adequate nitrogen amounts and following faba beans reacted with significant increase (up to 10%) in symbiotic nitrogen fixation. Maximum of arable weed biomass was observed in zero tillage-plots at the end of May or early in June. The abundance of the predominant weed wild mustard (Sinapis arvensis) increased with tillage intensity, whereas the abundance of creeping thistle (Cirsium arvense) increased in 2010 with decreasing tillage intensity. Average grain yield of faba beans was low with only 3.0 and 2.4 t ha-1 in 2009 and 2010, respectively.

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.

Arable weeds are one of the most endangered species groups in Europe. Modern agriculture and intensive land use management with the application of herbicides and fertilisers, enhanced seed cleaning, simplified crop rotations and abandonment of marginal arable sites are the main causes for the continuous decline of arable weeds. However, besides these changes in land use also global climate change may challenge the adaptability of arable weeds. Most scientists agree that the frequency of extreme meteorological conditions will increase in the future. As a consequence, plants of Central Europe will be subject to higher temperatures and reduced water supply due to longer intervals without precipitation during the growing season. We exposed seeds of five common and five endangered arable weed species to different temperatures and water potentials to study i) how this plant group responds to higher temperatures and lower moisture during germination in general and ii) whether there is a significant difference between common and endangered species in this respect.

Arable weeds are among those groups of plants that are most threatened in Europe due to management intensification and efficient cleaning of crop seeds in modern agriculture. Plant species loss in arable fields had been assessed in many European countries about 30 years ago, and has gained renewed interest during the last few years. A rich historical data set on plots where arable weeds had historically been recorded in Switzerland enabled the study of changes in arable weed species since the 1920s onward. In total, 232 locations with historical plots were revisited. There, we recorded all plant species and their abundances on 100m 2 plots. Across all plots the average number of species per plot declined dramatically by more than 60% during the last 90 years. Most species decreased in frequency, but common species stayed more frequent, while rare species − often characteristic weeds of traditionally managed crop fields − decreased in frequency or even disappeared. Plant groups with increasing species numbers and frequency were mostly neophytes, grasses and species with high nutrient demand. The above mentioned decline in species number and frequency of rare and characteristic weed species suggests that more effective conservation measures than hitherto taken are needed to ensure their preservation. [ABSTRACT FROM AUTHOR]

Time of seedling emergence is an important step in the life cycle of annual plants because it may determine subsequent performance and success. Timing of emergence is especially critical to plant performance in habitats like arable fields which are subject to frequent disturbances. Within-season variation in timing of germination in the range of only a few days is typical for many arable weeds. However, since it is unclear whether such small deviations in germination date translate into fitness differences in the course of the life cycle, the aim of this paper was to quantify the effects of short germination delays on plant performance. We conducted two generalized randomized block experiments in an unheated greenhouse to study the impact of delayed germination (1, 2, 3 and 7 d) with and without competition, respectively, on the fitness of the arable weed species Agrostemma githago (L.). We expected that delayed germination significantly reduces fitness in terms of several life-history traits, and that the decrease of fitness is higher in the presence of competition. Under realistic conditions with competition through barley, Agrostemma plants with delayed germination of 7 d produced 54% fewer shoots, 57% less biomass, 52% fewer flowers, 36% lighter seeds and were 23% shorter as compared to control plants without delayed germination. Without additional stress through competition with barley this pattern was less pronounced. Thus, in the situation of interspecific competition, early emerging seedlings have biologically significant fitness advantages over later emerging seedlings of the same species. [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]

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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]

The agricultural landscape of central Europe has changed dramatically in recent decades due to intensified cultivation, bringing many of its characteristic species to the brink of extinction. We investigated whether landscape structure affects the genetic structure and diversity of remnant populations of the two arable plant species Adonis aestivalis and Consolida regalis. We used dominant amplified fragment length polymorphism markers (AFLPs) and compared populations from six regions of 5 km2 in central Germany. These regions represent two different classes of landscape structural complexity: intensively used, homogeneous landscapes (>95% of area covered by arable land with low extent of field margins) or heterogeneous regions (<60% of area covered by arable land with large extent of field margins). Contrary to expectations, within-population diversity levels did not significantly differ between homogeneous and heterogeneous landscapes. No significant isolation-by-distance was found for either species, regardless of landscape structure, and genetic structures may still mirror more continuous conditions before large-scale restructuring commenced in Germany's arable landscapes from the 1950s onwards. These results suggest that current landscape complexity, as such, is not as important for local-level genetic structure for the species studied. Thus, homogenised and intensively used landscapes may also be important for the conservation of arable plant diversity and should not be neglected. [ABSTRACT FROM AUTHOR]