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• Rare arable plant cover can reduce the total number of aphids. • Cereal aphids decreased through predation of active hunting spiders. • Direct effects of rare arable plants only on active hunting spiders. In agricultural landscapes, arable plants are negatively affected by management intensification. These species can fulfill various ecosystem functions, such as biological pest control, by supporting predators. The ecosystem functions of common plant species are widely known. By contrast, the contribution of rare arable plants (RAPs) to biocontrol in cereal fields remains poorly understood. This study investigated the effect of RAPs on biocontrol potential. We compared cropped plots with and without sowing of rare and threatened arable plant species and investigated the effects on cereal aphids and their antagonistic predators, active hunting, and web-building spiders, as well as carnivorous/omnivorous carabids. We counted the total number of aphids on cereal shoots and trapped ground-dwelling arthropods on an experimental field and on 10 agricultural farms in the vicinity of Munich, Germany, in 2018 and 2019. The effects of the presence of RAPs were analyzed using linear mixed-effect models, whereas cover of RAPs was analyzed using structural equation models. Linear models revealed that the presence of RAPs did not significantly affect the aphid density and the activity densities of spiders and carabids. Structural equation models revealed direct negative effects of RAP cover on aphid density. However, no indirect effects via the predators of aphids were detected. Direct negative effects of active hunting spiders on aphids were determined, but not of the other potential predators. Our results suggest that RAPs may impact aphid infestation, however, the activity density of spiders and carabids were unsuitable indicators for such interactions. [ABSTRACT FROM AUTHOR]

• Sowing of rare arable plants had no significant effect on crop biomass. • Rare arable plants improved plant diversity without increasing arable plant biomass. • Rare arable plants addition did not show beneficial effects on soil fertility. Agricultural intensification has caused a strong agro-biodiversity decline in Europe, with high losses in rare arable plants. A better understanding of the relationship between these species, agricultural productivity, and other ecosystem functions can improve conservation management. The study was performed on an experimental field near Munich. To examine the results under field conditions, study plots were additionally established on ten arable fields distributed in the Munich Plain, an area with nutrient poor soils in southern Germany. We sowed a mixture of ten rare arable plant species at varying crop densities and compared them to plots without rare arable plants. To assess the effects on plant diversity and productivity, the cover and species richness of rare and common arable plants and the crop and arable plant biomass were assessed. The organic matter, nitrogen concentration, as well as the biomass and abundance of earthworm (biannually sampled for two years) were analyzed to determine the impact on soil fertility. Our results showed that sowing rare arable plants did not negatively affect crop biomass. Arable plant biomass and cover of rare arable plants were highest when no crops were sown. There was no difference between reduced and regular crop sowing densities on rare arable plant cover. In our field experiment, earthworm occurrence and soil organic matter were probably influenced by pre-crops (two years of clover grass before the experiment) and summer droughts during the study period. However, no significant effects of sowing rare arable plants on soil fertility were detected. These results were partly verified from results of the field study. At least on nutrient-poor soils, rare arable plant sowing may be a suitable tool to promote plant diversity conservation without negatively affecting crop production. That the sowing of rare arable plants did not significantly affect the indicators for soil fertility suggests that biomass production of rare arable plants was too low to have an impact on the crops and a benefit for soil fertility. Insignificant effects on crop biomass also suggest that sowing rare arable plants does not automatically lead to crop losses. As organic matter, nitrogen concentration and earthworm occurrence slowly respond to environmental changes, they should be investigated in further long-term experiments. This study shows that conservation of rare arable plants and food production on nutrient poor fields can be combined. Therefore, land sharing may be a suitable tool for nature conservation and ecosystem functionality on arable land. [ABSTRACT FROM AUTHOR]

Pervasive urbanization contributes to biodiversity declines globally, and with urbanization, road densities increase, amplifying habitat degradation and landscape homogenization. However, as a major part of urban green space, roadside vegetation permeates the urban fabric and, if enhanced, can be used to support insects, such as wild bees. To analyze local and landscape-scale effects of enhanced urban roadsides on wild bee communities and to identify bee traits affected by urban filtering, we established 78 wildflower patches with a native seed mixture along five major roads in Munich (S Germany). Species-poor roadsides with regular management were used as control. During a three-year experiment, we sampled wild bees with pan traps, monitored roadside vegetation, and analyzed landscape diversity and perimeter–area ratio of green space within a radius of 500 m. We gathered information on wild bee morphological, behavioral, phenological, and foraging traits and calculated their abundance, species richness and functional dispersion. Wild bee abundance, richness and functional dispersion increased with vegetation diversity. Functional dispersion was positively correlated with landscape diversity and distance from the city center, indicating trait-based urban filtering. A fourth corner analysis revealed that small, short-lived, and univoltine bees were disadvantaged at urban roadsides. While univoltine bees were discriminated in areas of high landscape diversity, large bees prevailed in the city outskirts, and solitary bees were associated with green space edges. We conclude that enhanced roadsides contribute to urban wild bee diversity and that identifying functional groups affected by urbanization can help to draw recommendations for effective conservation. • Enhanced roadside vegetation benefitted wild bee species and functional diversity. • Functional diversity increased with distance from the center, and landscape diversity. • Small, short-lived, and univoltine bees were disadvantaged at enhanced roadsides. • Bee species sensitive to urban filtering were associated with green space edges. • Analysis of trait-environment interactions optimizes urban wild bee conservation. [ABSTRACT FROM AUTHOR]