Predatory arthropods contribute to biological control, but to become an integral part of agricultural management, it is essential to identify drivers of their spatio-temporal distribution at the landscape scale. This study focuses on how agricultural land use affects the community composition, emergence and dispersal tendency of predatory arthropods. The arthropods were collected in emergence traps during the growing season (14 weeks) in a gradient of agricultural land uses from intensively managed sugar beet fields, over winter wheat fields, to less intensively managed grasslands. The emergence traps were equipped with one pitfall trap and a collecting bottle at the top. The distribution of the arthropods between these two collecting methods was assumed to represent their tendency to move out of the habitat. The grasslands had the highest numbers of spiders, while the winter wheat fields had the highest numbers of omnivorous rove beetles and macropterous predaceous ground beetles. The phenology of emergence differed between the land-use types, resulting in seasonal differences in community composition. The overall dispersal tendency of predatory arthropods was higher in crop fields than in grasslands. This study suggests that only a diverse mix of agricultural land uses will provide high levels of predators from different functional groups, throughout the growing season.
Agricultural management practices and extreme weather events associated with climate change can influence the diversity and abundance of arbuscular mycorrhizal fungi (AMF) with potential consequences for crop production. However, the importance of the interactive effects of long-term agricultural management and extreme weather events on AMF communities in agricultural soils is not yet fully explored. A short-term drought experiment with rainout-shelters was performed in winter wheat fields in a long-term agricultural trial with organic (biodynamic) and conventional management practices. During four months of the winter wheat growing period (March–June 2017), the rainout-shelters reduced the ambient precipitation by 65% on average. At two sampling dates, the AMF diversity and community composition were assessed using a single-molecule real-time (SMRT) DNA sequencing. A total of 955 amplicon sequence variants (ASVs), belonging to twelve genera were identified. The long-term farming systems and the short-term experimental drought did not affect AMF ASV diversity levels. The AMF community composition at the genus level differed between the organic and the conventional farming systems, but no distinctive communities were found in response to the experimental drought. The three most abundant genera Acaulospora, Paraglomus and Funneliformis were correlated to the two farming practices. Our study demonstrates that AMF communities in agricultural soils are responsive to long-term farming systems, and are resistant to one short-term summer drought event.
It is crucial to consider the effects of large-scale drivers on species presences and ecological interactions to understand what structures communities. In our study, we investigated how the species composition and the potential interaction networks of herbivore and parasitoid communities in oilseed rape fields are affected by agricultural landscape characteristics. Insect communities of 26 winter oilseed rape fields in southern Sweden were captured in water traps over a continuous time span of 30 ± 2 days. In total, 31% of the variation in the composition of herbivore host communities was explained by a combination of the surrounding oilseed rape area in the study year and the previous year and distance to the nearest forest. The oilseed rape area in the study year and distance to forest also explained 14% of the variation in the composition of parasitoid communities. Distance to the nearest forest together with the area of oilseed rape in the previous year explained 45% of the variation in asymmetry of interaction webs. These results indicate that several measures of landscape configuration are important both for the composition of host and parasitoid communities and also for the structure of interaction networks. Our results support the view that it is an appropriate strategy to cultivate oilseed rape in landscapes that are far away from forests, in order to minimize recolonization by pest species and at the same time to attract parasitoid species from the open landscape.