Monoculture and intensive use of chemical synthetic plant protection products (scPPP) in conventional agriculture are underlying reasons for the current dramatic loss of biodiversity. Although species diversity is, on average, 34% higher in organic farming, the yield of organic cereals is up to 50% less than in conventional agriculture (Tscharntke et al., 2021). Therefore, a comprehensive conversion of conventional farming to organic may seem unviable. NOcsPS farming which does not implement csPPP and has significantly lower yield loss compared to organic, could solve this dilemma by allowing for biodiversity-friendly and, at the same time, high-yield agriculture. A distinctive feature of the NOcsPS cropping system is its broad and resilient crop rotations that integrate protein crops, clover-grass and catch crops in addition to cereals and maize. Such diversified crop rotations could result in a significant increase in the biodiversity of associated wildlife species, especially when no csPPP is implemented. However, this theory has only been studied as an example in research. Ongoing studies focus on a few selected groups of organisms, such as soil (micro)organisms (CP5), plant pathogens (CP9, CP10), predatory flies (CP11), and aphids and antagonistic insects (CP13). Nonetheless, no attention has been paid to the extremely diverse group of aboveground arthropods, including ecologically important ground beetles, rove beetles, and arachnids. Most aboveground arthropods are predators, which makes them very important in natural pest control, especially with their complementary synergy with flying arthropods (Thies et al., 2011; Dainese et al., 2017). Current insect diversity assessments focus primarily on aphids and their antagonists (CP13). These assessments take place exclusively in fields with winter wheat, and a substantial range of crops are excluded. An issue here is that the crop species - both in the sampling year and in the previous crop type in the crop rotation sequence - largely affects the diversity and composition of associated insect communities (Meyer et al., 2019). Hence, biodiversity assessments are required at each crop rotation cultivation period to evaluate NOcsPS cropping systems' biodiversity potential holistically. Arthropod species associated with farming demand different resources and habitats during their life cycle, depending on their mobility at different temporal and spatial scales (Grass et al., 2021). Therefore, the biodiversity conservation potential of NOcsPS farming depends on the landscape context in which it is practiced, making landscape-scale studies critical for implementing NOcsPS farming systems on a large scale.

This research project aims to extensively assess the species diversity, abundance, and composition of insect and arachnid populations in different NOcsPS cropping systems. The assessments for this purpose are complementary to existing studies, i.e., CP5, CP9, CP10, CP11, and CP13. The data collected aim to provide a comprehensive understanding of the effects of spatiotemporal resource dynamics of different crop rotation variations on biodiversity. Investigations of NOcsPS cropping systems in different landscape contexts will also enable predictions of the biodiversity potential of a large-scale conversion to agriculture without csPPP. Specifically, the following hypotheses will be tested:

• Compared to conventional cropping, NOcsPS cropping systems result in higher local species diversity, abundance, and functional diversity of associated insects and arachnids.
• The composition of the insect and arachnid populations is influenced by the crop type in the sampling year as well as by the crop type in the precious crop rotation period.
• The biodiversity impacts of NOcsPS cropping systems also depend on (i) field size, (ii) landscape structure, and (iii) spatiotemporal land-use dynamics.

Our biodiversity studies will take place at various spatial scales both in the systematic trials in Heidfeldhof and on sample farms and in close coordination with ongoing studies on aphids and their antagonists (CP13), local habitat conditions (CP3, CP8), fungal pathogen occurrence (CP9, CP10), and predatory fly abundance (CP11). In the first year of the project (2022), plant-inhabiting and flying insect species, as well as aboveground insects and arachnids, will be recorded in all crop types of the crop rotation variations and their replicates. Plant-inhabiting and flying species were recorded with an insect vacuum sampler, complementary and with an identical methodology to CP13 (56 plots) and in all other crop rotation episodes (122 plots). Aboveground arthropods will be collected using pit-fall traps in all 168 plots. The taxonomic identification of the prospective species groups (flies, bugs, beetles, ichneumon flies, wild bees, arachnids, etc.) is very difficult and laborious with classical methods and often can only be performed by a few international experts. Instead, modern molecular biological methods are used. DNA metabarcoding enables rapid and cost-effective determination of large numbers of samples and is increasingly becoming instrumental in large-scale biodiversity monitoring of agricultural landscapes (Yu et al., 2012; Hausmann et al., 2020). In the second year of the project (2023), existing samples of CP13 from 50 plots in csPPP-free farms (KraichgauKorn) that have been evaluated regarding aphids will also be analyzed for their overall species diversity using DNA metabarcoding. The data obtained will be integrated into the spatiotemporal modeling of CP13, providing results for understanding important factors influencing biodiversity in NOcsPS cropping systems at different scales. In addition to analysis of these existing samples, pilot studies of biodiversity in large-scale csPPP-free farms are planned. On farms of Denree GmbH in eastern Germany (e.g., Hofgut Eichigt, 4000 ha), insects and arachnids are recorded on a large scale, and effects of a landscape-wide conversion to csPPP-free agriculture are being measured.