Comparison of soil-dwelling predatory arthropod activity-density and diversity under annual and perennial cereal production in Europe

Frequent soil tillage, as associated with soil disturbance and the lack of permanent vegetation cover, may negatively impact soil and soil-dwelling organisms. To mitigate the serious constraints of annual crop production, a concept is the reversed shift from predominant annual to perennial grain crop production. Thinopyrum intermedium L. (Intermediate Wheatgrass, IWG, Kernza®) is a recently domesticated perennial grain crop and can be grown for several years. We assumed that activity-density and diversity of soil-dwelling arthropods will differ between IWG and winter wheat, and we particularly expected higher activity-density and diversity in the IWG system compared to annual wheat. To test this, we recorded soil-dwelling predatory arthropods (Araneae, Carabidae, Staphylinidae) in two different study regions of Europe (France and Sweden), in two years in France and one year in Sweden. The overall results do not confirm our initial hypothesis that soil-dwelling Araneae, Carabidae and Staphylinidae show higher activity-density and diversity in the perennial IWG system compared to annual winter wheat. This observation is true regardless of year and country, despite considerable differences in abundance and species composition of the communities with a high effect of geographic location. Rather, there were even significantly higher activity-densities in wheat than in IWG, as it was the case for the Carabidae and Staphylindae in Sweden, the Staphylinidae in France in 2022, and the Carabidae in France in 2023. Only the Araneae showed higher numbers of individuals in IWG than in wheat in France and in Sweden in 2022, but the differences were not significant.