Promotion of ground beetles by integrating perennial energy crops into existing agricultural landscapes

Abstract

Perennial energy crops as an alternative to maize (Zea mays L.) have the potential to promote biodiversity and associated ecosystem services in agricultural landscapes. Ground beetle (Carabidae) assemblages of cup plant (Silphium perfoliatum L.), Virginia mallow (Sida hermaphrodita L.) and tall wheatgrass (Thinopyrum ponticum Podp.) were assessed in four replicated field trials in Bavaria and compared to an annual crop rotation (winter rye (Secale cereale L.)), maize, winter wheat (Triticum aestivum L.)). Additionally ground beetle fauna in cup plant was compared to that in maize on fields under real farm conditions at six sites in Bavaria with widely diverging soil–climate conditions. Ground beetles were collected in pitfall traps in winter (one field trial), spring (four field trials) and summer (six fields) in 2017.Overall, results for activity density and species richness of ground beetles under perennials compared to annuals were site-specific and there were no pronounced differences of species compositions.The highest activity density of seed-eating ground beetles occurred in Virginia mallow, which was invaded by weeds. Some indication of benefits for hibernation and larval development in cup plant were found. Tall wheat-grass had the lowest ground beetle diversity and activity density of all crops. Species accumulation curves on farmed fields in summer indicated higher species richness of ground beetle fauna in cup plant than in maize. Diversification of cultivated plants with perennial energy crops can provide additional niches for ground beetles, such as undisturbed soil. Effects, however, varied with site and species/genus in a complex manner.