Pennycress-corn double-cropping increases ground beetle diversity

• The ground beetle diversity of a pennycress-corn double-cropping system was studied.
• It was compared with a mustard-corn, green fallow-corn and bare fallow-corn system.
• The novel pennycress-corn system was more diverse than the other three systems.
• Plant cover during winter and early in the season was a driving factor.
• Bioenergy from double-cropped pennycress may support ground beetle diversity.

Pennycress has been suggested as an alternative feedstock for bioenergy. Especially its cultivation in a double-cropping system with corn seems promising for a sustainable production. In this study we investigated the effect of a pennycress-corn double-cropping system on ground beetle diversity as an aspect of its sustainability. In a randomized block design we used 60 pitfall traps to compare the system's ground beetle diversity to that of three commonly applied corn rotations: mustard-corn, green fallow-corn and bare fallow-corn. Sampling was conducted from March 13th to July 10th and included the corresponding cultivation changes to corn. We found that the pennycress-corn system harbored a higher ground beetle abundance, richness, Shannon index and evenness than the other three systems. Plant cover over winter seemed to be a driving factor. Predatory species, the largest group in both abundance and richness, were only affected early in the year, whereas herbivorous species showed a positive response throughout the sampling period. We conclude that pennycress cultivation in the proposed double-cropping system does not have detrimental, but potentially positive effects on ground beetle diversity.