Does soil biota benefit from organic farming in complex vs. simple landscapes?

Organic farming can counteract detrimental effects of agricultural intensification on farmland biodiversity. Enhancing biodiversity with agri-environmental schemes is hypothesized to be more efficient in simple than complex landscapes, a pattern confirmed for many aboveground taxa. Although belowground biodiversity is an important part of the agroecosystem, studies on the interacting effects of local and landscape intensification on the belowground detritivore community, including bacteria, fungi, collembolans and earthworms are lacking. We sampled diversity and abundance of arable weeds, earthworms and collembolans, soil respiration rate and microbial biomass in 12 pairs of organically and conventionally managed fields in landscapes differing in structural complexity. Organic farming significantly enhanced species richness of arable weeds, while conventional farming enhanced soil respiration and abundance of Collembola with furca. This research shows that the landscape context plays a significant role in shaping effects of organic vs. conventional farming on soil biota. Earthworm species richness in simple landscapes, where predation pressure is reduced, was enhanced by organic farming, whereas in complex landscapes, conventional farming, which often causes reduced predation, fostered earthworm species richness. As the same pattern was found for microbial carbon biomass, earthworms may have enhanced microbial biomass. In contrast to earthworm and microbial diversity, aboveground biodiversity benefits most from organic farming in simple landscapes. In general, organic farming appears to be more efficient in conserving aboveground than belowground diversity.

► Organic farming can counteract detrimental effects of agricultural intensification (AI).
► Agricultural intensification and landscape effects interact.
► Landscape plays an important role in shaping effects both on weeds and soil biota.
► Organic farming appears to be more efficient in conserving aboveground biodiversity.