Systems Biology Colloquium 2 May 2014 - Does organic farming enhance biological activity and ecosystem services in soil ecosystems?

Organised by Biometris

Fri 7 March 2014 11:00 to 12:00

Venue Radix, gebouwnummer 107
Room W0.1

One of the central hypotheses behind the development of sustainable organic farming is that the soil food web becomes more important in terms of delivering important soil ecosystem functions, such as nutrient mineralisation, suppression of soil borne diseases and soil structure formation. The present study focused on the structure and functioning of soil food webs in organic and conventional farming in two contrasting environments: Iceland and Austria. Organic fields differed from the conventional fields in the absence of artificial fertilizers and pesticide use. At the sites we measured occurrence and abundance of bacteria, fungi, protozoa, nematodes and micro-arthropods. Additionally, we measured the taxa richness and diversity within the group of micro-arthropods. Although total and microbial biomass were higher in organic farms, these differences were not statistically significant. Nematode biomass was higher in organic fields than in conventional fields, while the biomass of omnivorous mites was consistently higher in conventional fields. No differences were found in carbon or nitrogen mineralisation rates between organic and conventional fields. Within the trophic groups though, we found that the organic fields had a consistently higher micro-arthropod taxa diversity compared to conventional fields. These results indicate that the trophic structure and functioning of the soil food webs was not very sensitive to management system, but the taxonomic diversity was. Although the higher micro-arthropod diversity in organic fields did not yield higher ecosystem services such as soil fertility or C sequestration, it implies a higher functional redundancy within the trophic groups of the soil food web is expected to create a higher resistance to disturbances and therefore enhance stability of ecosystem services.