Soil microbial and arthropod biodiversity under organic and biodynamic viticulture

Aims: The aim of the study was to investigate whether organic or biodynamic management have a long-term impact on 1) the microbial biomass and enzymatic activity in the soil, 2) the soil microbial community, 3) flying as well as soil living arthropods and associated fungi.

Methods and Results: The studies presented here were conducted in a field trial comparing integrated, organic and biodynamic viticulture at least 10 years after the implementation of the different management systems. The vineyard is located in Geisenheim, Germany, and the study is conducted on Vitis vinifera L. cv. Riesling.

One study assessed soil enzymatic activities (GLU, CAT, UR, DHA, PHO) and microbial biomass by quantifying PLFAs and NLFAs, respectively. For the second study soil fungal and bacterial biodiversity were investigated using an amplicon sequencing approach. For the third study eDNA was extracted from arthropods in bulk and soil samples. A DNA metabarcoding approach was used to investigate whether diversity of arthropods and fungi in these samples was affected by the management system.

Fungal and bacterial biomass as well as enzymatic activities in the soil were shown to be highly affected by the management system. The organic and the biodynamic systems had significantly more fungal and bacterial biomass. In contrast, the integrated system had a significantly higher mycorrhizal biomass compared to the organic and the biodynamic system. Enzymatic activities measured were significantly higher under organic and biodynamic management.

Fungal species richness assessed by DNA sequencing did not differ among management systems, but fungal community composition was significantly affected. Bacterial species richness was significantly higher under organic and biodynamic management, whereas bacterial community composition was less affected by the management system.

Richness of flying and soil-living arthropods and their related fungi assessed by eDNA sequencing was not significantly affected by the management system alone. In contrast, management systems significantly differed in the arthropod community composition in bulk samples as well as in fungal community composition associated with flying as well as soil-living arthropods.

Conclusions:

Different management systems have a clear impact on soil microbial activity, biomass, and biodiversity, as well as on arthropod biodiversity and fungal biodiversity associated with arthropods. In the current studies soil enzymatic activities as well as soil microbial biomass and bacterial species richness in the soil were positively affected by organic and biodynamic management. Fungal community composition in the soil, in samples of soil-living as well as in samples of flying arthropods were highly affected by the management system. The hypothesis of whether arthropods in the vineyard act as vectors for bacteria and fungi will be discussed.