Weeds influence soil bacterial and fungal communities

Background and aims Vineyards harbour a variety of weeds, which are usually controlled since they compete with grapevines for water and nutrients. However, weed plants may host groups of fungi and bacteria exerting important functions. Methods We grew three different common vineyard weeds (Taraxacum officinalis, Trifolium repens and Poa trivialis) in four different soils to investigate the effects of weeds and soil type on bacterial and fungal communities colonising bulk soil, rhizosphere and root compartments. Measurements were made using the cultivation-independent technique Automated Ribosomal Intergenic Spacer Analysis (ARISA). Results Weeds have a substantial effect on roots but less impact on the rhizosphere and bulk soil, while soil type affects all three compartments, in particular the bulk soil community. The fungal, but not the bacterial, bulk soil community structure was affected by the plants at the late experimental stage. Root communities contained a smaller number of Operational Taxonomic Units (OTUs) and different bacterial and fungal structures compared with rhizosphere and bulk soil communities. Conclusions Weed effect is localised to the rhizosphere and does not extend to bulk soil in the case of bacteria, although the structure of fungal communities in the bulk soil may be influenced by some weed plant