Weed-mediated stability of arbuscular mycorrhizal effectiveness in maize monocultures.
The influence of the accompanying flora of maize monocultures on the effectiveness of indigenous arbuscular mycorrhizal fungi (AMF) was investigated under field conditions in Hamburg, Germany. The maize monoculture without any accompanying flora resulted in a loss of spore types in the mycorrhizal community and lower effectiveness of the persistent AMF populations under both field and greenhouse conditions. The removal of mycorrhizal hosts resulted in a decline in maize biomass production. The presence of mycorrhizal hosts in the accompanying flora (Anagallis arvensis, Galinsoga parviflora, Lamium amplexicaule, Matricaria chamomilla [Chamomilla recutita], Poa annua, Sonchus asper, Spergula morisonii, Trifolium repens, Veronica agrestis, Vicia segetalis and Urtica urens), which contained spores of Glomus spp. and Acaulospora spp., guaranteed the persistence of a diverse indigenous AMF spore community, its high effectiveness in relation to maize and over-compensated weed-mediated reduction of maize biomass production. The role of a weed community tolerated at a low level on the effectiveness of the symbiosis on crop host plants is discussed.