Deficit watering reduces plant growth to a smaller extent with arbuscular mycorrhizal association than without it for non-invasive grass species but not for invasive grass species.
Symbiotic associations with the soil microbiota, particularly with arbuscular mycorrhizal fungi (AMF), might ameliorate the effects of environmental stress on plants, and this capacity may be different for resident and alien species. In a growth room pot experiment we tested if imposed water deficit leads to greater growth reduction in the absence of AMF than in the presence of AMF for two non-invasive resident (Danthonia alpina, Chrysopogon gryllus) and two invasive (Calamagrostis epigejos, Cynodon dactylon) grass species from semiarid temperate grasslands in Hungary. Both deficit watering and soil sterilization decreased biomass accumulation, but the non-invasive Danthonia and Chrysopogon performed better when grown in intact soil containing AMF than in sterilized soil. In contrast, the invasive Calamagrostis and Cynodon displayed mostly no difference in growth and biomass accumulation between intact and sterilized soil when subjected to water deficit. When plants were grown well-watered but deprived of AMF symbionts, both Danthonia and Chrysopogon achieved poorer growth than in AMF containing soil, while neither Calamagrostis nor Cynodon displayed any reduction. These results indicate that the influence of deficit watering was ameliorated by the presence of AMF in the soil for the resident non-invasive species, while not for the invasive species.