The response of arbuscular mycorrhizae to fertilization, mowing, and removal of dominant species in a diverse oligotrophic wet meadow

In a wet oligotrophic meadow located in the Czech Republic, a factorial experiment with treatments consisting of fertilization. mowing. and removal of the dominant species (Molinia caerulea) was established in 1994. In 1997 Holcus lanatus, Molinia caerulea. Potentilla erecta, Prunella vulgaris, and Ranunculus auricomus were examined for arbuscular mycorrhizal (AM) hyphae. arbuscles, and vesicles three times over the season. Time had a significant effect on AM in all five species. Except for Mulinia arbuscles. a modal effect occurred, with the second sampling having a greater level of AM structures than the first and the third. Fertilization had the greatest effect on AM levels by decreasing the level of Holcus hyphae and vesicles, Potentilla vesicles. Prunella hyphae. and Ranunculus hyphae and vesicles. Mowing significantly increased the number of Potentilla vesicles, and the removal of dominant species had no significant effects. Interactions between time and treatments were common. Significant effects to the arbuscle:vesicle ratio were infrequent, and those that occurred were related to changes over the season. Seasonal effects appear to have a more powerful effect on AM structures and the arbuscle:vesicle ratio than do treatment effects. In a second experiment, Ranunculus auricomus, R. acris, and R. nemorosus, sampled four times over the season, showed significant changes in AM colonization. Overall, AM structures either declined over the season or increased from April to May and then declined. There was no AM colonization response to a spring fertilization in the three species. It is postulated that the patterns observed are due to phosphorus availability and seasonal changes in soil moisture and rates of root growth and turnover.