The effects of repeated simulated grazing on big bluestem (Andropogon gerardii) plants, with and without mycorrhizal fungi, were measured Hetrick et al. in this greenhouse experiment. Big bluestem plants grown in soils where mycorrhizae were present had greater production than plants grown in soil that received fungicide application to remove mycorrhizae during the sixth week of the study. The presence of mycorrhizae allowed big bluestem to increase production under grazing conditions for the first three harvests, but in the successive harvests there were no differences between mycorrhizal plants and fungicide treated plants, most likely due to the reduced photosynthetic activity of the plant inhibiting mycorrhizal activity. Mycorrhizae can enhance big bluestem production but cannot counteract the effects of overgrazing, but eventually the benefits of mycorrhizae are reduced and big bluestem plants and their associated mycorrhizae will be damaged.
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