Influence of Mycotrophy on Native and Introduced Grass Regeneration in a Semiarid Grassland following Burning


Address correspondence to M. E. O’Dea, email


Prescribed burning is used in the southwestern United States to restore grasslands by reducing the abundance of encroaching woody species. Yet, the use of this tool appears to have the unintended effect of favoring the regeneration of some introduced grasses. Although both native and introduced perennial grasses evolved under the influence of fire, it is their response to mycotrophy in the immediate postburn environment that appears to give some grasses such as Lovegrass the advantage. In an exploratory study, two greenhouse experiments were completed in conjunction with a larger field study. A bioassay of soil from the study site found that soil exposed to burning had a significantly (p≤ 0.0001) lower mycorrhizal infection percentage than soil not exposed to burning, results which could not be explained by postburn erosion losses of inoculum alone. Results of the second greenhouse study revealed that differential response to mycotrophy clearly separated the Lovegrass (Eragrostis spp.) from the other genera studied. Lovegrass not infected by mycorrhizal fungi produced greater shoot biomass and inflorescence before the other noninfected studied grasses. Yet, infected Lovegrass did not develop inflorescence before harvest as the other genera infected by the mycorrhizal fungi did. Study results suggest that the lack of dependence by Lovegrass on mycorrhizal infection for reestablishing itself in the postburn environment gives it an advantage over those that do.