Effect of fire on the mycorrhizal ecology of little bluestem (Schizachyrium scoparium)
Fire in a prairie significantly affected subsequent vesicular–arbuscular mycorrhizal (VAM) fungal colonization and sporulation, plant aboveground production, and tissue inorganic nutrient concentration. Colonization levels of VAM fungi in little bluestem (Schizachyrium scoparium (Michx.) Nash) roots were significantly (p < 0.05) lower on the burned site than on the unburned site during the first growing season postburn, but there were no significant differences between sites during the 2nd year. On each sampling date during the first growing season postburn, the burned site had significantly higher aboveground production than the unburned site. Significantly higher tissue levels of available K, Ca, and Mg were found on the unburned site than on the burned site; however, when nutrients were expressed in terms of nutrients in tissue per square metre, there were no significant differences between the burned and unburned sites. Spore counts for soil collected from the rhizosphere of little bluestem and randomly on burned and unburned sand prairies decreased from May into summer and then increased in late summer and fall on both sites during the first growing season postburn. Rhizosphere spore numbers were significantly lower on the burned site than on the unburned site in May and June, but they were significantly higher on the burned site in October during the first growing season. The results suggest that the response of VAM fungi to fire may be attributable to changes in the host plant and not due to any direct effect of fire.