EFFECTS OF SIMULATED FIRE ON VESICULAR-ARBUSCULAR MYCORRHIZAE IN PINYON-JUNIPER WOODLAND SOIL

Effects of fire on vesicular-arbuscular mycorrhizal fungi were tested using microcosms constructed from soil, litter, and duff collected beneath canopies of pinyon pine [Pinus edulis] Utah juniper, [Juniperus osteosperma] and in the open space (interspace). Burning was conducted over wet and dry soils. Soil temperatures were monitored continuously throughout the microcosms during burning. Plants grown in soils burned when dry had a lower VAM colonization than soils burned when wet. Juniper soils demonstrated the greatest reduction, over 95%, compared to their respective controls. Plants grown in interspace soils burned when wet were least affected. There was a positive correlation (r2 = 0.90) between the decrease in VAM colonization and the soil temperature as a result of the fire. Temperature effects, and associated reductions in VAM, were related to amount of litter burned in each micocosm and the moisture content of the soils.