OVERWINTER SURVIVAL OF ARBUSCULAR MYCORRHIZAL HYPHAE IS FAVORED BY ATTACHMENT TO ROOTS BUT DIMINISHED BY DISTURBANCE

We investigated the overwinter survival in the field of indigenous arb uscular mycorrhizal (AM) hyphae either connected to corn roots or deta ched from them, and either intact or disrupted. We buried soil-filled pouches which either allowed root entry or excluded roots in the root zone of a field-grown corn (Zea mays) crop in eastern Canada. Followin g crop harvest In the fall, pouches either remained undisturbed, were disturbed outside the pouch, or were disturbed both inside and outside the pouch. Total and metabolically active AM hyphae in undisturbed po uches declined 20% and 33% (average of coarse- and fine-mesh treatment s), respectively, from fall to spring, presumably because of death ove rwinter. In the spring, living hyphae were more abundant in the presen ce of roots than in their absence, suggesting that attachment or proxi mity to roots favored overwinter survival. Total hyphal density, metab olically active hyphal density, and the proportion of total living hyp hae progressively diminished with increased disturbance.