Overwinter survival of arbuscular mycorrhizal hyphae is favored by attachment to roots but diminished by disturbance

Abstract

 We investigated the overwinter survival in the field of indigenous arbuscular mycorrhizal (AM) hyphae either connected to corn roots or detached 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. Following 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 pouches declined 20% and 33% (average of coarse- and fine-mesh treatments), respectively, from fall to spring, presumably because of death overwinter. In the spring, living hyphae were more abundant in the presence of roots than in their absence, suggesting that attachment or proximity to roots favored overwinter survival. Total hyphal density, metabolically active hyphal density, and the proportion of total living hyphae progressively diminished with increased disturbance.