Rhizosphere disturbance influences fungal colonization and community development on dead fine roots

Little is known about the community dynamics of fungi on decomposing fine roots, despite the importance of fine roots as a source of carbon to detrital systems in forests. We examined fungal communities on dead roots in a sugar-maple dominated northern hardwood forest to test the hypothesis that community development is sensitive to rhizosphere disruption. We generated cohorts of dead fine roots in root windows and disturbed the rhizosphere microbial community in half of the windows by moving roots into sieved bulk soil. We sampled root fragments repeatedly over time and cultured fungi from these fragments to explore temporal patterns of fungal species composition. Disturbing the root rhizosphere prior to initiating decomposition changed the dominant fungal taxa, the distribution of dominant species within the community, and the temporal development in the culturable fungal community. Dominance in control roots shifted from Neonectria in early decay to Umbelopsis in later decay. Disturbance roots were more evenly dominated over time by Trichoderma, Neonectria, another species of Umbelopsis, and Pochonia. Our results suggest that species interactions are important in the ecology of fine root decay fungi, with the rhizosphere community of the living root influencing development of the decay community.