Changes in root associated fungal communities during fine root decomposition in Abies balsamea and Picea rubens

Abstract

Fine roots are ephemeral roots < 2 mm in diameter that are frequently replaced during fine root turnover. As fine roots harbour symbiotic and commensal fungi, their trophic strategy may shift upon fine root senescence and decomposition. This study examined fungal communities in Abies balsamea and Picea rubens fine roots during decomposition. Observations of ectomycorrhizae showed that Cenococcum geophilum was recalcitrant, showing no appreciable decomposition after 16 months. Hyaline ectomycorrhizae were least recalcitrant and were not detected beyond four months. Differences between ectomycorrhizal recalcitrance may subsequently affect fine root decomposition. Molecular analysis showed: an ectomycorrhizal community becoming dominated by Piloderma; an increase in helotialian endophytes; and a relatively limited presence of saprotrophs. The most common saprotroph detected increased in concert with the endophytes. Increases in endophytic abundance suggests that they may be involved in the decomposition of fine roots in forest soils.