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

Abstract

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.

Effects of preparation of clear‐cut forest sites on the soil mycobiota with consequences for Scots pine growth and health

“…However, its thin hyphae, which measure 1–2 μm in diameter, may persist better in an undisturbed habitat. Umbelopsis is a later decay fungus which dominates in an undisturbed community (Fisk, Fahey, Sobieraj, Staniec, & Crist, ). The presence of Wilcoxina mikolae only in undisturbed soil was unexpected.…”

Maintaining connectivity: understanding the role of root order and mycelial networks in fine root decomposition of woody plants

“…These approaches limit rhizosphere disturbance and allow for functional comparisons among roots within the fine root branching system in situ (Dornbush et al 2002;Fisk et al 2011). Both the intact core and root window approaches maintain connectivity among belowground branching systems and do not require preliminary processing of root material (Dornbush et al 2002).…”

“…For first order roots to maintain situational context, they must decompose in the presence of intact rhizosphere soil, colonized by pre-mortem fungi (Li et al 2015). Fisk et al (2011) disrupted the rhizosphere of roots decaying under root windows inset into the soil in an Eastern hardwood forest and found that the dominant fungal taxa changed due to the disturbance; rhizosphere species were replaced by bulk soil fungal species. Dornbush et al (2002) decomposed recently senesced fine roots of silver maple using both litterbags and an intact core technique where roots are left to decompose within an intact soil core to limit rhizosphere disturbance.…”

“…While AM fungi are capable of releasing phosphatases from extraradical hyphae and have been shown to hydrolyse organic P when grown in culture (Koide and Kabir 2000;Bucher 2007;Sato et al 2015), the degree to which they produce extracellular enzymes to degrade SOM is thought to be minimal (Hodge 2017;Kuyper 2017). For these reasons, it seems clear that altering the rhizosphere environment and disturbing fungal symbionts is likely to influence the decomposition process but perhaps to a different extent in ECM compared to AM tree species, and in first compared to higher order roots (Dornbush et al 2002;Fisk et al 2011;Li et al 2015).…”

Roots Mediate the Effects of Snowpack Decline on Soil Bacteria, Fungi, and Nitrogen Cycling in a Northern Hardwood Forest

“…We sampled after plant senescence in October 2013, a period when tree C allocation belowground is likely to be at annual minima (Abramoff and Finzi, 2016), potentially affecting the root-associated fungal communities that we observed. For example, sugar maple associates primarily with arbuscular mycorrhizal fungi and AMF root-colonization, abundance, and biomass are likely to be highest during periods of higher plant C allocation belowground in mid-summer (Mandyam and Jumpponen, 2008; Soudzilovskaia et al, 2015) whereas saprotroph abundance would be expected to increase following root senescence (Fisk et al, 2011).…”