Exploring carbon flow through the root channel in a temperate forest soil food web

Soil food webs play an important role in forest ecosystem functions that may be sensitive to global environmental change. We traced a pulse of 13C from the root systems of young sugar maple stands through the soil food web to explore energy flow from roots to soil heterotrophs. Invasive earthworms (Lumbricidae) were the most highly-enriched taxa sampled, indicating that they were consuming significant quantities of live fine roots and mycorrhizae and assimilating significant amounts of root-derived C. Another invasive invertebrate, a weevil (Barypeithes pellucidus) also appeared to consume significant amounts of roots or root-derived C. High isotope enrichment in ants (Formicidae) may reflect their feeding on phloem-sucking coccids in soil. All the predators collected from the litter layer also exhibited high isotope enrichment, including the salamander Plethodon cinereus. Moreover, in the absence of invasive earthworms all the taxa of animals collected from surface soil were similarly highly-enriched in root-derived isotopes. The apparent importance of the root channel in supplying energy to the soil food web suggests that forest ecosystem functions could be highly sensitive to global changes that alter proportional tree C allocation belowground.