Earthworms promote the accumulation of rhizodeposit carbon to soil macroaggregate in a Mollisol of Northeast China, primarily in long-term no-till soil

As soil ecosystem engineers, earthworms are the main promoters of soil aggregation, a process that drives the production of ecosystem services by soils. A crucial factor in the ecosystem service of carbon sequestration is rhizodeposit carbon, which is the main energy source of soil food webs. The effects of earthworms on the distribution of rhizodeposit-carbon in soil aggregates remain unclear. Here, we conducted a 13CO2 labeling experiment to determine the effects of earthworms on maize rhizodeposit carbon in soil aggregates after 14 years (2002–2016), in both conventional tillage (CT) and conservation tillage (no tillage, NT) soils. Four treatments were established in total: NTE (no tillage soil with earthworms), CTE (conventional tillage soil with earthworms), NTC (control, no tillage soil without earthworms), and CTC (control, conventional tillage soil without earthworms). Earthworms significantly enhanced the abundance of soil macroaggregates (>2000 μm and 250– 2000 μm) on day 30 compared with day 2 (after labeling), especially in the NTsoils. On day 30, in the presence of earthworms, the amounts of rhizodeposit carbon in the >2000 μm and 250–2000 μm soil aggregates in the NTsoils were significantly higher than in those in the CTsoils (P < 0.05), and higher d13C signatures in the same size aggregates were observed in the NT soils than in the CT soils (P < 0.05). These findings indicated that compared with the CT soils, with the involvement of earthworm activity, the NT soils promoted more rhizodeposit carbon transformation to the soil macroaggregates. Our results clearly indicate that soil macroaggregates formed in different tillage soils in the presence of 2 different engineers (earthworms and roots) significantly differ from those formed in the presence of only one organism (roots) in the long term.