Protection of soil carbon by microaggregates within earthworm casts

Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization

“…In this case, earthworms converted a greater proportion of the earthworm-activated C (C act-w ) into the pool of stabilized C (C sta-w ) concomitant with a readily observed increase in CO 2 emission (C min-w ). Importantly, from the aggregates data in the literature 21 , there is strong evidence in support of this logic ( Fig. 5b; Supplementary Table S1).…”

“…5). The earthworm species studied here and previously 21 belong to the two largest taxonomic groups respectively, that is, Lumbricidae and Pheretimoid, which have spread throughout the temperate and tropical regions of the globe 12 . In addition, most earthworm individuals were alive and healthy in the present study throughout the experiment ( Supplementary Fig.…”

“…) values were calculated to quantify the balances between C mineralization and C stabilization in soil with and without earthworms, respectively. Estimation I: all litter-derived C in soil aggregates were assumed to be stabilized; estimation II: about 17% of litter-derived C in microaggregates within large macroaggregates and only 8% of litterderived C in microaggregates were assumed to be stabilized for soil with and without earthworms, respectively 21 . In (c) the two dot-dash axes represent the reference x axis and y axis in control soil without earthworms; the origin of the dot-dash axes refers to a reference point of no metabolic activity.…”

“…5b; Supplementary Table S1). Reanalysis of these data 21 indicates that the endogeic earthworm species (Aporrectodea caliginosa) increased both CO 2 emission and sequestration of both TOC and litter-derived C, with SQ basal (0.17) oSQ worm (0.73) o1 and SQ basal (0.02) oSQ worm (0.28)o1, respectively; whereas A. caliginosa increased the sequestration but reduced the mineralization of SOC-derived C, with SQ worm (1.34) 414SQ basal (0.29). A SQ worm 41, indicating that earthwormstabilized basal C was greater than earthworm-activated mineralizable C (Supplementary Table S1).…”

“…1,[18][19][20]; but the stabilized C may be re-distributed throughout the whole soil profile or even be transferred into ground water. Given that the earthworm-mediated aggregation processes may 'trap' activated C successfully 21 , we propose that earthworms may enhance C stabilization to a greater extent than C mineralization. If so, the greater the proportion of PMC activated by earthworms, the greater the proportion of PMC that may be stabilized.…”