Earthworm (Lumbricus rubellus and Aporrectodea caliginosa) effects on carbon flux in soil.
Zhang Q.L. | Hendrix P.F.
Effects of earthworm activities on litter and soil C flux were studied in a laboratory incubation experiment using two types of isotopic tracers and two earthworms with different ecological strategies-Lumbricus rubellus, an epigeic species, and Aporrectodea caliginosa, an endogeic species. The soil was prelabeled with 14C. Dry sorghum [Sorghum bicolor (L.) Moench] leaves labeled with 13C were applied to the soil surface. Activity of both earthworm species significantly (P < 0.001) enhanced total C efflux (479 +/- 8 [standard error], 483 +/- 4, and 395 +/- 5 mg C jar(-1) for L. rubellus, A. caliginosa, and the control, respectively) and significantly (P < 0.05) reduced total surface soil microbial biomass (251.7, 205.2, and 312.1 mg C kg(-1) soil for L. rubellus, A. caliginosa, and the control, respectively) during the 30-d incubation. Activity of A. caliginosa also reduced subsurface soil microbial biomass. The epigeic earthworms assimilated significantly more 13C from the litter and significantly less 14C from the soil than the endogeic species. In the absence of earthworms, 14C in the soil was translocated into the surface liner, as shown by a 15.5-fold increase in 14C enrichment in the surface litter by the end of the experiment. This translocation of soil C into the litter was significantly reduced by earthworm activities (155.43, 121.11, and 240.58 kBq kg(-1) litter for L. rubellus, A. caliginosa, and the control, respectively), possibly due to disruption by earthworms of fungal-hyphal connections between litter and soil. These interactions between earthworms and soil microbial processes have important implications for soil C turnover.
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