Soil aggregate organic carbon and clover root characteristics as affected by earthworms (Metaphire guillelmi).

Soil aggregate composition is an important factor that affects soil organic carbon (SOC) content. Earthworms can greatly affect soil aggregate composition. However, the effects of earthworms' activities on SOC content in soil aggregates and the stability of these compounds was not clear. To reveal the mechanism of earthworms impacts on soil carbon stock, different earthworms densities were set in soil columns planted with clovers (Trifolium repens L.). We then analyzed the relationship that earthworms had with soil physicochemical properties and clover plant growth. Earthworms increased the large (17.5%–35.6%) and medium aggregate content (0.6%–9.79%) and decreased the microaggregates content (19.8%–29%) of the surface soil. Soil aggregates in medium density treatment were more stable than those in others. Both the mean mass diameter and geometric mean diameter of soil aggregates increased with the densities of earthworms. The average SOC content in large‐, medium‐, and microaggregates were 5.5, 4.2, and 4.2 g kg−1 respectively in soils seeded with earthworms. There was a significant correlation between soil organic carbon content and macroaggregate organic carbon content (R2 = 0.623, p < 0.05). The root characteristic values (root length, surface area, diameter, and biomass) of earthworm‐treated clover‐planted soils were higher than those of control. Clover root indices were positively correlated with the soil organic carbon content and soil aggregates. Earthworms altered the soil aggregate content and enhanced soil organic carbon storage, and thus promoted the development of vegetation roots. This study provides scientific support for a deeper understanding of the mechanisms of earthworms in soil carbon storage. [ABSTRACT FROM AUTHOR]