Spatial variation of earthworm communities and soil organic carbon in temperate agroforestry

The aim of this study was to assess how soil organic C (SOC) stocks and earthwormcommunities were modified in agroforestrysystems compared to treeless control plots and within the agroforestryplots (tree rowsvs alleys). We used a network of 13 silvoarable agroforestrysites in France along a north/south gradient. Total earthwormabundance and biomass were significantly higher in the tree rowsthan those in the control plots, but were not modified in the alleyscompared to those in the control plots. Earthwormspecies richness, Shannon index, and species evennesswere significantly higher in the tree rowsthan those in the alleys. Total abundance of epigeic, epi-anecic, strict anecic, and endogeicwas higher in the tree rows. Surprisingly, earthwormindividual weight was significantly lower in the tree rowsthan that in the alleysand in the control plots. SOC stocks were significantly higher in the tree rowscompared to that in the control plots across all sites. Despite higher SOC stocks in the tree rows, the amount of available C per earthwormindividual was lower compared to those in the control. The absence of disturbance (no tillage, no fertilizers, no pesticides) in the tree rowsrather than increased SOC stocks therefore seems to be the main factor explaining the increased total abundance, biomass, and diversity of earthworms. The observed differences in earthwormcommunities between tree rowsand alleysmay lead to modified and spatially structured SOC dynamics within agroforestryplots.