EFFECTS OF BURROWING BY THE EARTHWORM APORRECTODEA-CALIGINOSA (SAVIGNY) ON BEECH LITTER DECOMPOSITION IN AN AGRICULTURAL AND IN A FOREST SOIL

A microcosm experiment was designed to study the effect of the endogeic earthworm Aporrectodea caliginosa (Savigny) on the C mineralization of C-14-labelled litter in the upper 10 cm of an agricultural and of a beech forest soil. The following treatments were set up for both soils: (1) control: (2) + 1 adult A. caliginosa; (3) daily mixing of the soils by hand; (4) as treatment (3) + addition of mineral N. The burrowing activity of A. caliginosa strongly stimulated C-14 mineralization. Mixing of soil and litter increased C-14 mineralization in the forest but not in the agricultural soil. The combined effect of mixing and N addition further increased C-14 mineralization in the forest soil and strongly increased it in the agricultural soil. While C-14 mineralization was still lower in treatment 4 than in treatment 2 of the beech forest soil, it was identical in those of the agricultural soil. It may thus be concluded that the effect of A. caliginosa on the mineralization of undecomposed litter in the agricultural soil is largely due to the combined effect of mixing of soil and litter and mobilization of N, while in the beech forest soil additional factors are important.