Aporrectodea caliginosa life history traits are improved by positive earthworm interaction and organic matter addition

Earthworm species interact with each other in soils, but these interactions are poorly understood. Moreover, these key soil organisms are influenced by abiotic soil components such as organic matter. Here, we investigated the influence of Allolobophora chlorotica and Aporrectodea nocturna, two earthworm species from different ecological categories, on the incorporation of organic matter, reproduction and weight change of the endogeic Aporrectodea caliginosa. Two different types of organic matter i) a compost and ii) a fresh refined organic material, both from green waste, were used. Earthworm parameters were monitored during an 8-weeks laboratory experiment using a vineyard soil in order to identify positive and negative interactions between species. Irrespective of species, earthworms interacted preferentially with smaller particles, more decomposed and with a lower C/N ratio. For an equivalent earthworm biomass, similar amount of green compost was incorporated by A. caliginosa and A. nocturna. However, A. chlorotica did not bury this material. The green compost increased the reproduction rate of A. caliginosa when associated to A. chlorotica. Moreover, the association with the epi-anecic A. nocturna increased the reproduction rate of A. caliginosa with the addition of refined organic matter (fresh material). Furthermore, in both earthworm associations, the weight loss of A. caliginosa was reduced by the addition of green compost to the soil surface. These results highlight the importance of earthworm interactions in maintaining populations, and emphasized the need of field studies to confirm these interactions, particularly in the context of soil fertility where organic amendments are often applied.