Litter decomposition and organic matter turnover by soil fauna in a sustainably managed olive grove

In Mediterranean orchards, soil organic matter (SOM) plays a crucial role and its level is principally determined by the continuous physical and chemical action of soil fauna. The aim of this study was to characterize and compare C/N dynamics and other soil physicochemical parameters, soil macrofauna abundance, bioturbation and litter/SOM decomposition indices in a Mediterranean olive (Olea europaea L.) orchard subjected to two different soil management systems (namely sustainable, Smng, and conventional, Cmng) for 18 years. The adoption of the Smng system significantly increased almost three times the abundance of earthworms and two times that of other macrofauna. Bioturbation due to soil fauna and roots was significantly higher in the Smng system, and this caused a significantly faster SOM decomposition measured both in local litter bags and in tea bags. The results highlighted that a great part of the soil quality and fertility of the Smng system could be due to the bioturbation activity of soil fauna, together with its interaction with decomposing microorganisms. It emerged that the role of soil fauna should be seriously taken into account in future land management strategies not exclusively focused on fruit yield and quality.