Soil Fauna Contribution To Soil Physical Quality: An Experimental Approach With 3D Image Analysis

The definition of "ecosystem engineers" has deeply influenced our assessment of the role of organisms in ecosystem functioning (Jones et al. 1994). Ecosystem engineers are organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials (Jones et al., 1994, 1997). They are primarily physical engineers, building resistant soil aggregates and pores. In that way, ecosystem engineers plays a key role in the formation of soil structure, providing an important contribution to the soil physical quality. In fact soil structure affects the soil ability to sustain animal and plant life necessary to maintaining agricultural productivity and environmental quality. Lavelle (2002) deduced that in soil the relative importance of regulation imposed by ecosystem engineering is likely to be greater than regulation by trophic relationships, because of the specific ecological constraints observed in this environment when compared to above-ground conditions. Some organisms are no longer considered to play a role only as elements of a food web, but they are studied from the viewpoint of being responsible for altering ecosystem dynamics through the modification, maintenance and/or creation of habitats for other organisms in the ecosystem. Earthworms are well known ecosystem engineers, however other species of macrofauna contribute to change the soil pore system by means of their burrowing activities. The X-ray tomography is a technique increasingly used to obtain non-destructive analysis of the pore netwoks produced by earthworms (Pagenkemper et al., 2015; Whalen et al., 2015; Capowiez et al., 2014, 2015; Auclerc et al., 2013). In this work it was developed an experimental approach based on the use of repacked soil mesocosms prepared in order to identify and quantify the contribution of different taxa of macrofauna to soil structure changes. At the end of the incubation period in the field or in the laboratory mesocosms were subjected to X-ray tomography. The resulting images were processed in order to obtain three-dimensional reconstructions and analysis of the identified biopores. Here are shown preliminary results about 5 mesocosms regarding 6 different species, both adult and larvae individuals.