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The soil fauna TRAits to link the Changes of Environment to Soil functions (TRACES)

The soil fauna TRAits to link the Changes of Environment to Soil functions (TRACES)

Summary
The role of soil is recognized in European public policy. This recognition requires data on soil biodiversity and its links with the soil functions. Biodiversity has a central role in the provision of most ecosystem services (production, maintenance, cultural, aesthetic). In terms of public policy, we can see the benefit of increased attention to the ecological functioning of ecosystems because they are at the heart of the relationship between biodiversity and ecosystem services. In terrestrial ecosystems, soil is one of the most biodiverse habitats. Paradoxically, our current knowledge of the taxonomy and the ecological functions of soil organisms are low. Biodiversity is essential to the production of Ecosystem Services and must be at the heart of any approach on the assessment of ecological functions. The evaluation of the impacts of human activities on soil functions is essential for the implementation of land management policy.
By integrating theoretical fields from different disciplines, this project aims to quantify the response traits and effect traits of some species assemblages in soil invertebrates (macrofauna saprophage, Collembola) and identify the effect of neighbourhood landscape structure on the local communities. More precisely, it was studied: the impact on local species assemblages of landscape and local organization levels, the biological mechanisms (dispersal, habitat preferences, competition) that shape these species assemblages, the impact of saprophagous species on the functioning of soil, which are the species traits that explain the responses and the effects of the soil species assemblages. Then the aim was to begin to develop a model of spatial linkage rules to analyze, based on the mechanisms underlying the sepcies distribution, the impact of factors that control the diversity and abundance of invertebrate species assemblages.
Principally, soil species communities are governed by habitat selection, indicating a match for these taxa of species distribution to the niche. However, in three cases (earthworms in both study areas and springtails in the Morvan) species distribution is a trad-off between the fit to the niche and dispersion. A hierarchical filtering of the traits species assembly at local scale resulting in a change in the functional diversity of local species assemblages according to the type of neighbourhood landscape is observed. This confirms empirically the theory that environmental factors act as nested filters on species traits. The local habitat type and the neighbourhood landscape structure influence the species assemblages in a complementary manner for a given habitat type and specifically to the habitat type with a filtering of ecological traits by the type of neighbourhood landscape and a filtering morphological traits by the nature of the land use in a type of local habitat.
The distribution of species of Collembola into forest or grassland habitat are the result of different trade-offs which determine their habitat preference. Forest species face a trade-off between tolerance to the desiccation and their preference for certain trophic ressources and / or physico-chemical environments, while most of the grassland species face a trade-off between competitive ability (low) and physiological tolerance (high). Some species of grassland show both a preference for soil and forest microclimate and so are probably excluded from the forest because of competition with forest species.
A micro-local scale, the trophic resources change the habitat exploration by species of springtails hemi- and euedaphiques even if these patterns are idiosyncratic in the same life form. The behaviors of habitat exploration by earthworms also have an idiosyncratic character and are influenced by the type of soil microbial communities as well as intra-specific density. They are the result of a trad-off between the mechanisms of niche construction where individuals are aggregated and intra-specific competition that pushes individuals to disperse. In addition, eco-morphological categories of earthworms are not proxys to predict functional groups of effect of the stability of soil aggregates. And earthworms have an overall neutral effect or protection on sol organic matter even if it appears that the mineralization could be increased in arable and grassland soils.
Finally, the heart of model of the response of Collembola species assembalge to landscape dynamic by multi-agent system at population scale is built.
The TRACES project confirms the interest to get out of approaches compartmentalized by discipline (soil science, taxonomy, soil ecology) and to use theories coming from different fields of ecology (plant ecology, community ecology, landscape ecology) for applied them to soil ecology. Very few studies use soil fauna to test models of functioning of metacommunities and, to our knowledge, this is the first attempt to analyze the combined effect of local factors and landscape factors. Mostly, the species assemblages of soil fauna are controlled by the fit to the niche but the dispersion also seems to play a role. The TRACES project confirms the role of the neighbourhood landscape type on local species assemblages of soil fauna. Thus, in terms of management and landscaping, if it is well recognized that the habitat quality has to be driven in order to improve soil biodiversity, the nature of neighbourhood landscape composition is also to integrate in landscaping in order to maintain soil biodiversity and the functions related.

 

Contact
Institut de Recherche et de Développement (Florence Dubs)

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