Urban soil can offer a large variety of functions linked to plant growth, carbon storage and water infiltration. Such functions are key components to consider in order to develop resilient and enjoyable cities. The urban soil quality is directly linked with their biological activity because soil living organisms contribute to soil functioning via decomposition, nutrient cycling, physical fertility, etc. Many threats can impair soil biodiversity in urban areas such as fragmentation, compaction and/or pollution. However, there is a gap of knowledge limiting our ability to predict soil biodiversity patterns across urban green spaces and to identify the management type and practices promoting soil biodiversity. Therefore, there is a need at a densification of biodiversity data in order to develop indicators of soil biological quality at large scale and long-term. The citizen science represents a promising approach to gather such data but also to promote public awareness about the importance of soil biodiversity. Here, we present the participatory monitoring of soil biological quality program, entitled "QUBS" that allows various observers to choose from a selected number of protocols to investigate the living fauna in their soil. The program has been launched in autumn 2022 and we present here its feature as well some preliminary results about the participation.

Dans le contexte du développement des sciences et recherches participatives (SRP), de plus en plus d’initiatives sur les sols ont été engagées ces dernières années. Les sols sont des objets particulièrement intéressants pour les SRP car, en tant qu’écosystème en interface directe avec les hommes et d’autres écosystèmes, ils sont affectés par les activités humaines et ils sont des leviers de transformation, que ce soit du point de vue de l’agroécologie, de la biodiversité, de l’alimentation ou du climat. Cet article présente : i) les résultats d’une enquête réalisée auprès de la vingtaine de porteurs de projets identifiés en France, une analyse des propriétés et contextes ciblés ainsi que du niveau d’association des acteurs de la recherche et de la société ; ii) les enseignements d’un colloque rassemblant les acteurs des projets de SRP sur les sols, notamment à propos des attentes, des productions pour la recherche et la société, des difficultés et pépites, des mutualisations possibles. Ce colloque a rassemblé une centaine de personnes et a jeté les bases d’une mise en réseau national des acteurs concernés.

<p>One quarter of the living beings are located beneath our feet but we know very little of them (FAO, 2020). This statement will perhaps quickly change because the soils are now on the political agenda. For France, soil is mentioned in the Green Pact at European level (Montanarella, 2020) and in the country government's Biodiversity Plan. The law on soil health is also planned for 2023 (Köninger et al., 2022). However, as its biological component remains poorly understood, the indicators used by stakeholders give only a biased view of soil quality (Lehmann et al., 2020). It is therefore urgent to catch up on the knowledge of soil biodiversity in order to establish benchmarks for bioindicators, based on standardised data.</p><p>In parallel, the French Biodiversity Office working on the linkages between all French terrestrial biodiversity monitorings, pointed out the absence of soil biodiversity monitoring in France.</p><p>Rather than creating <em>de novo</em> a soil biodiversity monitoring, it was preferred to add biodiversity surveys to the already existing French Soil Quality Monitoring Network (RMQS), hereafter called the RMQS-Biodiversity. The RMQS covers a big part of the French territory (the continental part as the over seas) since 2000. Every year, 180 study sites are sampled. Thus, all the sites are sampled in 10-12 years (Jolivet et al., 2018). The RMQS provides data about all physical and chemical aspects of soils. Regarding the soil biological component, microorganisms and enzymatic activities are also surveyed. By the past, soil fauna was studied on around 100 sites but the experience was not maintained (Imbert et al., 2021). Moreover, a major strength of the RMQS is the network of involved people included the 12 field teams, the coordination team, the funders and data users (researchers and stakeholders).</p><p>To implement the biological measurements, we gathered a group of experts on soil biodiversity. As meetings go by, five protocols were defined to assess the most exhaustively possible the soil biodiversity taxa and three functions (soil macroporosity, enzymatic activities and organic matter degradation).  </p><p>Then, the protocols were tested in real conditions on 30 RMQS study sites with the field teams. The duration of each protocol was quoted to clearly assess the costs.</p><p>We concluded that the biodiversity sampling of 180 RMQS study sites per year, would cost around 1 000 000 euros. We propose five scenarios giving compromises between financial costs and data quality.</p><p>If the RMQS-Biodiversity is maintained, it would make possible: 1) to advance on the still too partial knowledge of soil biodiversity and its interactions with agricultural practices and 2) based on the knowledge acquired, to develop bioindicators and their benchmarks, in order to accurately assess soil quality, in the context of Soil Health (Lehmann et al., 2020).  A complete soil monitoring, including its three components (physical, chemical and now biological), would thus provide a relevant tool to policy- makers to reach reconciling human activities and soil integrity.</p>

The study of humus systems provides a lot of information on soil ecological functioning, such as fauna functional community, soil nutrient status, organic matter decomposition, and microbial food web. Technosols have highly heterogeneous physicochemical properties and so far, their humus systems are poorly described and the mechanisms behind their formation are still largely to be studied. In order to fill this knowledge gap, this study was conducted to get better understanding of the factors involved in the development of different Technosols humus system after brownfield rehabilitation. Our sampling strategy followed a pollution diagnostic report and allowed to cope with the spatial heterogeneity of the studied area. We studied 24 soil profiles and identified 3 different humus systems on two different rehabilitation substrates: 7 Mull, 3 Amphi and 14 Techno-moder. Our results showed that the development of zoOH horizon resulted from the nature of underlying horizons but not from the main litter type. On Techno-moder, the accumulation of organic matter in the form of fecal pellets as a zoOH horizon resulted in an increase of 130% of nitrogen on soil surface. Contrary to what was expected, we did not find a threshold of heavy metals leading to the formation of zoOH horizon, with highest lead concentration found in the A horizon of Mull systems. Transmission electron microscopy (TEM) analysis showed that neoformed organic matter is biochemically stabilized as condensed polyphenols and melanized hyphae. EDX analysis revealed that such ultrastructures are associated with Ca and Zn that may explain their stability on the Technosols surface. Development of zoOH horizon on Technosols built from coking plant by-products allowed to improve soil surface chemical and biological properties. The evolution of the humus systems as a result of vegetation succession and microbial community composition should be further studied to specify the mechanisms involved in Technosols humus system dynamics.

This study investigated the potential lithogeochemical filiation of Macrotermes falciger termite mound materials and the parent substrate materials sampled in both the Sakania and Tshisenda areas of the Haut-Katanga Province of the Democratic Republic of Congo. These geological areas with predominantly autochthonous cover are characterized by lateritic type profiles. Mineralogical characterization of Macrotermes falciger termite mound materials by infrared on 20-63 mu m fractions indicated the presence of secondary minerals specific to tropical weathering. Further mineralogical analysis of 0-20 mu m fractions using XRD also identified such primary and secondary minerals in these materials. A multi-element chemical analysis was performed on the <125 mu m fractions of the different lithological substrates (granitic rock, feldspathic sandstone, and lateritic duricrust) as well as of the Macrotermes falciger termite mounds. Using log Fe2O3t/K2O vs logSiO2/Al2O3 ratios, all the samples were geochemically classified and lithogeochemical relationships were established. We showed that the yellow, grey and beige termite mounds were characterized by lithogeochemical facies of quartz-rich and slightly altered substrates (granite, arkose...) whereas the red termite mounds had lithogeochemical facies of clay formations associated with iron oxyhydroxides with less quartz. The accumulation of oxyhydroxides (Al, Fe, Mn) and the enrichment of low-mobility trace elements (Zr and Hf) in some mound materials allowed us to identify the Macrotermes falciger material supply zone between the accumulation horizon marked by chemical precipitation phenomena and the horizon of progressive transition to altered bedrock. Carrier phases of metals of interest, such as Cu, Co, Ni, Pb and Zn, were identified through scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) on constitutive particles of Macrotermes falciger termite mounds. These 5 metals of interest were sorted into <63 mu m, 20-63 mu m and 0-20 mu m fractions, then chemically analyzed to reveal their accumulation in the 0-20 mu m fractions. These results, provide clear evidence that Macrotermes falciger termite mound materials are ideal for providing information on lithogeochemical anomalies in geochemical prospection.

To meet the challenge of the sustainable city, a better knowledge of the ecology of urban ecosystems is essential, with a major issue linked to the biological quality of soils in connection with land use and management practices. Improving the weak knowledge of soil biodiversity is indeed essential to tackle soil multifunctionality associated to urban greening. The Bises project (Biodiversity of urban soils and sustainable cities), deployed in four French cities with contrasting biopedoclimatic and historical situations (Montpellier, Nancy, Nantes and Paris), aims to understand the links between soil quality, soil biodiversity and the associated ecosystem functions and services. All the major families of organisms (macro, meso, microfauna and microorganisms) will be evaluated spatially in order to develop and aggregated indicators of the biological quality of urban soils. A multi-scale sampling strategy was implemented in order to select 48 sites per city representative of the use of urban vegetated space for ornamental (parks, road sides), or food production (family and shared gardens, urban micro-farms). Lawn-type plant cover was selected for non-productive spaces to ensure homogeneity. Close collaboration with city services enabled accessing to spatial mapping of vegetated areas in cities. The selection of site location for each type of use integrates parameters such as site area, position along the urban-rural gradient (from city center to periurban areas), age and history of site, management method for nonproductive spaces (prestige=regular mowing, irrigation, fertilisation; rustic = one or two mowings per year) and type of valorisation of agricultural products (sales vs. not sales).

This work focuses on the comparative analysis of the influence of two termites of the Macrotermes (fungus-growing) and Cubitermes (soil-feeding termites) genera on the dynamics of soil lithogeochemical facies. The aim was to establish a general systematic recognition of the lithology of a large area, including its potential for Cu and Co mineralization. Eighty-eight samples of the mound material were collected from termite mounds of these two species along a 50 km transect in Lualaba Province, Democratic Republic of Congo (DRC) in order to carry out major and trace element analyses. Interpretation of the data was carried out through exploratory analysis, using the Ascending Hierarchical Classification (AHC) method and Principal Component Analysis (PCA), followed by statistical modeling using linear regression. After clustering the termite mounds into classes by AHC, an initial PCA was used to map the lithology of these classes using major elements. The results highlight the dependance of the lithological composition of the mounds on the behavior specific to each of the two termite species. Linear regression modeling allowed a delineation of the area of supply of building materials for each species, indicating the possible incorporation of Cu and Co mineralizations likely to be present in the environment of the termite mounds. The use of termite mounds as a tool in mining exploration is discussed.

Termites are key soil bioturbators in tropical ecosystems. Apart from mound nests constructed by some advanced lineages, most of the species use their faeces, oral secretions, debris, or soil aggregates to protect themselves from predators and desiccation when they go out to forage. Although this soil 'sheeting' is considered to play a key role in soil functioning, the properties of this termite-made material has been poorly studied. The few available data showed that sheeting properties are highly variable with positive, neutral or negative impacts on soil C and clay content, and consequently on soil aggregate stability. Therefore, the objective of this study was to determine the factors controlling the physical (particle size fractions and structural stability) and chemical (pH, electrical conductivity and carbon content) properties of soil sheeting produced by termite species encompassing all feeding and building categories using a dataset representative of an important diversity of biotopes coming from 21 countries from all continents colonized by termites. We showed that sheeting properties were explained by the properties of their environment, and especially by those of the bulk soil (linear relationships), followed in a lesser extent by the mean annual precipitation and biotope. Classic hypotheses related to termite feeding and building strategies were not hold by our analysis. However, the distinction of termites into fungus-growing and non-fungus growing species was useful when differentiating the impact of termites on soil electrical conductivity, C content, and structural stability. The large variability observed suggests the need to redefine termite functional groups based on their impacts on soil properties using a trait-based approach from morphological, anatomical and/or physiological traits.

Green infrastructures play a key role in the functionality and resilience of urban ecosystems. The physical, including thickness, chemical and biological properties of the Technosols of green infrastructures on rooftops are highly variable, leading to more or less favourable conditions for soil biodiversity. The aim of this study was to investigate the abundance and diversity of bacteria, fungi, nematodes, collembola and plants communities in relation with abiotic parameters of Technosols on 12 productive and extensive green roofs of the Paris region (France). Results showed that green roofs harboured a high level of abundance and diversity from microorganisms to micro and mesofauna. Microbial biomass ranged between 16.3 and 419.8 mu g DNA g-1, with a predominance of bacteria, nematodes represented 820-60,700 individuals per kg of soil and between 1000 and 60,700 collembolan were present per m2 of soil. A total of 13,986 bacterial OTU (Operational Taxonomic Unit), 33,559 fungal OTU, 47 Collembola species, 28 nematodes families, 16 cultivated plant species and 48 spontaneous plant species was identified on all the green roofs studied. Microbial, animals and plants communities were significantly different between the two types of green roofs. Productive and extensive rooftops represent contrasted habitats, which can strongly influence the soil biota. Any voluntary action to enhance soil biodiversity in cities would need to take-into-account both soil properties and the landscape around.

Anthropic activities such as mining, resource extraction or transformation profoundly modify ecosystems and may lead to Technosol formation. Post-industrial areas are examples of potentially degraded lands, due to soil contamination with metals or organic pollutants, as well as soil structure damage. Soil biodiversity being closely involved in many soil functions such as organic matter decomposition, formation and stabilization of soil structure, the recovery of degraded soil functions partly depends on soil fauna colonization. However, the relationship between Technosol abiotic parameters and soil fauna colonization is still to be disentangled. In an attempt to fill this gap, we studied a former coking plant area in north-eastern France, composed of Technosols resulting from coking plant embankments or thermally-treated industrial soils and compared them with two local soils considered as references. We hypothesized that the taxonomic and trophic diversity of Technosol-dwelling invertebrates would be more diverse and abundant in the soils with the higher soil physico-chemical quality (i.e higher fertility and lower pollutions levels). To test this hypothesis, we studied four Technosols that were settled following two different rehabilitation strategies within the same post-industrial area and we compared them with two local soils of reference using nested ANOVAs as well as multivariate analyses of soil abiotic parameters and soil fauna community indices, both within the soil and on its surface. The results on physico-chemical analyses showed that the substrates used for Technosol rehabilitation were impoverished in clay content when compared with local soils of reference (4.1 to 7.8-fold) and enriched in sandy materials. The use of coking plant by-products for Technosol implementation have led to poor chemical quality, with low nutrient content but high organic carbon content (41 to 51%) resulting from the use of coal and correlated with the higher lead concentration in the area. The use of thermally-treated industrial soil has led to more fertile Technosols with significantly lower lead content. Meso and macrofauna densities did not vary significantly between the Technosols and the local reference soils. Both Technosol-dwelling fauna trophic and taxonomic community compositions were impacted by the rehabilitation strategy. Few to no earthworms were found in Technosols (mean up to 16 ind.m(-2)) compared to the local soils of reference (mean of 118.4 and 201.6 ind.m(-2)). Conversely, Technosols resulting from coking plant embankments and thermally-treated industrial soils were dominated by epigeic soil fauna with an intense activity of soil surface macro-saprophages and micro-arthropods, as well as Formicidae. Our results suggest that the use of technogenic elements in the rehabilitation of post-industrial area led to the development of specific soil invertebrate communities, different from the reference. The gap between the high level of activity of epigeic organisms that we found on Technosols and the low trophic diversity of the litter and soil-dwelling communities suggest that the soil fauna community on a former coking plant is driven rather by soil physico-chemical properties than by colonization constraints.

Ecological engineering of degraded ecosystems often manipulates plants, with positive outcomes for their restoration or ecosystem services production. The importance of soil biota for successional plant communities has prompted consideration of direct inoculation (active) or attraction (passive) of soil organisms as a relevant restoration strategy. However, few attempts have manipulated soil invertebrates as part of nature based solutions for ecosystem restoration, despite their major role in many soil ecological processes and in plant-soil feedback processes. In addition, while ecological restoration and ecological engineering approaches successfully incorporate plant traits, soil invertebrate traits remain underused. Exploiting the functional diversity of soil communities by adopting a trait-based approach could enhance restoration of soil chemical, biological and physical properties. Here, we conduct a narrative review and identify a set of soil invertebrate functional traits with great potential in ecosystem restoration. We focus on traits related to four main ecological functions that are often at the core of restoration plans: nutrient cycling and carbon cycling, pollutant detoxification, soil structure arrangement, and biological control agent by prey/pest regulation. This paper further proposes guidelines for stakeholders that need to be addressed to successfully integrate soil organism traits into ecological engineering. Finally, we highlight main knowledge gaps and limitations currently impeding the use of soil invertebrate traits in ecological engineering, and identify avenues for future research. We especially bring out (i) that few studies still use soil invertebrates in restoration, so even fewer are based on traits, (ii) a lack of data about soil invertebrate species role in ecosystems, (iii) a lack of data about attributes from specific traits and groups in existing soil functional trait databases, (iv) the complex relationships between functions and traits and (v) that future studies are needed to demonstrate the benefits of such trait-based approaches compared to approaches relying on emblematic species.

Technosols are defined by the World Reference Base as soils subjected to a strong human influence and containing at least 20% of artefacts. The construction of Technosol using recycled waste material is considered an appealing sustainable use of both natural and anthropic resources. Constructed Technosol can attract and host a multitude of soil organisms, forming a reserve of biodiversity. In this study, we assessed the early colonization – in successional stages – of a constructed Technosol supporting grassland vegetation by the microarthropod community, in particular Collembola. To do this, the taxonomic and functional characteristics of microarthropod communities in a newly constructed Technosol in northeast France were studied for a period of four years. Collembola communities also increased in density and taxonomic richness, as well as in functional richness and dispersion. However, hemiedaphic Collembola dominated the community, particularly in the fourth year. Findings at the end of the survey indicated that the Collembola community in the studied Technosol remained very different to that of natural grassland, while it shared some characteristics with arable land. However, the present research clearly showed that waste material recycling to construct a Technosol could be an opportunity to support soil microarthropod biodiversity.

There is a multitude of life forms on our planet. This is especially true under our feet, in the soil. Earthworms, spiders, and millipedes are only a few examples of the vast number of soil organisms. Once you look what lives in soils, you realize the tremendous diversity of shapes and colors. But what if we take the time to describe all their characteristics: color, size, shape, number of legs, type of wings, lifespan, and climate preferences? All these characteristics, called traits, help us to understand what types of organisms can be found in a particular ecosystem, what they feed on, and how far they can travel. Scientists use this information to understand the different roles of organisms in soils, and to restore degraded soils. Analyzing traits can reveal the importance of soil organisms and the fundamental roles they play for human societies.