Although much work has been done on factors which influence the patterning of species and species trait assemblages in a variety of groups such as plants, vertebrates and invertebrates, few studies ...have been realized at a broad geographic scale. We analyzed patterns of relationships between species, species trait distribution/assembly, and environmental variables from the west of Europe to Slovakia, Poland and Sweden. We created a database by compiling traits and occurrence data of European collembolan species, using literature and personal field studies embracing a large range of environmental gradients (vertical stratification, habitat closure, humus form, soil acidity and moisture, temperature, rainfall, altitude) over which Collembola are supposed to be distributed. Occurrences of the 58 best-documented species, environmental variables and species traits allowed us to (i) show which environmental variables impact the distribution of the 58 species at broad scale and (ii) document to what extent environmental variables and species trait assemblages are related and which trends could be found in trait/environment relationships. The impact of vertical stratification, habitat closure, humus form, soil acidity, soil moisture, temperature, and to a lesser extent rainfall and altitude on species distribution, firstly revealed by indirect gradient analysis (correspondence analysis, CA), was further shown to be significant by direct gradient analysis (canonical correspondence analysis, CCA). RLQ analyses were performed to find linear combination of variables of table R (environmental variables) and linear combinations of the variables of table Q (species traits) of maximum covariance weighted by species occurrence data contained in table L. RLQ followed by permutation tests showed that all tested environmental variables apparently contributed significantly to the assemblages of the twelve species traits studied. A convergence was observed between traits related to vertical stratification and those related to habitat closure/aperture. Well-developed locomotory organs (furcula, legs), presence of sensorial organs sensitive to air movements and light (e.g. trichobothria and eye spots), spherical body, large body size, pigmentation (UV protection and signaling) and sexual reproduction largely occur in epigeic and open habitats, while most of woodland and edaphic habitats are characterized by short locomotory appendages, small body size, high number of defense organs (pseudocelli), presence of post-antennal organs and parthenogenesis. Climate and especially temperature exert an effect on the assemblage of traits that are mostly present above-ground and in open habitats. The contribution of combinations of some environmental variables to the occurrence of each species trait was tested by linear, logistic or multinomial regression (Generalized Linear Models). Vertical stratification, followed by temperature, played a dominant role in the variation of the twelve studied traits. Relationships between traits and environment tested here shows that it is possible to use some traits as proxies to identify potential ecological preferences or tolerances of invertebrate species. However, a significant part of species distribution remained unexplained, probably partly because some traits, like ecophysiological ones, or traits involved in biotic interactions (e.g. competition) were unavailable. The present work is thus a first step towards the creation of models predicting changes in collembolan communities. Further studies are required to inform ecophysiological traits, in order to complete such models. Moreover the niche width of species will have to be determined.
•A database compiling traits and occurrence data of European springtails has been created.•The distribution of best documented species (58) was impacted by environmental variables.•RLQ analyses showed that traits were impacted by vertical stratification, humus form, climate and habitat closure.•The contribution of each environmental variable was tested by GLM.
•The negative effect of pesticides was greatest in earthworms living in close proximity to the soil surface.•Insecticides have more negative influence on three earthworm species than herbicides and ...fungicides.•A 50% reduction of pesticide use is likely to lead to large increases in earthworm densities.
Agricultural intensification has led to reduced soil biodiversity in arable lands. The potential benefits from organic farming and from low-input cropping systems have not yet been precisely assessed. Earthworm, having important agro-ecological functions, may be affected by pesticide applications, especially those species living mainly in the surface soil layer. We used a five-year experimental database including conventional and organic cropping systems to establish simple relationships between the Treatment Frequency Index – a phytosanitary indicator of pesticide pressure – and the abundance of three important earthworm species. We found that insecticides have more negative influence on earthworm species than herbicides and fungicides, and that species living in the soil's surface layer were the most affected by pesticides. Density of these earthworm species could be multiplied by a factor 1.5–4 if the Treatment Frequency Index was halved, as is currently required by some European regulations. Our results thus demonstrate that a reduction in pesticide application would increase earthworm population density in agricultural fields.
In Europe an abundance of humus taxonomies exists starting with early approaches in the late 19th century. Frequently used in an international context, they do not cover all site conditions in the ...European area. Although having basic concepts and general lines, the European (and North American, Canadian) classification systems differ in important parameters used for the description and classification of humus forms. These discrepancies result in incongruities, so they require adjustments when exchanging partially compatible soil data, even between nearby countries. In 2003, 26 European specialists in humus forms met in Trento (Italy) and decided to formulate rules of classification based on morphogenetic descriptions and diagnostic horizons, adapted to European ecological conditions. Taking into account old and new European and North American systems of humus forms classification, six main references (Anmoor, Mull, Moder, Mor, Amphi and Tangel) were defined, each of them further divided into more detailed categories. This inventory assigned a strong discriminatory power to the action of soil animals. Both semiterrestrial (anoxic) and terrestrial (aerated) topsoils were classified. Descriptors of diagnostic horizons were conceived in accordance with recent international soil classifications. Assigning an ‘ecological value’ to each main humus form along a gradient from biologically active forms, degrading and incorporating all organic remains, to those characterized by the accumulation of poorly transformed organic matter, this European system of classification avoids a strong hierarchical structure and allows a flexible approach open to additional ecological contributions and renditions.
► European specialists conceive principles of a new classification of humus forms. ► Only morphological characters with evident functional effects were considered. ► Ten basic humus forms were circumscribed, available in a wide array of ecosystems. ► Environmental factors determine the structure of the classification tree.
Humus forms are the seat of most biological transformations taking place in terrestrial ecosystems, being at the interface between plants, animals and microbes. The diversity of terrestrial humus ...forms (mor, moder and mull) can be attributed to the existence of different patterns (strategies) for the capture and use of resources by ecosystems, in ascending order of biodiversity and bioavailability. Arguments are found in the parallel development of humus forms and terrestrial ecosystems, in exclusion mechanisms between organisms living in different humus forms, and in palaeontological studies. The diversification of terrestrial life forms in the course of Earth history, concomitant with an improvement in resource availability due to the development of sedimentary layers at the surface of continents, may explain the successive appearance of more active humus forms enabling the co-existence of an increasing number of organisms. Contradictory reports about the relationships between biodiversity and stability of ecosystems can be explained by the existence of different belowground pathways making ecosystems more stable.
Phylogenetically closely related plant species often share similar trait states (phylogenetic signal), but local assembly may favor dissimilar relatives and thereby decouple the diversity of a trait ...from the diversity of phylogenetic lineages. Associated fauna might either benefit from plant trait diversity, because it provides them complementary resources, or suffer from it due to dilution of preferred resources. We hence hypothesize that decoupling of trait and phylogenetic diversity weakens the relationship between the plant-trait diversity and the abundance and diversity of associated fauna. Studying permanent meadows, we tested for combined effects of plant phylogenetic diversity and diversity of two functional traits (specific leaf area, leaf dry matter content) on major groups of soil fauna (earthworms, mites, springtails, nematodes). We found that only in phylogenetically uniform plant communities, was uniformity in the functional traits associated with (i) high abundance in springtails, and (ii) high abundance of the sub-group that feeds more directly on plant material (in springtails and mites) or those that are more prone to disturbance (in nematodes), and (iii) high diversity in all three groups tested (springtails, earthworms, nematodes). Our results suggest that soil fauna profits from the resource concentration in local plant communities that are uniform in both functional traits and phylogenetic lineages. Soil fauna would hence benefit from co-occurrence of closely related plants that have conserved the same trait values, rather than of distantly related plants that have converged in traits. This might result in faster decomposition and a positive feedback between trait conservatism and ecosystem functioning.
Beside biotic interactions, habitat preference and dispersal ability of species play a prominent role in the building of animal species assemblages. However, these traits are usually very poorly ...documented for soil organisms. A soil transfer experiment was designed to study habitat preference (including land-use and soil preference) and dispersal ability of soil springtail species living in a meadow and in an adjoining deciduous forest. The study was performed in the Morvan Regional Natural Park (Central France), using untreated or defaunated soil blocks, transferred to another land-use or replaced in their original land-use. Land-use preference was quantified in untreated and untransferred samples from meadow and forest. Dispersal ability was estimated from the time at which species colonized defaunated samples in their own habitat. Soil preference was estimated from the colonization rate of defaunated samples by comparing transferred and untransferred soil blocks. Results showed that in the community, 6% of species were land-use generalists, 30% were soil generalists and 36% recolonized defaunated soil blocks within a week. Land-use preference, soil preference and dispersal ability were largely independent components of species characteristics. Although our experiment dealt only with small-scale colonization, comparisons between species showed that the dispersal type based on anatomical features (legs, antenna, furcula, visual apparatus) does not allow predicting the dispersal ability of these species. Discrepancies between land-use preference and soil preference suggest that other habitat features must be relevant for Collembola, and that a trade-off exists between eco-physiological and biotic interactions (including food requirements).
•A new method is proposed to measure allyl isothiocyanate concentration in mustard.•AITC concentration in mustard varied five-fold, depending on its use by date.•AITC concentration was about 4 times ...higher in the AITC solution than in the mustard one.•AITC and commercial mustard solutions had the same earthworm extracting efficiency.
Earthworms are target organisms both for scientists studying the biological component of soils and for farmers concerned with monitoring the quality of their soils. Different expellants are used to extract earthworms from the soil but differences in chemical properties and efficiency between commercial mustard and allyl isothiocyanate (AITC) solutions remain unknown. The objectives of this study were to compare (i) the concentration of irritating product (allyl isothiocyanate AITC) in two expellant solutions (diluted mustard or AITC solution) and (ii) their efficiency in extracting earthworms from the soil.
AITC concentration was analyzed according to a new method, based on AITC solvent extraction and HPLC quantification, in one commercial mustard brand to assess its variability within and between batches of jars. According to mustard spiking with AITC standard solution, extraction recovery was estimated as 98±2%. Earthworm field data were collected in spring 2012 in 22 cultivated fields located in east Île-de-France, comparing pure AITC to commercial mustard solutions. Species diversity, abundance and biomass of earthworms per plot were measured.
We showed that AITC concentration in commercial mustard varied according to the use by date but not according to the batch. We thus recommend using the freshest mustard available from the same batch. Moreover, AITC solution was found to be about four times more concentrated in AITC than the commercial mustard solution. Despite this result, no significant differences were found in the efficiency of commercial mustard or AITC solutions to bring earthworms to the soil surface in terms of abundance, biomass or diversity. We thus discuss the advantage and drawbacks of using both expellants in the field.
Inselbergs are hills rising abruptly from the surrounding plains where cyanobacteria are the only living organisms under conditions of intense solar radiation. A survival mechanism to prevent ...UV-damage has been associated with synthesis of the ultraviolet-screening, photostable sheath pigment scytonemin. The organic extract of Scytonema sp., collected on the Mitaraka inselberg, French Guyana, yielded three new pigments, tetramethoxyscytonemin (1), dimethoxyscytonemin (2), and scytonine (3), derived from the scytoneman skeleton of scytonemin. These structures were assigned mainly on the basis of (1)H and (13)C NMR and MS experiments.
Springtail communities (Hexapoda: Collembola) were sampled in the Morvan Nature Regional Park (Burgundy, France) in six land use units (LUUs) 1 km
2 each, which had been selected in order to cover a ...range of increasing intensity of land use. Human influence increased from LUU 1 (old deciduous forest) to LUU 6 (agricultural land mainly devoted to cereal crops), passing by planted coniferous forests (LUU 2) and variegated landscapes made of cereal crops, pastures, hay meadows, conifer plantations and small relict deciduous groves in varying proportion (LUUs 3–5). Sixteen core samples were taken inside each LUU, at intersections of a regular grid. Species composition, species richness and total abundance of collembolan communities varied according to land use and landscape properties. Land use types affected these communities through changes in the degree of opening of woody landscape (woodland opposed to grassland) and changes in humus forms (measured by the Humus Index). A decrease in species richness and total abundance was observed from old deciduous forests to cereal crops. Although the regional species richness was not affected by the intensification gradient (40–50 species were recorded in every LUU), a marked decrease in local biodiversity was observed when the variety of land use types increased. In variegated landscapes the observed collapse in local species richness was not due to a different distribution of land use types, since it affected mainly woodland areas. Results indicated the detrimental influence of the rapid afforestation of previous agricultural land, which did not afford time for the development of better adapted soil animal communities.
Core Ideas
A common humus classification system improves communication among soil scientists.
A cellular phone application can be used for global soil mapping and monitoring purposes.
The humus ...classification can be combined with different soil classification systems.
The name TerrHum is an abbreviation of the words “Terrestrial” (not hydromorphic, not submerged) and “Humipedon” (organic and organic‐mineral humus horizons). With this application, it is possible to describe and classify terrestrial forest and grassland topsoils in a system published as a Special Issue entitled “Humusica 1– Terrestrial Natural Humipedons” in the journal Applied Soil Ecology. The iOS application TerrHum allows the storage of the main content of Humusica 1 on a cellular phone. Images, diagrams and simplified tables of classification may be recalled with a few touches on the screen. Humus forms, representing five humus systems, are classified based on the vertical arrangement of diagnostic horizons and their attributes. TerrHum allows accessing specific figures that are stored in a virtual cloud and can be downloaded the first time the user recalls them. Once all figures have been opened in the device, the application is ready to use, without any further internet connection. The application is in continuous evolution.
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