ABSTRACT Understanding the status and global trends of soil invertebrate diversity requires accurate and comparable data across geographical regions. However, soil animal extraction approaches still vary among laboratories, and no commonly accepted, openly available and well‐documented protocols exist across taxa. Here, we present harmonized methodologies, assembled by an international group of experts, for extracting soil‐ and litter‐inhabiting nematodes, enchytraeids, microarthropods, and larger invertebrates. Illustrated with images and videos, the protocols include advice for overcoming the most frequently encountered issues (’expert tips’) for maximizing extraction efficiency and reproducibility. In addition, we provide results from two pilot experiments that test certain steps in nematode and large invertebrate extractions. We show that using two layers of milk filters instead of one in wet extraction of nematodes yields very similar extraction efficiency and has little effect on the sample cleanliness. Further, we demonstrate that on average 31.3% of large soil animals (body length 3 mm and longer) are overlooked during hand sorting but were captured by heat extraction of the sorted samples across three geographically distinct laboratories. Observed differences among the laboratories call for standardized tests of extraction efficiency of large soil animals across regions and research groups. Overall, we provide openly available expert protocols for assessing soil animal taxa in ecological studies worldwide, ultimately facilitating comparisons for a better understanding of the distribution and dynamics of soil biodiversity.
In enchytraeid reproduction tests lambda-cyhalothrin and pyrimethanil were examined under three different soil moisture levels (30, 50 and 70 % of the soil water holding capacity). The tests were performed with Enchytraeus bigeminus Nielsen & Christensen, 1963, a species that differs from other enchytraeid test species by its asexual mode of reproduction (fragmentation). The effect of chemical stressors depended on the soil moisture content. A higher toxicity was observed in soil with lower moisture levels. For lambda-cyhalothrin, the 21-day EC50 values for reproduction at the three levels of soil moisture were calculated to be 1.33, 3.79 and 4.75 mg active substance/kg dry weight soil, respectively. For pyrimethanil the values were 435, 499 and 829 mg active substance/kg dry weight soil. Apart from the evaluation of the combined effects of chemical stress and soil moisture, the appropriateness of the fragmenting test species Enchytraeus bigeminus was assessed. E. bigeminus tolerated temperature and pH variations, allowed obtaining reliable concentration-response relationships and was easy to handle and to culture in the laboratory. Hence this fragmenting species is considered to be suitable as an additional test species in ecotoxicological standard tests.
Within a project aiming to improve the preconditions for the protection of the habitat function of soils in Germany, the database Bo-Info was established, in which soil-biological data from permanent soil monitoring sites of several German states as well as from the literature was compiled. Soil-biological data on the occurrence and abundance of earthworms were analysed with respect to their distribution and relation to site (habitat type, land use) and soil properties (pH, texture, organic matter). Reliable data for earthworms were available from 294 sites. In total, 32 species (all species known to occur in Germany) were present in the database, 10 of which were very common. Ecological preferences regarding land use, pH, soil organic matter (SOM) and texture were derived for these 10 species. The occurrence of earthworms at the species and ecological-group level is determined by land use and soil pH value and less by soil texture. A clear distinction between epigeic species on the one hand and endogeic and anecic species on the other hand was found regarding SOM. Earthworm communities of habitat types representing the four major land use types (grassland, crop sites, deciduous and coniferous forests) clearly differed. Using three examples from different land use forms, typical species could be identified at the next sub-division level of habitat types, provided a sufficient number of data was available. As a result, qualitative expectation (= reference) values (species richness and composition) are proposed for the most important habitat types (e.g. different types of crop sites, grassland and coniferous forests). Due to their ecological relevance, the use of earthworms for soil biological site classification and assessment is recommended.
Soil invertebrates are among the least understood metazoans on Earth. Thus far, the lack of taxonomically broad and dense genomic resources has made it hard to thoroughly investigate their evolution and ecology. With MetaInvert we provide draft genome assemblies for 232 soil invertebrate species, representing 14 common groups and 94 families. We show that this data substantially extends the taxonomic scope of DNA- or RNA-based taxonomic identification. Moreover, we confirm that theories of genome evolution cannot be generalised across evolutionarily distinct invertebrate groups. The soil invertebrate genomes presented here will support the management of soil biodiversity through molecular monitoring of community composition and function, and the discovery of evolutionary adaptations to the challenges of soil conditions.
In the framework of the German-Brazilian project SOLOBIOMA (‘Soil biota and biogeochemistry in the Southern Atlantic rainforests of Brazil’), soil invertebrates were sampled in different regeneration stages of forest: pastures, young, medium and advanced secondary forests as well as old-growth forests. Thirty-nine study sites were located in two private nature reserves situated in neighbouring regions of the southern Atlantic Forest (Mata Atlântica) in Paraná, Brazil. All sites were characterized in terms of climate, history of use (age), vegetation, and soil properties. Here we report on the species diversity of pot worms (Oligochaeta: Enchytraeidae) in these sites, sampled with ISO standard methods. At each site ten soil cores of 5.7 cm diameter were taken once between 2003 and 2008, wet extracted and all pot worms identified alive soon after sampling. Most of the 61 species found in this study were new to science. The enchytraeid fauna of the region is dominated by species of the genera Achaeta, Guaranidrilus and Hemienchytraeus. To date, six species of the genus Achaeta, three species of the new genus Xetadrilus and four species of the species-rich genus Guaranidrilus were described by some of the authors. The terrestrial enchytraeid fauna of Paraná is composed partly of (probably) endemic species (e.g. Achaeta paranensis), partly of species with a known wider distribution within South America (e.g. Hemienchytraeus patricii). Species-poor genera are Fridericia, Enchytraeusand Marionina. On average, enchytraeid abundance was low (i.e. less than 5000 ind m-2). Highest abundance was found in old-growth forests. Species assemblages respond to soil type and vegetation type, and some preferences at the species or genus level could be identified. Due to their small size, low abundance and resulting low biomass enchytraeid worms seem to have little ecological importance in terms of energy flux and nutrient turnover, especially when compared with earthworms. However, due to their species richness they may be useful to indicate the biological status of a site in terms of biological soil quality or perturbation.
