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Most studies evaluating the effects of grazing intensities on soils in Brazilian grasslands have focused on abiotic parameters, especially chemical or physical properties. In this context, soil arthropods have been largely unexplored, especially Collembola. This research addressed the effect of different grazing intensities on the composition and structure (abundance, richness, diversity, and evenness) of Collembola communities under different grazing intensity levels. Collembola were collected at different cattle grazing intensity level treatments (high, moderate, and low) in southern Brazilian native grasslands (also known as Campos). Our findings indicated significant changes in the composition of Collembola communities through grazing intensities. The treatment with the lowest grazing intensity was found to be substantially different from all others, probably because of a high abundance of some taxa (i.e. Entomobrya spp). We also observed that morphospecies richness and diversity tended to peak at moderate grazing intensities, whereas total abundance was higher in the lowest grazing intensity treatment. This study provides experimental evidence that disturbances caused by cattle grazing in native grasslands might impact soil faunal communities: increases in grazing intensity affected soil arthropod composition and structure by reducing their abundance, richness and diversity. It is important to highlight taxonomical richness and diversity as an intrinsic characteristic of communities insuring their functionality as a consequence of niche occupation and complementarity.

Land-use change has been identified, among global changes, as the main threat causing biodiversity loss, locally and regionally. This is especially true in Southern Brazil with the two main biomes (Pampa and Atlantic forest) facing high conversion rate into agricultural land to meet increasing demand for food and fuel. Within this region, we focused on epigeic biota across three land-use types (forest, grassland and Eucalyptus plantation). We used both a taxonomical and a trait-based approach to depict the changes of Epigeic Collembola assemblages across land-use types. Furthermore, we tested trait-convergence and trait-divergence across land-use types to infer how the environmental filtering and biotic interactions can affect assembly rules and collembolan community composition. Results differed according to the approach used (either taxonomical or trait-based). In general, diversity indices based on the taxonomical approach did not significantly differ between forest and grassland, whereas Eucalyptus plantation showed significantly lower values. Functional diversity was significantly higher in forest and similar between grassland and Eucalyptus plantation. Furthermore, we found both convergence and divergence of subsets of traits related to the land-use types. The trait-convergence tended to be higher in grassland sites and rather linked to sensorial traits (number of ocelli, antenna length, and trichobothria), drought tolerance traits (body size) and habitat preference traits (pigmentation level, furca development, scale, number of ocelli, antenna length, and body size). On the opposite, Trait-divergence was only linked to sensorial traits (antenna length and postantennal organ) and greatest in forest sites. Our findings showed that a trait-based approach associated with a taxonomic one provides a better understanding of the collembolan community structuring in response to biotic and abiotic changes across different land-use types.

Different soil management in crop cultures like maize can produce a variety of effects on soil fauna. Conventional cropping includes soil tillage, promoting organic matter losses and destruction of soil structure, whereas no-tillage cropping includes a herbicide application which can potentially affect soil fauna. In both management systems, insecticides are often used, such as pyrethroid insecticides, to prevent insect pests. Understanding the impact of these different cropping systems in their different phases on soil mesofauna and investigating the ability of soil communities to recover may provide important information to select cropping strategies which are more protective of soil biodiversity. With this aim, a terrestrial model ecosystem experiment was performed over eighty-nine days. The test treatments, all including maize, were: undisturbed soil; conventional tillage; conventional tillage with insecticide; no-tillage soil with herbicide; no-tillage soil with herbicide and insecticide. In each TME, soil samples from 0 to 5 and 5-10 cm of the top layer were collected from which collembolans and mites were identified to species, genus or subfamily level, and enchytraeid abundance was determined. Soil tillage did not affect soil communities, but insecticide application did. For collembolans and enchytraeids, the impact of the insecticide was independent of soil management, but for mites, insecticide impact was longer in conventional tillage than in no-tillage system. Changes on collembolan abundance, in general, did not promote changes in mean community trait values and functional diversity. Data suggest that no-tillage management is more protective to soil fauna than conventional tillage.

Anthracene is a polycyclic aromatic hydrocarbon (PAH) that presents a high pollution potential and health risk and has been used as a model for degradation studies on PAHs because of its relative toxicity. This study aimed to evaluate anthracene degradation by Pseudomonas sp. isolated from a 14-year-old petrochemical sludge landfarming site. Three isolates were selected from 26 by the best growth in anthracene and two of them were identified by 16S rRNA gene sequencing as Ps. aeruginosa and Ps. citronellolis . They showed better growth at pH 7.0 and 30 °C in medium containing up to 2 g anthracene L −1 . They were also able to grow in medium containing phenanthrene, pyrene, gasoline and diesel oil. Analysis of anthracene degradation estimated by gas chromatography showed that Ps. aeruginosa isolate 312A had the highest rate of degradation (3.90 mg L −1 day −1 ), degrading 71% of the anthracene added to the medium (250 mg L −1 ) after 48 days. Ps. citronellolis 222A showed an intermediate level of degradation (51%), but Ps. aeruginosa 332C degraded only 24.4%. Isolate 312A was also responsible for the highest phenanthrene and pyrene degradation after 48 days. In order to establish the mechanisms involved in the PAH degradation, surfactant production by the isolates was assessed by an emulsification index and reduction of the surface tension in the mineral medium free of cells. Emulsification was not detected, indicating that the isolates did not produce high molecular weight surfactant, although reduction in surface tension indicated production of low molecular weight surfactant compounds. The medium containing Ps. citronellolis 222A showed the highest reduction in surface tension, which could increase anthracene bioavailability for biodegradation. To our knowledge, this is the first report concerning increase of anthracene degradation by surfactants produced by Ps. citronellolis . However, the highest degradation rate shown by Ps. aeruginosa 312A was not related to surfactant production, indicating that some other mechanism could be involved in anthracene degradation. The Pseudomonas isolates may be useful for the study of PAH degradation and for bioremediation purposes.