Coupling X-ray computed tomography and freeze-coring for the analysis of fine-grained low-cohesive soils

This paper presents the coupling of freeze-core sampling with X-ray CT scanning for the analysis of the soil structure of fine-grained, low-cohesive soils. We used a medical scanner to image the 3D soil structure of the frozen soil cores, providing X-ray CT data at a millimetric resolution over freeze-cores that are up to 62.5 cm long and 25 cm wide. The obtained data and the changes in gray level values could be successfully used to identify and characterize different soil units with distinctly different physical properties. Traditional measurements of soil bulk density, carbon and particle size analyses were conducted within each of the identified soil units. These observations were used to develop a 3D model of soil bulk density and organic matter distribution for five freeze-cores obtained at a restored floodplain in Switzerland. The millimetric X-ray CT scanning was applied to detect the impact of freeze-coring on the soil structural integrity. This allows identifying undisturbed zones, a critical precondition for any subsequent assessment of soil structure. The proposed coupling is thought to be applicable to a wide range of other low-cohesive soil types and has a large potential for applications in hydrogeology, biology or soil science

The synergistic action of imidacloprid and flumethrin and their release kinetics from collars applied for ectoparasite control in dogs and cats

<p>Abstract</p> <p>Background</p> <p>The control of tick and flea burdens in dogs and cats has become essential to the control of important and emerging vector borne diseases, some of which are zoonoses. Flea worry and flea bite hypersensitivity are additionally a significant disease entity in dogs and cats. Owner compliance in maintaining the pressure of control measures has been shown to be poor. For these reasons efforts are continuously being made to develop ectoparasiticides and application methods that are safe, effective and easy to apply for pet owners. A new polymer matrix collar has recently been developed which is registered for 8 months use in cats and dogs. The basic properties of this collar have been investigated in several <it>in vitro </it>and <it>in vivo </it>studies.</p> <p>Methods</p> <p>The effects of imidacloprid, flumethrin and the combination were evaluated in vitro by means of whole cell voltage clamp measurement experiments conducted on isolated neuron cells from <it>Spodoptera frugiperda</it>. The in vitro efficacy of the two compounds and the combination against three species of ticks and their life stages and fleas were evaluated in a dry surface glass vial assay. The kinetics of the compounds over time in the collar were evaluated by the change in mass of the collar and measurement of the surface concentrations and concentrations of the actives in the collar matrix by HPLC. Hair clipped from collar treated dogs and cats, collected at various time points, was used to assess the acaricidal efficacy of the actives ex vivo.</p> <p>Results</p> <p>An <it>in vitro </it>isolated insect nerve model demonstrated the synergistic neurotoxic effects of the pyrethroid flumethrin and the neonicotinoid imidacloprid. An <it>in vitro </it>glass vial efficacy and mortality study against various life stages of the ticks <it>Ixodes ricinus, Rhipicephalus sanguineus </it>and <it>Dermacentor reticulatus </it>and against the flea (<it>Ctenocephalides felis</it>) demonstrated that the combination of these products was highly effective against these parasites. The release kinetics of these actives from a neck collar (compounded with 10% imidacloprid and 4.5% flumethrin) was extensively studied in dogs and cats under laboratory and field conditions. Acaricidal concentrations of the actives were found to be consistently released from the collar matrix for 8 months. None of the collar studies in dogs or cats were associated with any significant collar related adverse event.</p> <p>Conclusion</p> <p>Here we demonstrated the synergism between the pyrethroid flumethrin and the neonicotinoid imidacloprid, both provided in therapeutically relevant doses by a slow release collar matrix system over 8 months. This collar is therefore a convenient and safe tool for a long-term protection against ectoparasites.</p

Earthworms as ecosystem engineers ::a review

The concept of ecosystem engineering has emerged decades ago and highlights the direct or indirect modulation of available resources by organisms through their biological activities. Ecosystem engineers create biogenic structures (aggregates, burrows) that may serve as habitats for other species than themselves. This chapter aims at overviewing the key role played by earthworms as ecosystem engineers through their bioturbation activities involving soil mixing as well as their influence on the decomposition and mineralization of litter by breaking down organic matter, and their influence on the gas and water exchange or nutrient transfer in the soil. Focus is made on the engineering processes and especially the formation of biogenic structures in relation to soil structure (burrows, casts) in the framework of soil function interactions, particularly in the drilosphere. Special attention is paid to soil aggregates’ fabric and new tools that may help to discriminate their origin. Finally, management and ecosystem engineer’s future challenges will be highlighted regarding soil ecosystem services in the context of ecosystem restoration

Earthworms as ecosystem engineers : a review

The concept of ecosystem engineering has emerged decades ago and highlights the direct or indirect modulation of available resources by organisms through their biological activities. Ecosystem engineers create biogenic structures (aggregates, burrows) that may serve as habitats for other species than themselves. This chapter aims at overviewing the key role played by earthworms as ecosystem engineers through their bioturbation activities involving soil mixing as well as their influence on the decomposition and mineralization of litter by breaking down organic matter, and their influence on the gas and water exchange or nutrient transfer in the soil. Focus is made on the engineering processes and especially the formation of biogenic structures in relation to soil structure (burrows, casts) in the framework of soil function interactions, particularly in the drilosphere. Special attention is paid to soil aggregates’ fabric and new tools that may help to discriminate their origin. Finally, management and ecosystem engineer’s future challenges will be highlighted regarding soil ecosystem services in the context of ecosystem restoration

Earthworms, plants, and Soils

The importance of engineers is increasingly recognized in soil science because of their implication in most important pedological processes. Furthermore, they contribute to ecological functions provided by soils in both natural and human-modified environments. In this review, we focus on the role of two ecosystem engineers: (1) plants, their root system, and associated microorganisms and (2) earthworms. First, we explain why they are considered as major soil engineers, and which variables (texture, porosity, nutrient, and moisture dynamics) control their activities in space and time (hotspots and hot moments). Then, their roles in three processes of soil formation are reviewed, namely, rock and mineral weathering, soil structure (formation, stabilization, and disintegration), and bioturbation. For each of them, the involved mechanisms that occur at different spatial scales (from local to landscape) are presented. On one hand, tree uprooting plays a key role in rock weathering and soil profile bioturbation. In addition, living and dead roots also contribute to rock alteration and aggregation. On the other hand, earthworms are mainly involved in the formation of aggregates and burrows through their bioturbation activities and to a less extent in weathering processes. The long-term effects of such mechanisms on soil heterogeneity, soil development, and pathways of pedogenesis are discussed. Finally, we show how these two main ecosystem engineers contribute to provisioning and regulating services. Through their physical activities of burrowing and soil aggregation, earthworms and plants increase plant productivity, water infiltration, and climate warming mitigation. They act as catalysts and provide, transform, and translocate organic matter and nutrients throughout the soil profile. Finally, due to inter- and intraspecific interactions and/or symbiosis with microorganisms (arbuscular fungi, bacteria), they enhance soil fertility, decrease parasitic action, and bioremediate some pollutants. Future research is, however, still needed for a better understanding of the relationships between adequate soil management, agricultural practices, and soil biota in a perspective of relevant maintenance and durability of ecological services

Composition and superposition of alluvial deposits drive macro-biological soil engineering and organic matter dynamics in floodplains

(IF 4.34 [2018]; Q1)International audienceSoil structure formation in alluvial soils is a fundamental process in near-natural floodplains. A stable soil structure is essential for many ecosystem services and helps to prevent river bank erosion. Plants and earthworms are successful soil engineering organisms that improve the soil structural stability through the incorporation of mineral and organic matter into soil aggregates. However, the heterogeneous succession of different textured mineral and buried organic matter layers could impede the development of a stable soil structure. Our study aims at improving the current understanding of soil structure formation and organic matter dynamics in near natural alluvial soils. We investigate the effects of soil engineering organisms, the composition, and the superimposition of different alluvial deposits on the structuration patterns, the aggregate stability, and organic matter dynamics in in vitro soil columns, representing sediment deposition processes in alluvial soils. Two successions of three different deposits, silt–buried litter–sand, and the inverse, were set up in mesocosms and allocated to four different treatments, i.e. plants, earthworms, plants + earthworms, and a control. X-ray computed tomography was used to identify structuration patterns generated by ecosystem engineers, i.e. plant root galleries and earthworm tunnels. Organic matter dynamics in macro-aggregates were investigated by Rock-Eval pyrolysis. Plant roots only extended in the top layers, whereas earthworms preferentially selected the buried litter and the silt layers. Soil structural stability measured via water stable aggregates (%WSA) increased in the presence of plants and in aggregates recovered from the buried litter layer. Organic matter dynamics were controlled by a complex interplay between the type of engineer, the composition (silt, sand, buried litter) and the succession of the deposits in the mesocosm. Our results indicate that the progress and efficiency of soil structure formation in alluvial soils strongly depends on the textural sequences of alluvial deposits

Association of Neonicotinoid Insensitivity with a Conserved Residue in the Loop D Binding Region of the Tick Nicotinic Acetylcholine Receptor

Neonicotinoid insecticides target nicotinic acetylcholine receptors (nAChR) in the nervous system of insects but are largely ineffective against ticks. This study aimed to identify the molecular basis for this insensitivity. A homology model of the nAChR binding domain was generated on the basis of the crystal structure of an acetylcholine-binding protein with the insecticide imidacloprid bound. We hypothesized that tick β-subunits would differ at a critical residue (Arg81) in their D loops. To test this, we sequenced nAChR genes from five tick species and found that instead of the conserved arginine found in insects, a glutamine was present in all the tick sequences