Isopod physiological and behavioral responses to drier conditions: An experiment with four species in the context of global warming

ACLIn the context of global warming, an increase in soil drought is suspected by the IPCC predictions and litter breakdown activity could be affected. An experiment was conducted using microcosms (controlled conditions) and woodlice which are recognized as shredders of litter and bioindicators of global warming. The impact of relative air humidity (90 and 50% RH) on litter breakdown by woodlice was studied through the monitoring of one behavioral (distribution of individuals on microcosms), one morphological (Absolute Growth Rate) and four physiological traits (Survival rate, Relative Consumption Rate, Relative Growth Rate, Feeding rate). Four species of isopods known to have different microclimatic sensitivities (Armadillidium vulgare, Porcellio scaber, Oniscus asellus, Philoscia muscorum) were used simultaneously. Sensitivities of males and females have also been tested. Main results showed that the seven studied parameters under the two relative humidity conditions were not affected in the same way according to the species nor genders. A. vulgare is the most affected species followed by O. asellus. The least affected species are P. scaber and P. muscorum. Their morphological and physiological differences allow to the most evolved species to be more resistant to drier conditions but in return they are no longer active, which can affect soil functionality. With global warming, it could be envisaged that woodlice spend less time foraging and more time seeking refuge to reduce the risk of mortality from desiccation stress. Modifying the feeding behavior of terrestrial isopods could slow down litter degradation with consequences on the process of organic matter recycling

Comparison of the interest of four types of organic mulches to reclaim degraded areas: a field study based on their relative attractiveness for soil macrofauna

ACLThe study focused on the attractiveness of mulches (consisting of the addition of a layer material to the soil surface) and their efficiency to promote recolonization by pedofauna of isolated and degraded areas. The experimental study was set up in the former coal mining area of Northern France. This area is particularly disturbed and fragmented by land-use change, urbanization, industry, intensive agriculture and metal pollution. To examine the movements of pedofauna, four kinds of mulches were applied: (i) Ramial Chipped Wood (RCW), (ii) chopped Miscanthus, (iii) dead leaves and (iv) wheat straw as well as plastic sheeting, a material often used in green spaces. A negative control consisted in soil without mulch addition. The experimental set-up consisted of a set of 18 bands of mulch (6 m long x 0.5 m width x 8 cm thick, i.e. a volume of 0.04 m3 per band) installed on three adjacent plots on a surface area which stretch on 4400 m2: (i) plot F1, a mixed plantation, (ii) plot M consisted of three rows of maples (both considered to be the reservoir of biodiversity) and (iii) plot BF, an ash plantation (with lower biodiversity). Faunistic communities of soil present within the mulches were monitoring using pitfall traps for four months (April to July), at a rate of eight surveys for each of the 90 traps installed, i.e. 720 samples. Different life traits and indices of diversity were studied, more specifically on carabid beetles. The main objective of the study was first to check whether mulches could or not reconnect different planted plots in a peri-urban landscape highly modified by human activities. The second aim was to find which type of mulch had the best efficiency in the recovery of the connectivity between plots. The last questions were which type of zoological groups could be favoured by the use of mulches and which benefits for ecosystem functioning. The main hypotheses of this study were: (i) Organic mulches would act as dispersal corridors and refuge zones to the soil organisms; (ii) organic mulches would be attractive to many organisms with various ecological needs. This study highlighted the potential benefits of using the mulching technique to support ecological connectivity in disturbed environment since this method highlighted the presence of individuals with different diets (saprophagous, predators, phytophagous and so forth), small and large size species which do not have the same dispersal capacities as well as species that are more dependent on forest environments and others that depend on more open environments. The study concluded that organic mulches are more favourable to pedofauna than soil without mulch or plastic sheeting. With regard to organic mulches, no difference was noted, either in terms of cumulative abundance or monthly monitoring. However, for carabids, it should be noted that dead leaves and wheat straw have higher specific richness than Miscanthus and RCW

Does adding fly ash to metal-contaminated soils play a role in soil functionality regarding metal availability, litter quality, microbial activity and the community structure of Diptera larvae?

ACLThis study aimed at evaluating the impact of the use of fly ash-aided phytostabilisation as a method to manage highly metal-contaminated soils on soil functionality taking into account the soil and the litter qualities, the Diptera larvae communities and the microbial activity. To reach this goal, 70 parameters were studied. The main results showed that the two studied fly ashes Soproline® and Sodeline® had a positive influence on soil characteristics especially the availability of metals, nearly 14 years after amendment. Regarding biological parameters, no positive or negative effects were found by adding fly ashes to the soil concerning soil basal respiration and urease activity. The fungal activity was even enhanced. In the same way, the fly ashes had no negative effect on the Diptera larvae community and a greater richness of larvae was even found in amended soils. Thus, this study confirmed that aided-phytostabilisation using these fly ashes should be an advantageous technique to manage metal-polluted soils and to recycle industrial wastes

Comparison of the interest of four types of organic mulches to reclaim degraded areas (Part 2): Microbial activities and abiotic factors

International audienc

Distribution of metals and cell wall compounds in leaf parts of three tree species suitable for the phytomanagement of heavy metal–contaminated soils

ACLPhytomanagement used on soils contaminated with metals aims to stabilize them in the soil. It generally uses less demanding tree species such as maple, poplar, and black locust. However, it is important to consider the rate of accumulation of metals in the leaves as well as their location (leaf blade/petiole) together with the contents of cell wall compounds (hemicelluloses, cellulose, lignin). These two aspects are likely not only to have repercussions on the decomposition of litter but also to lead to a possible transfer ofmetal contamination into the food chain via soil decomposers/detritivorous. A successful phytoremediation is therefore the result of compromise: no tree species can meet all these criteria. The results obtained show that poplar is not recommended due to a high accumulation of Cd and Zn. The most appropriate species among our 3 studied species, which seem the most suitable in terms of remediation of metal polluted soils, could be the black locust and the maple which are less susceptible to contribute to the transfer of exogenous metals such as Cd to the trophic chain. However, maple strongly accumulates Pb in the leaf blade and it is susceptible to degrade quickly due to its high hemicelluloses and cellulose contents and low lignin content. The black locust accumulates metals mainly in the petiole (little consumed by detritivorous). However, its exotic character and high lignin content may limit the interest of its use

Combined toxic effects and DNA damage to two plant species exposed to binary metal mixtures (Cd/Pb)

ACLAcute and long-term (3-, 10- and 56-day exposure) laboratory toxicity tests were carried out to assess the individual and combined toxic effects of cadmium (Cd) and lead (Pb) in Brassica oleracea and Trifolium repens. In addition to morphological parameters, this work also used comet assay to address endpoints in relation to genotoxicity. Bioaccumulation was measured to demonstrate the influence of the mixture on the concentrations of each metal in the plant. The statistical method reported by Ince et al. (1999) was used to evaluate the types of interaction between Cd and Pb in each treatment and concerning their combined effect. This study concludes that the combined effects of binary metal combinations of Cd/Pb on morphological parameters are most often additive, sometimes antagonistic and more rarely synergistic, thus extending the findings of previous publications on this subject. DNA damage analysis revealed concentration- and time-dependent interactions. Synergistic effects of mixed metals (more breaks than individually applied metals) are observed in T. repens after a short exposure. Antagonistic effects are statistically significant after 10 days-exposure, suggesting competition between metals. At 56 days, the rate of DNA damage observed in plants exposed to the Cd/Pb mixture was similar to that measured in plants exposed to lead only and was significantly lower than the rate of DNA damage induced by Cd. This supports the idea that there may be competition between metals and also strengthens the hypothesis that long-term reparation mechanisms may be implemented. Cd/Pb co-exposure does not significantly influence the bioaccumulation of each metal. It is nevertheless important to note that a statistically significant ‘interaction’ is not necessarily biologically relevant and should therefore be considered with caution when assessing heavy metals combined effect