Ecological changes in historically polluted soils: Metal(loid) bioaccumulation in microarthropods and their impact on community structure

International audienceSoil pollution by persistent metal(loid)s present environmental and sanitary risks. While the effects of metal(loid)s on vegetation and macrofauna have been widely studied, their impact on microarthropods (millimetre scale) and their bioaccumulation capacity have been less investigated. However, microarthropods provide important ecosystem services, contributing in particular to soil organic matter dynamics. This study focussed on the impact of metal(loid) pollution on the structure and distribution of microarthropod communities and their potential to bioaccumulate lead (Pb). Soil samples were collected from a contaminated historical site with a strong horizontal and vertical gradient of Pb concentrations. Microarthropods were extracted using the Berlese method. The field experiments showed that microarthropods were present even in extremely polluted soils (30,000 mg Pb kg− 1). However, while microarthropod abundance increased with increasing soil C/N content (R2 = 0.79), richness decreased with increasing pollution. A shift in the community structure from an oribatid-to a springtail-dominated community was observed in less polluted soils (R2 = 0.68). In addition, Pb bioamplification occurred in microarthropods, with higher Pb concentrations in predators than in detritivorous microarthropods. Finally, the importance of feeding and reproductive ecological traits as potentially relevant descriptors of springtail community structures was highlighted. This study demonstrates the interest of microarthropod communities with different trophic levels and ecological features for evaluating the global environmental impact of metal(loid) pollution on soil biological quality

Invasive Reynoutria taxa as a contaminant of soil. Does it reduce abundance and diversity of microarthropods and damage soil habitat?

Little is known about the impact of exotic invasive plant species on soil invertebrate communities. The influence of highly productive invader Reynoutria sachalinensis on the soil microarthropods was studied. Three sites, with different coverage of the invader, have been selected in the mixed forest in the Jura Krakowsko-Częstochowska. The lowest abundance of microarthropods and the lowest oribatid species richness were noted in the monospecific Reynoutria infestation stand. The reduction of abundance of saprophagous mites (Oribatida, Acaridida) and springtails were observed at the totally invaded site, whereas gamasid and actinedid mites reacted positively to the presence of Reynoutria. Observed abundances and species richness of microarthropods at studied sites were in accordance with theories on biodiversity. Antifungal activity of phenolic compounds present in leaves of R. sachalinensis may negatively influence on saprophagous representatives of microarthropods. On the other hand, predacious mites profited from the simplified vegetation structure

Table S4: Statistical results of the humidity occurrence niche analysis

Oribatid mites are abundant and diverse decomposers in almost all terrestrial microhabitats, especially in temperate forests. Although their functional importance in the decomposition system in these forests has been investigated, spatio-temporal patterns of oribatid mite communities inhabiting different microhabitats have largely been neglected. Therefore, we (i) investigated seasonal fluctuation (monthly over one year) in oribatid-mite community structure and specificity to three microhabitats (moss, dead wood and litter) and (ii) analyzed the influence of air temperature and overall air humidity on seasonal community changes. In total, 57,398 adult oribatid mite individuals were collected. Total abundance, species richness and diversity differed among microhabitats. Seasonal changes were most pronounced in moss and least in litter. While overall air humidity had no influence on species distribution and community changes, air temperature positively influenced species richness and diversity, again most pronounced in moss. The calculated environmental temperature occurrence niche showed that 35% of adult oribatid mite species occurred at higher air temperatures. Furthermore, interaction/bipartite networks were more generalized - i.e., species were more equally distributed among moss, dead wood and litter - when ambient air temperatures were higher. This pattern is probably due to the dispersal ability of adult oribatid mites, i.e., species enter a dispersal mode only at higher air temperatures