Adapting ecotoxicological tests based on earthworm behavior to assess the potential effectiveness of forest soil liming

Two laboratory experiments were carried out to determine the potential effects of lime application on the behavior of earthworms inoculated in an acidified forest soil from Vosges Mountains. Several field soils were studied: (i) a non-limed soil that had received decades of atmospheric acid depositions $({\text{pH}}_{{\text{H}}_2\text{O}}=3.9)$, (ii) an in situ limed soil that had been limed 6 years before at 2.5 t ha^?1 $({\text{pH}}_{{\text{H}}_2\text{O}}=4.2)$ and (iii) in vitro limed soils composed of non-limed soil mixed with several lime amounts in the laboratory corresponding to field rates of 1, 2.5, 5, 10 and 20 t ha^?1. Firstly, we adapted the earthworm avoidance test (ISO, 2006) by using Eisenia fetida as the model organism and Lumbricus castaneus, a local species, to determine earthworm preference between non-limed and limed soils. Secondly, a cast production (CP) study was performed according to Capowiez et al. (2009) with Lumbricus terrestris, in seven different treatments (non-limed soil, in situ limed and five in vitro limed soils with pH from 5 to 6.3). Both species avoided the non-limed soil in favour of in situ and in vitro limed soils for both species. Results of the CP bioassay showed that the bioturbation behavior of L. terrestris significantly increased with the increase of soil pH, following a dose–response curve. However, in the long term (>6 years), the application of lime was insufficient to significantly improve soil conditions for enhancing earthworm activity. In conclusion, we may recommend this kind of earthworm laboratory tests with field soils to assess any changes in soil quality over time due to liming application.     

Assessment of movement patterns in Folsomia candida (Hexapoda: Collembola) in the presence of food

We showed that Folsomia candida (a blind soil-dwelling Collembola) was able to shift from non-directional (random or search strategy) to directional (target-oriented) movements at short distance of food. We measured departure from linearity and access (or not) to food by the springtail according to distance to the target position. Video-records and image analysis were used to obtain numerical data at 0.2 s interval. The probability of food capture within 10 min (maximum duration of the experiment) was negatively related to distance. Two patterns can be observed along successful trajectories in our experimental conditions (22 °C, ambient light, still air), non-directional movement being followed by directional movement when the animals approach food at 25 mm.     

Experimental assessment of habitat preference and dispersal ability of soil springtails

Beside biotic interactions, habitat preference and dispersal ability of species play a prominent role in the building of animal species assemblages. However, these traits are usually very poorly documented for soil organisms. A soil transfer experiment was designed to study habitat preference (including land-use and soil preference) and dispersal ability of soil springtail species living in a meadow and in an adjoining deciduous forest. The study was performed in the Morvan Regional Natural Park (Central France), using untreated or defaunated soil blocks, transferred to another land-use or replaced in their original land-use. Land-use preference was quantified in untreated and untransferred samples from meadow and forest. Dispersal ability was estimated from the time at which species colonized defaunated samples in their own habitat. Soil preference was estimated from the colonization rate of defaunated samples by comparing transferred and untransferred soil blocks. Results showed that in the community, 6% of species were land-use generalists, 30% were soil generalists and 36% recolonized defaunated soil blocks within a week. Land-use preference, soil preference and dispersal ability were largely independent components of species characteristics. Although our experiment dealt only with small-scale colonization, comparisons between species showed that the dispersal type based on anatomical features (legs, antenna, furcula, visual apparatus) does not allow predicting the dispersal ability of these species. Discrepancies between land-use preference and soil preference suggest that other habitat features must be relevant for Collembola, and that a trade-off exists between eco-physiological and biotic interactions (including food requirements).     

Early colonization of constructed Technosols by macro-invertebrates

Journal of Soils and Sediments - Anthropogenic activities lead to soil degradation and loss of biodiversity, but also contribute to the creation of novel ecosystems. Pedological engineering aims at...