Le retour en communauté des détenus âgés : entre marginalisation et insertion, des expériences plurielles

À l’heure actuelle, au Canada, un détenu sous responsabilité fédérale sur cinq est âgé de plus de cinquante ans, ce qui représente une augmentation de 101% depuis le début des années 2000. Alors que tout semble indiquer qu’un nombre croissant de détenus âgés seront remis en liberté, très peu d’études se concentrent sur ce qu’ils vivent après la détention. Ce mémoire propose donc de comprendre leur expérience de retour en communauté et de faire ressortir le regard qu’ils posent sur celle-ci. Pour atteindre ces objectifs, nous nous sommes intéressées au vécu de dix-sept hommes âgés de cinquante ans et plus ayant purgé leur peine au sein d’établissements carcéraux québécois. Par l’entremise d’entrevues semi-dirigées, nous sommes parvenues à mettre en avant que le retour en communauté des détenus âgés est marqué par de multiples difficultés, exacerbées par leur âge, leur statut pénal et le cadre institutionnel dans lequel ils évoluent. Toutefois, cette expérience est vécue différemment selon la présence de solidarités familiales qui leur permettent d’accéder à un statut social valorisant et leur offrent la possibilité d’exister socialement.Nowadays in Canada, one out of five prisoners under federal jurisdiction is aged 50 and over, representing a 101% increase since the early 2000s. While everything seems to indicate that an increasing number of seniors will be released in the coming years, only a few studies have focused on life after prison. This thesis aims to understand their reentry process and to highlight the meaning they give to their experience. Our semi-structured interviews focused on the lived experiences of seventeen senior men, all of whom had served their sentence in Quebec detention centers. We found that the reentry of senior prisoners is marked by multiple difficulties, often intensified by their age, penal status and the institutional environment they evolved in. However, the reentry is experienced differently depending on whether the familial solidarity has allowed them to reach a gratifying social status and enables them to exist

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

Carbon storage and soil organic matter stabilisation in near-natural, restored and embanked Swiss floodplains

Over recent decades, the number of floodplain restoration projects has increased worldwide. In Switzerland, several projects have been implemented to maintain or recreate ecological functions of floodplains. Despite this, little is known about the potential of floodplain soils to release and/or accumulate carbon. In alluvial soils, carbon storage is strongly influenced by fluvial dynamics, and therefore a better understanding of carbon fluxes and stocks in such settings is clearly needed. To evaluate the impact of river restoration on carbon storage in alluvial soils, we aimed to quantify and explain carbon storage and soil organic matter (SOM) stabilisation in the uppermost soil humic layer. Three floodplains were investigated showing each of them different levels of human disturbance: a near-natural section along the Rhine River, and both restored and embanked sections along the Thur River and Emme River. Carbon storage was determined by total organic carbon (TOC) stocks. SOM stabilisation was evaluated by considering the TOC content in different granulometric fractions (1000–2000 μm, 500–1000 μm, and 250–500 μm) and the macro-aggregate formation, i.e. the abundance of water-stable aggregates (WSA) and the mean weight diameter of macro-aggregates (MWD). Our results show that the carbon storage and SOM stabilisation parameters were all related to soil properties such as clay, silt and total iron contents of the upper humic layer. Within each floodplain, carbon storage and SOM stabilisation parameters differed according to soil profile groups, thus reflecting a soil gradient evolution from bare alluvium soils to more stabilised soils and a hydric functioning (soils with hydromorphic features). In addition, river restoration showed various impacts on carbon storage and SOM stabilisation parameters depending on the floodplains, with a significant difference between embanked and restored sections for the Emme floodplain and no difference for the Thur floodplain

Earthworm communities in alluvial forests: Influence of altitude, vegetation stages and soil parameters

In many terrestrial ecosystems, soil parameters usually regulate the distribution of earthworm communities.In alluvial ecosystems, few studies have investigated the impact of periodic floods and alluvium deposition on soil fauna. In this context, we assumed that earthworm communities may vary depending on altitude (alpine, subalpine, mountain and hill levels), forest successional stage (post-pioneer to mature forests) and some soil parameters. Our results demonstrated that the composition of earthworm communities differed depending on altitudinal gradients. No earthworm was found at the alpine level while maximum density and biomass were observed at the hill level mainly due to the contribution of anecic species. A total of 27 species and subspecies were found over the three sampling sites, and Lumbricus moliboeus was discovered for the first time in carbonated soils. Soil texture had a major effect on epigeics that were often associated with coarse sandy texture in contrast to anecics which preferred deep soils and mature forest stages, which in combination provided the highest carbon content and the finest soil texture. In our study, carbonated fluviosols (Fluvisols according to the World Reference Base) were recorded; fluviosols typiques with well-structured A layers were generally found in mature or intermediate forest stages while most of fluviosols juveniles with heterogeneous texture were observed principally in post-pioneer forests. We conclude that in alluvial ecosystems, earthworm communities were highly dependent first on soil parameters, then altitude and to a lesser extent forest successional stages. Changes in earthworm communities tend to reflect a gradient of alluvial dynamics thus reinforcing the potential role of earthworms as bioindicators in natural and/or semi natural alluvial ecosystems

Impact of flood deposits on earthworm communities in alder forests from a subalpine floodplain (Kandersteg, Switzerland)

In many ecosystems, bioindication is a tool to estimate biodiversity and quality of environment. In soils,invertebrates are generally suitable bioindicators, especially earthworms. In floodplains, young alluvial soils are exposed to sedimentation and erosion, and little is known about soil bioindication. Moreover,a reference state is now needed to evaluate river restoration projects. The aim of our study was thus tom establish an “undisturbed” floodplain reference at the subalpine level based on earthworm communities and to test if they are indicators of fluvial dynamics. Seven plots were chosen along a stretch of the Kander River (BE, Switzerland). At each plot, a soil profile was described (carbonated Fluvisols) and topsoil was analysed. Earthworms were extracted in each plot using standard mustard extraction(3 x 1 m2) and “hand sorting” method (20 x 20 x 20 cm). Eight species were identified, and Lumbricus meliboeus was found for the first time in a carbonated environment. The absence of anecics was considered, at the subalpine level, as a bioindication of the fluvial dynamics (erosion and sedimentation processes). Biomass of epigeics was positively correlated to topsoil texture and organic matter quality,and thus epigeics, sensitive to variations of topsoil composition, are bioindicators of the latest flood event at the subalpine level

Rock-Eval pyrolysis discriminates soil macro-aggregates formed by plants and earthworms

Plants and earthworms, as soil ecosystem engineers, play a crucial role during stabilisation of organic matter in soil through its incorporation into soil aggregates. It is therefore essential to better understand the mechanisms and interactions of soil engineering organisms regarding soil organic matter stabilisation. Several methods have already been successfully applied to differentiate soil aggregates by their origin, but they cannot specify the degree of organic matter stability within soil aggregates. Rock-Eval pyrolysis has already been proved to be pertinent for analyses of soil organic matter bulk chemistry and thermal stability, but it has not yet been directly applied to identify biogenic organic matter signatures within soil aggregates. In this study, Rock-Eval pyrolysis was used for the identification of the soil aggregate origin as well as for the determination of the soil organic matter bulk chemistry and thermal stability in a controlled experiment. Mesocosms were set up, containing treatments with a plant, an earthworm species, or both. Water stable soil macro-aggregates > 250 μm were sampled and tested with Rock-Eval pyrolysis after a two-month incubation period. Rock-Eval pyrolysis was able to differentiate soil macro-aggregates by their origin, and to identify a specific signature for each treatment. Macro-aggregates from the plant and earthworm treatment were characterized by a mixed signature incoming from the two soil engineers, indicating that both engineers contribute concomitantly to soil aggregate formation. Organic matter thermal stability was not positively affected by earthworms and even tends to decrease for the plant treatment, emphasising that organic matter was mainly physically protected during the incubation period, but not stabilised. However, future research is required to test if signatures for the tested organisms are species-specific or generally assignable to other plant and earthworm species