Évaluation de la contribution fonctionnelle des espèces lombriciennes anéciques à la décomposition des litières prairiales : variabilité inter-espèces au sein d'une même catégorie écologique

Litter decomposition is a key process in soil functioning that contributes to many ecosystem services. In temperate climates, earthworms interacting with soil microorganisms contribute significantly to this process. However, knowledge about earthworms most often targets the three ecological categories in which they are defined: epigeics, endogeics and anecics. Anecics are very common in temperate soils, constitute the major part of the earthworm biomass and are involved in the litter decomposition. Several studies have observed behavioral, morphological and physiological traits that distinguish two subcategories within anecics: epi-anecics and strict-anecics. The first objective of this thesis was to verify if this distinction had a reality in the context of the litter decomposition process. Under controlled conditions, we evaluated (i) the role of the main anecic earthworm species in the decomposition process, (ii) the impact of these species on microorganism communities and (iii) soil enzymatic activities and (vi) the impact of interactions between anecic species on the decomposition process. Taking into account their major roles in various soil processes, based on field observations, the second objective of this thesis was to define the assembly of earthworm communities in grassland, The results obtained confirmed the distinction between epi and strict-anecic earthworms: only epic-anecics contribute to the litter decomposition process, which is correlated to the average individual biomass of each species. This contribution involved a greater stimulation of soil enzymatic activities, regardless of the species considered. In contrast to bacteria, soil fungal communities depend on the epi-anecic earthworm species with which they interact. This work also highlights that the abundance, biomass and diversity of earthworm communities in grassland soils are regulated by different environmental filters, including landscape diversity. This thesis highlights that the two ecological subcategories within the anecic category have different roles in the litter decomposition process and therefore contribute to ecosystem services provided by the soil in a differentiated way.La décomposition des litières est un processus clé du fonctionnement du sol contribuant à de nombreux services écosystémiques. En climat tempéré, les lombriciens en interaction avec les micro-organismes du sol, contribuent significativement à ce processus. Cependant, les connaissances sur les lombriciens ciblent le plus souvent les trois catégories écologiques selon lesquelles ils sont définis : les épigés, les endogés et les anéciques. Les anéciques sont très répandus dans les sols tempérés, constituent la majeur partie de la biomasse lombricienne et interviennent dans la décomposition des litières. Plusieurs études ont observé des traits comportementaux, morphologiques et physiologiques distinguant deux sous-catégories au sein des anéciques : les épi-anéciques et les anéciques stricts. Le premier objectif de ce travail de thèse était de vérifier si cette distinction avait une réalité dans le cadre du processus de décomposition des litières. En conditions contrôlées, nous avons évalué (i) le rôle des principales espèces anéciques dans le processus de décomposition, (ii) l’impact de ces espèces sur les communautés de microorganismes et (iii) les activités enzymatiques des microorganismes du sol et (vi) l’impact des interactions entre espèces anéciques sur le processus de décomposition. A partir d’observations sur le terrain, le second objectif de ce travail de thèse était de définir les règles d’assemblages des communautés lombriciennes en prairie compte-tenu de leurs rôles majeurs dans divers processus du sol. Les résultats obtenus ont confirmé la distinction entre lombriciens anéciques stricts et épi-anéciques : les épi-anéciques étant les seuls à contribuer au processus de décomposition des litières et celui-ci étant corrélé à la biomasse individuelle moyenne de chaque espèce. Cette contribution passe par une plus forte stimulation des activités enzymatiques du sol, indépendamment des espèces considérées. En revanche, contrairement aux bactéries, les communautés fongiques du sol dépendent de l’espèce épi-anécique avec laquelle ils interagissent. Ce travail met également en évidence que l’abondance, la biomasse et la diversité des communautés lombriciennes des sols prairiaux sont régulées par différents filtres environnementaux dont la diversité du paysage. Cette thèse met en évidence que les deux sous-catégories écologiques au sein des anéciques ont des rôles différents sur le processus de décomposition des litières et qu’elles contribuent donc à des services écosystémiques fournis par le sol de manière différenciée

Assessment of the functional contribution of anecic earthworm species to the decomposition of grasslandlitters

La décomposition des litières est un processus clé du fonctionnement du sol contribuant à de nombreux services écosystémiques. En climat tempéré, les lombriciens en interaction avec les micro-organismes du sol, contribuent significativement à ce processus. Cependant, les connaissances sur les lombriciens ciblent le plus souvent les trois catégories écologiques selon lesquelles ils sont définis : les épigés, les endogés et les anéciques. Les anéciques sont très répandus dans les sols tempérés, constituent la majeur partie de la biomasse lombricienne et interviennent dans la décomposition des litières. Plusieurs études ont observé des traits comportementaux, morphologiques et physiologiques distinguant deux sous-catégories au sein des anéciques : les épi-anéciques et les anéciques stricts. Le premier objectif de ce travail de thèse était de vérifier si cette distinction avait une réalité dans le cadre du processus de décomposition des litières. En conditions contrôlées, nous avons évalué (i) le rôle des principales espèces anéciques dans le processus de décomposition, (ii) l’impact de ces espèces sur les communautés de microorganismes et (iii) les activités enzymatiques des microorganismes du sol et (vi) l’impact des interactions entre espèces anéciques sur le processus de décomposition. A partir d’observations sur le terrain, le second objectif de ce travail de thèse était de définir les règles d’assemblages des communautés lombriciennes en prairie compte-tenu de leurs rôles majeurs dans divers processus du sol. Les résultats obtenus ont confirmé la distinction entre lombriciens anéciques stricts et épi-anéciques : les épi-anéciques étant les seuls à contribuer au processus de décomposition des litières et celui-ci étant corrélé à la biomasse individuelle moyenne de chaque espèce. Cette contribution passe par une plus forte stimulation des activités enzymatiques du sol, indépendamment des espèces considérées. En revanche, contrairement aux bactéries, les communautés fongiques du sol dépendent de l’espèce épi-anécique avec laquelle ils interagissent. Ce travail met également en évidence que l’abondance, la biomasse et la diversité des communautés lombriciennes des sols prairiaux sont régulées par différents filtres environnementaux dont la diversité du paysage. Cette thèse met en évidence que les deux sous-catégories écologiques au sein des anéciques ont des rôles différents sur le processus de décomposition des litières et qu’elles contribuent donc à des services écosystémiques fournis par le sol de manière différenciée.Litter decomposition is a key process in soil functioning that contributes to many ecosystem services. In temperate climates, earthworms interacting with soil microorganisms contribute significantly to this process. However, knowledge about earthworms most often targets the three ecological categories in which they are defined: epigeics, endogeics and anecics. Anecics are very common in temperate soils, constitute the major part of the earthworm biomass and are involved in the litter decomposition. Several studies have observed behavioral, morphological and physiological traits that distinguish two subcategories within anecics: epi-anecics and strict-anecics. The first objective of this thesis was to verify if this distinction had a reality in the context of the litter decomposition process. Under controlled conditions, we evaluated (i) the role of the main anecic earthworm species in the decomposition process, (ii) the impact of these species on microorganism communities and (iii) soil enzymatic activities and (vi) the impact of interactions between anecic species on the decomposition process. Taking into account their major roles in various soil processes, based on field observations, the second objective of this thesis was to define the assembly of earthworm communities in grassland, The results obtained confirmed the distinction between epi and strict-anecic earthworms: only epic-anecics contribute to the litter decomposition process, which is correlated to the average individual biomass of each species. This contribution involved a greater stimulation of soil enzymatic activities, regardless of the species considered. In contrast to bacteria, soil fungal communities depend on the epi-anecic earthworm species with which they interact. This work also highlights that the abundance, biomass and diversity of earthworm communities in grassland soils are regulated by different environmental filters, including landscape diversity. This thesis highlights that the two ecological subcategories within the anecic category have different roles in the litter decomposition process and therefore contribute to ecosystem services provided by the soil in a differentiated way

Évaluation de la contribution fonctionnelle des espèces lombriciennes anéciques à la décomposition des litières prairiales : variabilité inter-espèces au sein d'une même catégorie écologique

Litter decomposition is a key process in soil functioning that contributes to many ecosystem services. In temperate climates, earthworms interacting with soil microorganisms contribute significantly to this process. However, knowledge about earthworms most often targets the three ecological categories in which they are defined: epigeics, endogeics and anecics. Anecics are very common in temperate soils, constitute the major part of the earthworm biomass and are involved in the litter decomposition. Several studies have observed behavioral, morphological and physiological traits that distinguish two subcategories within anecics: epi-anecics and strict-anecics. The first objective of this thesis was to verify if this distinction had a reality in the context of the litter decomposition process. Under controlled conditions, we evaluated (i) the role of the main anecic earthworm species in the decomposition process, (ii) the impact of these species on microorganism communities and (iii) soil enzymatic activities and (vi) the impact of interactions between anecic species on the decomposition process. Taking into account their major roles in various soil processes, based on field observations, the second objective of this thesis was to define the assembly of earthworm communities in grassland, The results obtained confirmed the distinction between epi and strict-anecic earthworms: only epic-anecics contribute to the litter decomposition process, which is correlated to the average individual biomass of each species. This contribution involved a greater stimulation of soil enzymatic activities, regardless of the species considered. In contrast to bacteria, soil fungal communities depend on the epi-anecic earthworm species with which they interact. This work also highlights that the abundance, biomass and diversity of earthworm communities in grassland soils are regulated by different environmental filters, including landscape diversity. This thesis highlights that the two ecological subcategories within the anecic category have different roles in the litter decomposition process and therefore contribute to ecosystem services provided by the soil in a differentiated way.La décomposition des litières est un processus clé du fonctionnement du sol contribuant à de nombreux services écosystémiques. En climat tempéré, les lombriciens en interaction avec les micro-organismes du sol, contribuent significativement à ce processus. Cependant, les connaissances sur les lombriciens ciblent le plus souvent les trois catégories écologiques selon lesquelles ils sont définis : les épigés, les endogés et les anéciques. Les anéciques sont très répandus dans les sols tempérés, constituent la majeur partie de la biomasse lombricienne et interviennent dans la décomposition des litières. Plusieurs études ont observé des traits comportementaux, morphologiques et physiologiques distinguant deux sous-catégories au sein des anéciques : les épi-anéciques et les anéciques stricts. Le premier objectif de ce travail de thèse était de vérifier si cette distinction avait une réalité dans le cadre du processus de décomposition des litières. En conditions contrôlées, nous avons évalué (i) le rôle des principales espèces anéciques dans le processus de décomposition, (ii) l’impact de ces espèces sur les communautés de microorganismes et (iii) les activités enzymatiques des microorganismes du sol et (vi) l’impact des interactions entre espèces anéciques sur le processus de décomposition. A partir d’observations sur le terrain, le second objectif de ce travail de thèse était de définir les règles d’assemblages des communautés lombriciennes en prairie compte-tenu de leurs rôles majeurs dans divers processus du sol. Les résultats obtenus ont confirmé la distinction entre lombriciens anéciques stricts et épi-anéciques : les épi-anéciques étant les seuls à contribuer au processus de décomposition des litières et celui-ci étant corrélé à la biomasse individuelle moyenne de chaque espèce. Cette contribution passe par une plus forte stimulation des activités enzymatiques du sol, indépendamment des espèces considérées. En revanche, contrairement aux bactéries, les communautés fongiques du sol dépendent de l’espèce épi-anécique avec laquelle ils interagissent. Ce travail met également en évidence que l’abondance, la biomasse et la diversité des communautés lombriciennes des sols prairiaux sont régulées par différents filtres environnementaux dont la diversité du paysage. Cette thèse met en évidence que les deux sous-catégories écologiques au sein des anéciques ont des rôles différents sur le processus de décomposition des litières et qu’elles contribuent donc à des services écosystémiques fournis par le sol de manière différenciée

The Effects of Learning-Styles Information on the Achievement of Community College Developmental Math Students

Four out of five Americans will require some postsecondary education. Therefore, a majority of population will return to a community college for retraining and personal growth (McCabe, 2003). Since the turn of this century, many studies have been conducted to examine the success and challenges of the relatively new community college system. One of the most significant challenges is the large percentage of the U.S. population requiring remedial coursework. Fifty-five percent of students entering Florida\u27s postsecondary system require remediation. Of this large remedial population, only 51% will complete their preparatory classes. Students who do complete classes take an average of two years to finish preparatory classes and move on to college-level work. It is hypothesized that learning styles information will empower students with knowledge about their study habits and positively effect academic achievement. This research first examined the quantitative effect that learning styles information had on student achievement. The second qualitative phase of the study examined students\u27 perceptions of learning styles information. Three Introductory Algebra (MAT 0024) courses at a large suburban community college were intensively studied during one spring semester. Due to the size of the study (N=69), results obtained in the quantitative portion were not significant enough to accept the hypotheses. Responses in focus groups showed that students generally felt that learning styles information was useful and half the class used the information to modify how they studied. Half of the students in the control group modified their study habits in response to knowing more about their learning style. Although the qualitative data was supportive of the usefulness of learning styles information in the classroom the quantitative data did not support the hypotheses that learning styles information improves achievement

The Effects of Learning-Styles Information on the Achievement of Community College Developmental Math Students

Four out of five Americans will require some postsecondary education. Therefore, a majority of population will return to a community college for retraining and personal growth (McCabe, 2003). Since the turn of this century, many studies have been conducted to examine the success and challenges of the relatively new community college system. One of the most significant challenges is the large percentage of the U.S. population requiring remedial coursework. Fifty-five percent of students entering Florida\u27s postsecondary system require remediation. Of this large remedial population, only 51% will complete their preparatory classes. Students who do complete classes take an average of two years to finish preparatory classes and move on to college-level work. It is hypothesized that learning styles information will empower students with knowledge about their study habits and positively effect academic achievement. This research first examined the quantitative effect that learning styles information had on student achievement. The second qualitative phase of the study examined students\u27 perceptions of learning styles information. Three Introductory Algebra (MAT 0024) courses at a large suburban community college were intensively studied during one spring semester. Due to the size of the study (N=69), results obtained in the quantitative portion were not significant enough to accept the hypotheses. Responses in focus groups showed that students generally felt that learning styles information was useful and half the class used the information to modify how they studied. Half of the students in the control group modified their study habits in response to knowing more about their learning style. Although the qualitative data was supportive of the usefulness of learning styles information in the classroom the quantitative data did not support the hypotheses that learning styles information improves achievement

Effect of landscape management on earthworm communities in temperate grasslands

International audienceEarthworms provide a large number of ecosystem services that rely on the presence and association of specific species (Blouin et al., 2013). A better understanding of the factors ruling earthworm communities’ assembly is therefore essential. These assembly rules of earthworm communities are govern by the filter theory leading to a pool of local species (Lortie et al., 2004). Many studies focused on interactions between agriculture such as land use or management practices and earthworm communities. Landscape has already been shown to influence the distribution of various organisms, however, very few studies took into account the influence of landscape on earthworm communities (Crittenden et al., 2015; Regulska and Kolaczkowska, 2015) and to our knowledge, none were performed on grasslands. A landscape is composed of patches of habitats separated by ecological continuities. These ecological continuities (ditches, hedges, roads...) can be habitat for organisms, or can play the role of corridors or barriers for their dispersal between two environments. Dupont et al. (2015), observed population flows across the landscape leading to population diversification of A. icterica. The aim of this work was to determine the influence of landscape on earthworm communities’ assembly in grasslands by investigating a high spatial scale (250 and 500 m around each grasslands) and a finer one (within each grasslands).For the large scale, we selected 27 grasslands with a gradient of richness and diversity of the elements of landscape as well as of the hedgerow lines up to 500 m around. We sampled earthworms at 30 m from any natural or anthropogenic edge. For the fine scale, we selected 3 grasslands on which we sampled earthworms along a gradient at 1 m, 5 m, 10 m and 30 m from two borders, a hedgerow and a road. On each sampling point, earthworms were sampled with the application of formaldehyde followed by hand sorting on a square meter repeated three times. Each individual collected was identified to the species and weighed.Preliminary results showed that, at the large scale, the diversity of the landscape (richness or Shannon index) had a negative impact on the total richness of earthworm. The amount of hedges was positively correlated to the number of total and epi-anecic species but negatively related to epigeic species. At the fine scale, a specific effect of gradients on earthworm communities was observed for each of the three grasslands. For example, a positive gradient of earthworm abundance and biomass from the edge towards the centre of the grassland was observed in only one of the three grasslands. Some earthworm species such as A. caliginosa or A. chlorotica showed a negative gradient of their individual adult weight from the edge to the centre of the grassland. Overall no edge effect on the richness of earthworms was observed

Development of earthworm communities in a made soil at Hallside

International audienc

Roles of earthworms species in organic matter recycling and their impact on soil micro-organisms

National audienc

Response of soil microbial enzymatic activity to earthworm species

International audienceAs detritus feeders, earthworms are qualified as soil engineers and play a key role in the degradation of soil organic matter (SOM). Their contribution to this function is either direct by consuming dead organic matter or indirect by stimulating microbial communities in the soil (Brown, 1995). Most of the studies evaluating their contribution to this function were conducted at the level of three ecological categories (epigeic, anecic and endogeic). Each ecological category described in these studies is often represented by a single model species. However, the anatomical and physiological features of earthworms belonging to the same ecological category are different, which could modify their involvement in the degradation process of soil organic matter. Within the anecic earthworms, Jégou et al., (1998, 2000), based on studies from Bouché (1972, 1977), distinguished the strict anecic from the epi-anecic : strict anecic construct high density of non-permanent burrows and have low surface litter incorporation rates whereas the epi-anecic build permanent burrows into which they incorporate high quantities of fresh litter from the soil surface. These different behaviours could impact directly soil microbial activity by inducing changes in their habitat and impacting their production of extracellular enzymes contributing to different biogeochemical cycles (C, N, P) and thus to SOM decomposition. The objectives of this study were to determine and compare the contribution of different earthworm species within epi-anecic and strict anecic to the degradation of SOM through the analysis of soil enzymatic activity in their middens and burrows.To do this, an experiment using soil microcosms was conducted in 5 replicates to compare the impact of (1) three separate epi-anecic species (Lumbricus rubellus, L. centralis and L. terrestris), (2) three separate strict anecic species (Aporrectodea caliginosa meridionalis, A. nocturna and A. giardi) and (3) the mixing effects between these different species (by pairs of two species) on five enzymatic soil activities. Enzyme activities measured were (i) FDA (global soil activity), (ii) Beta-Glucosidase (carbon cycle), (iii) Cellulase (carbon cycle), (iv) Leucine Amino Peptidase (nitrogen cycle) and (v) Phosphatase (phosphorus cycle). Earthworms were fed with Lolium perenne during 30 days. Enzymatic activities were analysed at the end of the experiment (30 days) in middens and in the earthworm burrows and compared to those measured in microcosms of soil without earthworms (control). In monoculture and compared to the bulk soil (without earthworms), we observed that enzymatic activities were significantly stimulated in the presence of epi-anecic compared to strict-anecic species independently of the two micro-sites sampled (middens and earthworm burrows). These differences are more pronounced with FDA, Leucine Amino Peptidase and Beta-Glucosidase enzyme activities than with Cellulase and Phosphatase (respectively, +34, +57, +78 and +14, +8 %). Still in monoculture, no difference was found between species of the same ecological category. Interactions between earthworm species (intra- or inter-ecological category) on enzyme activity were mainly additive (functional redundancy). These initial results are in accordance with the grouping of the earthworms into functional groups initially based on morphological, physiological and ecological criteria that is thus consistent with the measurements of microbial activities carried out