Quantification de l'érosion des sols organiques de l'ouest de la Montérégie en production horticole par dosage du radioisotope césium-137

Les sols organiques cultivés de l'ouest de la Montérégie alimentent une grande part du secteur horticole de la province de Québec. Or, le drainage pour leur mise en culture les rend particulièrement vulnérables à la dégradation et aux pertes de sol. Des scientifiques présument que la moitié de leur dégradation s'expliquerait par l'érosion. Cependant, son intensité réelle est mal connue. Le présent projet de recherche réalisé dans le cadre de la maîtrise en sols et environnement présentait comme objectifs de quantifier l'érosion totale cumulée depuis 1963 en sols organiques cultivés et d'étudier la modulation de son intensité par des mesures de la redistribution spatiale du césium-137. Les taux d'érosion annuels obtenus varient de 0,4 à 8,8 t/ha, alors que ceux estimés initialement varient de 4,1 et 54,6 t/ha. Cependant, la valeur moyenne de 2,9 t/ha (avec un écart-type standard de 2,1 t/ha) obtenue était comparable à celle obtenue dans l'actuelle Étude sur l'état de santé des sols agricoles du Québec réalisée par l'IRDA qui était de 3,6 t/ha (avec un écart-type standard de 4,5 t/ha). Aucune différence significative entre les taux d'érosion annuels n'a pu être détectée au moyen d'analyses de la variance entre les groupes de champs à l'étude. De plus, les analyses comparatives entre les taux d'érosion des sols calculés à partir des teneurs résiduelles en césium-137 par rapport à ceux estimés à l'aide des différents paramètres physico-chimiques ne donnent pas de résultats significatifs. On peut émettre l'hypothèse que la part des pertes de sol par érosion serait plus importante que celle présumée au départ. De plus, plusieurs hypothèses sont avancées afin d'expliquer l'absence d'effet et de tendance significative détectée. Enfin, il semble qu'un nouveau modèle d'interprétation des inventaires de césium-137 en pertes de sol par érosion doive être développé pour les sols organiques cultivés et drainés.The cultivated organic soils of western Montérégie supply a large part of the horticultural sector of the province of Quebec. However, drainage for their cultivation makes them particularly vulnerable to degradation and soil loss. Scientists assume that half of their degradation can be explained by erosion. However, its real intensity is poorly known. The present research project carried out within the framework of the master's degree in soils and environment presented as objectives to quantify the total cumulative erosion since 1963 in cultivated organic soils and to study the modulation of its intensity by measurements of the spatial redistribution of caesium-137. The annual erosion rates obtained vary from 0.4 to 8.8 t/ha, while those initially estimated vary from 4.1 to 54.6 t/ha. However, the average value of 2.9 t/ha (with a standard deviation of 2.1 t/ha) obtained was comparable to that obtained in the current Study on the Health of Agricultural Soils in Quebec carried out by the IRDA which was 3.6 t/ha (with a standard deviation of 4.5 t/ha). No significant difference between the annual erosion rates could be detected by means of analyzes of variance between the groups of fields under study. In addition, the comparative analyzes between the soil erosion rates calculated from the residual caesium-137 contents compared to those estimated using the various physico-chemical parameters do not yield significant results. It can be hypothesized that the share of soil loss by erosion would be greater than presumed initially. In addition, several hypotheses are put forward to explain the lack of effect and significant trend detected. Finally, it seems that a new model for interpreting caesium-137 inventories in soil loss by erosion must be developed for cultivated and drained organic soils

Influence of patch shape on mallard nest survival in northern Iowa

Reproductive success of mallards (Anas platyrhynchos) is influenced by distribution and amount of wetlands and grasslands on the landscape during the breeding season. Most studies of mallard reproductive success have been conducted in areas with high wetland densities and large tracts of grasslands. We investigated nest survival of mallards in intensively cropped northern Iowa, USA, where wetland and grassland habitats were highly fragmented. We radiotracked female mallards nesting during 1998–2000 and located 318 nests in 6 types of land cover. Overall daily survival rate of nests was 0.945 ± 0.003 standard error (SE), corresponding to an estimated nest survival rate of 0.14. Hen success (i.e., the probability that an individual female will hatch a nest in one of her attempts) averaged 0.28 ± 0.03 SE. We used a model selection approach to examine covariates that might affect nest survival. Perimeter-to-area ratio (PAR) of the nest patch was the most important predictor of daily nest survival, with nest survival decreasing with increasing PAR. A greater percentage of nests hatched (18%) in habitats with low perimeter-to-area ratios (e.g., pastures, hayfields, Conservation Reserve Program fields, and managed grasslands) compared with habitats with high PAR (11%) such as drainage ditches, road-side ditches, fencerows, and waterways. Managing habitat in this region to increase mallard nest survival will be challenging, given the propensity of mallards to nest in linear habitats. If the climate change projections materialize in the 21st century, the southeastern portion of the Prairie Pothole Region could become a much more important breeding area for midcontinent mallards. Published 2016. This article is a U.S. Government work and is in the public domain in the USA

Des réseaux littéraires pour travailler la morphologie

Travail dirigé présenté à la Faculté des études supérieures en vue de l’obtention du grade de maître en éducation (M. Éd.) option didactique du françaisLe Programme de formation de l’école québécoise, insiste sur le fait que le développement des compétences en français requiert un environnement riche et stimulant au cœur duquel les livres occupent une place de choix. Une façon profitable d’intégrer les livres dans son enseignement est de planifier des réseaux littéraires. Relier des œuvres entre elles, autour d’un questionnement commun, permet de constater des ressemblances, des différences et des variantes entre les œuvres en plus d’intégrer les trois compétences de français. L’objectif général de ce travail dirigé est de fournir un réseau littéraire aux enseignants du premier cycle du primaire pour amener leurs élèves à développer une conscience morphologique. Le réseau, axé sur l’auteur Thierry Dedieu, permettra aux élèves de dégager les particularités de son style et de son univers, en plus d’apprendre à analyser morphologiquement des mots, dans le but de mieux comprendre ce qu’ils lisent et mieux orthographier les mots qu’ils écrivent.The Québec Education Program emphasizes that the development of French language skills requires a rich and stimulating environment at the heart of which books occupy a place of choice. A profitable way to integrate books into one's teaching is to plan literary networks. Linking works together, around a common questioning, allows us to see similarities, differences and variations between the works in addition to integrating the three French skills. The overall goal of this directed work is to provide a literary network for first cycle primary school teachers to help their students develop a morphological awareness. The network, based on the author Thierry Dedieu, will allow students to identify the particularities of his style and his universe, in addition to learning to morphologically analyze words, in order to better understand what they read and better spell the words they write

Nest-site selection, energetics of reproduction and comparative behaviour of mallard (anas platyrhynchos) and blue-winged teal (A. discors)

An organism's reproductive success may be affected by choice of breeding habitats and subsequent investment in offspring. Nest microclimate may profoundly influence energetic costs of incubation or embryonic survival, but few studies have evaluated whether birds select nest-sites based on microclimate. Likewise, increased investment of nutrients in eggs may have costs in terms of future survival and reproduction. These ideas have received only limited testing, particularly behavioural and physiological responses to clutch size variation of precocial birds. Therefore, I evaluated whether: (1) ducks select nest-sites for thermal features; and, (2) incubation behaviours, incubation periods, or energetic costs of incubation are related to clutch size. Blue-winged teal ( A. discors; hereafter teal) nested most often in grass or short shrub habitats, while mallard (Anas platyrhynchos) nested in all habitats. Within nesting habitats, microclimate followed a gradient from hot and sunny in grass-dominated sites to cool and shaded sites in aspen (Populus spp.) groves. I measured microclimatic conditions at mallard and teal nests and randomly located nonnest sites, to evaluate thermal consequences of nest-site selection. Duck nests received on average less solar insolation than nonnest sites, producing more moderate thermal conditions than at nonnest sites. When mallard and teal nests were concurrently monitored, teal selected warmer nest-sites than mallards. Thus, teal may choose warmer nests to offset costs of incubation, a hypothesis which has not been tested. Apart from egg formation costs, processes occurring during incubation may also limit clutch size of precocial birds. I tested if incubation periods were positively correlated with clutch size and found that incubation periods of captive mallards and wild teal, but not wild mallards, were longer for females incubating clutches enlarged by 50%. Incubating females may respond to increased energetic costs of incubation by: (1) losing more mass, (2) decreasing nest attendance, or (3) some combination of both. Mass loss and mass at hatch were unrelated to clutch enlargement, however, mass loss was positively correlated with mass at the start of incubation. While controlling for effects of weather, I found no change in incubation behaviours of mallards incubating enlarged clutches, but, teal increased overall recess frequency. Finally, I evaluated effects of clutch enlargement on incubation strategies, representing an integration of behaviour and body mass dynamics. When controlling for weather and body mass dynamics, clutch enlargement produced significant, yet subtle changes in incubation behaviours. Mallards took slightly shorter recesses, but maintained constancy, whereas teal increased recess frequency and decreased nest attendance. Energetic costs of incubation are controversial. I tested if incubation metabolic rates (IMR) were greater than resting metabolic rate (RMR). Incubation caused an increase in metabolic rate by mallard and red junglefowl (Gallus gallus spadiceus). I tested the assumption that IMR is positively correlated with clutch size and found that IMR of junglefowl within thermoneutrality was unrelated to clutch mass. Further work is needed to evaluate metabolic responses of precocial birds to clutch size variation. Overall, clutch size of precocial birds (particularly small species) may be limited by costs in terms of extended laying and incubation periods, as well as by subtle changes in incubation behaviours. Further integration of incubation costs with those associated with egg formation and brood-rearing, would provide a comprehensive and powerful analysis of factors limiting clutch size in precocial birds

Nutrient Availability for Lactuca sativa Cultivated in an Amended Peatland: An Ionic Exchange Study

Few conservation strategies have been applied to cultivated peatland. This field study over one growth cycle of Lactuca sativa examined the effect of plant-based, high-C/N-ratio amendments in a real farming situation on peatland. Plant Root Simulator (PRS®) probes were used directly in the field to assess the impacts of incorporating Miscanthus x giganteus straw and Salix miyabeana chips on nutrient availability for lettuce. The results showed that lettuce yield decreased by 35% in the miscanthus straw treatment and by 14% in the willow chip treatment. In addition, the nitrogen flux rate was severely reduced during crop growth (75% reduction) and the plant N uptake index was much lower in the amended treatments than in the control. The phosphorus supply rate was also significantly lower (24% reduction) in the willow treatment. The influence of sampling zone was significant as well, with most macro-nutrients being depleted in the root zone and most micro-nutrients being mobilized. Additional work is needed to optimize the proposed conservation strategy and investigate the effects of consecutive years of soil amendment on different vegetable crops and in different types of cultivated peatlands to confirm and generalize the findings of this study. Future field studies should also explore the long-term carbon dynamics under plant-based, high-C/N-ratio amendments to determine if they can offset annual C losses

Nutrient Availability for <i>Lactuca sativa</i> Cultivated in an Amended Peatland: An Ionic Exchange Study

Few conservation strategies have been applied to cultivated peatland. This field study over one growth cycle of Lactuca sativa examined the effect of plant-based, high-C/N-ratio amendments in a real farming situation on peatland. Plant Root Simulator (PRS®) probes were used directly in the field to assess the impacts of incorporating Miscanthus x giganteus straw and Salix miyabeana chips on nutrient availability for lettuce. The results showed that lettuce yield decreased by 35% in the miscanthus straw treatment and by 14% in the willow chip treatment. In addition, the nitrogen flux rate was severely reduced during crop growth (75% reduction) and the plant N uptake index was much lower in the amended treatments than in the control. The phosphorus supply rate was also significantly lower (24% reduction) in the willow treatment. The influence of sampling zone was significant as well, with most macro-nutrients being depleted in the root zone and most micro-nutrients being mobilized. Additional work is needed to optimize the proposed conservation strategy and investigate the effects of consecutive years of soil amendment on different vegetable crops and in different types of cultivated peatlands to confirm and generalize the findings of this study. Future field studies should also explore the long-term carbon dynamics under plant-based, high-C/N-ratio amendments to determine if they can offset annual C losses

Conspecific Brood Parasitism in Common Eiders (Somateria Mollissima): Do Brood Parasites Target Safe Nest Sites?

Several hypotheses have been proposed to explain the evolution of conspecific brood parasitism (CBP), and recent studies suggest that nest predation may be an important factor in shaping this behavior. We assessed whether individuals that engage in parasitic laying preferentially deposit their eggs in safe nest sites (i.e., risk assessment hypothesis). We tested the predictions of this hypothesis using a population of Common Eiders (Somateria mollissima dresseri) nesting at Table Bay, Labrador, Canada, in 2007. Common Eiders at this location nest in three habitats (dense woody vegetation, open grassy vegetation, and nest shelters) that vary in their exposure to avian predators. We used isoelectric focusing electrophoresis of egg albumen to quantify the frequency and distribution of CBP among habitats. Nest-site safety did not explain patterns of CBP among habitats, given that nests in dense woody vegetation had the highest probability of survival (0.70; 95% confidence interval [CI]: 0.50–0.89) yet had the lowest frequency of CBP(33%). There was also no indication that parasitized and nonparasitized nests differed in their probability of nest survival (0.65 [95% CI: 0.41–0.83] vs. 0.58 [95% CI: 0.33–0.80]). We propose explanations for why our data did not support the risk assessment hypothesis