Diminution des pertes du nitrate par lixiviation et augmentation de la diversité microbienne dans les systèmes agroforestiers

L'agroforesterie de type culture intercalaire (CI) est une pratique agricole alternative alliant rangées d'arbres et cultures conventionnelles. Supprimer la dichotomie entre agriculture et foresterie pourrait contribuer à rétablir une production domestique de bois de feuillu chancelante en plus de créer des bénéfices environnementaux. Parmi ces avantages on compte une augmentation de la qualité du sol. Cette dernière est souvent définie comme un amalgame de fertilité, biodiversité, contribution à la santé environnementale, qualité physique et absence de pathogènes. Le présent travail s'inscrit au sein de l'effort d'un collectif de chercheurs tentant d'étudier les possibles avantages de l'adoption des CI au Canada. Plus particulièrement, les pages qui suivent s'intéressent à deux aspects de la qualité du sol: la diversité microbienne et à la réduction du lessivage des nitrates dans les sols des CI. Dans le chapitre 1, l'utilisation des acides gras phospholipidiques des communautés microbiennes révèle une plus grande hétérogénéité spatiale (beta-diversité) microbienne dans une CI que dans une culture conventionnelle lorsqu'il y a une part d'argile assez importante dans le sol et/ou que les racines des arbres utilisés prolifèrent en surface. Bien que des tentatives de lier cette hétérogénéité à des propriétés physico-chimiques du sol et à une plus grande stabilité des communautés microbiennes demeurent pour l'instant infructueuses, ce travail a mis en lumière une présence accrue des mycorhizes arbusculaires dans les CI. Dans le chapitre 2, l'utilisation de lysimètres permet de détecter, pour la période de mai à mi-octobre, une diminution d'au moins 81% des nitrates lessivant dans l'eau du sol lorsque les racines des arbres d'une CI sont préservées, en comparaison avec une section où les racines sont tranchées et isolées du système. Ce travail suggère que l'adoption des CI pourrait contribuer à diminuer le lessivage de ce polluant dans les zones agricoles du Québec

Experiences from southern Quebec provide ecological insights for the implementation of tree-based intercropping systems

Paper presented at the 11th North American Agroforesty Conference, which was held May 31-June 3, 2009 in Columbia, Missouri.In Gold, M.A. and M.M. Hall, eds. Agroforestry Comes of Age: Putting Science into Practice. Proceedings, 11th North American Agroforestry Conference, Columbia, Mo., May 31-June 3, 2009.Recent experiments in Quebec aimed to provide scientific arguments favouring the adoption of tree-based intercropping (TBI) systems in eastern Canada's rural landscape. The specific objectives of this research were to: (1) test whether a soybean intercrop between tree rows increases soil microbial biomass C, soil N fertility and tree growth compared to a harrowing treatment between tree rows; (2) determine the effects of the soybean intercrop on the diversity of arbuscular mycorrhizal fungi (assessed using SSU rRNA genes) compared to harrowing; and (3) determine whether TBI increases soil microbial beta-diversity (assessed using extractable phospholipid fatty acid (PLFA) profiles) compared to an adjacent conventional monocropping system. The TBI field was set in 2000 in southwestern Quebec using alternating rows of hybrid poplars (Populus spp.) and hardwood species spaced 8 m apart. Soybean (Glycine max L. (Merr.)) was grown between tree rows since 2004. During the 2005-2006 study period, soil microbial biomass C and N availability were higher in the soybean intercrop treatment or on par with those in the harrowing treatment. Hybrid poplar biomass increment in the soybean intercrop treatment was greater by 51 [percent] to that in the harrowing treatment and diagnostic of leaf nutrient status indicated that hybrid poplars were positively affected by the increase in N supply provided through intercrop management. The arbuscular mycorrhizal fungal diversity, as expressed by the Shannon-Wiener indices, were 0.82 for the soybean and 0.70 for hybrid poplar under the soybean intercrop treatment, and 0.53 for hybrid poplar under the harrowing treatment. The neighboring trees and soybean plants hosted different arbuscular mycorrhizal fungal communities, suggesting that TBI systems may enhance arbuscular mycorrhizal fungal richness compared to monocultures. The soil microbial beta-diversity, based on a measure of dispersion among the PLFA profiles within each sampled grid, was higher in the TBI than in the conventional soybean monocropping system, suggesting that TBI systems could play an important ecological role in the conservation of microbial functions (e.g., nutrient cycling), even in the face of wide variations of environmental conditions and inputs.David Rivest (1), Vincent Chifflot (2), Simon Lacombe (3), Alain Cogliastro (4), Robert Bradley (3), Anne Vanasse (1), Damase Khasa (2) and Alain Olivier (1) ; 1. De_partement de phytologie, Universit� Laval, Qu�bec (QC), Canada. 2. D�partement des sciences du bois et de la for�t, Universit� Laval, Qu�bec (QC), Canada. 3. D�partement de biologie, Universit� de Sherbrooke, Sherbrooke (QC), Canada. 4. Institut de recherche en biologie v�g�tale, Universit� de Montr�al & Jardin botanique de Montr�al, Montr�al (QC), Canada.n and 0.70 forIncludes bibliographical references

Effects of resource availability and interspecific interactions on Arctic and red foxes' winter use of ungulate carrion in the Fennoscandian low-Arctic tundra

In the Arctic tundra, predators face recurrent periods of food scarcity and often turnto ungulate carcasses as an alternative food source. As important and localized re-source patches, carrion promotes co-occurrence of different individuals, and its useby predators is likely to be affected by interspecific competition. We studied howinterspecific competition and resource availability impact winter use of carrion byArctic and red foxes in low Arctic Fennoscandia. We predicted that the presence ofred foxes limits Arctic foxes' use of carrion, and that competition depends on theavailability of other resources. We monitored Arctic and red fox presence at supplied carrion using camera traps. From 2006 to 2021, between 16 and 20 cameraswere active for 2 months in late winter (288 camera-winters). Using a multi-speciesdynamic occupancy model at a week-to-week scale, we evaluated the use of carrionby foxes while accounting for the presence of competitors, rodent availability, andsupplemental feeding provided to Arctic foxes. Competition affected carrion use byincreasing both species' probability to leave occupied carcasses between consecu-tive weeks. This increase was similar for the two species, suggesting symmetricalavoidance. Increased rodent abundance was associated with a higher probability ofcolonizing carrion sites for both species. For Arctic foxes, however, this increase wasonly observed at carcasses unoccupied by red foxes, showing greater avoidance whenalternative preys are available. Supplementary feeding increased Arctic foxes' carrionuse, regardless of red fox presence. Contrary to expectations, we did not find strongsigns of asymmetric competition for carrion in winter, which suggests that interac-tions for resources at a short time scale are not necessarily aligned with interactionsat the scale of the population. In addition, we found that competition for carcassesdepends on the availability of other resources, suggesting that interactions betweenpredators depend on the ecological context.publishedVersio

Archives et création : nouvelles perspectives sur l'archivistique. Cahier 1

Ce cahier de recherche fait état des travaux menés au cours de la première étape (2013-2014) du projet « Archives et création : nouvelles perspectives sur l’archivistique ». Il comprend les textes suivants : Yvon Lemay et Anne Klein, « Introduction », p. 4-6; Yvon Lemay, « Archives et création : nouvelles perspectives sur l’archivistique », p. 7-19; Anne-Marie Lacombe, « Exploitation des archives à des fins de création : un aperçu de la littérature », p. 20-59; Simon Côté-Lapointe, « Archives sonores et création : une pratique à la croisée des chemins », p. 60-83; Hélène Brousseau, « Fibres, archives et société », p. 84-104; Annie Lecompte-Chauvin, « Comment les archives entrent dans nos vies par le biais de la littérature », p. 105-120; Aude Bertrand, « Valeurs, usages et usagers des archives », p. 121-150; Laure Guitard, « Indexation, émotions, archives », p. 151-168; Anne Klein, Denis Lessard et Anne-Marie Lacombe, « Archives et mise en archives dans le champ culturel. Synthèse du colloque « Archives et création, regards croisés : tournant archivistique, courant artistique », p. 169-178. De plus, dans le but de situer le projet dans un contexte plus large, le cahier inclut une bibliographie des travaux effectués sur les archives et la création depuis 2007, p. 179-182.Le projet de recherche est financé par le Conseil de recherches en sciences humaines du Canada (Programme Savoir, 2013-2016)

Aléria – Mare Stagno

Ce site n’avait jamais l’objet de recherche jusqu’à présent. Les sondages réalisés au printemps 2015 ont permis de déterminer l’existence d’un établissement romain dont le centre semble situé à 290 m au sud de la tour génoise de Mare Stagno. Les ruines romaines sont implantées au centre du cordon de terre qui sépare l’étang de Diane de la mer. Bien que l’opération archéologique ait privilégié une approche par sondages, on peut d’ores et déjà établir que les structures bâties de cette exploita..

General Survey of Polarization Observables in Deuteron Electrodisintegration

Polarization observables in inclusive and exclusive electrodisintegration of the deuteron using a polarized beam and an oriented target are systematically surveyed using the standard nonrelativistic framework of nuclear theory but with leading order relativistic contributions included. The structure functions and the asymmetries corresponding to the various nucleon polarization components are studied in a variety of kinematic regions with respect to their sensitivity to realistic $NN$-potential models, to subnuclear degrees of freedom in terms of meson exchange currents, isobar configurations and to relativistic effects in different kinematical regions, serving as a benchmark for a test of present standard nuclear theory with effective degrees of freedom.Comment: 56 pages, 32 figures, revtex

Aléria – Mare Stagno

La campagne de 2016 a confirmé l’importance du site qui avait fait l’objet de sondages en 2015. Les travaux concernent un établissement de taille modeste dans la sphère d’influence de la colonie d’Aléria. Les informations livrées par la fouille sont précieuses car une large part de la zone est couverte par le vignoble qui rend les vestiges inaccessibles. Les ruines romaines se situent à 290 m au sud de la tour Génoise de Mare Stagno, en plein centre d’un cordon de terre qui sépare l’étang de ..

Impact of soil and water conservation measuren on catchment hydrological response: a case in north Ethiopia

Impact studies of catchment management in the developing world rarely include detailed hydrological components. Here, changes in the hydrological response of a 200-ha catchment in north Ethiopia are investigated. The management included various soil and water conservation measures such as the construction of dry masonry stone bunds and check dams, the abandonment of post-harvest grazing, and the establishment of woody vegetation. Measurements at the catchment outlet indicated a runoff depth of 5 mm or a runoff coefficient (RC) of 1·6% in the rainy season of 2006. Combined with runoff measurements at plot scale, this allowed calculating the runoff curve number (CN) for various land uses and land management techniques. The pre-implementation runoff depth was then predicted using the CN values and a ponding adjustment factor, representing the abstraction of runoff induced by the 242 check dams in gullies. Using the 2006 rainfall depths, the runoff depth for the 2000 land management situation was predicted to be 26·5mm(RCD 8%), in line with current RCs of nearby catchments. Monitoring of the ground water level indicated a rise after catchment management. The yearly rise in water table after the onset of the rains (ΔT) relative to the water surplus (WS) over the same period increased between 2002-2003 (ΔT/WS D 3·4) and 2006 (ΔT/WS >11·1). Emerging wells and irrigation are other indicators for improved water supply in the managed catchment. Cropped fields in the gullies indicate that farmers are less frightened for the destructive effects of flash floods. Due to increased soil water content, the crop growing period is prolonged. It can be concluded that this catchment management has resulted in a higher infiltration rate and a reduction of direct runoff volume by 81% which has had a positive influence on the catchment water balance. © 2010 John Wiley & Sons, Ltd

Correlation Between the Deuteron Characteristics and the Low-energy Triplet np Scattering Parameters

The correlation relationship between the deuteron asymptotic normalization constant, $A_{S}$, and the triplet np scattering length, $a_{t}$, is investigated. It is found that 99.7% of the asymptotic constant $A_{S}$ is determined by the scattering length $a_{t}$. It is shown that the linear correlation relationship between the quantities $A_{S}^{-2}$ and $1/a_{t}$ provides a good test of correctness of various models of nucleon-nucleon interaction. It is revealed that, for the normalization constant $A_{S}$ and for the root-mean-square deuteron radius $r_{d}$, the results obtained with the experimental value recommended at present for the triplet scattering length $a_{t}$ are exaggerated with respect to their experimental counterparts. By using the latest experimental phase shifts of Arndt et al., we obtain, for the low-energy scattering parameters ($a_{t}$, $r_{t}$, $P_{t}$) and for the deuteron characteristics ($A_{S}$, $r_{d}$), results that comply well with experimental data.Comment: 19 pages, 1 figure, To be published in Physics of Atomic Nucle