The effect of tree planting density on the relative development of weeds and hybrid poplars on revegetated mine slopes vulnerable to erosion

In reclaimed waste rocks slopes, the soil cover spread for revegetation is prone to erosion. This soil needs to be immediately protected from soil erosion by above and belowground vegetation. The seeding of fast-growing herbaceous species used in agriculture is generally used on waste rock slopes to control erosion, but these compete with planted trees for resources needed for growth. The aim of this study was to assess the ability of an alternative to these herbaceous species (i.e. fast-growing hybrid poplars) to mitigate soil losses in the short-term. However, the growth of poplars could be impaired by competition from weeds’ colonization. Tree planting density was expected to change competition levels among trees and between trees and weeds, so influencing above and belowground vegetation development and hence effectiveness at controlling soil erosion processes. Five treatments were installed in 2013: 1 × 1, 2 × 2, 4 × 4 m spacing of hybrid poplars; 2 × 2 m spacing, with hydroseeding of fast-growing herbaceous plants; and a control plot with no tree planting or hydroseeding. The planting of hybrid poplars did not decrease soil losses compared to the control plot, regardless of the tree planting density. Weed development through natural colonization occurred in all the non-hydroseeded plots and was more effective at soil erosion control in the short-term than planted trees. The selected clone of hybrid poplar coped well with any competition from weeds for water, since 100% of trees survived after 3 years and since the non-hydroseeded plots produced greater length of roots per soil volume (root length density, RLD) for the poplars compared with the weed species. As early as the first year, the hydroseeded plots showed the highest RLD and a complete cover of vegetation which effectively controlled soil erosion compared to the control plots. However, both treatments with increased competition levels (i.e. highest tree planting density and hydroseeding treatment) showed less aboveground tree biomass. On the hydroseeded plots, where interspecific competition with weeds was the highest, a greater increase in root length was seen during the third year after planting. After 3 years, canopy closure was achieved in the 1 × 1 m spacing treatment, which reduced weed cover

Effet de la densité de plantation de peupliers à croissance rapide sur l’érosion des sols recouvrant des pentes de stériles miniers en région boréale

La gestion des résidus miniers représente un des principaux enjeux auxquels sont confrontées les compagnies minières. Une stratégie de restauration conforme à la règlementation environnementale et un engagement de responsabilité sociale de l’entreprise seront les conditions de l’acceptabilité sociale du projet minier. Dans un contexte de mine d’or à ciel ouvert, l'extraction de roches de faible teneur en minéraux et de fort tonnage est responsable d’importantes perturbations. L’intégration du parc à résidus dans le paysage forestier boréal dépendra de l’effectivité du mode de révégétalisation en termes de restauration écologique. Or la vulnérabilité à l’érosion des sites perturbés peut compromettre la colonisation des plantes naturelles. Le projet de recherche évalue l’influence de la densité de plantation d’arbres à croissance rapide sur le contrôle de l’érosion du sol recouvrant des stériles miniers pauvres en sulfures et métaux. Le dispositif expérimental consiste en blocs aléatoires complets avec trois répétitions pour l‘étude comparative de trois plantations de peupliers hybrides avec colonisation herbacée naturelle (espacement 1x1, 2x2 et 4x4 mètres), une plantation avec hydroensemencement d’herbacées commerciales (2x2 mètres) et un témoin avec sol seul. La mesure des pertes de sol a été mise en relation avec le développement aérien et racinaire des différentes strates de végétation dans les plantations. Après les deux premières années de plantation, le traitement hydroensemencé a connu les plus faibles pertes de sol en raison d’un recouvrement aérien et d’un "RLD" (Root Length Density) des herbacées plus important ; les parcelles témoin étant touchées par les plus grandes pertes, et les autres traitements montrant des résultats intermédiaires. Cependant, la croissance aérienne des arbres de ce traitement hydroensemencé était inhibée par les graminées commerciales, probablement du fait d’une compétition interspécifique accrue pour les ressources du sol. L'espacement 1x1 a permis d’obtenir une protection complète du sol par la canopée à partir de la troisième année de croissance. Cependant, la forte compétition intra-spécifique de ce traitement a favorisé une croissance en hauteur des arbres et pourrait accroître le risque d'instabilité des peuplements. Le plus fort espacement testé dans l’étude (4x4) limite le rôle des arbres pour la protection et la cohésion du sol. L’espacement intermédiaire (2x2) crée de meilleures conditions pour la croissance en biomasse des arbres et demeure plus performant pour le contrôle de l’érosion que le traitement 4x4 en raison d’un meilleur recouvrement de la canopée et d’une plus forte longueur de racines par unité de volume de sol (RLD). L’érosion a pu être contrôlée par la colonisation des herbacées, dès la seconde année et dans tous les traitements, ce qui fait recommander pour ce site d’étude les espacements les plus favorables à la croissance des arbres (2x2 ou 4x4) plutôt que les traitements susceptibles de mieux contrôler l'érosion (2x2 avec hydroensemencement ou 1x1). Finalement, des études similaires devraient être réalisées sur des sites plus vulnérables à l’érosion afin de préciser l'effet des différents espacements d’arbres, en particulier le 1x1, pour la protection des sols

Lujo e identidad cultural norteamericana

The article explores various cultural representations of luxury in America, both as a key element of the social project and as a cultural identity. It analyses how the assumption of luxury signs leads to the definition of an American taste and how this taste expresses itself through different cultural dimensions, from authenticity to nostalgia, from ostentation to understatement

La « vérité des carnations ». Le vocabulaire de la chair dans la peinture à l’âge classique

Bruno Remaury, professeur à l’IFM Le séminaire a abordé la question de la représentation de la chair dans la peinture, en rapprochant le savoir du peintre sur la carnation de celui du médecin sur les complexions et les humeurs. Il s’est agi, au croisement de deux savoirs, d’identifier un « vocabulaire de la chair » qui réponde à ces deux questions : comment le peintre de l’âge classique voit-il (sait-il) la peau ? Et surtout comment sa palette, c’est-à-dire les nuances de sa représentation, r..

Arcuate Nucleus Transcriptome Profiling Identifies Ankyrin Repeat and Suppressor of Cytokine Signalling Box-Containing Protein 4 as a Gene Regulated by Fasting in Central Nervous System Feeding Circuits

The arcuate nucleus of the hypothalamus is a primary site for sensing blood borne nutrients and hormonal messengers that reflect caloric status. To identify novel energy homeostatic genes, we examined RNA extracts from the microdissected arcuate nucleus of fed and 48-h fasted rats using oligonucleotide microarrays. The relative abundance of 118 mRNA transcripts was increased and 203 mRNA transcripts was decreased during fasting. One of the down-regulated mRNAs was ankyrin-repeat and suppressor of cytokine signalling box-containing protein 4 (Asb-4). The predicted structure of Asb-4 protein suggested that it might encode an intracellular regulatory protein, and therefore its mRNA expression was investigated further. Reverse transcription quantitative polymerase chain reaction was used to validate down-regulation of Asb-4 mRNA in the arcuate nucleus of the fasted Sprague-Dawley rat (relative expression of Asb-4 mRNA: fed = 4.66 ± 0.26; fasted = 3.96 ± 0.23; n = 4, P < 0.01). Down-regulation was also demonstrated in the obese fa/fa Zucker rat, another model of energy disequilibrium (relative expression of Asb-4 mRNA: lean Zucker = 3.91 ± 0.32; fa/fa  = 2.93 ± 0.26; n = 5, P < 0.001). In situ hybridisation shows that Asb-4 mRNA is expressed in brain areas linked to energy homeostasis, including the arcuate nucleus, paraventricular nucleus, dorsomedial nucleus, lateral hypothalamus and posterodorsal medial amygdaloid area. Double in situ hybridisation revealed that Asb-4 mRNA colocalises with key energy homeostatic neurones. In the fed state, Asb-4 mRNA is expressed by 95.6% of pro-opiomelanocortin (POMC) neurones and 46.4% of neuropeptide Y (NPY) neurones. By contrast, in the fasted state, the percentage of POMC neurones expressing Asb-4 mRNA drops to 73.2% (P  <  0.001). Moreover, the density of Asb-4 mRNA per fasted POMC neurone is markedly decreased. Conversely, expression of Asb-4 mRNA by NPY neurones in the fasted state is modestly increased to 52.7% (P  <  0.05). Based on its differential expression, neuroanatomical distribution and colocalisation, we hypothesise that Asb-4 is a gene involved in energy homeostasis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73490/1/j.1365-2826.2005.01317.x.pd

Ex-ante economic and ecosystem service potential of simulated conservation practices in Ghana using a minimum data approach

Master of ScienceDepartment of Agricultural EconomicsTimothy J. DaltonGiven the changing climate paradigm, food and poverty are likely to become more severe in Africa. Farmers can adapt to climate change, especially through conservation agriculture. This study relies on a minimum data approach developed by Antle and Valvidia (2006) to estimate the spatial distribution of opportunity cost for farmers in switching to conservation practices in Wa, Ghana. It assesses the economic feasibility of several scenarios that rely on production techniques currently studied by the CRSP SANREM project. We also explore the possibility that these practices can provide income from carbon sequestration payments implemented by the Kyoto protocol’s Clean Development Mechanisms. The methodology uses data from both a recent survey and information from secondary sources to assess simulated management practices. Results indicate that all the simulated management practices would theoretically benefit farmers. In fact, adoption rates for the four scenarios range from 52% to 65%, even without any carbon payment. Adding a proportional payment to the amount of carbon sequestered with these practices does not seem enough to influence farmers switch to switch to alternative scenarios. The analysis shows that these results hold even when additional fixed costs to adopt these practices are included. This case study demonstrates the usefulness of the minimum data approach in estimating the economic potential of conservation practices in Ghana. These production techniques may represent environmentally-friendly alternatives that are more profitable for farmers than current practices. The next step in assessing implementation of such practices would require studying farmers’ willingness to adopt these production systems, given their ex-ante economic returns