Understorey light profiles in temperate deciduous forests: recovery process following selection cutting

1 We investigated recovery following small-scale disturbance, i.e. selection cutting, by determining how understorey light profiles vary over time in temperate deciduous forests in Quebec (Canada). 2 We measured light availability (% PPFD, photosynthetic photon flux density) 0.2, 1, 2 and 5 m above the forest floor, as well as the density of saplings < 5 m in height, in seven Acer saccharum-Betula alleghaniensis-Fagus grandifolia stands that had been subjected to selection cutting 1-13 years before the study, and in adjacent uncut plots. 3 In the most recent cut (1 year old), mean % PPFD was 3. 5 to 5 times higher (depending on height) than in the uncut plot. Light availability rapidly decreased over time following selection cutting, especially near the forest floor. By about 13 years after cutting, light availability was similar to levels observed in the uncut plots. 4 Light profiles were used to assess the temporal pattern of recovery of the understorey after selection cutting, and four recovery phases could be identified. Uncut stands were characterized by profiles with low light near the forest floor and with a rather slow increase in light with increasing height, and recent cuts (1-4 years old) were characterized by J-shaped light profiles with relatively high % PPFD at all heights. Intermediate-age cuts (7-8 years old) were characterized by reverse J-shaped profiles that had a high % PPFD (13-46%) at 5 m, and very dark conditions (< 2%) near the forest floor, and were associated with high abundance of saplings. The relative frequency of the various profiles found in older cuts (11-13 years old) was generally similar to that observed in the uncut stands, except that the reverse J-shaped profiles were slightly more frequent. 5 As the microsuccession that follows canopy disturbance is very much influenced by local understorey structure and composition, forestry practices should consider such microscale forest characteristics in their harvest planning to regenerate the desired tree species

Prevalence of claims-based recurrent low back pain in a Canadian population: A secondary analysis of an administrative database

BACKGROUND: There is a vast literature reporting that the point prevalence of low back pain (LBP) is high and increasing. It is also known that a large proportion of acute LBP episodes are recurrent within 12 months. However, few studies report the annual trends in the prevalence of recurrent LBP or describe these trends according to age and sex categories. METHODS: We conducted a retrospective cohort study involving 401 264 adults selected from the administrative database of physician claims for the province of Quebec, Canada. These adults, aged 18 years and over, met the criteria of having consulted a physician three times within a 365-day period between 2000 and 2007 for a LBP condition corresponding to ICD-9 codes 721, 722, 724 or 739. All data were analyzed by sex and clustered according to specific age categories. RESULTS: We observed a decrease from 1.64% to 1.33% in the annual prevalence between 2000 and 2007 for men. This decrease in prevalence was mostly observed between 35 and 59 years of age. Older (≥65 years) women were 1.35 times more at risk to consult a physician for LBP in a recurrent manner than older men. The most frequently reported diagnosis was non-specific LBP between 2000 to 2007. During the same period, sequelae of previous back surgery and spinal stenosis were the categories with the largest increases. CONCLUSION: The annual prevalence of claims-based recurrent LBP progressively decreased between 2000 and 2007 for younger adults (<65 years) while older adults (≥65 years) showed an increase. Given the aging Canadian population, recurrent low back pain could have an increasing impact on the quality of life of the elderly as well as on the healthcare system

Comparing composition and structure in old-growth and harvested (selection and diameter-limit cuts) northern hardwood stands in Quebec

Single-tree selection cutting is sometimes believed to be similar to the natural gap disturbance regime of hardwood forests, but few studies have specifically compared the compositional and structural characteristics of old-growth hardwood stands, undergoing natural gap dynamics and hardwood stands previously subjected to partial cuts. This study characterized and compared the composition (saplings and trees) and structure (gaps, foliage distribution, tree diameter and density, snags and coarse woody debris) of old-growth stands (OG), 12-year-old selection cuts (SC), and 28-33-year-old diameter-limit cuts (DLC) in sugar maple (Acer saccharum)-dominated northern hardwood stands. Results showed marked structural differences between OG and harvested stands, with stronger differences between DLC and OG than between SC and OG. The synchronized formation of numerous canopy openings in harvested stands induced a massive post-harvest recruitment of advance regeneration in both SC and DLC that created a dense foliage layer in the understory. Large living trees (dbh > 39.1 cm) and defective trees were less numerous in SC than OG, which can have a detrimental impact on species dependent on these structural elements, and on the future availability and characteristics of coarse woody debris. Relatively few compositional differences were noticed among stand types, although a greater proportion of mid-tolerant species was found in the post-harvest recruitment cohorts of harvested stands compared to OG, and a lower proportion of beech (Fagus grandifolia Ehrh.) saplings was observed in DLC compared to OG and SC. We argue that even if selection cutting is closer to the natural disturbance regime of hardwood forests than diameter-limit cutting, and therefore representing progress toward the development and implementation of a natural-disturbance-based management, a recurring application of selection cutting might lead to a homogenization of forest structure and composition, a reduction of key structural features and a reduction in biological diversity at both the stand and landscape scales. Some management recommendations are proposed

L’EROP : 10 ans pour le rétablissement des oiseaux de proie au Québec

L’Équipe de rétablissement des oiseaux de proie du Québec (EROP) a été fondée en 2004, à la suite de la fusion des équipes de rétablissement du faucon pèlerin (Falco peregrinus), du pygargue à tête blanche (Haliaeetus leucocephalus) et de l’aigle royal (Aquila chrysaetos). À ces espèces d’intérêt pour l’EROP s’est ajouté récemment le hibou des marais (Asio flammeus). À l’aide des plans de rétablissement de chacune des espèces, l’EROP veille à la mise en oeuvre de mesures de conservation (p. ex. acquisition de connaissances, sensibilisation, protection) visant à redresser la situation des populations d’oiseaux de proie en situation précaire au Québec. Cet article présente le mandat, le mode de fonctionnement et les principales réalisations de l’EROP au cours de la dernière décennie. The Québec raptor recovery team (EROP) was established in 2004 following the merger of the peregrine falcon (Falcoperegrinus), bald eagle (Haliaeetus leucocephalus) and golden eagle (Aquilachrysaetos) recovery teams. Recently, the short-eared owl (Asioflammeus) has also been added to the list of species covered by EROP. The team aims to foster conservation measures (e.g., data collection, public awareness and protection) to improve the population status of endangered birds of prey, and achieves this through the publication of species recovery plans. This article outlines the mission, and the working and main achievements of EROP over the past decade

A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function

Accélération du développement de la résistance initiale (1 à 3 jours) des bétons ordinaires de 20 à 40 mpa sans affecter leur résistance contractuelle à 28 jours

Cette recherche a permis de trouver un moyen d'accélérer le développement de la résistance à très court terme d'un béton ordinaire, sans pour autant augmenter sa résistance contractuelle à 28 jours. Suite à la réalisation de 80 essais sur mortier et à la fabrication de 210 gâchées de béton en laboratoire, nous avons pu déterminer les effets des différents moyens d'accélérer la résistance initiale du béton et l'influence de plus d'une trentaine de produits chimiques différents sur les propriétés des bétons frais et durcis, cette recherche nous a permis de sélectionner un groupe particulier de produits chimiques que nous avons identifié par l'expression "accélérateur spécial", afin de ne pas en divulguer la composition, car notre recherche a été effectuée pour le compte d'un laboratoire de recherche privé. Ainsi pour fabriquer un béton à haute résistance initiale qui conserve une résistance contractuelle donnée à 28 jours, et pour minimiser le coût de production d'un tel béton, il nous a fallu à partir d'un béton de base: - Substituer une certaine quantité de ciment par un volume équivalent de sable. - Abaisser le rapport eau/ciment - Utiliser un superplastifiant - Utiliser un accélérateur spécial. Bien qu'à date aucun essai de chantier n'ait été réalisé, il nous semble plausible de croire que les résultats obtenus en laboratoire sur nos bétons soient industriellement applicables parce que nous avons pris soin de respecter du mieux possible toutes les contraintes de chantier

Accélération du développement de la résistance initiale (1 à 3 jours) des bétons ordinaires de 20 à 40 mpa sans affecter leur résistance contractuelle à 28 jours

Cette recherche a permis de trouver un moyen d'accélérer le développement de la résistance à très court terme d'un béton ordinaire, sans pour autant augmenter sa résistance contractuelle à 28 jours. Suite à la réalisation de 80 essais sur mortier et à la fabrication de 210 gâchées de béton en laboratoire, nous avons pu déterminer les effets des différents moyens d'accélérer la résistance initiale du béton et l'influence de plus d'une trentaine de produits chimiques différents sur les propriétés des bétons frais et durcis, cette recherche nous a permis de sélectionner un groupe particulier de produits chimiques que nous avons identifié par l'expression "accélérateur spécial", afin de ne pas en divulguer la composition, car notre recherche a été effectuée pour le compte d'un laboratoire de recherche privé. Ainsi pour fabriquer un béton à haute résistance initiale qui conserve une résistance contractuelle donnée à 28 jours, et pour minimiser le coût de production d'un tel béton, il nous a fallu à partir d'un béton de base: - Substituer une certaine quantité de ciment par un volume équivalent de sable. - Abaisser le rapport eau/ciment - Utiliser un superplastifiant - Utiliser un accélérateur spécial. Bien qu'à date aucun essai de chantier n'ait été réalisé, il nous semble plausible de croire que les résultats obtenus en laboratoire sur nos bétons soient industriellement applicables parce que nous avons pris soin de respecter du mieux possible toutes les contraintes de chantier