Identifier, détecter et localiser les centralités économiques : une proposition inspirée de l'algorithme DBSCAN

En sciences régionales, la notion de centre(s) revêt une importance capitale pour plusieurs modèles théoriques et cadres conceptuels. Les dynamiques urbaines et locales ont conduit à une multiplication des centres rendant le polycentrisme la norme dans la plupart des aires métropolitaines. Or, la localisation du centre (ou des centres) est souvent postulée comme exogène, déterminée à l’avance. Elle s’avère souvent un intrant nécessaire afin d’identifier les multiples centres. Cette note de recherche propose de développer un algorithme permettant d’identifier, de détecter et de localiser les différents centres à partir d’une typologie issue de critères économiques (unités de logements et commerciales). Afin de présenter son implémentation, deux applications fictives sont développées. Une première sur une ville monocentrique, et une seconde sur une ville polycentrique. Une application empirique permet d’identifier et de localiser les centralités de 31 régions métropolitaines de recensement (RMR) et agglomérations de recensement (AR) du Québec à partir d’information sur les unités d’évaluation contenues dans les rôles d’évaluations municipaux

Contributions of a global network of tree diversity experiments to sustainable forest plantations

status: publishe

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

No stress memory pattern was detected in sugar maple and white spruce seedlings subjected to experimental droughts

Abstract An increase in the frequency and magnitude of drought events threatens the health of forests and the economic, ecological, and societal services they provide. It has been widely demonstrated that trees undergoing a succession of stresses may accumulate lesions that in turn lead to a decrease in their vigor and eventually to death. However, recent studies have shown that a nonlethal stress should also initiate a stress memory, which triggers a faster and stronger plant defensive response when a new stress occurs. Although this mechanism is well understood in many herbaceous plants, a better understanding in trees is needed. The aim of our study was to explore the capacity of two forest tree species to develop a stress memory. A greenhouse experiment was conducted to evaluate the tree seedlings' vigor after one or two consecutive droughts separate from a rehydration period during the same growing season. No stress memory pattern was observed for the two tree species as, on the contrary, we even observed a stress accumulation pattern in sugar maple. It remains possible that some individuals in our study developed stress memory, but that we were not able to detect it. The fine‐tuning of experimental parameters and the conducting of longitudinal studies would be helpful to detect individual capacity in stress memory activation

Using Macronutrient Distributions within Trees to Define a Branch Diameter Threshold for Biomass Harvest in Sugar Maple-Dominated Stands

As the use of forest harvesting residues for energy production gains popularity, debate continues regarding the long-term sustainability of whole tree harvesting (WTH). This practice removes nutrient-rich twigs that only account for a small fraction of harvest residues, emphasising the need to develop nutrient-efficient alternatives to WTH. This study assessed N, P, K, Ca, and Mg distributions within sugar maple (Acer saccharum Marshall) and yellow birch (Betula alleghaniensis Britton) branches of various sizes in order to determine the branch diameter threshold that would represent the best compromise between the quantity of harvested biomass and nutrient losses that were generated. Quantities of nutrients that were exported with harvesting were then modelled at the stand level using different biomass harvest scenarios to explore what factors ultimately drove total quantities of nutrients exported with harvest. We found that the branch diameter threshold for biomass harvesting should be set at 2 cm for most nutrients in both tree species. An exception was Mg in yellow birch, for which the harvesting of branches larger than 10 cm would always generate larger nutrient export than gains in terms of biomass. At the stand scale, we provide evidence that the intensity of biomass harvest (i.e., the number of branch compartments harvested) is the principal factor responsible for the quantity of nutrient that is exported with harvesting

The successional status of sugar maple (Acer saccharum), revisited

Two complementary experimental designs at two contrasting scales (landscape/long term; individual tree/short term) were used for an in-depth evaluation of the successional status of sugar maple (AS: Acer saccharum Marsh.). First, forest disturbances during the 20th century and composition were mapped for two landscapes in the Du Lièvre watershed of southern Quebec. Our results show that, as well as dominating stands in the absence of fire, AS often rapidly developed dominance after fire, especially in the south of our study area. Similarly, a majority of AS-dominated stands clearcut in 1928 continued to be AS-dominated 60 years later. Second, we examined AS seedlings planted under two very contrasting light regimes. AS seedlings showed a combination of traits particularly adapted to tolerate shade under a low light regime. However, owing to a surprisingly high phenotypic plasticity, AS also exhibited efficient development under high light. This suggests the classification of AS as a late-successional species should indeed be revised and that generalist or trans-successional would be a more appropriate designation for this species. We discuss the ramifications of such a status revision, with an emphasis on the implications for its silviculture.Révision du statut successionnel de l'érable à sucre (Acer saccharum). Deux dispositifs expérimentaux complémentaires, établis à deux échelles différentes (paysage/long terme et individu/court terme), ont été utilisés afin de mieux évaluer le statut successionnel de l'érable à sucre (AS: Acer saccharum Marsh.). D'abord, une cartographie des perturbations et de la composition forestière au cours du 20$^{\rm e}$ siècle a été réalisée pour deux paysages du bassin du Lièvre dans le Sud du Québec. Nos résultats ont démontré qu'en plus de dominer les peuplements en absence de perturbation du couvert, AS établissait souvent et rapidement une dominance dans les peuplements ayant brûlé, et cela, particulièrement dans le paysage le plus au sud de l'air d'étude. De la même façon, une majorité de peuplements dominés par AS et coupés à blanc en 1928 s'est révélée encore dominée par AS à peine 60 ans après coupe. Ensuite, en réalisant le suivi de semis plantés sous deux régimes lumineux très différents, AS a montré un ensemble de caractéristiques particulièrement adaptées à une bonne tolérance à l'ombre. Cependant, grâce à une étonnante plasticité phénotypique, AS a aussi démontré un développement compétitif sous des régimes lumineux plus élevés. L'ensemble de ces résultats suggère donc une remise en question du statut de fin de succession de AS, lequel répondrait mieux à une appellation d'espèce généraliste ou trans-successionnelle. Les implications d'une telle révision sur la sylviculture de cette essence sont discutées

Increased levels of harvest may favour sugar maple regeneration over American beech in northern hardwoods

The increasing dominance of American beech regeneration (Fagus grandifolia Ehrh.) to the expense of sugar maple (Acer saccharum Marsh.) challenges the long-term economic viability of forest management in northern hardwoods. Based on earlier studies showing that more light in the understory favours sugar maple over beech, the irregular shelterwood system has shifted from experimental to operational over the last decade. In this paper, we evaluate the success of this shift toward irregular shelterwood for promoting sugar maple over beech by measuring the frequency, abundance of sugar maple and beech seedlings and saplings, and growth of seedlings three to six years after logging in northern hardwood forests of western Quebec, Canada. Results showed a dominance of beech regeneration regardless of the harvest intensity, particularly among tall seedlings and saplings. However, we found that the transition probability indices (projected relative combined abundance and growth) of sugar maple could be favoured, albeit to a limited extent, by an increased basal area removal, particularly where the initial occurrence of sugar maple in the advance seedling regeneration is lower than 60% and the initial beech basal area is low in the overstory (i.e. < 6 m2 ha−1). Our results highlight the importance of refining our operational management strategy to effectively limit the increasing abundance of regeneration of American beech over sugar maple in northern hardwood forests

Fishing at Arapus-Mangaasi, Efate, Vanuatu (2800-2200 BP): New methodological approaches and results

The Arapus-Mangaasi site, located on the north-west coast of the island of Efate, Vanuatu, and first settled around 2800 BP, was excavated between 1999 and 2003 within the framework of a joint Australian National University-Vanuatu National Museum research and training program. The site yielded not only a range of cultural material that allowed the re-interpretation of the Central Vanuatu ceramic sequence but also well-preserved faunal remains, including a substantial number of fish bones. The present study focuses on the analysis of the ichthyofauna recovered in the area of Arapus and on the assessment of the most efficient identification protocol with a view to obtain precise faunal data leading to the characterisation of the fishing economy. Out of a total of 8080 fish remains, 2387 were taxonomically identified. The general assemblage is composed of 23 families of marine fishes, belonging to the Teleostei and Elasmobranchii groups, and dominated by surgeonfishes (Acanthuridae), parrotfishes (Scaridae), and groupers (Serranidae). The study of vertebrae allowed the identification of most acanthurids and hence proved to be essential in obtaining a detailed inventory of the fish spectrum. The assemblage composition highlights the presence of a large variety of inshore and reef-associated taxa, likely to have been caught by means of polyvalent and broad-spectrum fishing gear, possibly mass capturing devices, such as nets or traps, combined with angling and/or spearing. The results also suggest an opportunistic exploitation of ichthyofaunal resources during the Arapus period (2800 BP) and a probable decrease in the consumption of fish from the beginning of the Erueti period (2800–2200 BP) onwards

Revisiting the Functional Zoning Concept under Climate Change to Expand the Portfolio of Adaptation Options

Climate change is threatening our ability to manage forest ecosystems sustainably. Despite strong consensus on the need for a broad portfolio of options to face this challenge, diversified management options have yet to be widely implemented. Inspired by functional zoning, a concept aimed at optimizing biodiversity conservation and wood production in multiple-use forest landscapes, we present a portfolio of management options that intersects management objectives with forest vulnerability to better address the wide range of goals inherent to forest management under climate change. Using this approach, we illustrate how different adaptation options could be implemented when faced with impacts related to climate change and its uncertainty. These options range from establishing ecological reserves in climatic refuges, where self-organizing ecological processes can result in resilient forests, to intensive plantation silviculture that could ensure a stable wood supply in an uncertain future. While adaptation measures in forests that are less vulnerable correspond to the traditional functional zoning management objectives, forests with higher vulnerability might be candidates for transformative measures as they may be more susceptible to abrupt changes in structure and composition. To illustrate how this portfolio of management options could be applied, we present a theoretical case study for the eastern boreal forest of Canada. Even if these options are supported by solid evidence, their implementation across the landscape may present some challenges and will require good communication among stakeholders and with the public

Fishing at Arapus-Mangaasi, Efate, Vanuatu (2800–2200 BP): New methodological approaches and results

International audienceThe Arapus-Mangaasi site, located on the northwest coast of the island of Efate, Vanuatu, and first settled around 2800 BP, was excavated between 1999 and 2003 within the framework of a joint Australian National University-Vanuatu National Museum research and training program. The site yielded not only a range of cultural material that allowed the re-interpretation of the Central Vanuatu ceramic sequence but also well-preserved faunal remains, including a substantial number of fish bones. The present study focuses on the analysis of the ichthyofauna recovered in the area of Arapus and on the assessment of the most efficient identification protocol with a view to obtain precise faunal data leading to the characterisation of the fishing economy. Out of a total of 8080 fish remains, 2387 were taxonomically identified. The general assemblage is composed of 23 families of marine fishes, belonging to the Teleostei and Elasmobranchii groups, and dominated by surgeonfishes (Acanthuridae), parrotfishes (Scaridae), and groupers (Serranidae). The study of vertebrae allowed the identification of most acanthurids and hence proved to be essential in obtaining a detailed inventory of the fish spectrum. The assemblage composition highlights the presence of a large variety of inshore and reef-associated taxa, likely to have been caught by means of polyvalent and broad-spectrum fishing gear, possibly mass capturing devices, such as nets or traps, combined with angling and/or spearing. The results also suggest an op-portunistic exploitation of ichthyofaunal resources during the Arapus period (2800 BP) and a probable decrease in the consumption of fish from the beginning of the Erueti period (2800-2200 BP) onwards