Divergence of Arctic shrub growth associated with sea ice decline

Arctic sea ice extent (SIE) is declining at an accelerating rate with a wide range of ecological consequences. However, determining sea ice effects on tundra vegetation remains a challenge. In this study, we examined the universality or lack thereof in tundra shrub growth responses to changes in SIE and summer climate across the Pan-Arctic, taking advantage of 23 tundra shrub-ring chronologies from 19 widely distributed sites (56°N to 83°N). We show a clear divergence in shrub growth responses to SIE that began in the mid-1990s, with 39% of the chronologies showing declines and 57% showing increases in radial growth (decreasers and increasers, respectively). Structural equation models revealed that declining SIE was associated with rising air temperature and precipitation for increasers and with increasingly dry conditions for decreasers. Decreasers tended to be from areas of the Arctic with lower summer precipitation and their growth decline was related to decreases in the standardized precipitation evapotranspiration index. Our findings suggest that moisture limitation, associated with declining SIE, might inhibit the positive effects of warming on shrub growth over a considerable part of the terrestrial Arctic, thereby complicating predictions of vegetation change and future tundra productivity

Growth rings show limited evidence for ungulates' potential to suppress shrubs across the Arctic

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across the Arctic tundra biome, we assembled dendroecological data from 20 sites, comprising 1153 individual shrubs and 223 63 annual growth rings. Evidence for ungulates suppressing shrub radial growth was only observed at intermediate summer temperatures (6.5 degrees C-9 degrees C), and even at these temperatures the effect was not strong. Multiple factors, including forage preferences and landscape use by the ungulates, and favourable climatic conditions enabling effective compensatory growth of shrubs, may weaken the effects of ungulates on shrubs, possibly explaining the weakness of observed ungulate effects. Earlier local studies have shown that ungulates may counteract the impacts of warming on tundra shrub growth, but we demonstrate that ungulates' potential to suppress shrub radial growth is not always evident, and may be limited to certain climatic conditions

Determinants of the access to remote specialised services provided by national sarcoma reference centres

BACKGROUND: Spatial inequalities in cancer management have been evidenced by studies reporting lower quality of care or/and lower survival for patients living in remote or socially deprived areas. NETSARC+ is a national reference network implemented to improve the outcome of sarcoma patients in France since 2010, providing remote access to specialized diagnosis and Multidisciplinary Tumour Board (MTB). The IGéAS research program aims to assess the potential of this innovative organization, with remote management of cancers including rare tumours, to go through geographical barriers usually impeding the optimal management of cancer patients. METHODS: Using the nationwide NETSARC+ databases, the individual, clinical and geographical determinants of the access to sarcoma-specialized diagnosis and MTB were analysed. The IGéAS cohort (n = 20,590) includes all patients living in France with first sarcoma diagnosis between 2011 and 2014. Early access was defined as specialised review performed before 30 days of sampling and as first sarcoma MTB discussion performed before the first surgery. RESULTS: Some clinical populations are at highest risk of initial management without access to sarcoma specialized services, such as patients with non-GIST visceral sarcoma for diagnosis [OR 1.96, 95% CI 1.78 to 2.15] and MTB discussion [OR 3.56, 95% CI 3.16 to 4.01]. Social deprivation of the municipality is not associated with early access on NETSARC+ remote services. The quintile of patients furthest away from reference centres have lower chances of early access to specialized diagnosis [OR 1.18, 95% CI 1.06 to 1.31] and MTB discussion [OR 1.24, 95% CI 1.10 to 1.40] but this influence of the distance is slight in comparison with clinical factors and previous studies on the access to cancer-specialized facilities. CONCLUSIONS: In the context of national organization driven by reference network, distance to reference centres slightly alters the early access to sarcoma specialized services and social deprivation has no impact on it. The reference networks' organization, designed to improve the access to specialized services and the quality of cancer management, can be considered as an interesting device to reduce social and spatial inequalities in cancer management. The potential of this organization must be confirmed by further studies, including survival analysis

Growth rings show limited evidence for ungulates’ potential to suppress shrubs across the Arctic

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across the Arctic tundra biome, we assembled dendroecological data from 20 sites, comprising 1153 individual shrubs and 223 63 annual growth rings. Evidence for ungulates suppressing shrub radial growth was only observed at intermediate summer temperatures (6.5 ◦C–9 ◦C), and even at these temperatures the effect was not strong. Multiple factors, including forage preferences and landscape use by the ungulates, and favourable climatic conditions enabling effective compensatory growth of shrubs, may weaken the effects of ungulates on shrubs, possibly explaining the weakness of observed ungulate effects. Earlier local studies have shown that ungulates may counteract the impacts of warming on tundra shrub growth, but we demonstrate that ungulates’ potential to suppress shrub radial growth is not always evident, and may be limited to certain climatic conditions.Research Council of Norwayhttp://iopscience.iop.org/1748-9326dm2022Mammal Research InstituteZoology and Entomolog

Réponse du bouleau glanduleux (Betula glandulosa Michx.) aux changements climatiques récents : implications pour l'écotone forêt boréale-toundra, Nunavik

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2015-2016Au cœur des changements environnementaux enregistrés dans les régions arctiques et subarctiques, la densification de la strate arbustive est probablement l’un des plus importants. Cette thèse propose d’en étudier la dynamique récente à l’écotone forêt boréale-toundra (Nunavik) afin de mieux en cerner les causes et d’en évaluer les conséquences. Dans un premier temps, la comparaison d’images aériennes (1957 et 2008) nous révèle une densification importante de la strate arbustive dans la région d’étude. Largement attribuée à Betula glandulosa, cette densification a été plus importante sur les terrasses que sur les sommets et hétérogène à l’échelle du paysage. Par la suite, je me suis attardée aux causes de l’hétérogénéité de la densification de la strate arbustive et ai trouvé que celle-ci était principalement attribuable à un ensemble de facteurs historiques et topographiques. De plus, j’ai pu montrer que la densification de la strate arbustive a une influence négative sur l’abondance des espèces arbustives non impliquées dans ce phénomène, mais qu’aucune relation n’a été décelée avec la diversité spécifique (richesse spécifique et indice de diversité de Shannon). Finalement, j’ai montré que la croissance radiale et axiale de B. glandulosa était fortement associée aux températures estivales chez les individus établis sur des sites bien drainés et aux précipitations hivernales chez ceux établis dans les combes à neige (milieu mal drainé où la neige persiste dans la saison de croissance). De surcroît, la forte augmentation de la croissance radiale de B. glandulosa entre 1990 et 2002 suggère que la densification de la strate arbustive observée dans la région d’étude est un phénomène récent. En somme, cette thèse a permis de mieux comprendre la dynamique de l’écotone forêt boréale-toundra au Québec subarctique dans un contexte de changements climatiques. Elle a aussi contribué à saisir toute l’importance d’une analyse à fine échelle de la croissance des espèces impliquées dans la densification de la strate arbustive ainsi qu’à approfondir nos connaissances sur une espèce structurante du Québec subarctique, B. glandulosa.One of the major changes observed in northern terrestrial regions in response to climate change is arguably the recent shrub expansion. This thesis aims to study the recent dynamic of the shrub expansion at the forest tundra ecotone, northern Québec, in order to find its causes and evaluate its consequences on plant community. First, I compared two sets of aerial photographs (taken in 1957 and 2008) and found an increase in shrub cover that was mainly attributed to Betula glandulosa, a largely distributed erect shrub species. This increase was higher on terraces than on hilltops and strongly heterogeneous at the regional scale. Second, I found that the heterogeneity of the shrub expansion depended on both historical and topographic variables. Moreover, I showed that an increase in B. glandulosa cover had a negative influence on the abundance of other shrub species, but not on their diversity (species richness and Shannon diversity index). Finally, I found that B. glandulosa radial and axial growth were strongly associated with summer temperature when growing on well-drained sites, whereas they were mainly associated with winter precipitation when growing in snowbeds (well-watered sites where snow cover persist in the growing season). Dendrochronological analyses showed a sharp B. glandulosa growth increase between 1990 and 2002, therefore suggesting that the shrub expansion observed in the study region is quite recent. Overall, this thesis significantly improved our knowledge of the recent dynamic of the forest tundra ecotone in northern Québec. It also contributed to underline the importance of studying shrub expansion at the local scale and to improve our knowledge of B. glandulosa

Le rôle des herbivores vertébrés sur la dynamique des communautés végétales au Nunavik

Les changements environnementaux influencent la végétation nordique, mais également les herbivores qui s’en nourrissent. Comme ces changements s’accentueront, un état de la situation au Nunavik (Québec, Canada) devient nécessaire. Nous discutons ici de l’influence qu’exercent les herbivores vertébrés sur les communautés végétales, et décrivons l’état des populations des deux principales espèces d’herbivores de cette guilde au Nunavik. Réparti en deux troupeaux, le caribou migrateur (Rangifer tarandus) est un élément structurant des écosystèmes du Nunavik. À forte densité, il peut réduire la productivité végétale dans son aire d’estivage et limiter la croissance des espèces consommées. Espèce introduite dans les années 1960, le boeuf musqué (Ovibos moschatus) colonise maintenant l’essentiel des côtes de la région. Quoiqu’il soit connu pour limiter l’expansion arbustive ailleurs dans l’Arctique, l’influence du bovidé au Nunavik demeure marginale jusqu’à maintenant. Sauf pour la bernache du Canada (Branta canadensis) qui niche en grandes colonies, l’influence des autres herbivores vertébrés sur les communautés végétales sera vraisemblablement localisée. L’augmentation du couvert arbustif procure des ressources alimentaires et un abri à diverses espèces qui pourraient voir leur aire de répartition se déplacer vers le nord. Les préférences alimentaires de ces herbivores pourraient moduler la réponse des espèces végétales aux changements climatiques.Environmental changes influence northern plant communities and the populations of herbivores that feed on them. Given the predicted increased rates of change in the north, it is essential to understand the situation in Nunavik (Québec, Canada). This review outlines the influence of vertebrate herbivores on plant communities and describes the population status of the two main members of this guild in the region. The migratory caribou (Rangifer tarandus) is a keystone species, and two herds are present. At high densities, it can reduce plant productivity in its summer range and limit the growth of the species consumed. The muskox (Ovibos moschatus), which was introduced in the 1960s, has now colonized most of the region’s coastal area. Although it may limit shrub expansion elsewhere in the Arctic, to date, its influence in Nunavik remains marginal. Except for the Canada goose (Branta canadensis), which nests in large colonies, the impact of other vertebrate herbivores on plant communities is likely localized. Increases in shrub cover will provide food and shelter for various herbivores that may experience a northward shift in range. Finally, the food preferences of herbivores present in Nunavik is expected to influence the response of plant species to climate change

Compendium de recherche 2017-2022 environnement, santé, innovation

Dans le contexte d'un changement climatique et d'un développement socio-économique accéléré dans l'Arctique et le Subarctique, le programme de recherche Sentinelle Nord de l'Université Laval contribue à la génération des connaissances nécessaires pour améliorer notre compréhension de l'environnement nordique en évolution et de son impact sur les humains et leur santé. Aborder les problèmes complexes résultant de ces changements nécessite une approche de recherche qui transcende les frontières disciplinaires traditionnelles. Sentinelle Nord favorise la convergence d'expertises en ingénierie, sciences naturelles, sociales et de la santé pour catalyser la découverte scientifique et l'innovation en soutien à une santé et un développement durables dans le Nord. Ce recueil rassemble une sélection de résultats de recherche du programme Sentinelle Nord de 2017 à 2022. Les résultats ont été intégrés dans cinq chapitres interdisciplinaires abordant les principaux enjeux nordiques

Compendium of research 2017-2022 : environment, health, innovation

In the context of accelerating climate change and socioeconomic development in the Arctic and Subarctic, the Sentinel North research program at Université Laval helps generate the knowledge needed to improve our understanding of the changing northern environment and its impact on humans and their health. Addressing the complex issues brought on by these changes requires a research approach that transcends traditional disciplinary boundaries. Sentinel North fosters the convergence of expertise in the engineering, natural, social and health sciences to catalyze scientific discovery and innovation in support of sustainable health and development in the North. This compendium gathers a selection of research results from the Sentinel North program from 2017 to 2022. Results have been integrated into five interdisciplinary chapters addressing major northern issues

Terrestrial ecosystem dynamics and responses to change

Arctic and Subarctic terrestrial ecosystems face significant ecological changes in response to climate shifts. In recent decades, a widespread yet heterogenous greening has been observed. This greening trend occurs at the expense of the natural flora of slow-growing plants, mosses and lichens. Some of these plants have developed unique biochemical adaptations to protect themselves from the harsh conditions, including bioactive molecules with pharmaceutical applications. As their growth and distribution patterns are changing, there is an urgent need to describe the ensemble of phytochemicals that these plants produce. While climate change impacts species at the individual level, it will also impact the network of trophic links relating the different species within an ecosystem. A spatial or temporal mismatch may separate previously interacting species, while novel interactions may appear due to new spatial co-occurrences. Through modelling, researchers can better predict the effects that different climate change scenarios will have on species distributions, and thus on species interactions. The work by Sentinel North research teams described in this chapter looks at the threatened chemodiversity of Arctic and subarctic plant species; the tundra ecosystem greening trend and its multifaceted impacts; the changing animal communities and the development of new technologies to monitor them; the modelling approaches to predict ecosystem interactions, vulnerability, and resilience; and the challenges facing northern biodiversity conservation

Des molécules aux réseaux trophiques : dynamique des écosystèmes terrestres du Nord en réponse aux changements environnementaux

Les écosystèmes terrestres arctiques et subarctiques font face à d’importantes transformations écologiques en réponse aux changements climatiques. Au cours des dernières décennies, un verdissement (greening) généralisé mais hétérogène a été observé. Ce verdissement se produit au détriment de la flore à croissance lente, de la mousse et des lichens de la toundra. Pourtant, certaines de ces plantes ont développé des adaptations biochimiques uniques pour se protéger des conditions difficiles auxquelles elles font face, y compris des molécules bioactives ayant des applications pharmaceutiques. Alors que leurs patrons de croissance et répartition sont en pleine mutation, il devient urgent de décrire les substances phytochimiques produites par ces plantes. Bien que les changements climatiques aient une incidence sur les espèces, ils en ont également sur le réseau de liens trophiques qu’entretiennent ces dernières au sein d’un écosystème. Un découplage spatial ou temporel peut séparer des espèces qui interagissaient auparavant, tandis que de nouvelles interactions peuvent apparaître en raison de nouvelles cooccurrences spatiales. Grâce à la modélisation, les chercheurs peuvent mieux prévoir les effets que les différents scénarios de changement climatique auront sur la répartition des espèces, et donc sur leurs interactions. Les travaux des équipes de Sentinelle Nord décrits dans ce chapitre portent sur la chimiodiversité menacée des espèces végétales arctiques et subarctiques, sur l’arbustation de la toundra et ses impacts multiples, sur l'évolution des communautés animales et le développement de nouvelles technologies pour les surveiller, sur les approches de modélisation visant à prévoir les interactions, la vulnérabilité et la résilience des écosystèmes, ainsi que sur les défis à relever en matière de conservation de la biodiversité nordique