Aim
Climate‐induced range expansion ultimately implies recruitment at sites that were previously unoccupied by a species (i.e. colonization events). Using evidence on abiotic conditions and biotic ...interactions at these migration sites, we aimed to identify migration pathways from northern temperate to boreal forests for species showing northward range expansion.
Location
Quebec, Canada.
Taxon
Trees of northern temperate/boreal forests.
Methods
Using past (1970–1977) and recently updated (2003–2015) forest inventories across 761,100 km2, we first quantified latitudinal shifts for saplings of eight tree species and investigated colonization events at migration sites. We used field evidence and a consensus modelling approach to determine environmental suitability and identify edaphic, climatic and disturbance conditions, as well as species co‐occurrence patterns, characterizing recent colonization events. The results were interpreted in relation to novel species associations facilitating species migration in unsuitable landscapes.
Results
All species showed northward latitudinal shifts driven by increased recruitment and colonization northward. Colonization events occurred largely at historically unsuitable sites. Migration sites showed a shift towards humus types characteristic of the boreal forest and not typically found in the core range of most temperate species. Climatic conditions at migration sites were initially colder than at occupied sites, but warming suggests recent climatic suitability. A decrease in conifer basal area at migration sites following disturbances reduced priority effects that possibly constrained deciduous species establishment. Co‐occurrence patterns pointed to deciduous species tolerant of boreal edaphic conditions, leading the way for other temperate species.
Main conclusions
Temperate tree species can recruit into sites typical of boreal forests, even under environmentally challenging conditions. Warming and disturbances open up the way for some novel species associations that in turn have the potential to facilitate the recruitment of temperate species into the boreal forest, revealing migration pathways.
Climate change is expected to result in a reorganization of the continental distribution of tree species. Recent shifts in distribution patterns have been reported, but it is not always clear how ...climate change influences these patterns locally, especially in relation to other disturbances.
We investigated latitudinal shifts of four ecologically important tree species between 1970 and 2014 within a study area that encompasses their northernmost range limit in northeastern North America (Quebec, Canada; ~761,000 km2). Changes in latitudinal limits were defined in relation to changes in tree saplings’ occurrence patterns within forest plots resampled over two time periods (1970–1977 and 2003–2014). By examining changes in the frequency of occurrences in different portions of the study area along a latitudinal gradient, we were able to identify spatially explicit patterns of loss or gain (sapling recruitment) resulting in the shifts observed. We then estimated the probability of observing a recruitment event in response to changes in climate, disturbance and their interaction, using a multimodel selection approach.
Latitudinal limits of all four species shifted northward, but these shifts resulted from different patterns of plot occurrence changes, depending on the species and the location examined. Greater recruitment at northern locations than at southern ones drove shifts for Acer saccharum Marsh., Fagus grandifolia Ehrh. and Acer rubrum L., but less so for Betula alleghaniensis Britt. Climate variables indicating changes in early or late growing season conditions were most often selected in models. Warming tended to reduce recruitment probability in the south but increase it in the north, leading to divergent responses for a given species across the study area. Disturbance effects were generally less important than climate change effects, as was their interaction.
Synthesis. Spatially explicit and divergent responses to climate change and disturbance drive recruitment patterns underlying latitudinal shifts of tree species. The importance of early‐ or late‐season climate variables points towards biological processes being affected at critical stages of the life cycle. Understanding the factors that influence species’ migration capacity in a changing climate is crucial to inform adaptive management and conservation practices.
Spatially explicit and divergent responses to climate change and disturbance drive recruitment patterns underlying northward latitudinal shifts of four tree species at their range limit in northeastern North America. The importance of early‐ or late‐season climate variables points towards biological processes being affected at critical stages of the life cycle.
Ecologists are increasingly asking large‐scale and/or broad‐scope questions that require vast datasets. In response, various top‐down efforts and incentives have been implemented to encourage data ...sharing and integration. However, despite general consensus on the critical need for more open ecological data, several roadblocks still discourage compliance and participation in these projects; as a result, ecological data remain largely unavailable. Grassroots initiatives (i.e. efforts initiated and led by cohesive groups of scientists focused on specific goals) have thus far been overlooked as a powerful means to meet these challenges. These bottom‐up collaborative data integration projects can play a crucial role in making high quality datasets available because they tackle the heterogeneity of ecological data at a scale where it is still manageable, all the while offering the support and structure to do so. These initiatives foster best practices in data management and provide tangible rewards to researchers who choose to invest time in sound data stewardship. By maintaining proximity between data generators and data users, grassroots initiatives improve data interpretation and ensure high‐quality data integration while providing fair acknowledgement to data generators. We encourage researchers to formalize existing collaborations and to engage in local activities that improve the availability and distribution of ecological data. By fostering communication and interaction among scientists, we are convinced that grassroots initiatives can significantly support the development of global‐scale data repositories. In doing so, these projects help address important ecological questions and support policy decisions.
Ecologists increasingly ask broad questions that require vast datasets. Despite strong mobilization to make ecological data more open, most datasets remain unavailable. We highlight the overlooked role of bottom‐up collaborative initiatives in making high‐quality datasets available. Crucially, such initiatives can improve data management practices, data interoperability and interpretation, while addressing many of the sociocultural barriers to sharing data.
Overgeneral autobiographical memory (OGM) refers to the tendency toward increased general memory and reduced specific memory recall, observed in various psychiatric disorders. Previous studies have ...suggested that inhibitory processes involved in resolving competition between competing memories may reduce memory specificity via retrieval-induced forgetting (RIF). However, it remains unclear whether the repeated retrieval of general memories can induce forgetting of specific memories. We adapted the RIF paradigm to address this question across three experiments. Participants first generated specific memories in response to positively and negatively valenced cue words. They then generated and repeatedly retrieved general memories for half of the cue words. Recall for all of the original specific memories was later tested. Experiment 1 showed that the retrieval practice of general memories reduced the recall of associated specific memories, regardless of cue valence. Experiment 2 demonstrated that this forgetting effect was cue independent, occurring even when novel retrieval cues were used on the final test. Experiment 3 suggested that this effect was competition dependent, finding a greater RIF effect following practice of general memories (high competition) than following a cue-color association task (low competition). These results suggest that repeated retrieval of general memories suppressed specific memory representations through RIF. These findings are discussed in relation to hierarchical models of autobiographical memory, mechanisms that maintain overgeneral memory tendencies, and the role of retrieval in shaping autobiographical memory.
Aim
Species distribution models typically project climatically suitable habitat for trees in eastern North America to shift hundreds of kilometres this century. We simulated potential migration, ...accounting for various traits that affect species' ability to track climatically suitable habitat.
Location
Eastern Canada, covering ~3.7 million km2.
Methods
We simulated migration‐constrained range shifts through 2100 using a hybrid approach combining projections of climatically suitable habitat based on two Representative Concentration Pathways (RCP4.5, RCP8.5) for three time periods and two species distribution modelling approaches with process‐based models parameterized using data related to dispersal ability and generation time. We developed a unique “migration kernel” that uses seed dispersal traits and observed migration velocities to obtain kernel shape and dispersal probabilities for each tree species. We then calculated lags between the migration‐constrained range limits obtained through simulations and limits of climatically suitable habitat.
Results
All species demonstrated northward range shifts at the leading edge of their simulated distribution through 2100, but the magnitude and rate of that shift varied by species and time period. Climatically suitable habitat limits were found to be north of simulated distribution limits across both RCPs, with lags increasing through time. On average, simulated distribution that remained within climatically suitable habitat declined more under RCP8.5 than RCP4.5, with large areas of the rear edge of the simulated distribution becoming partially or completely climatically unsuitable for many species.
Main conclusions
Climatically suitable habitat limits projected for 2100 far exceeded migration‐constrained range limits for all 10 tree species, particularly for temperate species. This study underlines the limited extent to which tree species will track climate change via natural migration. Integrating observed migration velocities, seed dispersal and generation time with SDM outputs allows for more realistic evaluations of tree migration ability under climate change and may help orient forest conservation and restoration efforts.
Depressive disturbances are common in patients with Parkinson’s disease (PD) and influence many other clinical aspects of the disease. In addition to causing inherent emotional distress, depressive ...disorders negatively impact quality of life, motor and cognitive deficits, functional disability, and other psychiatric comorbidities in patients with PD. Knowledge of the pathophysiology of PD depression remains limited. However, clinical studies demonstrate the efficacy of medications and psychotherapies for PD depression, underscoring the importance of their timely detection and concerted management.
Anxiety disturbances are recognized as common psychiatric comorbidities in Parkinson’s disease (PD) and contribute to significant impairments in areas of cognitive, functional, motor and social ...performance. Anxiety in PD results in reduced quality of life, higher levels of care dependency and increased caregiver burden. Surprisingly, there is a paucity of treatment data. In one randomized, controlled study, bromazepam was found to be effective for anxiety in PD. However, usage of benzodiazepines in the PD population is limited by potential risk of confusion and falls. There are no controlled studies of selective serotonin reuptake inhibitors (SSRIs) for anxiety in PD. However, results from uncontrolled studies suggest that SSRIs are effective for anxiety in PD, although in these studies anxiety outcomes were secondary. This review underscores that, given the high prevalence of anxiety disturbances in PD, there is a significant paucity of treatment data for this population. Additional studies are warranted. In the meantime, clinicians should rely on empiric assessments of known risks and putative benefits to guide treatment decisions. Cognitive and behavioral therapies (with or without pharmacotherapy) have demonstrated efficacy and warrant consideration. When feasible, a targeted and individualized multimodal approach utilizing psychotherapeutic interventions along with pharmacologic therapies should be considered.
The management of delayed cerebral ischemia after aneurysmal subarachnoid hemorrhage (aSAH) remains one of the most important targets for neurocritical care. Advances in monitoring technology have ...facilitated a more thorough understanding of the pathophysiology and therapeutic approaches, but interventions are generally limited to either systemic therapies or passive CSF drainage. The authors present a novel approach that combines a multimodal monitoring bolt-based system with an irrigating ventricular drain capable of delivering intrathecal medications and describe their early experience in patients with aSAH.
The authors performed a retrospective review of cases treated with the combined Hummingbird multimodal bolt system and the IRRAflow irrigating ventriculostomy.
Nine patients were treated with the combined multimodal bolt system with irrigating ventriculostomy approach. The median number of days to clearance of the third and fourth ventricles was 3 days in patients with obstructive intraventricular hemorrhage. Two patients received intrathecal alteplase for intraventricular hemorrhage clearance, and 2 patients received intrathecal nicardipine as rescue therapy for severe symptomatic angiographic vasospasm.
Combined CSF drainage, irrigation, multimodality monitoring, and automated local drug delivery are feasible using a single twist-drill hole device. Further investigation of irrigation settings and treatment approaches in high-risk cases is warranted.
Intraspecific trait variability (ITV) provides the material for species' adaptation to environmental changes. To advance our understanding of how ITV can contribute to species' adaptation to a wide ...range of environmental conditions, we studied five widespread understorey forest species exposed to both continental‐scale climate gradients, and local soil and disturbance gradients. We investigated the environmental drivers of between‐site leaf and root trait variation, and tested whether higher between‐site ITV was associated with increased trait sensitivity to environmental variation (i.e. environmental fit).
We measured morphological (specific leaf area: SLA, specific root length: SRL) and chemical traits (Leaf and Root N, P, K, Mg, Ca) of five forest understorey vascular plant species at 78 sites across Canada. A total of 261 species‐by‐site combinations spanning ~4300 km were sampled, capturing important abiotic and biotic environmental gradients (neighbourhood composition, canopy structure, soil conditions, climate). We used multivariate and univariate linear mixed models to identify drivers of ITV and test the association of between‐site ITV with environmental fit.
Between‐site ITV of leaf traits was primarily driven by canopy structure and climate. Comparatively, environmental drivers explained only a small proportion of variability in root traits: these relationships were trait specific and included soil conditions (Root P), canopy structure (Root N) and neighbourhood composition (SRL, Root K). Between‐site ITV was associated with increased environmental fit only for a minority of traits, primarily in response to climate (SLA, Leaf N, SRL).
Synthesis. By studying how ITV is structured along environmental gradients among species adapted to a wide range of conditions, we can begin to understand how individual species might respond to environmental change. Our results show that generalisable trait–environment relationships occur primarily aboveground, and only accounted for a small proportion of variability. For our group of species with broad ecological niches, variability in traits was only rarely associated with higher environmental fit, and primarily along climatic gradients. These results point to promising research avenues on the various ways in which trait variation can affect species' performance along different environmental gradients.
Résumé
La variabilité intraspécifique des traits (VIT) fournit le matériel nécessaire à l'adaptation des espèces aux changements environnementaux. Pour mieux comprendre comment la VIT peut contribuer à l'adaptation des espèces à un large éventail de conditions environnementales, nous avons étudié cinq espèces forestières de sous‐bois très répandues, exposées à la fois à des gradients climatiques à l'échelle continentale et à des gradients locaux de conditions édaphiques et de perturbation. Nous avons étudié les déterminants environnementaux de la variation intraspécifique des traits foliaires et racinaires. Nous avons ensuite testé si une VIT inter‐site (d'un site à l'autre) plus élevée était associée à une sensibilité accrue des traits à la variation environnementale (c.‐à‐d. un ajustement environnemental).
Nous avons mesuré les traits morphologiques (surface foliaire spécifique, SFS; longueur racinaire spécifique, LRS) et chimiques (N, P, K, Mg, Ca des feuilles et des racines) de cinq espèces vasculaires de sous‐bois dans 78 sites au Canada. Un total de 261 combinaisons d'espèces par site couvrant approx. 4300 km a été échantillonné, représentant d'importants gradients abiotiques et biotiques (composition du voisinage, structure de la canopée, conditions du sol, climat). Nous avons utilisé des modèles linéaires mixtes univariés et multivariés pour identifier les déterminants de la VIT inter‐site et tester l'association de la VIT inter‐site avec l'ajustement environnemental.
La VIT inter‐site des traits foliaires était principalement déterminée par la structure de la canopée et le climat. En comparaison, les facteurs environnementaux n'expliquaient qu'une faible proportion de la variabilité des traits racinaires : ces relations étaient spécifiques à chaque trait, incluant les conditions du sol (P racinaire), la structure de la canopée (N racinaire) et la composition du voisinage (LRS, K racinaire). La VIT inter‐site n'était associée à un ajustement environnemental accru que pour une minorité de traits, principalement en réponse au climat (SFS, N foliaire, LRS).
Synthèse. En étudiant la façon dont la VIT est structurée le long des gradients environnementaux parmi des espèces adaptées à un large éventail de conditions, nous pouvons commencer à comprendre comment ces espèces peuvent répondre aux changements environnementaux. Nos résultats montrent que des associations trait‐environnement généralisables existent principalement au‐dessus du sol et ne représentent qu'une faible proportion de la variabilité. Pour notre groupe d'espèces ubiquistes, la variabilité des traits n'était que rarement associée à un meilleur ajustement environnemental, et principalement le long des gradients climatiques. Ces résultats soulèvent des pistes de recherche prometteuses sur les différentes façons dont la variation des traits peut affecter la performance des espèces le long de différents gradients environnementaux.
By studying how ITV is structured along environmental gradients among species adapted to a wide range of conditions, we can begin to understand how individual species might respond to environmental change. Our results show that generalisable trait–environment relationships occur primarily aboveground, and only accounted for a small proportion of variability. For our group of species with broad ecological niches, variability in traits was only rarely associated with higher environmental fit, and primarily along climatic gradients. These results point to promising research avenues on the various ways in which trait variation can affect species' performance along different environmental gradients.
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