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Remnant populations of Betula papyrifera Marshall have persisted in the Great Plains after the Wisconsin Glaciation along the Niobrara River Valley, Nebraska. Population health has declined in recent years, which has been hypothesized to be due to climate change. We used dendrochronological techniques to assess the response of B. papyrifera to microclimate (1950-2014) and the normalized difference vegetation index (NDVI) derived from satellite imagery (Landsat 5 TM (1985-2011) and MODIS (2000-2014)) as a proxy for population health. Growing-season streamflow and precipitation were positively correlated with raw and standardized tree-ring widths and basal area increment increase. Increasing winter and spring temperatures were unfavorable for tree growth, while increasing summer temperatures were favorable in the absence of drought. The strongest predictor for standardized tree rings was the Palmer Drought Severity Index, suggesting that B. papyrifera is highly responsive to a combination of temperature and water availability. The NDVI from the vegetation community was positively correlated with standardized tree-ring growth, indicating the potential of these techniques to be used as a proxy for ex situ monitoring of B. papyrifera. These results aid in forecasting the dynamics of the species in the face of climate variability and change in both remnant populations and across its current distribution in northern latitudes of North America. Key words: paper birch, tree rings, riparian, MODIS, Landsat, NDVI, water, temperature, Nebraska Sandhills. Des populations reliques de Betula papyrifera Marshall ont persiste dans les grandes plaines apres la glaciation du Wisconsin le long de la vallee de la riviere Niobrara, au Nebraska. L'etat de sante des populations s'est deteriore au cours des recentes annees, vraisemblablement a cause des changements climatiques. Nous avons utilise les techniques dendrochronologiques pour evaluer la reaction de B. papyrifera au microclimat (1950-2014), ainsi que l'indice de vegetation NDVI derive de l'imagerie satellitaire (Landsat 5 TM (1985-2011) et MODIS (2000-2014)) en tant que substitut refletant l'etat de sante des populations. La precipitation et l'ecoulement fluvial durant la saison se croissance etaient positivement correles avec l'augmentation de l'accroissement de la surface terriere et la largeur brute et standardisee des cernes annuels. L'augmentation des temperatures hivernales et printanieres etait defavorable pour la croissance des arbres tandis que l'augmentation des temperatures estivales etait favorable en l'absence de secheresse. Le meilleur predicteur pour les cernes annuels standardises etait l'indice de severite de la secheresse de Palmer, ce qui indique que B. papyrifera est tres sensible aune combinaison de temperature et de disponibilite de l'eau. L'indice NDVI de la communaute vegetale etait positivement correle a la croissance des cernes annuels standardises, ce qui indique que ces techniques peuvent etre utilisees comme substitut pour le suivi ex situ de B. papyrifera. Ces resultats vont aider a predire la dynamique de cette espece face aux changements climatiques tant dans les populations reliques que partout dans son aire de repartition actuelle sous les latitudes septentrionales de l'Amerique du Nord. [Traduit par la Redaction] Mots-cles: bouleau blanc, cernes annuels, riverain, MODIS, Landsat, indice de vegetation NDVI, eau, temperature, dunes du Nebraska., 1. Introduction Paper birch (Betula papyrifera Marshall) is a widely distributed deciduous tree species across continental North America. It grows in the boreal forest from Newfoundland in eastern Canada all [...]

Background: Many youth saw a rise in body mass index and obesity during the COVID-19 pandemic associated with virtual schooling and a lack of physical exercise options due to lockdown orders. However, the impact of the worldwide COVID-19 pandemic on body mass index in HIV-infected youth on anti-viral therapy has not been studied., Objective: This study examined COVID-19's impact on body mass index in 157 behaviorally acquired and 39 perinatally acquired youth living with HIV., Methods: Retrospective chart analysis was conducted for body mass index records across pre-COVID, COVID, and post-COVID periods., Results: Age and acquired type showed significant associations with increased body mass index. Limitations included missing data and physiological body mass index changes., Conclusion: The perinatally acquired group's body mass index increased by 1.6 during and 2.3 post-pandemic compared to pre-pandemic levels. Longitudinal follow-up of body mass index changes is needed in this vulnerable population., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2024.)

Macroclimate drives vegetation distributions, but fine-scale topographic variation can generate microclimate refugia for plant persistence in unsuitable areas. However, we lack quantitative descriptions of topography-driven microclimatic variation and how it shapes forest structure, diversity, and composition. We hypothesized that topographic variation and the presence of the forest overstory cause spatiotemporal microclimate variation affecting tree performance, causing forest structure, diversity, and composition to vary with topography and microclimate, and topography and the overstory to buffer microclimate. In a 20.2-ha inventory plot in the North American Great Plains, we censused woody stems ≥1 cm in diameter and collected detailed topographic and microclimatic data. Across 59-m of elevation, microclimate covaried with topography to create a sharp desiccation gradient, and topography and the overstory buffered understory microclimate. The magnitude of microclimatic variation mirrored that of regional-scale variation: with increasing elevation, there was a decrease in soil moisture corresponding to the difference across ~2.1° of longitude along the east-to-west aridity gradient and an increase in air temperature corresponding to the difference across ~2.7° of latitude along the north-to-south gradient. More complex forest structure and higher diversity occurred in moister, less-exposed habitats, and species occupied distinct topographic niches. Our study demonstrates how topographic and microclimatic gradients structure forests in putative climate-change refugia, by revealing ecological processes enabling populations to be maintained during periods of unfavorable macroclimate., Competing Interests: The authors have no conflicts of interest to declare., (© 2024 The Authors. Plant‐Environment Interactions published by John Wiley & Sons Ltd and New Phytologist Foundation.)

Background: A previously proposed immune risk profile (IRP), based on T cell phenotype and CMV serotype, is associated with mortality in the elderly and increased infections post-kidney transplant. To evaluate if NK cells contribute to the IRP and if the IRP can be predicted by a clinical T cell functional assays, we conducted a cross sectional study in renal transplant candidates to determine the incidence of IRP and its association with specific NK cell characteristics and ImmuKnow® value. Material and Methods: Sixty five subjects were enrolled in 5 cohorts designated by age and dialysis status. We determined T and NK cell phenotypes by flow cytometry and analyzed multiple factors contributing to IRP. Results: We identified 14 IRP+ [CMV seropositivity and CD4/CD8 ratio < 1 or being in the highest quintile of CD8+ senescent (28CD-/CD57+) T cells] individuals equally divided amongst the cohorts. Multivariable linear regression revealed a distinct IRP+ group. Age and dialysis status did not predict immune senescence in kidney transplant candidates. NK cell features alone could discriminate IRP- and IRP+ patients, suggesting that NK cells significantly contribute to the overall immune status in kidney transplant candidates and that a combined T and NK cell phenotyping can provide a more detailed IRP definition. ImmuKnow® value was negatively correlated to age and significantly lower in IRP+ patients and predicts IRP when used alone or in combination with NK cell features. Conclusion: NK cells contribute to overall immune senescence in kidney transplant candidates.