Large herbivore diversity slows sea ice-associated decline in arctic tundra diversity.

Biodiversity is declining globally in response to multiple human stressors, including climate forcing. Nonetheless, local diversity trends are inconsistent in some taxa, obscuring contributions of local processes to global patterns. Arctic tundra diversity, including plants, fungi, and lichens, declined during a 15-year experiment that combined warming with exclusion of large herbivores known to influence tundra vegetation composition. Tundra diversity declined regardless of experimental treatment, as background growing season temperatures rose with sea ice loss. However, diversity declined slower with large herbivores than without them. This difference was associated with an increase in effective diversity of large herbivores as formerly abundant caribou declined and muskoxen increased. Efforts that promote herbivore diversity, such as rewilding, may help mitigate impacts of warming on tundra diversity.

Late surgical start time is associated with increased blood transfusion following gastric bypass surgery.

BACKGROUND: Surgical start time (SST) has demonstrated conflicting effects on perioperative outcomes due to confounding factors, such as increased acuity in later SST cases. This study investigated the effect of SST on blood transfusion after gastric bypass surgery, a complication-prone elective surgical procedure. METHODS: This retrospective cohort study included all patients undergoing gastric bypass surgery at a single academic medical center from 2016 through 2021 (n = 299). The primary independent variable was SST (before vs. after 15:00). The primary outcome was blood transfusion. Secondary outcomes included postoperative respiratory failure, length of stay, acute kidney injury, and mortality. The associations between SST and outcomes were investigated with univariate analyses. Multivariate and receiver operating characteristic (ROC) analyses were applied to the primary outcome, adjusting for demographic and operative characteristics. RESULTS: On univariate analysis, 15:00-18:43 SST was associated with an increased risk of blood transfusion (relative risk 4.32, 95% confidence interval 1.27 to 14.63, p = 0.032), but not postoperative respiratory failure, acute kidney injury, length of stay, or mortality. On multivariate analysis, the only independent predictor of postoperative blood transfusion was a 15:00-18:43 SST (adjusted odds ratio 4.32, 95% confidence interval 1.06 to 15.96, c-statistic = 0.638). ROC analysis demonstrated that compared to the 15:00 threshold, a 14:34 threshold predicted postoperative blood transfusion with better accuracy (sensitivity = 70.0%, specificity = 83.0%). CONCLUSIONS: Despite having similar demographic and operative characteristics, gastric bypass patients in the late SST cohort had a greater incidence of postoperative blood transfusion in this single-center study.

Large herbivores facilitate the persistence of rare taxa under tundra warming.

Ecological rarity, characterized by low abundance or limited distribution, is typical of most species, yet our understanding of what factors contribute to the persistence of rare species remains limited. Consequently, little is also known about whether rare species might respond differently than common species to direct (e.g., abiotic) and indirect (e.g., biotic) effects of climate change. We investigated the effects of warming and exclusion of large herbivores on 14 tundra taxa, three of which were common and 11 of which were rare, at an inland, low-arctic study site near Kangerlussuaq, Greenland. Across all taxa, pooled commonness was reduced by experimental warming, and more strongly under herbivore exclusion than under herbivory. However, taxon-specific analyses revealed that although warming elicited variable effects on commonness, herbivore exclusion disproportionately reduced the commonness of rare taxa. Over the 15-year duration of the experiment, we also observed trends in commonness and rarity under all treatments through time. Sitewide commonness increased for two common taxa, the deciduous shrubs Betula nana and Salix glauca, and declined in six other taxa, all of which were rare. Rates of increase or decline in commonness (i.e., temporal trends over the duration of the experiment) were strongly related to baseline commonness of taxa early in the experiment under all treatments except warming with grazing. Hence, commonness itself may be a strong predictor of species' responses to climate change in the arctic tundra biome, but large herbivores may mediate such responses in rare taxa, perhaps facilitating their persistence.

Earlier spring reduces potential for gene flow via reduced flowering synchrony across an elevational gradient.

PREMISE: One of the best-documented ecological responses to climate warming involves temporal shifts of phenological events. However, we lack an understanding of how phenological responses to climate change vary among populations of the same species. Such variability has the potential to affect flowering synchrony among populations and hence the potential for gene flow. METHODS: To test whether an earlier start of the growing season affects the potential for gene flow among populations, we quantified the distributions of flowering times of two spring-flowering plants (Trillium erectum and Erythronium americanum) over 6 years along an elevational gradient. We developed a novel model-based metric of potential gene flow between pairs of populations to quantify the potential for pollen-mediated gene flow based on flowering phenology. RESULTS: Earlier onset of spring led to greater separation of peak flowering dates across the elevational gradient for both species investigated, but was only associated with a reduction in potential gene flow in T. erectum, not E. americanum. CONCLUSIONS: Our study suggests that climate change could decrease gene flow via phenological separation among populations along climatic gradients. We also provide a novel method for quantifying potential pollen-mediated gene flow using data on flowering phenology, based on a quantitative, more biologically interpretable model than other available metrics.

Technical Note: Use of commercial multilayer Faraday cup for offline daily beam range verification at the McLaren Proton Therapy Center.

PURPOSE: Daily verification of the proton beam range in proton radiation therapy is a vital part of the quality assurance (QA) program. The objective of this work is to study the use of a multilayer Faraday cup (MLFC) to perform a quick and precise daily range verification of proton beams produced by a synchrotron. METHODS: Proton beam depth dose measurements were performed at room iso-center in water using PTW water tank and Bragg Peak ion chamber. The IBA Giraffe, calibrated against the water tank data, was used to measure the water equivalent thickness (WET) of the sample copper plates. The WET measurements provided the range calibration factors for the MLFC. To establish a baseline for in room measurements, range measurements for energies from 70 to 250 MeV in steps of 10 MeV were performed using the Pyramid MLFC at room iso-center. For the daily range verification measurements, the MLFC is permanently placed at the end of the beam line, inside the accelerator vault. The daily range constancy is performed for five representative beam energies; namely 70, 100, 150, 200, and 250 MeV. Data collected over a period of more than 100 days are analyzed and presented. RESULTS: The measured WET values of the copper plates increased with increasing energy. The centroid channel number in the MLFC where the protons stop, was converted to depth in water and compared to the depth of the distal 80% (d80) obtained from the water tank measurements. The depths agreed to within 2 mm, with the maximum deviation of 1.97 mm observed for 250 MeV beam. The daily variation in the ranges measured by the MLFC was within ±0.5 mm. The total time to verify five proton beam ranges varies between 4 and 5 min. CONCLUSION: Based on the result of our measurements, the MLFC can be used for a daily range constancy check with submillimeter accuracy. It is a quick and simple method to perform range constancy verification on a daily basis.