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26 result(s) for "McGregor, Ian R."
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Tree height and leaf drought tolerance traits shape growth responses across droughts in a temperate broadleaf forest
As climate change drives increased drought in many forested regions, mechanistic understanding of the factors conferring drought tolerance in trees is increasingly important. The dendrochronological record provides a window through which we can understand how tree size and traits shape growth responses to droughts. We analyzed tree-ring records for 12 species in a broadleaf deciduous forest in Virginia (USA) to test hypotheses for how tree height, microenvironment characteristics, and species’ traits shaped drought responses across the three strongest regional droughts over a 60-yr period. Drought tolerance (resistance, recovery, and resilience) decreased with tree height, which was strongly correlated with exposure to higher solar radiation and evaporative demand. The potentially greater rooting volume of larger trees did not confer a resistance advantage, but marginally increased recovery and resilience, in sites with low topographic wetness index. Drought tolerance was greater among species whose leaves lost turgor (wilted) at more negative water potentials and experienced less shrinkage upon desiccation. The tree-ring record reveals that tree height and leaf drought tolerance traits influenced growth responses during and after significant droughts in the meteorological record. As climate change-induced droughts intensify, tall trees with drought-sensitive leaves will be most vulnerable to immediate and longer-term growth reductions.
Long-Term Impacts of Invasive Insects and Pathogens on Composition, Biomass, and Diversity of Forests in Virginia’s Blue Ridge Mountains
Exotic forest insects and pathogens (EFIP) have become regular features of temperate forest ecosystems, yet we lack a long-term perspective on their net impacts on tree mortality, carbon sequestration, and tree species diversity. Here, we analyze 3 decades (1987–2019) of forest monitoring data from the Blue Ridge Mountains ecoregion in eastern North America, including 67 plots totaling 29.4 ha, along with a historical survey from 1939. Over the past century, EFIP substantially affected at least eight tree genera. Tree host taxa had anomalously high mortality rates (≥ 6% year⁻¹ from 2008 to 2019 vs 1.4% year⁻¹ for less-impacted taxa). Following the arrival of EFIP, affected taxa declined in abundance (- 25 to - 100%) and live aboveground biomass (AGB; - 13 to -100%) within our monitoring plots. We estimate that EFIP were responsible for 21–29% of ecosystem AGB loss through mortality (- 87 g m⁻² year⁻¹) from 1991 to 2013 across 66 sites. Over a century, net AGB loss among affected species totaled roughly 6.6–10 kg m⁻². The affected host taxa accounted for 23–29% of genera losses at the plot scale, with mixed net effects on α-diversity. Several taxa were lost from our monitoring plots but not completely extirpated from the region. Despite these losses, both total AGB and α-diversity were largely recovered through increases in sympatric genera. These results indicate that EFIP have been an important force shaping forest composition, carbon cycling, and diversity. At the same time, less-affected taxa in these relatively diverse temperate forests have conferred substantial resilience with regard to biomass and α-diversity.
Warm springs alter timing but not total growth of temperate deciduous trees
As the climate changes, warmer spring temperatures are causing earlier leaf-out 1 – 3 and commencement of CO 2 uptake 1 , 3 in temperate deciduous forests, resulting in a tendency towards increased growing season length 3 and annual CO 2 uptake 1 , 3 – 7 . However, less is known about how spring temperatures affect tree stem growth 8 , 9 , which sequesters carbon in wood that has a long residence time in the ecosystem 10 , 11 . Here we show that warmer spring temperatures shifted stem diameter growth of deciduous trees earlier but had no consistent effect on peak growing season length, maximum growth rates, or annual growth, using dendrometer band measurements from 440 trees across two forests. The latter finding was confirmed on the centennial scale by 207 tree-ring chronologies from 108 forests across eastern North America, where annual ring width was far more sensitive to temperatures during the peak growing season than in the spring. These findings imply that any extra CO 2 uptake in years with warmer spring temperatures 4 , 5 does not significantly contribute to increased sequestration in long-lived woody stem biomass. Rather, contradicting projections from global carbon cycle models 1 , 12 , our empirical results imply that warming spring temperatures are unlikely to increase woody productivity enough to strengthen the long-term CO 2 sink of temperate deciduous forests. Warmer spring temperatures affect the timing of stem diameter growth of temperate deciduous trees but have little effect on annual growth.
A Review of Geospatial Content in IEEE Visualization Publications
Geospatial analysis is crucial for addressing many of the world's most pressing challenges. Given this, there is immense value in improving and expanding the visualization techniques used to communicate geospatial data. In this work, we explore this important intersection -- between geospatial analytics and visualization -- by examining a set of recent IEEE VIS Conference papers (a selection from 2017-2019) to assess the inclusion of geospatial data and geospatial analyses within these papers. After removing the papers with no geospatial data, we organize the remaining literature into geospatial data domain categories and provide insight into how these categories relate to VIS Conference paper types. We also contextualize our results by investigating the use of geospatial terms in IEEE Visualization publications over the last 30 years. Our work provides an understanding of the quantity and role of geospatial subject matter in recent IEEE VIS publications and supplies a foundation for future meta-analytical work around geospatial analytics and geovisualization that may shed light on opportunities for innovation.
The Wisdom in Virtue: Pursuit of Virtue Predicts Wise Reasoning About Personal Conflicts
Most people can reason relatively wisely about others' social conflicts, but often struggle to do so about their own (i.e., Solomon's paradox). We suggest that true wisdom should involve the ability to reason wisely about both others' and one's own social conflicts, and we investigated the pursuit of virtue as a construct that predicts this broader capacity for wisdom. Results across two studies support prior findings regarding Solomon's paradox: Participants (N = 623) more strongly endorsed wise-reasoning strategies (e.g., intellectual humility, adopting an outsider's perspective) for resolving other people's social conflicts than for resolving their own. The pursuit of virtue (e.g., pursuing personal ideals and contributing to other people) moderated this effect of conflict type. In both studies, greater endorsement of the pursuit of virtue was associated with greater endorsement of wise-reasoning strategies for one's own personal conflicts; as a result, participants who highly endorsed the pursuit of virtue endorsed wise-reasoning strategies at similar levels for resolving their own social conflicts and resolving other people's social conflicts. Implications of these results and underlying mechanisms are explored and discussed.
The Effects of Kin on Child Mortality in Rural Gambia
We analyzed data that were collected continuously between 1950 and 1974 from a rural area of the Gambia to determine the effects of kin on child mortality. Multilevel event-history models were used to demonstrate that having a living mother, maternal grandmother, or elder sisters had a significant positive effect on the survival probabilities of children, whereas having a living father, paternal grandmother, grandfather, or elder brothers had no effect. The mother's remarriage to a new husband had a detrimental effect on child survival, but there was little difference in the mortality rates of children who were born to monogamous or polygynous fathers. The implications of these results for understanding the evolution of human life-history are discussed.
Maternal grandmothers improve nutritional status and survival of children in rural Gambia
Hypotheses for the evolution of human female life-history characteristics have often focused on the social nature of human societies, which allows women to share the burden of childcare and provisioning amongst other members of their kin group. We test the hypothesis that child health and survival probabilities will be improved by the presence of kin using a longitudinal database from rural Gambia. We find that the only kin to improve the nutritional status of children significantly (apart from mothers) are maternal grandmothers, and that this is reflected in higher survival probabilities for children with living maternal grandmothers. There is also evidence that the reproductive status of the maternal grandmother influences child nutrition, with young children being taller in the presence of non-reproductive grandmothers than grandmothers who are still reproductively active. Paternal grandmothers and male kin, including fathers, have negligible impacts on the nutritional status and survival of children.
IRIS analyser assessment reveals sub-hourly variability of isotope ratios in carbon dioxide at Baring Head, New Zealand's atmospheric observatory in the Southern Ocean
We assess the performance of an isotope ratio infrared spectrometer (IRIS) to measure carbon (δ13C) and oxygen (δ18O) isotope ratios in atmospheric carbon dioxide (CO2) and report observations from a 26 d field deployment trial at Baring Head, New Zealand, NIWA's atmospheric observatory for Southern Ocean baseline air. Our study describes an operational method to improve the performance in comparison to previous publications on this analytical instrument. By using a calibration technique that reflected the principle of identical treatment of sample and reference gases, we achieved a reproducibility of 0.07 ‰ for δ13C-CO2 and 0.06 ‰ for δ18O-CO2 over multiple days. This performance is within the extended compatibility goal of 0.1 ‰ for both δ13C-CO2 and δ18O-CO2, which was recommended by the World Meteorological Organization (WMO). Further improvement in measurement performance is desirable to also meet the WMO network compatibility goals of 0.01 ‰ for δ13C-CO2 and 0.05 ‰ for δ18O-CO2, which is needed to resolve the small variability that is typical for background air observatories such as Baring Head. One objective of this study was to assess the capabilities and limitations of the IRIS analyser to resolve δ13C-CO2 and δ18O-CO2 variations under field conditions. Therefore, we selected multiple events within the 26 d record for Keeling plot analysis. This resolved the isotopic composition of endmembers with an uncertainty of ≤ 1 ‰ when the magnitude of CO2 signals is larger than 10 ppm. The uncertainty of the Keeling plot analysis strongly increased for smaller CO2 events (2–7 ppm), where the instrument performance is the limiting factor and may only allow for the distinction between very different endmembers, such as the role of terrestrial versus oceanic carbon cycle processes.
Conservative Shift among Liberals and Conservatives Following 9/11/01
Political orientation and political attitudes were measured in two independent adult samples. One sample was taken several months before the terrorist attacks on 9/11/01; the other, shortly after. Liberal and conservative participants alike reported more conservative attitudes following 9/11/01 than before. This conservative shift was strongest on two items with the greatest relevance to 9/11/01: George W. Bush and Increasing Military Spending. Marginally significant conservative shifts were observed on two other items (Conservatives, Socialized Medicine), and the direction of change on eight of eight items was in a conservative direction. These results provide support for the motivated social cognition model of conservatism (Jost et al., 2003 ) over predictions derived from terror management theory (e.g., Greenberg et al., 1992 ).
Oral cannabinoid-rich THC/CBD cannabis extract for secondary prevention of chemotherapy-induced nausea and vomiting: a study protocol for a pilot and definitive randomised double-blind placebo-controlled trial (CannabisCINV)
IntroductionChemotherapy-induced nausea and vomiting (CINV) remains an important issue for patients receiving chemotherapy despite guideline-consistent antiemetic therapy. Trials using delta-9-tetrahydrocannabinol-rich (THC) products demonstrate limited antiemetic effect, significant adverse events and flawed study design. Trials using cannabidiol-rich (CBD) products demonstrate improved efficacy and psychological adverse event profile. No definitive trials have been conducted to support the use of cannabinoids for this indication, nor has the potential economic impact of incorporating such regimens into the Australian healthcare system been established. CannabisCINV aims to assess the efficacy, safety and cost-effectiveness of adding TN-TC11M, an oral THC/CBD extract to guideline-consistent antiemetics in the secondary prevention of CINV.Methods and analysisThe current multicentre, 1:1 randomised cross-over, placebo-controlled pilot study will recruit 80 adult patients with any malignancy, experiencing CINV during moderate to highly emetogenic chemotherapy despite guideline-consistent antiemetics. Patients receive oral TN-TC11M (THC 2.5mg/CBD 2.5 mg) capsules or placebo capsules three times a day on day −1 to day 5 of cycle A of chemotherapy, followed by the alternative drug regimen during cycle B of chemotherapy and the preferred drug regimen during cycle C. The primary endpoint is the proportion of subjects attaining a complete response to CINV. Secondary and tertiary endpoints include regimen tolerability, impact on quality of life and health system resource use. The primary assessment tool is patient diaries, which are filled from day −1 to day 5. A subsequent randomised placebo-controlled parallel phase III trial will recruit a further 250 patients.Ethics and disseminationThe protocol was approved by ethics review committees for all participating sites. Results will be disseminated in peer-reviewed journals and at scientific conferences.Drug supplyTilray.Protocol version2.0, 9 June 2017.Trial registration numberANZCTR12616001036404; Pre-results.