Colony densities and spatial patterns of harvester ants (Pogonomyrmex occidentalis and Pogonomyrmex rugosus) in grazed and ungrazed areas of northern Arizona.

Harvester ants play a crucial role as ecosystem engineers, particularly in nest-building activities that involve clearing nest-disks of vegetation. These clearings can be large and influence plant communities affecting rangeland management. In some cases, colony density may be increased by grazing but studies are sparse with conflicting results.

Forest restoration treatments increased growth and did not change survival of ponderosa pines in severe drought, Arizona.

We report on survival and growth of ponderosa pines (Pinus ponderosa Douglas ex P. Lawson & C. Lawson) 2 decades after forest restoration treatments in the G.

Cover and density of southwestern ponderosa pine understory plants in permanent chart quadrats (2002-2020).

This data set consists of 101 permanent 1 m × 1 m (1-m ) quadrats located within southwestern ponderosa pine ecosystems near Flagstaff, Arizona, USA. Individual plants in these quadrats were identified and mapped annually for 19 years (2002-2020). The original chart quadrats were established between 1912 and 1927 to determine the effects of domestic livestock grazing on herbaceous plants and pine seedlings.

Predictors of Inappropriate Helicopter Transport.

Background: Helicopter transport (HT) is an efficient, but costly, means for injured patients to receive life-saving, definitive trauma care. Identifying the characteristics of inappropriate HT presents an opportunity to improve the utilization of this finite medical resource.

Methods: Trauma registry records of all HT for a 3-year period (2016-2018) to an urban Level I trauma center were reviewed.

The Net Effect of Functional Traits on Fitness.

Generalizing the effect of traits on performance across species may be achievable if traits explain variation in population fitness. However, testing relationships between traits and vital rates to infer effects on fitness can be misleading. Demographic trade-offs can generate variation in vital rates that yield equal population growth rates, thereby obscuring the net effect of traits on fitness.

End-tidal carbon dioxide underestimates plasma carbon dioxide during emergent trauma laparotomy leading to hypoventilation and misguided resuscitation: A Western Trauma Association Multicenter Study.

Background: End-tidal carbon dioxide (ETCO2) is routinely used during elective surgery to monitor ventilation. The role of ETCO2 monitoring in emergent trauma operations is poorly understood. We hypothesized that ETCO2 values underestimate plasma carbon dioxide (pCO2) values during resuscitation for hemorrhagic shock.

An experimental test of the Community Assembly by Trait Selection (CATS) model.

The Community Assembly by Trait Selection (CATS) model of community assembly predicts species abundances along environmental gradients in relatively undisturbed vegetation. Here we ask whether this model, when calibrated with data from natural plant communities, can predict the abundances of five dominant grass species (Bouteloua gracilis, Elymus elymoides, Festuca arizonica, Muhlenbergia montana, and Poa fendleriana) in a greenhouse experiment that manipulated light and soil properties. To address this question, we used generalized additive models (GAMs) to model community-weighted mean (CWM) seed mass, mean Julian flowering date, and specific root length (SRL) as non-linear functions of two environmental variables (soil pH and pine basal area) in natural vegetation.

To shunt or not to shunt in combined orthopedic and vascular extremity trauma.

Background: There exists a long established but not validated practice of placing temporary intravascular shunts (TIVS) in cases of combined vascular and orthopedic extremity trauma. Though logical to prioritize blood flow, large-scale data to support this practice is lacking. We hypothesize that the order of repair yields no difference in outcomes in combined vascular and orthopedic extremity trauma and offer a larger-scale analysis than is previously available.

Survival rates indicate that correlations between community-weighted mean traits and environments can be unreliable estimates of the adaptive value of traits.

Correlations between community-weighted mean (CWM) traits and environmental gradients are often assumed to quantify the adaptive value of traits. We tested this assumption by comparing these correlations with models of survival probability using 46 perennial species from long-term permanent plots in pine forests of Arizona. Survival was modelled as a function of trait × environment interactions, plant size, climatic variation and neighbourhood competition.

Slow lifelong growth predisposes Populus tremuloides trees to mortality.

Widespread dieback of aspen forests, sometimes called sudden aspen decline, has been observed throughout much of western North America, with the highest mortality rates in the southwestern United States. Recent aspen mortality has been linked to drought stress and elevated temperatures characteristic of conditions expected under climate change, but the role of individual aspen tree growth patterns in contributing to recent tree mortality is less well known. We used tree-ring data to investigate the relationship between an individual aspen tree's lifetime growth patterns and mortality.

Impact of age and anticoagulation: need for neurosurgical intervention in trauma patients with mild traumatic brain injury.

Background: Of the 500,000 brain injuries in the United States annually, 80% are considered mild (mild traumatic brain injury). Unfortunately, 2% to 3% of them will subsequently deteriorate and result in severe neurologic dysfunction. Intracerebral changes in the elderly, chronic oral anticoagulation, and platelet inhibition may contribute to the development of intracranial bleeding after minor head injury.

A century of increasing pine density and associated shifts in understory plant strategies.

We analyzed one of the longest-term ecological data sets to evaluate how forest overstory structure is related to herbaceous understory plant strategies in a ponderosa pine forest. Eighty-two permanent 1-m2 chart quadrats that were established as early as 1912 were remeasured in 2007. We reconstructed historical forest structure using dendrochronological techniques.

Controls on vegetation structure in Southwestern ponderosa pine forests, 1941 and 2004.

Long-term studies can broaden our ecological understanding and are particularly important when examining contingent effects that involve changes to dominance by long-lived species. Such a change occurred during the last century in Southwestern (USA) ponderosa pine (Pinus ponderosa) forests. We used five livestock grazing exclosures established in 1912 to quantify vegetation structure in 1941 and 2004.