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. A. Pearson Natural Area, northern Arizona. Despite protection from harvest that conserved old trees, a dense forest susceptible to uncharacteristically severe disturbance had developed during more than a century of exclusion of the previous frequent surface-fire regime that ceased upon Euro-American settlement in approximately 1876. Trees were thinned in 1993 to emulate prefire-exclusion forest conditions, accumulated forest floor was removed, and surface fire was re-introduced at 4-years intervals (full restoration). There was also a partial restoration treatment consisting of thinning alone. Compared with untreated controls, mortality of old trees (mean age 243 years, maximum 462 years) differed by <1 tree ha-1 and old-tree survival was statistically indistinguishable between treatments (90.5% control, 92.3% full, 82.6% partial). Post-treatment growth as measured by basal area increment of both old (pre-1876) and young (post-1876) pines was significantly higher in both treatments than counterpart control trees for more than 2 decades following thinning. Drought meeting the definition of megadrought affected the region almost all the time since the onset of the experiment, including 3 years that were severely dry. Growth of all trees declined in the driest 3 years, but old and young treated trees had significantly less decline. Association of tree growth with temperature (negative correlation) and precipitation (positive correlation) was much weaker in treated trees, indicating that they may experience less growth decline from warmer, drier conditions predicted in future decades. Overall, tree responses after the first 2 decades following treatment suggest that forest restoration treatments have led to substantial, sustained improvement in the growth of old and young ponderosa pines without affecting old-tree survival, thereby improving resilience to a warming climate.

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-m2 ) 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. Today these data provide opportunities to examine the effects of climate and land-use change on plant demography, population dynamics, and community processes. We provide the following data and data formats: (1) digitized maps of all plant locations in shapefile and geodatabase format, (2) shapefiles showing annual locations of each individual plant species, (3) annual maps of each quadrat in TIFF and PDF format, (4) annual basal area of each species per quadrat for species mapped as polygons, (5) tabular representation of polygon areas and centroid locations for plant species mapped as polygons, (6) tabular representation of point locations for plant species mapped as points, (7) plot-scale 20 m × 20 m overstory tree canopy cover, tree basal area, parent material, and elevation, (8) quadrat-scale information (e.g., quadrat site and number, coordinates in UTM Zone 12 and latitude/longitude, and descriptive comments for each quadrat), (9) plant species list, (10) summary of plant species observed in each quadrat, (11) summary of quadrats mapped by site and year, and (12) data formatted for use in Integral Projection Models (IPM) and plant population analyses. There are no copyright restrictions; please cite this paper and the associated data set when data are used in publications.

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. HT was defined as inappropriate for patients who were discharged home from the emergency department or had a hospital length of stay <1 day, and who were discharged alive. Chi-square analysis and Student's t-test were used for univariate analysis. Predictors with a P value of less than .15 were subject to binary logistic regression analysis. A P value ≤.05 was considered significant. RESULTS: There were 713 patients who received HT during the study period. One-hundred and forty-eight (20.8%) patients met the criteria as an inappropriate HT. In univariate analysis, Glasgow Coma Scale >8, Shock Index <0.9, and fall mechanism were found to be significantly associated with inappropriate HT. Age >55 was found to be associated with an appropriate HT. The average Injury Severity Score of the inappropriate HT group was 3.86 (±3.85) compared with 16.80 (±11.23) (P = .0001, Student's t-test). DISCUSSION: Our findings suggest that there are evidence-based predictors of patients receiving inappropriate HT. Triage of HT using these predictors has the potential to decrease unnecessary deployments and reduce health care costs.

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. To address this problem, we describe a diversity of approaches to quantify intrinsic growth rates of plant populations, including experiments beyond range boundaries, density-dependent population models built from long-term demographic data, theoretical models, and methods that leverage widely available monitoring data. Linking plant traits directly to intrinsic growth rates is a fundamental step toward rigorous predictions of population dynamics and community assembly.

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. METHODS: Multicenter trial was performed analyzing the correlation between ETCO2 and pCO2 levels. RESULTS: Two hundred fifty-six patients resulted in 587 matched pairs of ETCO2 and pCO2. Correlation between these two values was very poor with an R of 0.04. 40.2% of patients presented to the operating room acidotic and hypercarbic with a pH less than 7.30 and a pCO2 greater than 45 mm Hg. Correlation was worse in patients that were either acidotic or hypercarbic. Forty-five percent of patients have a difference greater than 10 mm Hg between ETCO2 and pCO2. A pH less than 7.30 was predictive of an ETCO2 to pCO2 difference greater than 10 mm Hg. A difference greater than 10 mm Hg was predictive of mortality independent of confounders. CONCLUSION: Nearly one half (45%) of patients were found to have an ETCO2 level greater than 10 mm Hg discordant from their PCO2 level. Reliance on the discordant values may have contributed to the 40% of patients in the operating room that were both acidotic and hypercarbic. Early blood gas analysis is warranted, and a lower early goal of ETCO2 should be considered. LEVEL OF EVIDENCE: Therapeutic, level IV.

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. The model-fitted CWM traits were then used as constraints in the CATS model to predict the relative abundance of the five grass species that were seeded in a mixture at equal densities into a 2×2 factorial experiment with soil parent material and light level as crossed factors. Light was the most important factor influencing seedling community composition, especially the abundances of Bouteloua gracilis and Poa fendleriana. The model-predicted relative abundances were significantly correlated with the observed relative abundances, and the model accurately predicted the dominant species in every treatment. P. fendleriana was correctly predicted to be the most abundant species in both shade treatments and the sun-basalt treatment, and B. gracilis was correctly predicted to be the most abundant species in the sun-limestone treatment. Our results provide experimental evidence that environmental filtering of the species pool occurs in the early stages of community assembly (including germination, emergence, and early growth), and that trait-based models calibrated with data from natural plant communities can be used to predict the outcome of the early stages of community assembly under experimental conditions.

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. METHODS: A retrospective chart review was conducted at six Level I trauma centers from 2004 to 2015 comparing patients who received a TIVS during their initial surgery versus those who did not. Nonshunted patients were further divided into initial definitive vascular repair versus initial orthopedic fixation groups. Metrics were used to control for sampling bias while revision rate, amputation, hospital length of stay (HLOS), and development of thrombosis and compartment syndrome were used to assess outcomes. RESULTS: Of 291 total patients, 72 had TIVS placement, 97 had initial definitive vascular repair, and 122 had initial orthopedic fixation. The shunted group had a higher Abbreviated Injury Scale (3.0 vs. 2.8 p = 0.04) and Mangled Extremity Severity Score (6.1 vs. 5.7 p = 0.006) and a significantly lower rate of compartment syndrome (15% vs. 34% p = 0.002). Among patients who developed compartment syndrome, those who were shunted were younger (23 vs. 35 yrs, p = 0.03) and were more likely sustain a penetrating injury (p = 0.007). Those receiving initial orthopedic fixation had a longer HLOS (HLOS >15 days in 61% vs. 38%, p = 0.049) and a higher amputation rate (20% vs. 7%, p = 0.006) when compared with those undergoing initial definitive vascular repair. CONCLUSION: Lack of TIVS was associated with a significant increase in the development of compartment syndrome. Though it seems to have become common practice to proceed directly to vascular repair during the initial surgery, morbidity is improved with the placement of a TIVS. LEVEL OF EVIDENCE: Therapeutic cohort, level III.

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. The effect of traits on survival depended on the environmental conditions, but the two statistical approaches were inconsistent. For example, CWM-specific leaf area (SLA) and soil fertility were uncorrelated. However, survival was highest for species with low SLA in infertile soil, a result which agreed with expectations derived from the physiological trade-off underpinning leaf economic theory. CWM trait-environment relationships were unreliable estimates of how traits affected survival, and should only be used in predictive models when there is empirical support for an evolutionary trade-off that affects vital rates.

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. Surviving aspen trees had consistently higher average growth rates for at least 100 years than dead trees. Contrary to observations from late successional species, slow initial growth rates were not associated with a longer lifespan in aspen. Aspen trees that died had slower lifetime growth and slower growth at various stages of their lives than those that survived. Differences in average diameter growth between live and dead trees were significant (α = 0.05) across all time periods tested. Our best logistical model of aspen mortality indicates that younger aspen trees with lower recent growth rates and higher frequencies of abrupt growth declines had an increased risk of mortality. Our findings highlight the need for species-specific mortality functions in forest succession models. Size-dependent mortality functions suitable for late successional species may not be appropriate for species with different life history strategies. For some early successional species, like aspen, slow growth at various stages of the tree's life is associated with increased mortality risk.

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. We sought to investigate the association of age and the use of anticoagulation and antiplatelet therapy with neurologic deterioration and the need for neurosurgical intervention in patients presenting with mild traumatic brain injury. METHODS: A retrospective review of all adult (>14 years) patients admitted to our Level I trauma service with a Glasgow Coma Scale (GCS) score of 14 to 15 who underwent neurosurgical intervention during their hospital stay was performed. Patients were stratified into two groups, age <65 years and age ≥ 65 years. Each group was then further stratified by the use of anticoagulants: warfarin, aspirin, clopidogrel, or a combination. Mechanism of injury, prehospital complaints, admission GCS, type of neurosurgical intervention, intensive care unit length of stay, hospital length of stay, and discharge disposition were evaluated. Z test and logistic regression were used to compare proportions or percentages from different groups. RESULTS: Of the 7,678 patients evaluated during the study period, 101 (1.3%) required neurosurgical intervention. The ≥ 65 years population underwent significantly more interventions as did those patients on anticoagulants. CONCLUSION: All patients aged 65 years or older who present with a GCS score of >13 after head trauma should undergo a screening computed tomography of the head regardless of prehospital use of anticoagulation. Patients younger than 65 years can be selectively screened based on presenting complaints and mechanism of injury provided they are not on anticoagulation.

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. Ponderosa pine basal area increased from an average of 4 m2/ha in the early 1900s to 29 m2/ha in 2007. Understory plant foliar cover declined by 21%, species richness declined by two species per square meter, and functional diversity also declined. The relative cover of C4 graminoids decreased by 18% and C3 graminoids increased by 19%. Herbaceous plant species with low leaf and fine root nitrogen concentrations, low specific leaf area, high leaf dry matter content, large seed mass, low specific root length, short maximum height, and early flowering date increased in relative abundance in sites where pine basal area increased the most. Overall, we observed a long-term shift in composition toward more conservative shade- and stress-tolerant herbaceous species. Our analysis of temporal changes in plant strategies provides a general framework for evaluating compositional and functional changes in terrestrial plant communities.

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. Our objectives were to (1) assess the effects of historical livestock grazing on overstory structure and age distribution, (2) assess the effects of recent livestock grazing and overstory on understory vegetation, and (3) quantify and explain changes in understory vegetation between 1941 and 2004. In 1941, canopy cover of tree regeneration was significantly higher inside exclosures. In 2004, total tree canopy cover was twice as high, density was three times higher, trees were smaller, and total basal area was 40% higher inside exclosures. Understory species density, herbaceous plant density, and herbaceous cover were negatively correlated with overstory vegetation in both years. Most understory variables did not differ between grazing treatments in 1941 but were lower inside exclosures in 2004. Differences between grazing treatments disappeared once overstory effects were accounted for, indicating that they were due to the differential overstory response to historical livestock grazing practices. Between 1941 and 2004, species density declined by 34%, herbaceous plant density by 37%, shrub cover by 69%, total herbaceous cover by 59%, graminoid cover by 39%, and forb cover by 82%. However, these variables did not differ between grazing treatments or years once overstory effects were accounted for, indicating that the declines were driven by the increased dominance of the overstory during this period. Our results demonstrate that historical livestock grazing practices are an aspect of land-use history that can affect ecosystem development. Grazing history must be considered when extrapolating results from one site to another. In addition, the understory vegetation was more strongly controlled by the ponderosa pine overstory than by recent livestock grazing or by temporal dynamics, indicating that overstory effects must be accounted for when examining understory responses in this ecosystem.