Redesigning the Senior Leader Engagement Program of the United States Africa Command

AFRICOM conducts hundreds of senior leader engagements (SLEs) each year throughout the African continent in order to create strategic partnerships and military relationships that preserve American interests abroad. While AFRICOM has been planning and executing these engagements since the inception of the organization in 2008, it lacks a well-defined method to systemize its SLE process. As a result, SLE development is largely ad hoc, potentially decreasing the strategic effectiveness of the engagements and increasing their cost. This paper delineates a decision-making framework to redesign and enhance AFRICOM’s SLE program. In particular, it posits a multiple objective decision analysis model that quantifies key stakeholder values and develops several alternatives for future evaluation. Of note, potential solutions imagine a more expansive system where subsets of Senior Leaders (SLs) are assigned to clusters of African countries based on the SLs’ similarity to countries within each cluster, providing a basis for relationship ownership and mutual trust

Climatic Stress during Stand Development Alters the Sign and Magnitude of Age-Related Growth Responses in a Subtropical Mountain Pine

The modification of typical age-related growth by environmental changes is poorly understood, In part because there is a lack of consensus at individual tree level regarding age-dependent growth responses to climate warming as stands develop. To increase our current understanding about how multiple drivers of environmental change can modify growth responses as trees age we used tree ring data of a mountain subtropical pine species along an altitudinal gradient covering more than 2,200 m of altitude. We applied mixed-linear models to determine how absolute and relative age-dependent growth varies depending on stand development; and to quantify the relative importance of tree age and climate on individual tree growth responses. Tree age was the most important factor for tree growth in models parameterised using data from all forest developmental stages. Contrastingly, the relationship found between tree age and growth became non-significant in models parameterised using data corresponding to mature stages. These results suggest that although absolute tree growth can continuously increase along tree size when trees reach maturity age had no effect on growth. Tree growth was strongly reduced under increased annual temperature, leading to more constant age-related growth responses. Furthermore, young trees were the most sensitive to reductions in relative growth rates, but absolute growth was strongly reduced under increased temperature in old trees. Our results help to reconcile previous contrasting findings of age-related growth responses at the individual tree level, suggesting that the sign and magnitude of age-related growth responses vary with stand development. The different responses found to climate for absolute and relative growth rates suggest that young trees are particularly vulnerable under warming climate, but reduced absolute growth in old trees could alter the species' potential as a carbon sink in the future

Cenozoic climate change and the evolution of North American mammalian predator ecomorphology

Abstract: The trend of global cooling across the Cenozoic transformed the North American landscape from closed forest to more open grasslands, resulting in dietary adaptations in herbivores in response to shifting resources. In contrast, the material properties of the predator food source (muscle, skin, and bone) have remained constant over this transition, suggesting a corresponding lack of change in predator dietary adaptations. We investigated the North American mammalian predator fossil record using a tooth-shape metric and body mass, predicting that the former would exhibit stability. Instead, we found that mean molar morphology became more blade-like, with our tooth-shape metric sharply increasing in the late Eocene and remaining high from the Oligocene onward. Subsequent tests in extant carnivorans reveal taxa with more bladelike teeth are prevalent in more open environments. Our results reveal an unexpected functional shift among North American predators in response to large-scale environmental changes across the Cenozoic

Interactive effects of tree age and climate on basal area increment and relative tree growth.

<p>Predicted (a) basal area increment (m² yr^-1) and (b) relative tree growth (% yr^-1) along tree age (No. years) and mean annual temperature (°C); and (c) relative tree growth along tree age (No. years) and mean annual precipitation (mm) in models parameterised using data from all developmental stages.</p

Predicted basal area increment and relative tree growth along against age, temperature and precipitation.

<p>Predicted tree basal area increment (m² yr^-1) and relative tree growth (% yr^-1) for all data and mature stage data in relation to: ((a) and (b), respectively) tree age (No. years), ((c) and (d), respectively) mean annual temperature (°C), and ((e) and (f), respectively) annual precipitation (mm).</p

PinusTaiwanensis

This is the original data for each tree (treeid) in each study site (site id; B: bottom, L: low, M: medium, H:high, t: top) from 1960. The variables include: year (yr), basal area increment (BAI, mm2 yr-1), relative tree growth (RTG, % yr-1), tree age (ta, No. years), mean annual temperature (MAT, ºC), annual precipitation (PP, mm)

Predicted basal area increment and relative tree growth along against age, temperature and precipitation.

<p>Predicted tree basal area increment (m² yr^-1) and relative tree growth (% yr^-1) for all data and mature stage data in relation to: ((a) and (b), respectively) tree age (No. years), ((c) and (d), respectively) mean annual temperature (°C), and ((e) and (f), respectively) annual precipitation (mm).</p

Alternative models of basal area increment and relative tree growth based on Akaike Information Criterion.

<p>Full models include the main effects of tree age (TA), mean annual temperature (MAT) and annual precipitation (PP). Alternative models ignore the effects (‘No’) of the main effects of each explanatory variable or interactions. The best fitting model is determined by ∆AIC value of zero and it is given in italics. The selected model includes the effect of tree age and it is given in bold.</p><p>Alternative models of basal area increment and relative tree growth based on Akaike Information Criterion.</p

Map of <i>Pinus taiwanensis</i> sites sampled in Taiwan.

<p>We included <i>Pinus taiwanensis</i> distribution [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126581#pone.0126581.ref065" target="_blank">65</a>] and the altitudinal gradient in Taiwan (digital elevation model STRM30, SRTM V2, <a href="http://www2.jpl.nasa.gov/srtm/" target="_blank">http://www2.jpl.nasa.gov/srtm/</a>).</p

Interactive effects of tree age and climate on basal area increment and relative tree growth.

<p>Predicted (a) basal area increment (m² yr^-1) and (b) relative tree growth (% yr^-1) along tree age (No. years) and mean annual temperature (°C); and (c) relative tree growth along tree age (No. years) and mean annual precipitation (mm) in models parameterised using data from all developmental stages.</p