Southwestern US Research Articles

Moisture and vegetation cover limit ponderosa pine regeneration in high-severity burn patches in the southwestern US

BackgroundFire regimes are shifting in ponderosa pine (Pinus ponderosa Lawson & C. Lawson)-dominated forests, raising concern regarding future vegetation patterns and forest resilience, particularly within high-severity burn patches. The southwestern US has recently experienced a marked increase in large fires that produce large, high-severity patch interiors, with few surviving trees. These areas could be more susceptible for forest loss and conversions to alternative vegetation types than areas closer to the forest edge with more available seed sources. To better understand forest recovery, we surveyed ponderosa pine regeneration within edge and core areas (>200 m from edge) of high-severity patches in ten fires that burned between 1996 to 2008 across Arizona and New Mexico, USA. Specifically, we compared regeneration density, height, and canopy cover in patch edge and core areas and used generalized linear models to investigate the abiotic and biotic factors that contribute to ponderosa pine seedling establishment and density.ResultsHigh-severity burn-patch edge and core plots were not significantly different in seedling density, height, or canopy cover across fires. Seedling establishment was more likely at higher-elevation mesic sites and less likely when Gambel oak (Quercus gambelii Nutt.) was more abundant. Seedling density was negatively impacted by shrub, grass, and Gambel oak cover.ConclusionsRegeneration density varied among fires but analysis of regeneration in aggregated edge and core plots showed that abundance of seed availability was not the sole factor that limited ponderosa pine regeneration, probably because of surviving tree refugia within high-severity burn patches. Furthermore, our findings emphasize that ponderosa pine regeneration in our study area was significantly impacted by xeric topographic environments and vegetation competition. Continued warm and dry conditions and increased wildfire activity may delay the natural recovery of ponderosa pine forests, underscoring the importance of restoration efforts in large, high-severity burn patches.

Pathology of Lagovirus europaeus GI.2/RHDV2/b (Rabbit Hemorrhagic Disease Virus 2) in Native North American Lagomorphs.

Rabbit hemorrhagic disease, a notifiable foreign animal disease in the US, was reported for the first time in wild native North American lagomorphs in April 2020 in the southwestern US. Affected species included the desert cottontail (Sylvilagus audubonii), mountain cottontail (Sylvilagus nuttallii), black-tailed jackrabbit (Lepus californicus), and antelope jackrabbit (Lepus alleni). Desert cottontails (n=7) and black-tailed jackrabbits (n=7) collected in April and May 2020 were necropsied at the US Geological Survey National Wildlife Health Center and tested positive for Lagovirus europaeus GI.2, also known as rabbit hemorrhagic disease virus 2 (GI.2/RHDV2/b), by real-time PCR at the US Department of Agriculture's Foreign Animal Disease Diagnostic Laboratory. Gross and microscopic lesions were similar to those reported in European rabbits (Oryctolagus cuniculus) and other hare (Lepus) species with GI.2/RHDV2/b infection; they included epistaxis (12/13; 92%); massive hepatocellular dissociation (14/14; 100%) and necrosis or apoptosis (11/11; 100%); pulmonary congestion (12/12; 100%), edema (12/13; 92%), and hemorrhage (11/12; 92%); and acute renal tubular injury (3/8; 38%). As in previous reports, massive hepatocellular dissociation and necrosis or apoptosis was the most diagnostically distinct finding. As North American Sylvilagus and Lepus species appear to be susceptible to fatal GI.2/RHDV2/b infection, additional work is needed to understand the host range, pathogenicity, and potential population effects of GI.2/RHDV2/b in North America.

The influence of orbital parameters on the North American Monsoon system during the Last Interglacial Period

ABSTRACTThe response of summer precipitation in the western United States to climate variability remains a subject of uncertainty. For example, palaeoclimate records indicate the North American Monsoon (NAM) was stronger and spatially more extensive during the Holocene, whereas recent modelling suggests a weakened NAM response to increasing temperatures. These illustrate diverging pictures of the NAM response to warming. Here, we examine summer precipitation in the southwestern US related to Last Interglacial insolation forcing. Using a high‐resolution climate model, we find that Eemian insolation forcing results in overall wetter conditions throughout most of the southwestern US, but significantly drier than present conditions over Arizona. The overall wetter conditions are associated with a northward shift of the anticyclonic circulation aloft and increased moisture in the lower and mid‐troposphere during the Eemian. Increased advection of Gulf of Mexico moisture is responsible for increasing precipitation in New Mexico and the northern edges of the NAM region. Drier conditions over Arizona are likely related to reduced local convection associated with reduced vertical moisture transport. These results highlight the spatial complexity of the NAM response to increasing radiative forcing and allow a better understanding of monsoon dynamics and variability in response to a warming climate.

Jennifer Graber, The Gods of Indian Country: Religion and the Struggle for the American West

American Religion 2, no. 2 (Spring 2021), pp. 151–153 Copyright © 2021, The Trustees of Indiana University • doi: 10.2979/amerreli.2.2.13 Book Review Jennifer Graber, The Gods of Indian Country: Religion and the Struggle for the American West (New York: Oxford University Press, 2018) Natalie Avalos University of Colorado, Boulder, USA For Native peoples on the southern plains, ceremonial life was the place where they formed political alliances based on a shared sacred understanding of the world. Jennifer Graber’s The Gods of Indian Country notes that with the arrival of settlers in what would soon be known as “Indian Territory,” religion remained a connection point—not to consecrate political agreements with Native nations but as a rationale and means to dispossess them. This book narrates the activities of Protestant and Catholic “friends of the Indian” in the nineteenth-centurylong struggle to settle the West through their missionary and reform work with Indians in the southern Plains, specifically the Kiowa. Through careful use of government, denominational, and Kiowa sources, such as calendars and ledger drawings, Graber makes the case that these “friends of the Indian” operationalized a particular kind of white Christian civility to help materialize the structural foundations of US settler colonialism. The book is organized into three sections—open lands, closed lands, and divided lands—in order to convey the distinct shifts in ideology and practice of nineteenth-century US expansion. Beginning with the Louisiana Purchase in 1803, chapters one and two outline the debates around Indian removal during the first half of the century in response to settler demands for land. Religious American Religion 2:2 152 actors, initially resistant to policies of removal, sought a moral solution to the “Indian problem,” arguing that Indians could be civilized and eventually assimilated through religious conversion. Graber contrasts these debates with a detailed contextualization of Kiowa life on the open plains as one of the region’s central power brokers—their relationship to nearby tribes as well as to the unseen world. As settlers and reformers trickled into the region, the Kiowa were pathologized as the fiercest of “wild” Indians due to their frequent raids into the Southwestern US and Mexico and their yearly observance of the Sun Dance. After skirmishes with US troops, who carried out a series of Indian massacres in the region, the Kiowa were confined to reservation lands. Here, the historical discourse involving Indian agents, federal representatives, and Kiowas demonstrates the breathtaking level of racist paternalism and deceit that operated together to facilitate land dispossession. Food provisions were promised but always fell short. Farming was encouraged yet poor instruction led to failed crops. While their Quaker reservation agent implored the federal government to act on good faith, noting that deprivations would only demoralize the Kiowas, the federal body’s uneven response communicated their long game—Indian elimination. Chapters three through five, covering the period from 1868–1881, chronicle the consolidation of Indian territory into an open-air prison that experimented with compulsory forms of social engineering aimed at civilizing Indians: changes in dress, food, and complete re-education programs via missionization and boarding schools. Pacifist reservations agents, frustrated by Kiowas who continued dancing, hunting, and raiding, became despots, invited US troops to occupy Kiowa lands, and withheld food as a form of coercion. The Kiowa were incredulous—why would they give up their lifeways on their sovereign lands? As they contemplated revolt, they took refuge in the Sun Dance and religious life, supplicating spiritual power to empower them in their duress. Kiowa assertions of autonomy in the face of this coercion are salient here. As one Kiowa leader noted, it would take the white men many years to kill all Indians, but if all Indians die, “then the world will turn to water or burn up. [The world] can’t live when the Indians are all dead” (108). It is in the aftermath of the Kiowa’s armed resistance in the Red River War—the imprisonment of Kiowa warriors and spike in public support for Indian elimination—that the Kiowa realized they had very little choice but to tolerate this social engineering or starve. In chapters six and seven, Graber links the...

Stable isotopes of tree rings reveal seasonal-to-decadal patterns during the emergence of a megadrought in the Southwestern US.

Recent evidence has revealed the emergence of a megadrought in southwestern North America since 2000. Megadroughts extend for at least 2 decades, making it challenging to identify such events until they are well established. Here, we examined tree-ring growth and stable isotope ratios in Pinus ponderosa at its driest niche edge to investigate whether trees growing near their aridity limit were sensitive to the megadrought climatic pre-conditions, and were capable of informing predictive efforts. During the decade before the megadrought, trees in four populations revealed increases in the cellulose δ13C content of earlywood, latewood, and false latewood, which, based on past studies are correlated with increased intrinsic water-use efficiency. However, radial growth and cellulose δ18O were not sensitive to pre-megadrought conditions. During the 2 decades preceding the megadrought, at all four sites, the changes in δ13C were caused by the high sensitivity of needle carbon and water exchange to drought trends in key winter months, and for three of the four sites during crucial summer months. Such pre-megadrought physiological sensitivity appears to be unique for trees near their arid range limit, as similar patterns were not observed in trees in ten reference sites located along a latitudinal gradient in the same megadrought domain, despite similar drying trends. Our results reveal the utility of tree-ring δ13C to reconstruct spatiotemporal patterns during the organizational phase of a megadrought, demonstrating that trees near the arid boundaries of a species' distribution might be useful in the early detection of long-lasting droughts.

Menstrual Knowledge and Understandings of Normal and Extreme Bleeding: College Students’ Overestimation of the Typical Amount of Menstrual Blood

Accurate biological information about menstruation is crucial for menstrual health literacy. A diverse group of students (N = 125) at a large southwestern US university estimated—by pouring liquid into containers—the amount of menstrual blood produced during an average menstrual period. Only 14% could give a relatively accurate estimate, whereas 55% overestimated by at least 65 ml. Further, 7% gave extreme overestimations of one liter or more. Gender and race did not impact accurate knowledge, but queer/pansexual participants and women’s and gender studies or social justice majors were significantly more accurate. Implications for health education and recognizing heavy bleeding are explored.

Divergent morphological responses to millennia of climate change in two species of bats from Hall's Cave, Texas, USA.

How species will respond to ongoing and future climate change is one of the most important questions facing biodiversity scientists today. The fossil record provides unparalleled insight into past ecological and evolutionary responses to climate change, but the resource remains virtually untapped for many organisms. We use geometric morphometrics and a 25,000 year fossil record to quantify changes in body size and mandible shape through time and across climate regimes for two bat species present in Quaternary paleontological deposits of central Texas: Myotis velifer, a bat distributed throughout the Southwestern US and Mexico that is still found in central Texas today, and Eptesicus fuscus, a bat widely distributed throughout North America that has been extirpated in central Texas. Because of ecogeographic rules like Bergmann’s rule, which posits that endotherms are larger in colder environments, we hypothesized that both species were larger during cooler time intervals. Additionally, we hypothesized that both species would show variation in dental morphology across the studied sequence as a response to climate change. While we found a decrease in centroid size–a proxy for ­­body size–through time for both species, we could not establish a clear relationship between centroid size and temperature alone. However, we did find that specimens from drier environments were significantly larger than those from wetter ones. Furthermore, we found significant dental shape variation between environments reflecting different temperature levels for both species. Yet only M. velifer exhibited significant variation between environments of varying precipitation levels. This result was surprising because present-day populations of E. fuscus are highly variable across both temperature and precipitation gradients. We determined that the morphological change experienced by M. velifer through time, and between warmer and cooler temperatures, was associated with the coronoid process, condylar process, and the mandibular symphysis. These parts play a pivotal role in bite force, so changes in these features might relate to changes in diet. We show that long-term datasets derived from fossil material provide invaluable insight not only into the validity of ecogeographic rules, but also into the adaptive capacities of extant taxa when faced with environmental changes. Our results highlight diverging responses to a variety of climate factors that are relevant to consider in biodiversity research given ongoing global change.

Sex Differences in Stroke Hospitalization Incidence, 30-Day Mortality, and Readmission in a Regional Medical Center in the Southwestern United States

This study explores sex differences in ischemic stroke hospitalization incidence, 30-day mortality, and 30-day readmission in a southwestern US medical center. Ischemic stroke admissions in a regional medical center in the southwestern United States were obtained for a 6.5-year time frame (N = 1968). Logistic regression models examine the adjusted effects of sex on 30-day mortality and 30-day readmission outcomes among individuals hospitalized for ischemic stroke. Findings confirm that although women experience higher mortality than men (9.1% vs 6.7%), the sex disparity in mortality is explained by the age distribution of strokes. Women experience far more strokes and deaths because of stroke at older ages. No differences in principal procedure or 30-day readmission emerged. Men experienced higher stroke hospitalization incidence, although women exhibited higher 30-day mortality. Age composition explained sex differences in mortality, but higher male stroke hospitalization incidence represents a larger public health issue that suggests the need for behavioral change at the population level. No meaningful sex differences emerged in treatment, mortality, or readmission.

Teacher corps stability: articulating the social capital enabled when teachers stay

PurposeThe evidence is strong that the instability of teacher rosters in urban school settings has negative consequences for student learning, but our concern is with the opposite phenomenon: What is the value added to the organization when a school's teaching roster is stable over time? Our theory of teacher corps stability hinges on the claim that the stability of a teacher corps over time is a sine qua non that, under certain conditions, permits formation of the social capital needed to catalyze school effectiveness.Design/methodology/approachWe test this claim using longitudinal data from 72 schools in a large, urban southwestern US school district. We first identified a subset of 47 schools with either chronic teacher turnover (high, stable turnover) or a stable teacher roster (low, stable turnover) via school-level HLM growth modeling techniques. These classifications were then used as a covariate in a series of HLM growth models investigating its relationship to growth in structural, relational and cognitive social capital over time.FindingsOur findings sustain a claim of the importance of teacher corps stability. In our sample of urban schools, we found robust increases in the relational and cognitive dimensions of social capital over time in those schools with stable rosters. Furthermore, schools with chronic turnover were declining significantly in relational social capital, but no appreciable growth in structural social capital was found in either stable roster or chronic teacher turnover schools.Practical implicationsGiven the nature of teacher corps stability and its relationship to key organizational outcomes, school leaders play a central role in realizing teacher corps stability within their school. A certain amount of this effort must necessarily be focused on retaining a stable corps of quality, happy, committed teachers. However, building social capital concerns the active engagement of all actors; thus, school leaders need to think beyond retention to how the teachers that remain can play larger leadership roles in this process.Originality/valueFew studies have examined the positive benefits that can emerge in schools where the majority of teachers remain year after year. Collectively, the study findings suggest that teacher corps stability can provide fertile conditions for the development of social capital that has the potential to enhance school effectiveness and that its staff can leverage for school improvement.

Response of dust emissions in southwestern North America to 21st century trends in climate, CO<sub>2</sub> fertilization, and land use: implications for air quality

Abstract. Climate models predict a shift toward warmer and drier environments in southwestern North America. The consequences of such a shift for dust mobilization and dust concentration are unknown, but they could have large implications for human health, given the connections between dust inhalation and disease. Here we link a dynamic vegetation model (LPJ-LMfire) to a chemical transport model (GEOS-Chem) to assess the impacts of future changes in three factors – climate, CO2 fertilization, and land use practices – on vegetation in this region. From there, we investigate the impacts of changing vegetation on dust mobilization and assess the net effect on fine dust concentration (defined as dust particles less than 2.5 µm in diameter) on surface air quality. We find that surface temperatures in southwestern North America warm by 3.3 K and precipitation decreases by nearly 40 % by 2100 in the most extreme warming scenario (RCP8.5; RCP refers to Representative Concentration Pathway) in spring (March, April, and May) – the season of greatest dust emissions. Such conditions reveal an increased vulnerability to drought and vegetation die-off. Enhanced CO2 fertilization, however, offsets the modeled effects of warming temperatures and rainfall deficit on vegetation in some areas of the southwestern US. Considering all three factors in the RCP8.5 scenario, dust concentrations decrease over Arizona and New Mexico in spring by the late 21st century due to greater CO2 fertilization and a more densely vegetated environment, which inhibits dust mobilization. Along Mexico's northern border, dust concentrations increase as a result of the intensification of anthropogenic land use. In contrast, when CO2 fertilization is not considered in the RCP8.5 scenario, vegetation cover declines significantly across most of the domain by 2100, leading to widespread increases in fine dust concentrations, especially in southeastern New Mexico (up to ∼ 2.0 µg m−3 relative to the present day) and along the border between New Mexico and Mexico (up to ∼ 2.5 µg m−3). Our results have implications for human health, especially for the health of the indigenous people who make up a large percentage of the population in this region.

Centipede Bites.

The genus Scolopendra includes large centipedes that inhabit tropical regions of Southeast Asia and the Pacific Islands as well as South America and the Southwestern US. They are capable of inflicting a clinically significant venomous bite. These multilegged arthropods may enter tents or buildings at night in search of prey and tend to hide in bedding and clothing. Presentation and management are discussed.

Genetic analysis reveals an east-west divide within North American Vitis species that mirrors their resistance to Pierce's disease.

Pierce's disease (PD) caused by the bacterium Xylella fastidiosa is a deadly disease of grapevines. This study used 20 SSR markers to genotype 326 accessions of grape species collected from the southeastern and southwestern United States, Mexico and Costa Rica. Two hundred sixty-six of these accessions, and an additional 12 PD resistant hybrid cultivars developed from southeastern US grape species, were evaluated for PD resistance. Disease resistance was evaluated by quantifying the level of bacteria in stems and measuring PD symptoms on the canes and leaves. Both Bayesian clustering and principal coordinate analyses identified two groups with an east-west divide: group 1 consisted of grape species from the southeastern US and Mexico, and group 2 consisted of accessions collected from the southwestern US and Mexico. The Sierra Madre Oriental mountain range appeared to be a phylogeographic barrier. The state of Texas was identified as a potential hybridization zone. The hierarchal STRUCTURE analysis on each group showed clustering of unique grape species. An east-west divide was also observed for PD resistance. With the exception of Vitis candicans and V. cinerea accessions collected from Mexico, all other grape species as well as the resistant southeastern hybrid cultivars were susceptible to the disease. Southwestern US grape accessions from drier desert regions showed stronger resistance to the disease. Strong PD resistance was observed within three distinct genetic clusters of V. arizonica which is adapted to drier environments and hybridizes freely with other species across its wide range.

Assessing sleep quality in older adults: A comparison of three measurement approaches

Discrepancies between subjective and objective sleep measures have been reported for some time; however, it is critical to consider the implications of inaccurate or incomplete sleep assessment for frail older adults who are struggling to maintain independence. To compare sleep assessment methods, we collected objective sleep measurements (via wrist actigraphy), subjective measures via self-report sleep surveys (Pittsburgh Sleep Quality Index; Insomnia Severity Index, Sleep Hygiene Index), and qualitative data through semi-structured audio-recorded interviews, from 8 older adults who self-reported sleep problems while living in a retirement community in southwestern US. Participants’ objective sleep (Total Sleep Time, Sleep Onset Latency, Wake After Sleep Onset, and Sleep Efficiency) and qualitative narratives were congruent, but self-report measures failed to capture several unique sleep problems identified in the sample. Disordered sleep in older adults has been linked to increased incidence of falls, depression and anxiety, cognitive impairment, institutionalization, and mortality, but traditional sleep assessment instruments, designed for the general adult population, fail to capture many of the experiences and causes that are unique to older adults. functioning. A sleep assessment tool designed to measure older people’s sleep experiences could provide more accurate and sensitive data.

Do policy and training changes influence patterns of police use of force? An interrupted time-series analysis

PurposeThe current study examines the effect of changing a specific use-of-force policy coupled with de-escalation training implementation on patterns of police use of force.Design/methodology/approachAn interrupted time-series analysis was used to examine changes in police use-of-force incident records gathered from a large, southwestern US metropolitan police department from 2013 to 2017 based on a TASER policy change and de-escalation training implementation mid-2015.FindingsResults demonstrate that changes to use-of-force policy regarding one type of force (i.e. use of TASERs) coinciding with de-escalation training influence the prevalence of use-of-force incidents by increasing the reported police use-of-force incidents after the changes were implemented. This finding is somewhat consistent with prior literature but not always in the desired direction.Practical implicationsWhen police departments make adjustments to use-of-force policies and/or trainings, unintended consequences may occur. Police administrators should measure policy and training outcomes under an evidence-based policing paradigm prior to making those adjustments.Originality/valueThis study is the first to measure the effects of changing use-of-force policy and implementing de-escalation techniques in training on patterns of police use of force and shows that these changes can have a ripple effect across types of force used by police officers.

157 Spectroscopic analysis of tissues collected from male goats differing in genetic propensity to consume juniper

Abstract Juniper (Juniperus spp.) foliage is consumed by free-ranging goats in the southwestern US. Junipers contain monoterpenes which have toxicological and pharmacological effects. We sampled 20 male Spanish goats (Capra hircus; 10 young [2-year-old] and 10 old [3-5-year-old]) from a herd selected for their propensity to consume a high (estimated breeding value [EBV] = 13.01 ± 0.20) or low (EBV = -14.76 ± 0.48) proportion of juniper in the diet to determine the ability of near infrared spectroscopy (NIRS) in detecting physico-chemical differences in animal tissues. Heart (ventricle; interior and exterior surfaces), liver (caudate lobe), and muscle (longissimus dorsi) samples as well as an entire kidney and testicle, were collected at harvest (n = 5 of each age [i.e. length of exposure to monoterpenes] and juniper EBV combination). Tissue samples were stored in whirl-pac bags at -20o C and later thawed to ~24o C for NIRS analysis. Spectra (400–2500 nm) were obtained with an ASD Field Spec using a contact probe directly through the whirl-pac sample bag. Principal component and partial least squares regression procedures were accomplished in SAS; P < 0.05 indicated statistical significance. Both age (RSQ, 0.2 to 0.6; P < 0.05) and juniper EBV (RSQ, 0.2 to 0.65; P < 0.05) were correlated with near infrared (NIR) spectral characteristics. Propensity to consume juniper was most strongly correlated with NIR spectra in testicular tissue (RSQ = 0.65, MSE = 0.25, P < 0.01), and least strongly correlated in the heart interior surface (RSQ = 0.21, MSE = 0.21, P < 0.05). Spectral correlations with propensity to consume juniper were stronger in tissues from old (RSQ ~ 0.68) than young (RSQ ~ 0.52) goats, especially in liver, kidney, muscle, and testicle. Physico-chemical differences in goat tissues were affected by genetic propensity to consume juniper, and these were detected by NIRS.

Estimating Surface Water Presence and Infiltration in Ephemeral to Intermittent Streams in the Southwestern US

Streamflow in arid and semi-arid regions is predominantly temporary, an integral part of mountain block hydrology and of significant importance for groundwater recharge and biogeochemical processes. However, temporary streamflow regimes, especially ephemeral flow, remain poorly quantified. We use electrical resistance sensors and USGS stream gauge data in 15 southern Arizona streams spanning a climate gradient (mean annual precipitation from 160 to 750 mm) to quantify temporary streamflow as streamflow presence and water presence, which includes streamflow, ponding and soil moisture. We use stream channel sediment data to estimate saturated hydraulic conductivity and potential annual infiltration. Annual streamflow ranged 0.6–82.4% or 2–301 days; while water presence ranged from 2.6 to 82.4% or 10 to over 301 days, or 4–33 times longer than streamflow. We identified 5 statistically distinct flow regimes based on the annual percent streamflow and water presence: (1) dry-ephemeral, (2) wet-ephemeral, (3) dry-intermittent, (4) wet-intermittent, and (5) seasonally-intermittent. In contrast to our expectations, stream channel density was a better predictor of annual streamflow and water presence than annual rainfall alone. Whereas, the dry-ephemeral and wet-ephemeral flow regimes varied with seasonal precipitation, the dry-intermittent, wet intermittent and seasonally-intermittent flow regimes did not. These results coupled with the potential infiltration estimates indicate that streamflow at the driest sites occurs in response to rainfall and overland flow while groundwater discharge and vadose zone contributions enhance streamflow at the wetter sites. We suggest that on a short temporal scale, and with respect to water presence, wetter sites might be buffered better against shifts in the timing and distribution of precipitation in response to climate change. Flow regime classifications that include both stream flow and water presence, rather than on stream flow alone, may be important for predicting thresholds in ecological functions and refugia in these dryland systems.

Recent land cover changes in the Southwestern US lead to an increase in surface temperature

The increase in large-scale land cover change (LCC) in recent decades, particularly in response to climate-driven disturbances, has potential to impact local and regional changes in climate due to modification of carbon sources and sinks, albedo, surface roughness and energy fluxes. Using observational data, we predict the impact of two of the most extensive LCCs occurring in the Southwestern US: drought-induced tree mortality and shrub encroachment into grasslands, on surface temperature. We developed a new energy balance method that extracts the biophysical responses to environmental conditions, to predict how structural changes in albedo, surface roughness and canopy conductance following LCC will alter surface temperature. This method allows us not only to explain the observed differences in surface temperature between two non-adjacent study sites with different environmental conditions, but also to separate the contribution of biophysical and non-biophysical properties to surface temperature. Our results suggest that changes in biophysical properties due to shrub encroachment and tree mortality in the Southwestern US (independent of changes in other environmental properties) can potentially lead to an increase in midday surface temperature (11AM to 2PM) of 1 to 2 degrees Celsius, comparable to changes in surface temperature following deforestation. Although the average surface temperature increase in response to both shrub encroachment and tree mortality is similar, the biophysical properties driving the temperature change are different in each scenario. Change in aerodynamic conductance following tree mortality is the largest contributor to heating, while reduced albedo and canopy conductance drive the increase in surface temperature following shrub encroachment. We also show how this increase in daytime surface temperature could be further intensified with future climate, especially with the expected reduction in soil water availability in the Southwest.

Sociodemographic and Psychosocial Factors Associated With Diet Quality in 6 Rural Native American Communities

ObjectiveTo identify psychosocial and household environmental factors related to diet quality among Native Americans (NA). DesignAnalysis of baseline data from a community-randomized obesity prevention trial. SettingSix rural NA communities in the Midwest and the Southwestern US. ParticipantsA total of 580 tribal members, aged 18–75 years old (mean 45 years), 74% female, self-identified as the main household food purchaser. Variables MeasuredDiet quality (Healthy Eating Index–2015 [HEI]) was derived from a semiquantitative food frequency questionnaire. Sociodemographic, psychosocial, and home food environment factors were assessed via interviewer-administered questionnaires. AnalysisOne-way ANOVA, linear regression models, and 2-tailed t tests compared HEI scores among sociodemographic categories. Multiple linear regression models assessed the relationship between psychosocial factors, home food environment, and HEI. ResultsPrevalence of obesity was 59%. Mean HEI–2015 score was 49.3 (SD = 8.1). Average HEI scores were 3.0 points lower in smokers than nonsmokers (P < 0.001), and 2.2 points higher in females than males (P < 0.01). Higher self-efficacy (β = 0.97; P < 0.001) and healthier eating intentions (β = 0.78; P < 0.001) were positively associated with HEI. Healthier household food patterns score was associated with higher HEI (β = 0.48; P < 0.01). Conclusions and ImplicationsPsychosocial factors were associated with diet quality, a finding that supports the use of social-cognitive intervention approaches in rural NA communities in the Midwest and Southwest, and warrants evaluation in other locations. There remains a need to elucidate the association between the Food Distribution Program on Indian Reservations and diet quality.

A climatic dipole drives short- and long-term patterns of postfire forest recovery in the western United States

Researchers are increasingly examining patterns and drivers of postfire forest recovery amid growing concern that climate change and intensifying fires will trigger ecosystem transformations. Diminished seed availability and postfire drought have emerged as key constraints on conifer recruitment. However, the spatial and temporal extent to which recurring modes of climatic variability shape patterns of postfire recovery remain largely unexplored. Here, we identify a north-south dipole in annual climatic moisture deficit anomalies across the Interior West of the US and characterize its influence on forest recovery from fire. We use annually resolved establishment models from dendrochronological records to correlate this climatic dipole with short-term postfire juvenile recruitment. We also examine longer-term recovery trajectories using Forest Inventory and Analysis data from 989 burned plots. We show that annual postfire ponderosa pine recruitment probabilities in the northern Rocky Mountains (NR) and the southwestern US (SW) track the strength of the dipole, while declining overall due to increasing aridity. This indicates that divergent recovery trajectories may be triggered concurrently across large spatial scales: favorable conditions in the SW can correspond to drought in the NR that inhibits ponderosa pine establishment, and vice versa. The imprint of this climatic dipole is manifest for years postfire, as evidenced by dampened long-term likelihoods of juvenile ponderosa pine presence in areas that experienced postfire drought. These findings underscore the importance of climatic variability at multiple spatiotemporal scales in driving cross-regional patterns of forest recovery and have implications for understanding ecosystem transformations and species range dynamics under global change.

Temporal controls on crown nonstructural carbohydrates in southwestern US tree species.

In trees, large uncertainties remain in how nonstructural carbohydrates (NSCs) respond to variation in water availability in natural, intact ecosystems. Variation in NSC pools reflects temporal fluctuations in supply and demand, as well as physiological coordination across tree organs in ways that differ across species and NSC fractions (e.g., soluble sugars vs starch). Using landscape-scale crown (leaves and twigs) NSC concentration measurements in three foundation tree species (Populus tremuloides, Pinus edulis, Juniperus osteosperma), we evaluated in situ, seasonal variation in NSC responses to moisture stress on three timescales: short-term (via predawn water potential), seasonal (via leaf δ13C) and annual (via current year's ring width index). Crown NSC responses to moisture stress appeared to depend on hydraulic strategy, where J. osteosperma appears to regulate osmotic potentials (via higher sugar concentrations), P. edulis NSC responses suggest respiratory depletion and P. tremuloides responses were consistent with direct sink limitations. We also show that overly simplistic models can mask seasonal and tissue variation in NSC responses, as well as strong interactions among moisture stress at different timescales. In general, our results suggest large seasonal variation in crown NSC concentrations reflecting the multiple cofunctions of NSCs in plant tissues, including storage, growth and osmotic regulation of hydraulically vulnerable leaves. We emphasize that crown NSC pool size cannot be viewed as a simple physiological metric of stress; in situ NSC dynamics are complex, varying temporally, across species, among NSC fractions and among tissue types.