Evaluating Thunderstorm Gust Fronts in New Mexico and Arizona

Strong winds generated by thunderstorm gust fronts can cause sudden changes in fire behavior and threaten the safety of wildland firefighters. Wildfires in complex terrain are particularly vulnerable as gust fronts can be channeled and enhanced by local topography. Despite this, knowledge of gust front characteristics primarily stems from studies of well-organized thunderstorms in flatter areas such as the Great Plains, where the modification of gust fronts by topography is less likely. Here, we broaden the investigation of gust fronts in complex terrain by statistically comparing characteristics of gust fronts that are pushed uphill and propagate atop the Mogollon Rim in Arizona to those that propagate down into and along the Rio Grande Valley in New Mexico. Using operational WSR-88D data and in situ observations from Automated Surface Observing System (ASOS) stations, 122 gust fronts in these regions are assessed to quantify changes in temperature, wind, relative humidity, and propagation speed as they pass over the weather stations. Gust fronts that propagated down into and along the Rio Grande Valley in New Mexico were generally associated with faster propagation speeds, larger decreases in temperature, and larger increases in wind speeds compared to gust fronts that reached the crest of the Mogollon Rim in Arizona. Gust fronts atop the Mogollon Rim in Arizona behaved less in accordance with density current theory compared to those in the Rio Grande Valley in New Mexico. The potential reasons for these results, and their implications for our understanding of terrain influence on gust front characteristics, are discussed.

Holocene Population Decline and Conservation Implication for the Western Hercules Beetle, Dynastes grantii (Coleoptera, Scarabaeidae)

The Western Hercules beetle (Dynastes grantii) is endemic to the highland forest habitats of southwestern United States and northern Mexico. The habitats harbor many endemic species, but are being threatened by rapid climate change and urban development. In this study, the genetic structure of D. grantii populations from southwestern United States was investigated. Specifically, genomic data from double-digest restriction-site-associated DNA sequencing libraries were utilized to test whether geographically distant populations from the Mogollon Rim (Arizona [N = 12 individuals] and New Mexico [N = 10 individuals]) are genetically structured. The study also estimated the effective population size of the Mogollon Rim populations based on genetic diversity. The results indicated that the 2 geographic populations from the Mogollon Rim were not genetically structured. A population size reduction was detected since the end of the last glacial period, which coincided with a reduction of forest habitat in the study area. The results implied that the connectivity and the size of highland forest habitats in the Mogollon Rim could have been the major factors shaping the population genetic structure and demographic history of D. grantii. The Western Hercules beetle could be a useful flagship species for local natural history education and to promote the conservation of highland forest habitats.

First Report of the Armillaria Root Disease Pathogen, Armillaria gallica, on Douglas-fir (Pseudotsuga menziesii) in Arizona

In August 2010, a mycelial fan (isolate AZ32F) of Armillaria sp. was collected from the root collar of a living Douglas-fir tree on the Mogollon Rim within the Coconino National Forest (approximate location 34°25′31.26″N, 111°20′41.04″W, elevation 2,293 m) in central Arizona. Mycelial fans under the bark of living trees are a sign of pathogenicity, and symptoms of the diseased tree included resinosis, sloughing bark, and thinning crown. The infected tree was located on a south-facing slope with approximately 30% tree cover, dominated by ponderosa pine (Pinus ponderosa), with lesser components of Douglas-fir and Gambel oak (Quercus gambelii). Based on three replications of somatic incompatibility tests against 24 tester isolates representing seven North American Armillaria spp., isolate AZ32F showed 100% intraspecific compatibility (colorless antagonism) with all four A. gallica isolates, 22% compatibility with A. calvescens, and 0% compatibility with the remaining Armillaria spp. Based on GenBank BLASTn of isolate AZ32F sequences, the partial LSU-IGS1 (GenBank Accession No. KF186682) showed 99 to 100% similarity to A. gallica and two other related Armillaria spp. with 99 to 100% coverage, and translation elongation factor-1 alpha (tef-1α) sequences (KC525954) showed 96% similarity to A. gallica (JF895844) with 100% coverage. Thus, isolate AZ32F was identified as A. gallica, based on somatic incompatibility tests and DNA sequences (partial LSU-IGS1 and tef-1α). Although the isolate is identified as A. gallica with similarities to other North American isolates, evidence is mounting that currently recognized A. gallica likely represents a species complex that comprises multiple phylogenetic species (4). Previous surveys in Arizona have noted A. mellea and A. solidipes (as A. ostoyae) (3), but A. gallica has never been previously confirmed in this state. Within North America, A. gallica is commonly reported east of the Rocky Mountains and in West Coast states of the United States, where it infects hardwoods and conifers including Douglas-fir (1,2). Its ecological behavior ranges from saprophyte to weak/aggressive pathogen (1,2). Because damage by A. gallica appears to increase on hosts predisposed by stress (1), further surveys are needed to document its distribution, frequency, and ecological behavior in the southwestern United States, where climate change will likely cause tree stress due to maladaptation. Continued surveys for Armillaria spp. will better determine their potential threat within the geologically and ecologically unique Mogollon Rim of Arizona. References: (1) K. Baumgartner and D. M. Rizzo. Plant Dis. 85:947, 2001. (2) N. J. Brazee and R. L. Wick. For. Ecol. Manage. 258:1605, 2009. (3) R. L. Gilbertson and D. M. Bigelow. J. Arizona-Nevada Acad. Sci. 31:13, 1998. (4) M.-S. Kim et al. Phytopathology 102:S4.63, 2012.

Mogollon Plateau: Fires Present and Future

Early on June 19, 2002, Paul Garcia looked off the rim of the Mogollon Plateau and did not like what he saw. Down toward Cibecue, the capital of the Fort Apache Reservation, home of the White Mountain Apaches, dark smoke boiled into the Arizona sky. The wind was pushing it in Garcia’s direction, toward the rim, as the prevailing southwest wind always pushed fires that start down on the Rez. The churning smoke—dark-tinged because of solid materials that volatilized without burning—told Garcia that the fire was gaining energy, building strength. He was the fire management officer of the Lakeside Ranger District, a unit of the Sitgreaves National Forest. His boss, a couple of steps up the chain of command, was Forest Supervisor John Bedell, who remembers getting a call from Garcia: “He said, ‘You know, this thing has some potential. . . . If they don’t catch it today, it’s going to get pretty big.’ ” The firefighters on the reservation didn’t catch it. The Rodeo Fire, which began as an act of arson near the Cibecue rodeo grounds, grew from a size of 1,000 acres on June 18 to 55,000 acres the next day. Garcia, Bedell, and a burgeoning army of Forest Service firefighters scrambled to meet the fire atop the rim, hoping to hold it at the rim road that marked the boundary between the reservation and the National Forest. They did not succeed. By mid-afternoon the fire had developed multiple towering plumes of smoke and ash. Its front advanced at an average rate of four miles an hour. Whole stands of eighty-foot trees ignited in an instant, shooting flames 400 feet high and lofting aerial firebrands half a mile downwind. By 4:00 p.m., some of those firebrands were spotting across the rim road. The Mogollon Rim is one of the most pronounced topographic features of the Southwest.

Performing the Feast: Visual Display and Suprahousehold Commensalism in the Puebloan Southwest

Ceramic bowls from the Greater Southwest are used to show how changes in the exterior decoration of serving vessels are associated with the proxemics of ritual performances. Across the northern Southwest the first use of exterior designs and polychrome ceramics is during the Pueblo III period, which corresponds to a shift in settlement aggregation and the use of open plaza spaces. With the transition to the more enclosed plazas of the Early Pueblo IV period, smaller and less visible exterior designs were used. The trend reversed itself with the use of larger plazas at later Pueblo IV period sites, where serving bowls with greater visual impact were used. Panregional trends are bolstered by a case study from the Mogollon Rim region of Arizona to show how changes in the visual performance characteristics of bowls are associated with the spatial and social proxemics of suprahousehold feasting rituals. I use several characteristics of serving bowls including their size, slip colors, paint and slip contrasts, and the size of exterior designs. These are related to the size and diversity of performance spaces, including plazas, and to other evidence for changes in feasting practices, such as roasting features and faunal remains. I conclude that the changes seen in serving vessels are important for looking at shifts in the scale, visibility, and diversity of public gatherings within Ancestral Pueblo social and ritual trajectories.