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Ancient Maya regional settlement and inter-site analysis: The 2013 West-Central Belize LiDAR survey
Get PDFDuring April and May 2013, a total of 1057 km2 of LiDAR was flown by NCALM for a consortium of archaeologists working in West-central Belize, making this the largest surveyed area within the Mayan lowlands. Encompassing the Belize Valley and the Vaca Plateau, West-central Belize is one of the most actively researched parts of the Maya lowlands; however, until this effort, no comprehensive survey connecting all settlement had been conducted. Archaeological projects have investigated at least 18 different sites within this region. Thus, a large body of archaeological research provides both the temporal and spatial parameters for the varied ancient Maya centers that once occupied this area; importantly, these data can be used to help interpret the collected LiDAR data. The goal of the 2013 LiDAR campaign was to gain information on the distribution of ancient Maya settlement and sites on the landscape and, particularly, to determine how the landscape was used between known centers. The data that were acquired through the 2013 LiDAR campaign have significance for interpreting both the composition and limits of ancient Maya political units. This paper presents the initial results of these new data and suggests a developmental model for ancient Maya polities
Perceptions of trekking tourism and social and environmental change in Nepal's Himalayas
Get PDFThe Himalayas are among the world’s youngest mountain ranges. In addition to the geologic processes of mountain building and erosion, they are also highly vulnerable to human influenced change, occurring at local, national, regional, and international scales. A photo-elicitation methodology is employed to show how residents perceive those changes from historical perspectives, as well as their current conditions and impacts on their daily lives. Nepal’s Khumbu region has undergone major social and environmental transformations since the 1960s when international trekking first began to influence the area's economy. The current perceptions of Khumbu residents of these changes is assessed through photo-elicitation interviews. Their responses are placed in the historical context of: (i) institutional and political changes, much of which have been driven by national government policies; (ii) social and economic changes, for which the tourism economy has been central; and (iii) environmental changes, reflecting the impacts of resource management and climate change. The mostly positive perceptions of Khumbu residents toward how their region has changed reflects general improvements in the physical and cultural landscapes of the Khumbu over time, as well as its continuing geographic isolation, which has helped to slow the rate of globalization, while also keeping the region a dynamic and popular tourist destination
Chemical abrasion applied to LA-ICP-MS U-Pb zircon geochronology
Get PDFZircon (ZrSiO4) is the most commonly used mineral in U-Pb geochronology. Although it has proven to be a robust chronometer, it can suffer from Pb-loss or elevated common Pb, both of which impede precision and accuracy of age determinations. Chemical abrasion of zircon involves thermal annealing followed by relatively low temperature partial dissolution in HF acid. It was specifically developed to minimize or eliminate the effects of Pb-loss prior to analysis using Thermal Ionization Mass Spectrometry (TIMS). Here we test the application of chemical abrasion to Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) by analyzing zircons from both untreated and chemically abraded samples. Rates of ablation for high alpha-dose non-treated zircons are up to 25% faster than chemically abraded equivalents. Ablation of 91500 zircon reference material demonstrates a ca. 3% greater down-hole fractionation of Pb-206/U-238 for non-treated zircons. These disparities necessitate using chemical abrasion for both primary reference material and unknowns to avoid applying an incorrect laser induced fractionation correction. All treated samples display a marked increase in the degree of concordance and/or lowering of common Pb, thereby illustrating the effectiveness of chemical abrasion to LA-ICP-MS U-Pb zircon geochronology
Genomic epidemiology of the Haitian cholera outbreak: a single introduction followed by rapid, extensive, and continued spread characterized the onset of the epidemic.
Get PDFFor centuries, cholera has been one of the most feared diseases. The causative agent Vibrio cholerae is a waterborne Gram-negative enteric pathogen eliciting a severe watery diarrheal disease. In October 2010, the seventh pandemic reached Haiti, a country that had not experienced cholera for more than a century. By using whole-genome sequence typing and mapping strategies of 116 serotype O1 strains from global sources, including 44 Haitian genomes, we present a detailed reconstructed evolutionary history of the seventh pandemic with a focus on the Haitian outbreak. We catalogued subtle genomic alterations at the nucleotide level in the genome core and architectural rearrangements from whole-genome map comparisons. Isolates closely related to the Haitian isolates caused several recent outbreaks in southern Asia. This study provides evidence for a single-source introduction of cholera from Nepal into Haiti followed by rapid, extensive, and continued clonal expansion. The phylogeographic patterns in both southern Asia and Haiti argue for the rapid dissemination of V. cholerae across the landscape necessitating real-time surveillance efforts to complement the whole-genome epidemiological analysis. As eradication efforts move forward, phylogeographic knowledge will be important for identifying persistent sources and monitoring success at regional levels. The results of molecular and epidemiological analyses of this outbreak suggest that an indigenous Haitian source of V. cholerae is unlikely and that an indigenous source has not contributed to the genomic evolution of this clade. In this genomic epidemiology study, we have applied high-resolution whole-genome-based sequence typing methodologies on a comprehensive set of genome sequences that have become available in the aftermath of the Haitian cholera epidemic. These sequence resources enabled us to reassess the degree of genomic heterogeneity within the Vibrio cholerae O1 serotype and to refine boundaries and evolutionary relationships. The established phylogenomic framework showed how outbreak isolates fit into the global phylogeographic patterns compared to a comprehensive globally and temporally diverse strain collection and provides strong molecular evidence that points to a nonindigenous source of the 2010 Haitian cholera outbreak and refines epidemiological standards used in outbreak investigations for outbreak inclusion/exclusion following the concept of genomic epidemiology. The generated phylogenomic data have major public health relevance in translating sequence-based information to assist in future diagnostic, epidemiological, surveillance, and forensic studies of cholera
Fact sheet: Ecology of Rusby's Milkvetch (Astragulus rusbyi), a rare endemic of northern Arizona ponderosa pine forests.
Get PDFAstragalus rusbyi (Rusby's milkvetch) grows primarily in ponderosa pine forests and in aspen groves, but it also may be found in mixed-conifer forests. Populations are mainly concentrated on basaltic soils in two areas in northern Arizona: around the San Francisco Peaks (primarily on the southern and western sides of the Peaks) and also in the vicinity of Kendrick Mountain. It is ranked 'vulnerable' (G3) by NatureServe, a non-profit conservation organization, and is on the U.S. Forest Service sensitive species list for Region 3 (Southwestern Region). Some of its habitat has been subjected to large wildfires over the last few decades. Other areas have under-gone ecological restoration treatments (tree thinning and prescribed burning), and much of its range is slated to undergo such treatments in the near future. This fact sheet summarizes findings from previous research conduct-ed within its habitat and range
Fact Sheet: What Are the Consequences of Cutting Old Ponderosa Pine Trees? A Systematic Review
Get PDFIn ponderosa pine forests, restoration treatments (including thinning and prescribed burning) are being implemented to reduce the threat of stand-replacing fire and to restore ecosystem structure, composition, and function to within the natural range of variability. In implementing treatments, old trees (>150 years) are typically retained due to their relative rarity and as-sumed ecological importance, and because old trees take centuries to replace. The oldest ponderosa pine have unique morphological and presumably functional characteristics and can exceed 700 years in age (Huckaby et al. 2003). The morphology of such trees often includes large trunks and branches, deeply furrowed bark, deformities in crown structure, epicormic branching, big mistletoe brooms, or external fire scars (Harrington and Sackett 1992; Huckaby et al. 2003; Morgan et al. 2002; Swetnam and Brown 1992), and thus they may have different functions than younger trees related to these different structures. As treatments are implemented at increasingly larger scales, a wide variety of thinning treatments, including cutting old trees, have been proposed. We used systematic review methodology to specifically address the question: What are the consequences to ecosystem function of cutting old ponderosa pine trees; particularly, do old trees serve a different function than younger trees
Fact Sheet: Unsupported inferences of high-severity fire in historical dry forests of the western United States: response to Williams and Baker.
Get PDFA recent study in Global Ecology and Biogeography (Williams and Baker 2012, hereafter W&B) described the historical conditions of forest structure and fire regimes on four large landscapes in Arizona, Colorado and Oregon. W&B used notes made by land surveyors who worked in these landscapes in the late 1800s and early 1900s, a period before many impacts of modern land uses, such as large-scale fire control, took place. Based on these data, W&B developed an interpretation of past conditions in ponderosa pine and dry mixed conifer forests that differs from previous research. W&B asserted that these forests historically included relatively high densities because of past fire regimes of moderate to high severity fires. Natural regeneration following such fires would lead to numerous, small and similar aged trees. W&B concluded that current management practices of thinning small trees and using low-severity prescribed burns would damage forests, rather than restore them. The inferences drawn by W&B about past forest ecology contrast sharply those reported by numerous previous researchers, who used tree-ring and historical data to show that dry forests had predominantly surface fire regimes with relatively open, uneven-aged forests. A group of 18 forest ecologists, concerned about the lack of scientific support for the conclusions by W&B, wrote a response (Fule et al. 2013). This fact sheet summarizes the key issues of our response. A rebuttal to the response was published by Williams and Baker (2014)
Issues in forest restoration: The history of the four forest restoration initiative: 1980s-2010
Get PDFIn this paper, we (Dave Egan and Erik Nielsen) present our account of how a divergent group of people, with a variety of values, interests and resources, recognized a social and ecological problem, and came together to find a collective answer. This is the story of the landscape-scale forest restoration effort known as the Four Forest Restoration Initiative (4FRI) and the ideas, groups of people, and series of related events as well as collaborative projects from which it eventually emerged. It is a record of the progress these people made from the mid-1990s until 2010. This is the latest chapter in the long and dynamic story of people as members of the ponderosa pine ecosystem in Arizona. As such, it provides a glimpse into the multi-dimensional interplay between humans and the environment in the American Southwest today. Our information is based on earlier work by Windy Greer Selig and Nielsen designed to record the history of 4FRI. That work included identifying a timeline, compiling stakeholder comments about the importance of different events and documents as well as conducting stakeholder interviews. We used their study along with documentary evidence, both published and unpublished, and more recent interviews of other 4FRI stakeholders to produce this history of 4FRI
Heads or tails: do stranded fish (mosquitofish, Gambusia affinis) know where they are on a slope and how to return to the water?
Get PDFAquatic vertebrates that emerge onto land to spawn, feed, or evade aquatic predators must return to the water to avoid dehydration or asphyxiation. How do such aquatic organisms determine their location on land? Do particular behaviors facilitate a safe return to the aquatic realm? In this study, we asked: will fully-aquatic mosquitofish (Gambusia affinis) stranded on a slope modulate locomotor behavior according to body position to facilitate movement back into the water? To address this question, mosquitofish (n = 53) were placed in four positions relative to an artificial slope (30° inclination) and their responses to stranding were recorded, categorized, and quantified. We found that mosquitofish may remain immobile for up to three minutes after being stranded and then initiate either a “roll” or a “leap”. During a roll, mass is destabilized to trigger a downslope tumble; during a leap, the fish jumps up, above the substrate. When mosquitofish are oriented with the long axis of the body at 90° to the slope, they almost always (97%) initiate a roll. A roll is an energetically inexpensive way to move back into the water from a cross-slope body orientation because potential energy is converted back into kinetic energy. When placed with their heads toward the apex of the slope, most mosquitofish (>50%) produce a tail-flip jump to leap into ballistic flight. Because a tail-flip generates a caudually-oriented flight trajectory, this locomotor movement will effectively propel a fish downhill when the head is oriented up-slope. However, because the mass of the body is elevated against gravity, leaps require more mechanical work than rolls. We suggest that mosquitofish use the otolith-vestibular system to sense body position and generate a behavior that is “matched” to their orientation on a slope, thereby increasing the probability of a safe return to the water, relative to the energy expended
An econometric analysis of the impact of forest restoration on agriculture in the Verde River Watershed, Arizona: Working paper series--14-04
Get PDFKnown as the Four Forest Restoration Initiative (4FRI), the US Forest Service is planning a large-scale restoration of ponderosa pine forests in the Verde River watershed in central Arizona. This paper uses a reduced-form econometric regression model with 1969-2010 time-series data to estimate the economic benefits of the increased water yield due to planned forest restoration of the first phase of 4FRI. We split data sample into 1969-1989 and 1990-2010 time periods, and conclude that during the second time period, water use is statistically and economically significant. This is consistent with the reality that the Verde River watershed has been in drought since the early 1990s. Our central finding is that, if water use increases by 1%, the farm income will increase by 1.33%. If a 5-10% increase in water yield caused by the first phase of the 4FRI is all used by agriculture, agricultural income will increase by 6.65-13.3% annually