1925 research outputs found
Sort by
Working paper 36: Wildlife and fire: Impacts of wildfire and prescribed fire on wildlife and habitats in southwestern coniferous forests
Get PDFThe southwestern United States has experienced over a century of fire suppression that has altered natural fire regimes and caused an increase in fuel loads and increased fire frequency, severity, intensity, and size
of wildfires (Covington and Moore 1994, Moore et al. 1999, Swetnam et al. 2001). Long-term fire exclusion, livestock grazing, and management practices have resulted in more dense forest structure that is departed from its natural range of variability, and forests that once experienced frequent low intensity fires are now more susceptible to large scale, high intensity stand-replacing fires, drought, and insect attacks (Covington and Moore 1994, Moore et al. 1999, Allen et al. 2002, Schoennagel et al. 2004). Large intense wildfires can have substantial effects on native plants and animals and their habitats. Changes in vegetative structure and composition,
cover type conversions, habitat fragmentation, and the creation of edge effects are some of the major impacts that large-scale fires can have on wildlife habitat.
The return of fire-driven processes to dry coniferous forests in the Southwest can aid in restoring ecological processes, create ecologically important early successional habitats, and it helps maintain biodiversity of wildlife habitats (Brawn et al. 2001). Fire is natural disturbance that plays an important role in creating a mosaic of habitats and successional stages that support a suite of native plants and wildlife within a landscape (Angelstam 1998). A mosaic of habitat types at the landscape scale increases the complexity of landscape structure and composition, and increases diversity on multiple levels by providing multiple seral stages that many animals can use throughout their life cycle. Historical fire exclusion along with other management activities has reduced landscape- scale heterogeneity by reducing the amount of fire- generated early successional forests and the complexity of habitats that were historically maintained by frequent low-severity fire (Noss et al. 2006a). Restoring and facilitating natural fire regimes can meet both restoration and conservation objectives, and return functional processes to our forests while reducing the risk of large catastrophic wildfires that impact wildlife species.
Understanding how fire severity, extent, seasonality, spatial complexity, and post-fire forest conditions influence species response is important for predicting the effects of wildfire and management actions on wildlife. Site specific factors, disturbance history, and fire severity are important elements in understanding species abundance and distribution after fire events. This paper focuses on the use and effects of wildfire (natural ignition), prescribed fire (purposeful ignition), and restoration treatments (thinning and prescribed fire) on terrestrial fauna in dry coniferous forests primarily in the southwestern U.S
The effects of education on students' perception of modeling in software engineering
Get PDFModels in software engineering bring significant potential in improvements of productivity of engineers, and improved quality of the artifacts they produce. Despite this significant potential, modeling adoption in practice remains rather low. Computer Science and software engineering curriculums may be one factor that causes this low adoption. In this study, we investigate the effects of education on students’ perception of modeling. We conducted a survey in three separate institutions, in Canada, Israel, and the U.S. The survey covers various aspects of modeling and addresses students ranging from a first year in undergraduate studies until final years in graduate studies.
The survey’s findings suggest that the perception of undergraduate students towards modeling declines as they progress in their studies. While graduate students tend to be more favorable of modeling, their perception also declines over the years. The results also suggest that students prefer more modeling content to be integrated earlier in the curriculum
Reference Conditions and Spatial Dynamics in a Southwestern Dry Mixed-Conifer Forest
Get PDFStructural conditions in southwestern “frequent-fire” forests, or forests that have a history of frequent, low-severity fire, have changed considerably since Euro-American settlement (ca. late 1800's); these changes are primarily due to excessive livestock grazing, extractive logging, road construction, and organized fire suppression. As a result of these land-use changes, forest densities in many locations have increased, contributing to increases in fire size and severity and alterations to ecosystem function. A recognition of these impacts has prompted interest in forest restoration treatments across broad swaths of the landscape. Forest restoration attempts to mimic the natural range of variability - or the structure and function inherent to intact natural ecosystems - but many aspects of these ecosystems are poorly understood. In combination with studies of the natural disturbance regime, reference conditions and studies of the natural range of variability also provide an ecological basis for silvicultural treatments. Spatial pattern, or the horizontal distribution of trees, is an important component of the natural range of variability and influences a wide array of ecological processes.
With this study, we reconstructed historical structure (density and spatial pattern) and species composition for four dry mixed-conifer stands on the Mogollon Rim,
Arizona, USA. We reconstructed conditions from the year 1879, the time of the widespread cessation of fire in the area. We found that these forests showed evidence of increased tree density between 1879 and 2014 with major increases in density in the smaller size classes. During this time period, the number of live trees ha-1 increased from an average of 129.5 to 744.3, basal area increased from 10.1 to 41.9 m2 ha-1, and mean canopy cover increased from 14.8 to 54.7 percent. Our results also showed shifts in species composition to a higher relative proportion of Abies concolor, and Pseudotsuga menziesii, and a lower relative proportion of Pinus ponderosa and Quercus gambelii. Mean group size, or the average number of trees in explicit tree groups, also increased as tree canopy cover became more continuous. Finally, we investigated the roles of different species groups within fine-scale spatial pattern. Species groups showed distinctly different patterns, suggesting that the patterns of individual species are an important consideration during the implementation of silvicultural treatments that are meant to mimic natural patterns and processes. Mechanical treatments and thinning operations in dry mixed-conifer forests on the Mogollon Rim should target an aggregated spatial structure of leave trees with a range of group sizes within a given site. Treatments based on the natural range of variability are likely to increase resistance and resilience of these ecosystems in the face of uncertain future conditions
A new drought tipping point for conifer mortality
Get PDF(Huang et al 2015 Environ. Res. Lett. 10 024011) present a method for predicting mortality of ponderosa pine (Pinus ponderosa) and pinyon pine (Pinus edulis) in the Southwestern US during severe drought based on the relationship between the standardized precipitation–evapotranspiration index (SPEI) and annual tree ring growth. Ring growth was zero when SPEI for September to July was −1.64. The threshold SPEI of −1.64 was successful in distinguishing areas with high tree mortality during recent severe drought from areas with low mortality, and is proposed to be a tipping point of drought severity leading to tree mortality. Below, I discuss this work in more detail
Comparative analysis of subtyping methods against a whole-genome-sequencing standard for Salmonella enterica serotype Enteritidis.
Get PDFA retrospective investigation was performed to evaluate whole-genome sequencing as a benchmark for comparing molecular subtyping methods for Salmonella enterica serotype Enteritidis and survey the population structure of commonly encountered S. enterica serotype Enteritidis outbreak isolates in the United States. A total of 52 S. enterica serotype Enteritidis isolates representing 16 major outbreaks and three sporadic cases collected between 2001 and 2012 were sequenced and subjected to subtyping by four different methods: (i) whole-genome single-nucleotide-polymorphism typing (WGST), (ii) multiple-locus variable-number tandem-repeat (VNTR) analysis (MLVA), (iii) clustered regularly interspaced short palindromic repeats combined with multi-virulence-locus sequence typing (CRISPR-MVLST), and (iv) pulsed-field gel electrophoresis (PFGE). WGST resolved all outbreak clusters and provided useful robust phylogenetic inference results with high epidemiological correlation. While both MLVA and CRISPR-MVLST yielded higher discriminatory power than PFGE, MLVA outperformed the other methods in delineating outbreak clusters whereas CRISPR-MVLST showed the potential to trace major lineages and ecological origins of S. enterica serotype Enteritidis. Our results suggested that whole-genome sequencing makes a viable platform for the evaluation and benchmarking of molecular subtyping methods
Mapped permanent quadrats: A window through time into herbaceous plant demography
Get PDFLong-term spatially explicit mapped datasets of herbaceous plant population dynamics are rare and intrinsically valuable beyond measure. These types of data can provide vital information to address key ecological questions related to plant demography, population and community responses to climate and anthropogenic modifications across the landscape. The long-term historical dataset, which is the focus of this thesis, provides examples of the ecological value of data derived from long-term permanent chart quadrats.
In Chapter 2, I provide metadata from a long-term dataset that consists of 98 permanent 1-m2 quadrats located in the ponderosa pine-bunchgrass ecosystem surrounding Flagstaff, Arizona, USA. Individual plants in these quadrats were identified and mapped annually from 2002-2014. Original quadrats were established in 1912-1927 and were mapped sporadically until 1940. Quadrats were located in ungrazed exclosures and in pastures grazed at various intensities by livestock. I provide the following data and data formats: (1) high-resolution image files (*.tiff); (2) the digitized maps in shapefile format; (3) a tabular representation of centroid or point location (x, y coordinates), and basal cover for plants mapped as polygons; (4) a species list including the total records for each species; (5) quadrat inventory of the years each quadrat was sampled; (6) quadrat information including GPS coordinates and elevation; and (7) monthly precipitation and temperature records. The metadata results (data products) will be published in research archives. In addition, data from these permanent chart quadrats will be used to determine species-specific vital rates in Chapter 4.
In Chapter 3, I developed an electronic field data collection method to remap the herbaceous vegetation on the chart quadrats described above. The method uses ESRI ArcMap to collect plant data on field computers, which: (1) creates a digital data capture system; (2) allows the ability to search and manipulate the data from directly in the field; (3) allows for a visual display of the previous year’s data map for reference in the field; (4) reduces the likelihood of data transposition errors; and (5) removes the need to digitize maps from paper copies. I tested the electronic field data collection method against the traditional paper mapping method to assess the efficiency of each method. The electronic data collection method increased the amount of time necessary to map the vegetation on each quadrat, however, the electronic method significantly diminished the amount of time needed to process each quadrat in the office. Implementing the electronic method can reduce the amount of time and resources needed to annually re-map permanent chart quadrats.
In Chapter 4, I used detailed local climate variables and data from the annually remapped data set (2002-2014) described above to examine the effects of climate on the demographic rates of a dominant graminoid, Arizona fescue (Festuca arizonica Vasey). I constructed life tables to examine vital rates (e.g., survival probabilities, growth, and life expectancies) for this focal species. I made population projections using the species’ state (size) and precipitation variables using Integral Projection Models (IPMs) to quantify the direct influence of seasonal precipitation on the vital rates of this dominant perennial bunchgrass.
We found that altering the size structure of the population of Arizona fescue can increase life span by increasing the number of individuals belonging to the larger size classes with higher probabilities of survival. Furthermore, we found that the survival and growth of Arizona fescue was strongly linked with winter and spring precipitation, respectively.
In summary, in this thesis I compiled metadata from a historical dataset, developed an electronic field capture method, and used these data to examine the demographic rates of a dominant bunchgrass species in northern Arizona. Gaining a better understanding of the climatic factors that drive plant populations will allow land managers to make informed decisions regarding land-use practices and the implementation of restoration treatments in the Southwest. In an era characterized by anthropogenic climate and land-use change, understanding the impacts these changes may have on forest ecosystems is crucial in our effort to anticipate how plant communities may respond over time
2015 Annual Report to the USDA Forest Service under Sponsor Award #14-DG-11031600-055 for 2014 (NAU Projects 1002442-1002446) and #15-DG-11031600-073 for 2015 (NAU Projects 1002742-1002747)
Get PDFThis report presents an integrated and coordinated series of actions for $2.4 million awarded to the ERI in Fiscal Years 2014 and 2015 under CFDA 10.694, Southwest Forest Health and Wildfire Prevention.
The information provided herein reflects our annual progress as of 07/01/2015 and comprises the final report for 2014 deliverables conducted under #14-DG-11031600-055 (NAU Projects 1002442-1002446). 2015 deliverables under #15-DG-11031600-073 for 2015 (NAU Projects 1002742-1002747) have just started.
All of the activities (deliverables) summarized in this report respond to land manager and stakeholder requests and needs. The deliverables are informed by best available science and scientific evidence which is translated into the language and product appropriate for the target audience. The ERI actively delivers information using a variety of approaches that includes individual and group presentations and discussions, to printed and electronically accessible fact sheets, short technical reports, longer white papers and management reports, and peer reviewed archival literature
Profits and pragmatism: The commercial lives of market universities in Kenya and Uganda
Get PDFThe increased commercialization of higher education is a theme that has attracted considerable global attention. In response to changes in traditional sources of funding, many universities, public and private, have opted to source revenue from the marketplace. This article delves into the complexities of the entry into the marketplace by Kenyan and Ugandan universities. The local and international impetus for this movement in both countries and not in Tanzania are discussed, the perverseness and limits of commercialization delineated, and the positive and negative consequences of commercialization chronicled, all within the shifting global paradigm of higher education development. The Kenyan and Ugandan context cautions that ensuring a healthy mix between entry into the marketplace and the retention of the core mission of universities remains a critical challenge for governments and university administrators
North America's net terrestrial CO2 exchange with the atmosphere 1990–2009
Get PDFScientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1