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We conducted a natural removal experiment, utilizing a local outbreak of sylvatic plague (Yersinia pestis) as the removal agent, to test the effects of removal of Gunnison's prairie dogs (Cynomys gunnisoni) on plant and nocturnal rodent assemblages in three grassland habitats (ponderosa, pinyon-juniper, and desert grasslands) in northern Arizona. We measured plant cover, rodent abundance, plant and rodent species richness, and plant and rodent composition at three treatment locations: active prairie dog colonies (n=15), inactive colonies (n=15), and control locations (n=15). Only the amount of plant cover differed significantly among treatments. As landscape level heterogeneity among habitat types increased, rodent...
Invasion by Tamarix (L.) can severely alter riparian areas of the western U.S., which are globally rare ecosystems. The upper Verde River, Arizona, is a relatively free-flowing river and has abundant native riparian vegetation. Tamarix is present on the upper Verde but is a minor component of the vegetation (8% of stems). This study sought to determine whether riparian vegetation characteristics differed between sites where Tamarix was present and sites where Tamarix was absent during the invasion of the upper Verde. We hypothesized that herbaceous understory and woody plant communities would differ between Tamarix present and absent sites. Our hypothesis was generally confirmed, the two types of sites were different....
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Vegetation and land-cover changes are not always directional but follow complex trajectories over space and time, driven by changing anthropogenic and abiotic conditions. We present a multi-observational approach to land-change analysis that addresses the complex geographic and temporal variability of vegetation changes related to climate and land use. Using land-ownership data as a proxy for land-use practices, multitemporal land-cover maps, and repeat photography dating to the late 19th century, we examine changing spatial and temporal distributions of two vegetation types with high conservation value in the southwestern United States: grasslands and riparian vegetation. In contrast to many reported vegetation...
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Final Report - Executive Summary: This final project report is prepared to summarize the research project titled “Assessing evapotranspiration rate changes for proposed restoration of the forested uplands of the Desert Landscape Conservation Cooperatives (LCC)” for the Desert LCC of the Bureau of Reclamation as a requirement for closing out the project. This report includes the scope of work, summary of research project, results, and conclusions.Among all of the components of the terrestrial water cycle, evapotranspiration (ET) consumes the largest amount of water. Accurate estimation of ET is very important to understand the influence of ET to the hydrologic response of recharge and runoff processes in the water...
Categories: Data, Publication; Types: Citation, Map Service, OGC WFS Layer, OGC WMS Layer, OGC WMS Service; Tags: 2012, ATMOSPHERE, ATMOSPHERE, ATMOSPHERIC WATER VAPOR, ATMOSPHERIC WATER VAPOR, All tags...
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Description: The upper Gila River in New Mexico is one of the few unobstructed rivers in the Colorado River Basin with largely intact native fish populations, including four federally listed and one state listed species.Freshwater systems throughout the West continue to be threatened by human encroachment and water development. Methodologies or decision support tools to evaluate resource management practices that foster an understanding of how fish species adapt to the effects of climate change are critical to future resource management planning.
Range managers in the Southwestern States are increasingly being required to develop management strategies that take into consideration the conservation of wildlife populations. However, information on many aspects of the fundamental biology and impacts of grazing on individual species is still lacking in the scientific and government literature. This report documents a project designed to assemble this information for terrestrial wildlife in Arizona and New Mexico that have the potential to be negatively impacted by grazing or range management practices. To achieve this, a two-stage panel process was developed that employed a variety of wildlife experts to create a list of potentially vulnerable species and to...
This study examined whether an individual plant's risk of herbivory was affected by its nearest neighbor. Individually potted tillers of Bouteloua gracilis were placed in a natural habitat with one of two neighbors (B. gracilis conspecifics or Aristida spp.), and in one of two cover treatments (high: in center of neighbor canopy, and low: at periphery of canopy). After one month, the experimental tillers were collected and scored for herbivory. We found that the less palatable neighbor, Aristida spp., reduced the probability that herbivores would feed upon experimental tillers in one of the two years of our study, but in both years increased the amount of feeding on those tillers that were attacked. The amount of...
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The influence of landscape spatial structure on ecological processes has recently received much attention. Comparisons are made here between the spatial structure of grasslands, and active and extirpated Gunnison's prairie dog (Cynomys gunnisoni Hollister) towns at the Petrified Forest National Park, Arizona, U.S.A. The spatial structure of bare ground was quatified using a box-counting technique to extract landscape fractal dimensions, D, and bare-ground patch size. These landscapes are fractal, and active prairie dog towns had higher fractal dimensions, i.e. a more homogeneous spatial structure as D approaches 2, than inactive towns, which had higher fractal dimensions than unmodified grasslands. Morisita's index...
Gasification of German oil shale and coal using concentrated solar energy as a heat source is studied in a fixed bed reactor under an argon atmosphere. The reactor allows direct absorption of irradiation resulting in high rates of temperature increase and hence in simultaneous decomposition of organic matter and carbonates present in the shale. Synthesis gases are produced consisting of H2, CO, CH4, and CO2. Basic considerations on stoichiometrics of shale gasification are presented. A macrokinetic modeling of the shale reaction rate based on conversion is established and verified experimentally. Further experiments are carried out with different irradiation times, shale-particle sizes, gasification temperatures...
Categories: Publication; Types: Citation; Tags: Arizona, Solar, Workforce
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Fish occurrence data to support high-resolution distribution models and test various community and macroecological hypotheses have not been available at the national scale. We present IchthyMaps, a database of high-quality historical fish occurrences covering fishes of the conterminous United States. Designed on the principles of metacommunity ecology, IchthyMaps is a compilation of presence records from atlases up to 1990, at the resolution of the 1:100,000 National Hydrography Database Plus (NHDPlus) inter-confluence stream segment, readily aggregated into hierarchically coarser units (e.g. hydrologic unit code 8-digit and 12-digit watersheds). IchthyMaps contains about 606,550 presence records for 1,038 species...
Categories: Data, Publication; Types: Citation; Tags: Alabama, Arizona, Arkansas, Biological Data, Biological sampling, All tags...
Distribution data on biodiversity features is a major component of conservation planning that are often inaccurate; thus, the true distribution of each feature is commonly over- or underrepresented. The selection of distribution data sets may therefore lead to variability in the spatial configuration and size of proposed reserve networks and uncertainty regarding the extent to which these networks actually contain the biodiversity features they were identified to protect. Our goals were to investigate the impact on reserve selection of choosing different distribution data sets and to propose novel methods to minimize uncertainty about target attainment within reserves. To do so, we used common prioritization methods...
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Article Abstract: Although riparian and aquatic ecosystems make up a small fraction of the area in arid and semi-arid lands, they are critical for the survival of desert life. There are, however, few compendia of efforts to define the quantity of water needed to maintain these ecosystems and understand the risks and stressors to them. Through our analysis we found that 62% of the rivers examined in the deserts of the U.S. and Mexico have had just one study over the past four decades and 67% of studies used qualitative methods. Furthermore, only one-third of the 312 species catalogued in our work have been studied more than once and only 5% have been considered five or more times. The most common risks or stressors...
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We analyzed variation in canopy closure around 47 Mexican spotted owl (Strix occidentalis lucida) nest sires and 47 random forest sites on the Coconino National Forest in northcentral Arizona. We mapped distinct habitat polygons on 1:15,840 color aerial photographs, assigned each polygon to one of 4 canopy-closure classes (70%), and measured the area in each canopy class within 5 concentric analysis zones with radii of 0.1, 0.4, 0.8, 1.2, and 1.6 km (delineating rings of about 4, 47, 150, 252, and 352 ha). Landscape composition differed between spotted owl nest and random sites (P 70% canopy-closure class and less area in the 70% canopy predominated Nesting spotted owls selected areas with denser canopy than randomly...
The current distribution and status of populations of the southwestern toad, Bufo microscaphus, are of considerable interest given the suspected decline in anuran amphibians in the western United States (Blaustein and Wake 1990, Sweet 1991). This bufonid, typically associated with riparian habitats in the desert Southwest, is largely absent from much of its former range in southern California (Sweet personal communication). In Arizona and Utah, B. microscaphus is known to hybridize with a closely related toad, B. woodhousii, and it appears that B. woodhousii has replaced B. microscaphus at a number of localities (Sullivan 1986). Given the interest in this species and the lack of information on populations in Arizona,...
Ecologists increasingly use plot-scale data to inform research and policy related to regional and global environmental change. For soil chemistry research, scaling from the plot to the region is especially difficult due to high spatial variability at all scales. We used a hierarchical Bayesian model of plot-scale soil nutrient pools to predict storage of soil organic carbon (oC), inorganic carbon (iC), total nitrogen (N), and available phosphorus (avP) in a 7962-km2 area including the Phoenix, Arizona, USA, metropolitan area and its desert and agricultural surroundings. The Bayesian approach was compared to a traditional approach that multiplied mean values for urban mesic residential, urban xeric residential, nonresidential...
Arid grasslands are often presumed to exist in one of two alternate stable states: grassland or desertified shrubland. While the conversion to shrubland can occur rather rapidly following intense overgrazing, the recovery of perennial grasses is often presumed to be difficult or impossible even with livestock removal. We examined vegetation and rodent communities at a desertified shrubland site from which livestock had been removed for more than four decades. Total shrub cover was similar but differed in composition across the grazing fence. Larrea tridentata had significantly higher cover outside while Parthenium incanum had significantly higher cover inside the fence. Basal perennial grass cover was significantly...
Sympatric populations of Cophosaurus texanus and Callisaurus draconoides were periodically sampled from March 1973 through April 1974 at Burro Creek, Mohave County, Arizona. Callisaurus were also sampled at Rock Valley, Nye County, Nevada. Sex ratios were skewed in favor of males in the adult Cophosaurus but were equal in both adult populations of Callisaurus. Both species became sexually mature as yearlings. Mean clutch sizes were 3.55 (+/- 0.83) for Cophosaurus, and 4.25 (+/- 1.08) and 5.07 (+/- 1.33) for Callisaurus at Burro Creek and Rock Valley respectively. Evidence of multiple clutches was exhibited by both species. Egg weight/body weight ratios for both species and clutch weight/body weight ratios for Cophosaurus...
The southwestern willow flycatcher (SWFL; Empidonax traillii extimus) is an endangered songbird whose habitat has declined dramatically over the last century. Understanding habitat selection patterns and the ability to identify potential breeding areas for the SWFL is crucial to the management and conservation of this species. We developed a multiscaled model of SWFL breeding habitat with a Geographic Information System (GIS), survey data, GIS variables, and multiple logistic regressions. We obtained presence and absence survey data from a riverine ecosystem and a reservoir delta in south-central Arizona, USA, in 1999. We extracted the GIS variables from satellite imagery and digital elevation models to characterize...
Encroachment of woody plants into grasslands, and subsequent brush management, are among the most prominent changes to occur in arid and semiarid systems over the past century. Despite the resulting widespread changes in landcover, substantial uncertainty about the biogeochemical impacts of woody proliferation and brush management exists. We explored the role of shrub encroachment and brush management on leaf litter decomposition in a semidesert grassland where velvet mesquite (Prosopis velutina) abundance has increased over the past 100 years. This change in physiognomy may affect decomposition directly, through altered litter quality or quantity, and indirectly through altered canopy structure. To assess the direct...
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Successful implementation of environmental flow projects depends on land and water managers having clear objectives and access to reliable data. This guidebook provides information on a variety of methods that can be utilized under different fiscal or temporal constraints to determine and implement appropriate environmental flow targets. Based on evidence from cases focused in the Southwestern United States and Northern Mexico, steps are suggested to help ensure maintenance of flows under uncertain future natural and socioeconomic conditions. The importance of education and engagement to increase acceptance of environmental flows based projects and gain key player and community buy in is described. Limitations on...
map background search result map search result map The Gunnison's prairie dog structures a high desert grassland landscape as a keystone engineer Canopy closure around nest sites of Mexican spotted owls in northcentral Arizona Historical Stream Fish Distribution Database for the Conterminous United States (1950-1990): IchthyMaps Historical and Contemporary Geographic Data Reveal Complex Spatial and Temporal Responses of Vegetation to Climate and Land Stewardship Report and Publications: Assessing Evapotranspiration Rate Changes for Proposed Restoration of the Forested Uplands of the DLCC Desert Flows Methodology Guidebook Environmental flows in the desert rivers of the United States and Mexico: Synthesis of available data and gap analysis Science Brief for Resource Managers: Metacommunity Dynamics of Gila River Fishes The Gunnison's prairie dog structures a high desert grassland landscape as a keystone engineer Canopy closure around nest sites of Mexican spotted owls in northcentral Arizona Historical and Contemporary Geographic Data Reveal Complex Spatial and Temporal Responses of Vegetation to Climate and Land Stewardship Science Brief for Resource Managers: Metacommunity Dynamics of Gila River Fishes Report and Publications: Assessing Evapotranspiration Rate Changes for Proposed Restoration of the Forested Uplands of the DLCC Desert Flows Methodology Guidebook Environmental flows in the desert rivers of the United States and Mexico: Synthesis of available data and gap analysis Historical Stream Fish Distribution Database for the Conterminous United States (1950-1990): IchthyMaps