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Assessing Cheatgrass (Bromus Tectorum) Genetic Diversity And Population Structure Using Rapd And Microsatellite Molecular Markers, Michael C. Ashley, William S. Longland Apr 2009

Assessing Cheatgrass (Bromus Tectorum) Genetic Diversity And Population Structure Using Rapd And Microsatellite Molecular Markers, Michael C. Ashley, William S. Longland

Western North American Naturalist

Two molecular marker systems, random amplified polymorphic DNA (RAPD) and microsatellites, were used to evaluate population diversity and differentiation in 4 northern Nevada Bromus tectorum populations. From 80 RAPD primers, we found 16 (20%) that yielded 165 strong repeatable bands. Of those bands, 60 (35.8%) were polymorphic. Of those, 21 met data-pruning guidelines for final analysis. RAPD variation was moderate (x̄ = 0.363, sx̄ = 0.022), ranging from 0.312 to 0.404. Microsatellite variation was similar (x̄ = 0.234, sx̄ = 0.051) but varied more widely, ranging from 0.009 to 0.551. All populations were out of Hardy-Weinberg …

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Relationship Between Cheatgrass Coverage And The Relative Abundance Of Snakes On Antelope Island, Utah, Lucas K. Hall, John F. Mull, John F. Cavitt Apr 2009

Relationship Between Cheatgrass Coverage And The Relative Abundance Of Snakes On Antelope Island, Utah, Lucas K. Hall, John F. Mull, John F. Cavitt

Western North American Naturalist

Cheatgrass (Bromus tectorum) is an invasive annual known to negatively impact many shrub-dependent organisms; however, relatively little research has examined how it affects snake communities. Bromus tectorum is abundant at Antelope Island State Park, Davis County, Utah, and could be a possible threat to snake populations. Study sites representing different B. tectorum coverage percentages were established to measure relative abundance of snakes. Snakes were captured from June to September 2005 primarily by using funnel traps attached to drift-fence arrays. Linear regression revealed a negative relationship between B. tectorum coverage (%) and the relative abundance of the Great Basin …

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A Comparison Of Two Common Classification Procedures For Economical Urban Land Cover Mapping Using Naip Imagery, Kent Lowell Simons Mar 2009

A Comparison Of Two Common Classification Procedures For Economical Urban Land Cover Mapping Using Naip Imagery, Kent Lowell Simons

Theses and Dissertations

Detailed urban land cover maps are increasingly useful and important applications of remote sensing. Municipal agencies and others use land cover maps and data for numerous critical local planning and monitoring functions and for urban geographical research studies. Because of this, there is a demand for accurate urban land cover maps that can be produced quickly and economically. The availability of very high resolution multispectral imagery is an important factor in enabling such production, as the judicious selection of source imagery has a large impact on the resulting map products. Likewise, the implementation of appropriate digital image processing methods is …

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Influence Of Pocket Gopher Mounds On Nonnative Plant Establishment In A Shrubsteppe Ecosystem, G. Page Kyle, Andrew Kulmatiski, Karen H. Beard Sep 2008

Influence Of Pocket Gopher Mounds On Nonnative Plant Establishment In A Shrubsteppe Ecosystem, G. Page Kyle, Andrew Kulmatiski, Karen H. Beard

Western North American Naturalist

Soil disturbances across a wide range of spatial scales have been found to promote the establishment of invasive plant species. This study addresses whether mounds built by northern pocket gophers (Thomomys talpoides) in the shrubsteppe environment of north central Washington are facilitating plant invasions into native-dominated fields. Research was conducted in native-dominated plant communities adjacent to ex-arable, nonnative-dominated fields. To determine the effect of mounds on plant growth, we recorded new establishment and persistence of all plant species over 2 growing seasons on 10–19 mound and intermound areas in 10 fields. Nonnative plant establishment was not affected by …

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Use Of A Mine By Eastern Pipistrelles (Perimyotis Subflavus) In East Central Nebraska, Jason P. Damm, Keith Geluso Sep 2008

Use Of A Mine By Eastern Pipistrelles (Perimyotis Subflavus) In East Central Nebraska, Jason P. Damm, Keith Geluso

Western North American Naturalist

The eastern pipistrelle (Perimyotis subflavus) is relatively common and widespread throughout the eastern United States. In recent decades, the distribution of P. subflavus has expanded westward across the Great Plains, and little information exists on its natural history in this region. In east central Nebraska, we monitored the use of a mine by eastern pipistrelles for >1 year. A few males occupied the roost in summer, but during the period of hibernation (late September–early May), the mine was used by at least 30 individuals composed of both sexes. Most individuals first entered the mine during late September through …

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Arthropod And Plant Communities As Indicators Of Land Rehabilitation Effectiveness In A Semi-Arid Shrub-Steppe, Eric T. Gardner Jul 2008

Arthropod And Plant Communities As Indicators Of Land Rehabilitation Effectiveness In A Semi-Arid Shrub-Steppe, Eric T. Gardner

Theses and Dissertations

We describe a case study evaluating the ecological impact of Bromus tectorum L. (cheatgrass) invasion following fire disturbance and the effectiveness of revegetation in improving ecological integrity in a degraded semi-arid shrub steppe system. The effectiveness of rehabilitation efforts was assessed from measurements of arthropod richness, vegetation and arthropod community composition, and ground cover characteristics in three habitats: undisturbed, burned and weed-infested (B. tectorum), and burned and rehabilitated with native and non-native vegetation. Arthropods were collected in each habitat using pitfall traps. Differences in arthropod richness were compared using rarefaction curves. Non-metric multidimensional scaling, and non-parametric multivariate statistical procedures including …

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Entropy-Based Fuzzy Set Optimisation For Reducing Ecological Model Complexity, A. M. Mouton, Bernard De Baets, A. Peter, G. Holzer, R. Müller, Peter L. M. Goethals Jul 2008

Entropy-Based Fuzzy Set Optimisation For Reducing Ecological Model Complexity, A. M. Mouton, Bernard De Baets, A. Peter, G. Holzer, R. Müller, Peter L. M. Goethals

International Congress on Environmental Modelling and Software

In recent years, fuzzy logic has been acknowledged as a suitable approach for species distribution modelling due to its transparency and its ability to incorporate the ecological gradient theory. Specifically, the overlapping class boundaries of a fuzzy model are similar to the transitions between different environmental conditions. However, the need for ecological expert knowledge is an important constraint when applying fuzzy species distribution models. Recent research has shown that data-driven fuzzy models may solve this ‘knowledge acquisition bottleneck’ and this paper is a further contribution. The aim was to reduce the complexity of a data-driven fuzzy habitat suitability model for …

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Demography Of The Yarrow's Spiny Lizard, Sceloporus Jarrovii, From The Central Chihuahuan Desert, Héctor Gadsden, José L. Estrada-Rodríguez Mar 2008

Demography Of The Yarrow's Spiny Lizard, Sceloporus Jarrovii, From The Central Chihuahuan Desert, Héctor Gadsden, José L. Estrada-Rodríguez

Western North American Naturalist

The demography of a population of Yarrow's spiny lizard, Sceloporus jarrovii, was examined from 2004 to 2006 in the canyon Las Piedras Encimadas, located in Gomez Palacio, Durango, México. Lizards were studied using a mark-recapture technique. Reproduction in females occurred between November and May, coinciding with dry conditions. Reproductive activity was highest (percent of females with vitellogenic follicles or embryos) in the middle of the dry season (November and December). Thirteen percent of females reached sexual maturity at an average age of 8.5 months. The population structure was similar in spring and fall, but not in summer. A notable …

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Geographic Patterns Of Ground-Dwelling Arthropods Across An Ecoregional Transition In The North American Southwest, David C. Lightfoot, Sandra L. Brantley, Craig D. Allen Mar 2008

Geographic Patterns Of Ground-Dwelling Arthropods Across An Ecoregional Transition In The North American Southwest, David C. Lightfoot, Sandra L. Brantley, Craig D. Allen

Western North American Naturalist

We examined the biogeographic patterns of ground-dwelling arthropod communities across a heterogeneous semiarid region of the Southern Rio Grande Rift Valley of New Mexico. Our 3 sites included portions of 5 ecoregions, with the middle site a transition area where all ecoregions converged. We addressed the following 3 questions: (1) Do the species assemblage patterns for ground arthropods across habitats and sites conform to recognized ecoregions? (2) Are arthropod assemblages in distinct vegetation-defined habitats within an ecoregion more similar to each other or to assemblages in similar vegetation-defined habitats in other ecoregions? (3) Is there a detectable edge effect with …

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Moistened Seeds Increase Rodent Trap Success, John C. Tull, Michael W. Sears Dec 2007

Moistened Seeds Increase Rodent Trap Success, John C. Tull, Michael W. Sears

Western North American Naturalist

Seed moisture has been shown to influence the rates of seed cache removal by rodents. Although the precise mechanism is not known, this knowledge might prove useful in field applications. We examined whether moistened bait would increase trap success in desert rodent populations. We placed traps 15 m apart in grids within a 500-ha study area and randomly baited traps with either dry or moistened seeds. We found that traps baited with moistened seeds had 34.9% higher success than traps baited with dry seeds (n = 190, χ2 = 5.389, df = 1, P = 0.020). Our results …

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Seasonality And Fidelity In Roost Use Of The Mexican Free-Tailed Bat, Tadarida Brasiliensis, In An Urban Setting, Jeffrey A. Scales, Kenneth T. Wilkins Sep 2007

Seasonality And Fidelity In Roost Use Of The Mexican Free-Tailed Bat, Tadarida Brasiliensis, In An Urban Setting, Jeffrey A. Scales, Kenneth T. Wilkins

Western North American Naturalist

We studied 7 urban roosts occupied by Mexican free-tailed bats (Tadarida brasiliensis) in downtown Waco, Texas, from August 2001 to September 2002. We examined frequency of roost use, colony sizes, and roost fidelity in relation to gender. Use of roosts and colony sizes were highest in the fall and lowest in the winter, but fluctuated widely during the study. These roosts were not used by maternity colonies, and patterns of occupancy suggested that they served as stopover sites during migratory seasons. Individual bats exhibited high fidelity to discrete roosts included in the study. However, the bats commonly left …

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Roadside Foraging By Kangaroo Rats In A Grazed Short-Grass Prairie Landscape, Paul Stapp, Mark D. Lindquist Sep 2007

Roadside Foraging By Kangaroo Rats In A Grazed Short-Grass Prairie Landscape, Paul Stapp, Mark D. Lindquist

Western North American Naturalist

We used live-trapping and foraging experiments to describe use of roadside vegetation by kangaroo rats (Dipodomys ordii) in short-grass prairie in Colorado, and to determine whether this species' perception of predation risk differed between roadside habitats, where predators were expected to be most active, and locations 120 m into adjacent grazed pastures. Giving-up densities (GUDs) were measured in paired seed trays placed beneath saltbush (Atriplex canescens) shrubs and in the open, 3 m from shrubs along transects in roadside and pasture locations. Trials were conducted on nights with a partial (1st-quarter), full, and new moon to …

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Changes In Kit Fox–Coyote–Prey Relationships In The Great Basin Desert, Utah, Wendy M. Arjo, Eric M. Gese, Tim J. Bennett, Adam J. Kozlowski Sep 2007

Changes In Kit Fox–Coyote–Prey Relationships In The Great Basin Desert, Utah, Wendy M. Arjo, Eric M. Gese, Tim J. Bennett, Adam J. Kozlowski

Western North American Naturalist

Variation in kit fox (Vulpes macrotis) population parameters can be influenced by vegetative cover and the distribution and abundance of other predator and prey species. Dramatic changes to Great Basin Desert habitats, which can potentially impact mammalian species, have occurred in some areas in Utah. We examined kit fox demographics and prey populations from 1999 to 2001 on Dugway Proving Ground (DPG), a U.S. Army facility in Utah, and compared some parameters to historical levels (1956–1958, 1966–1969). Adult survival rates were fairly consistent between 1999 and 2000 and between 1999 and 2001; however, survival was greater in 2001 …

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Differential Resource Allocation In Deer Mice Exposed To Sin Nombre Virus, Eric Wilson, Erin M. Lehmer, Christine A. Clay, Stephen St. Jeor, Denise M. Dearing Sep 2007

Differential Resource Allocation In Deer Mice Exposed To Sin Nombre Virus, Eric Wilson, Erin M. Lehmer, Christine A. Clay, Stephen St. Jeor, Denise M. Dearing

Faculty Publications

The resource allocation hypothesis predicts that reproductive activity suppresses immunocompetence; however, this has never been tested in an endemic disease system with free-ranging mammals. We tested the resource allocation hypothesis in wild deer mice (Peromyscus maniculatus) with natural exposure to Sin Nombre Virus (SNV). Immunocompetence was estimated from the extent of swelling elicited after deer mice were injected with phytohemagglutinin (PHA); swelling is positively correlated with immunocompetence. After livetrapping deer mice, we determined their reproductive state and SNV infection status. Males were more likely to be seropositive for SNV than females (37% vs. 25%) and exhibited 10% less swelling after …

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Effects Of Exotic Grasses On Soil Seed Banks In Southeastern Arizona Grasslands, Steven P. Mclaughlin, Janice E. Bowers Jun 2007

Effects Of Exotic Grasses On Soil Seed Banks In Southeastern Arizona Grasslands, Steven P. Mclaughlin, Janice E. Bowers

Western North American Naturalist

At the Appleton-Whittell Research Ranch, an ungrazed grassland preserve in southeastern Arizona, soil seed banks were sampled in June, August, and October 2002 and June 2003. Wildfire had previously burned 90% of the research ranch in May 2002. Seed density and species richness in burned native grassland (2 plots) were compared to those in burned exotic grassland (2 plots). Averaged over 4 sample dates, seed densities were as follows: burned native grassland, 591 ± 243.1 seeds · m−2 and 784 ± 334.9 seeds · m−2; burned exotic grassland, 501 ± 198.9 seeds · m−2 and 196 …

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Use Of Agricultural Lands By San Joaquin Kit Foxes, Gregory D. Warrick, Howard O. Clark Jr., Patrick A. Kelly, Daniel F. Williams, Brian L. Cypher Jun 2007

Use Of Agricultural Lands By San Joaquin Kit Foxes, Gregory D. Warrick, Howard O. Clark Jr., Patrick A. Kelly, Daniel F. Williams, Brian L. Cypher

Western North American Naturalist

Although the current range of the endangered San Joaquin kit fox (Vulpes macrotis mutica) borders large areas of farmland, the ecology of this species rarely has been studied within an agricultural setting. In central California, we examined habitat use, prey availability, and diet of radio-collared kit foxes inhabiting an aqueduct right-of-way (ROW) bordered by farmland. During both years of study (1998–1999), nocturnal locations of foxes occurred more often than expected (based on habitat availability) in the ROW and less often than expected within annual crops. Orchards were used disproportionately more than their availability during 1998 and were used …

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Dispersal And Extraterritorial Movements Of Swift Foxes (Vulpes Velox) In Northwestern Texas, Kerry L. Nicholson, Warren B. Ballard, Brady K. Mcgee, Heather A. Whitlaw Mar 2007

Dispersal And Extraterritorial Movements Of Swift Foxes (Vulpes Velox) In Northwestern Texas, Kerry L. Nicholson, Warren B. Ballard, Brady K. Mcgee, Heather A. Whitlaw

Western North American Naturalist

Dispersal plays an important role in the population dynamics of many carnivores, yet little information exists about the dispersal and movement patterns of swift foxes (Vulpes velox). We radio-collared and monitored 68 swift foxes for dispersal at 2 study sites in northwestern Texas from January 2002 to April 2004. Dispersal distance for juveniles (13.1 ± 0.3 km, s), adults (10 ± 4.7 km) and transients (25.4 ± 9.1 km) did not differ by age class (F = 1.49, df = 2, P = 0.24) or sex (F = 0.23, df = 1, P = 0.63) …

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Art, Ecology And Art Education: Locating Art Education In A Critical Place-Based Pedagogy, Mark Graham Jan 2007

Art, Ecology And Art Education: Locating Art Education In A Critical Place-Based Pedagogy, Mark Graham

Faculty Publications

In contemporary life and education, the local is marginalized in favor of large-scale economies of consumption that are indifferent to ecological concerns. The consequences of neglecting local human and natural communities include a degraded habitat, loss of wilderness, alienation, rootlessness, and lack of connection to communities. Critical place-based pedagogy provides a robust framework for the theory and practice of art education that is concerned with ecological issues. This article locates art education within a critical pedagogy of place as a prelude to describing contemporary art and art education that is engaged with ecological Issues.

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Contemporary Art, Science, Ecology, And A Critical Pedagogy Of Place, Mark Graham Jan 2007

Contemporary Art, Science, Ecology, And A Critical Pedagogy Of Place, Mark Graham

Faculty Publications

In contemporary life and education, the local is marginalized in favor of large-scale economies of consumption that are indifferent to ecological concerns. The consequences of neglecting local human and natural communities include a degraded habitat, loss of wilderness, alienation, rootlessness, and lack of connection to communities. Place-based education responds to this indifference to local ecological concerns by grounding student learning in the experiences of their own lives, communities, and regions. Critical place-based pedagogy broadens the scope of place-based learning by incorporating critical theory into the curriculum of the local. This article describes a critical pedagogy of place as a prelude …

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Biological Status Of Leatherside Chub: A Framework For Conservation Of Western Freshwater Fishes, Mark C. Belk, Jerald B. Johnson Jan 2007

Biological Status Of Leatherside Chub: A Framework For Conservation Of Western Freshwater Fishes, Mark C. Belk, Jerald B. Johnson

Faculty Publications

Outside of anadromous salmonids and a few endangered species, biology of native freshwater fishes of western North America is poorly known. What do we need to know to effectively manage native species and avoid decline and extinction? A recent analysis of the role of science in the Pacific salmon controversy outlines a clear framework for biological evaluation and management of native species. This framework has three components: (1) determine status of populations based on genetic and ecological variation, (2) identify and quantify threats to populations, and (3) determine actions to alleviate threats and promote conservation of populations. We use our …

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Long-Term Effects Of Tebuthiuron On Bromus Tectorum, Dana M. Blumenthal, Urszula Norton, Justin D. Derner, Jean D. Reeder Dec 2006

Long-Term Effects Of Tebuthiuron On Bromus Tectorum, Dana M. Blumenthal, Urszula Norton, Justin D. Derner, Jean D. Reeder

Western North American Naturalist

Use of herbicides to thin dense stands of Artemisia spp. (sagebrush) can free up resources for herbaceous plants and increase forage production, but may also facilitate weed invasion. We revisited a sagebrush thinning experiment in a north central Wyoming big sagebrush–grassland 11 years after application of tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N-N′-dimethylurea) to determine the long-term responses of shrubs, available soil resources, perennial grasses, and Bromus tectorum L. (downy brome). Tebuthiuron reduced shrub cover by more than half, from 31% in untreated plots to 15% in treated plots (P = 0.002), and increased downy brome cover approximately 4-fold, from 0.9% in untreated plots …

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Plant Composition And Erosion Potential Of A Grazed Wetland In The Salmon River Subbasin, Idaho, Kristine N. Hopfensperger, Joan Q. Wu, Richard A. Gill Aug 2006

Plant Composition And Erosion Potential Of A Grazed Wetland In The Salmon River Subbasin, Idaho, Kristine N. Hopfensperger, Joan Q. Wu, Richard A. Gill

Western North American Naturalist

Wetlands are dynamic habitats with many unique, important functions including filtering sediments and providing diverse habitats for fish and wildlife. Wetlands in the western United States are particularly important because they offer habitat for a number of protected runs of endangered fish species. Historically, livestock grazing has altered wetland and riparian area form and function by facilitating exotic species invasions, altering spatial heterogeneity of vegetation, and increasing erosion. In this study we examined vegetation structure and erosion potential in a wetland meadow exposed to unregulated grazing along Deer Creek in the Salmon River subbasin, Idaho. We characterized the vegetation composition …

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Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White Jul 2006

Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White

International Congress on Environmental Modelling and Software

Many process-based models on carbon (C) and nitrogen (N) cycles have been developed for northern forest ecosystems. These models are widely used to evaluate the long-term decisions in forest management dealing with effects like particulate pollution, productivity and climate change. Regarding climate change, one of the key questions that have sensitive political implications is whether northern forests will sequester atmospheric C or not. Whilst many process-based models have been tested for accuracy by evaluating or validating against observed data, few have dealt with the complexity of the incorporated procedures to estimate uncertainties associated with model predictions or the sensitivity of …

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New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel Jul 2006

New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel

International Congress on Environmental Modelling and Software

The aim of this paper is to discuss scientific challenges and new possibilities for a better modelling of consequences of land use changes in heterogeneous landscapes on ecosystem functions in space and time. The landscape or regional scale means an area of about 100 km2 up to some 1000 km2. Main problems on this scale are high complexity, structural diversity, ecological heterogeneity and uncertainty in data, in understanding of the process dynamic and by uncertainty in models.

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New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel Jul 2006

New Directions And Challenges In Spatial Dynamic Modelling Of Ecosystem Functions In Heterogeneous Landscapes As Basis For A Better Sustainable Landscape Management, Karl-Otto Wenkel, Ralf Wieland, Wilfried Mirschel

International Congress on Environmental Modelling and Software

The aim of this paper is to discuss scientific challenges and new possibilities for a better modelling of consequences of land use changes in heterogeneous landscapes on ecosystem functions in space and time. The landscape or regional scale means an area of about 100 km2 up to some 1000 km2. Main problems on this scale are high complexity, structural diversity, ecological heterogeneity and uncertainty in data, in understanding of the process dynamic and by uncertainty in models.

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Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White Jul 2006

Dealing With Uncertainty And Sensitivity Issues In Process-Based Models Of Carbon And Nitrogen Cycles In Northern Forest Ecosystems, G. R. Larocque, J. S. Bhatti, A. M. Gordon, N. Luckai, Jinxun Liu, Shuguang Liu, P. A. Arp, C. -F Zhang, Alexander Komarov, Pavel Grabarnik, M. Wattenbach, C. Peng, Jianfeng Sun, Thomas White

International Congress on Environmental Modelling and Software

Many process-based models on carbon (C) and nitrogen (N) cycles have been developed for northern forest ecosystems. These models are widely used to evaluate the long-term decisions in forest management dealing with effects like particulate pollution, productivity and climate change. Regarding climate change, one of the key questions that have sensitive political implications is whether northern forests will sequester atmospheric C or not. Whilst many process-based models have been tested for accuracy by evaluating or validating against observed data, few have dealt with the complexity of the incorporated procedures to estimate uncertainties associated with model predictions or the sensitivity of …

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Tamarix Aphylla: A Newly Invasive Tree In Southern Nevada, Lawrence R. Walker, Pamela L. Barnes, Elizabeth A. Powell May 2006

Tamarix Aphylla: A Newly Invasive Tree In Southern Nevada, Lawrence R. Walker, Pamela L. Barnes, Elizabeth A. Powell

Western North American Naturalist

In the southwestern United States, the nonnative athel pine (Tamarix aphylla) was presumed to be sterile and therefore not as likely to spread as its widely distributed, nonnative congener, T. ramosissima. However, at Lake Mead National Recreation Area (LMNRA) in southern Nevada, populations of T. aphylla have recently spread beyond their limited pre-1990 distribution and now form extensive monospecific stands. Over a 3-year period, we quantified seed production and germination from 60 T. aphylla trees at LMNRA. The annual mean seed production period was 50.6 days, and the mean potential germination (under laboratory conditions) was 22%, indicating …

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The Effect Of Livestock Grazing On The Rainbow Grasshopper: Population Differences And Ecological Correlates, Sandra J. Debano May 2006

The Effect Of Livestock Grazing On The Rainbow Grasshopper: Population Differences And Ecological Correlates, Sandra J. Debano

Western North American Naturalist

This study examined the effect of livestock grazing on a common herbivore in semiarid grasslands of the Southwest: the rainbow grasshopper, Dactylotum variegatum. Population attributes and key environmental variables were compared between sites on active cattle ranches and sites on a 3160-ha ungrazed sanctuary. Although density of D. variegatum nymphs did not differ significantly between grazed and ungrazed sites, adult density was significantly lower on grazed sites, and sex ratios differed between grazed and ungrazed sites over time. Grazed sites had higher percentages of bare ground and fewer Baccharis pteronioides, a common shrub. However, only bare ground was …

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Characteristics Of Swift Fox Dens In Northwest Texas, Brady K. Mcgee, Kerry L. Nicholson, Warren B. Ballard, Matthew J. Butler May 2006

Characteristics Of Swift Fox Dens In Northwest Texas, Brady K. Mcgee, Kerry L. Nicholson, Warren B. Ballard, Matthew J. Butler

Western North American Naturalist

The swift fox (Vulpes velox) was classified in 1995 as a candidate for listing under the Endangered Species Act. Since then, several studies have addressed survey methods for monitoring swift fox populations. The purpose of this paper is to assist field researchers in documenting the presence of swift foxes by identification of recently active den sites. We propose that swift foxes have unique external den characteristics that can be distinguished during aerial surveys. We collected data from 30 swift fox den complexes on both continuous rangeland and landscapes fragmented by cropland in northwest Texas. There were no differences …

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Dietary Overlap In Giant Salamanders (Dicamptodon): Applying Null Models To Resource Partitioning, Craig A. Steele, Colin Brammer Feb 2006

Dietary Overlap In Giant Salamanders (Dicamptodon): Applying Null Models To Resource Partitioning, Craig A. Steele, Colin Brammer

Western North American Naturalist

We examined stomach contents of preserved specimens of larval Pacific giant salamander (Dicamptodon tenebrosus) and Cope's giant salamander (D. copei) collected from sympatric and allopatric stream populations. The dietary components of these specimens were used to calculate dietary overlap between the 2 species and to determine if changes in overlap existed between sympatric and allopatric populations. To statistically test overlap values, a randomization algorithm was used to construct a simulated data matrix (i.e., null model) in order to compare observed values of dietary overlap to a distribution of overlap values from the null model. Significant levels …

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