Physical Sciences and Mathematics Commons^™

Plant Community Response To Fire: A Chronosequence Study, Scott R. Abella, E. Cayenne Engel

Public Policy and Leadership Faculty Publications

Fires are becoming more prevalent events across the landscape in the southwestern US. Over the next several decades the already arid southwest is predicted to become warmer and drier, with longer summers, and an increase of “extreme” weather events such as lightening inducing thunderstorms. While the “hotter and drier” forecast may indicate less abundant plant life, and thus less available biomass for fuel, exotic invasive plant species are becoming more dominant across the landscape with increases in human travel and commerce. Exotic species (particularly many of the invasive grasses) are adding fuel for the fires to burn when the annuals …

Fire History And Forest Structural Change In The Spring Mountains, Scott R. Abella

Public Policy and Leadership Faculty Publications

Since early 2006 we have been working to develop a partnership with the Spring Mountains District of the Humboldt-Toiyabe National Forest to provide science support for understanding fire history and forest structural changes in support of ecologically based management strategies. We teamed up with the Ecological Restoration Institute (ERI) at Northern Arizona University and the University of Arizona Tree Ring Lab to deliver a workshop on March 6, 2008 at the interagency office in Las Vegas, Nevada. On September 16-18, we again teamed up with colleagues at ERI to conduct a preliminary field assessment of forest change at 10 sites …

Opportunities For New Collaborative Projects, Scott R. Abella, Jill E. Craig

Public Policy and Leadership Faculty Publications

The Research Group is currently working in successful partnerships with Lake Mead National Recreation Area, BLM Las Vegas, Desert National Wildlife Refuge (U.S. Fish and Wildlife Service), Joshua Tree National Park, and in collaboration with the Ecological Restoration Institute, the U.S. Forest Service (Region 3).

Species Richness And Soil Properties In Pinus Ponderosa Forests: A Structural Equation Modeling Analysis, Daniel C. Laughlin, Scott R. Abella, W. Wallace Covington, James B. Grace

Public Policy and Leadership Faculty Publications

Question: How are the effects of mineral soil properties on understory plant species richness propagated through a network of processes involving the forest overstory, soil organic matter, soil nitrogen, and understory plant abundance? Location: North-central Arizona, USA. Methods: We sampled 75 0.05-ha plots across a broad soil gradient in a Pinus ponderosa (ponderosa pine) forest ecosystem. We evaluated multivariate models of plant species richness using structural equation modeling. Results: Richness was highest at intermediate levels of understory plant cover, suggesting that both colonization success and competitive exclusion can limit richness in this system. We did not detect a reciprocal positive …

Forest-Floor Treatments In Arizona Ponderosa Pine Restoration Ecosystems: No Short-Term Effects On Plant Communities, Scott R. Abella, W. Wallace Covington

Public Policy and Leadership Faculty Publications

Leaf litter accumulation during fire exclusion and increases in tree density in postsettlement southwestern Pinus ponderosa forests may limit the establishment of understory vegetation. We performed an experiment in P. ponderosa forests of northern Arizona to ascertain plant community responses to forest-floor scarification and Oi removal on thirty-six 100-m2 plots overlaid on an existing ecological restoration experiment that involved tree thinning and prescribed burning. Constrasting with findings from many other forest types, forest-floor treatments had no effect on community diversity or composition during the 2-year experiment. Sørensen similarities were as high as 97% between posttreatment years within treatments; and successional …

Past, Present, And Future Old Growth In Frequent-Fire Conifer Forests Of The Western United States, Scott R. Abella, W. Wallace Covington, Peter Z. Fule, Leigh B. Lentile, Andrew J. Sanchez Meador, Penelope Morgan

Public Policy and Leadership Faculty Publications

Old growth in the frequent-fire conifer forests of the western United States, such as those containing ponderosa pine (Pinus ponderosa), Jeffrey pine (P. jeffreyi), giant sequoia (Sequioa giganteum) and other species, has undergone major changes since Euro-American settlement. Understanding past changes and anticipating future changes under different potential management scenarios are fundamental to developing ecologically based fuel reduction or ecological restoration treatments. Some of the many changes that have occurred in these forests include shifts from historically frequent surface fire to no fire or to stand-replacing fire regimes, increases in tree density, increased abundance of fire-intolerant trees, decreases in understory …

Uncertainty, Climate Change And Nuclear Power, David M. Hassenzahl

Public Policy and Leadership Faculty Publications

Long time-horizon environmental risks with potential for global impacts have increased in visibility over the past several decades. Such issues as climate change, the nuclear fuel cycle, persistent synthetic chemicals, and stratospheric ozone depletion share some characteristics, including intergenerational impacts, strongly decoupled incidence of risks and benefits, substantial decision stakes and extreme uncertainty. What is not well understood are the similarities and differences among sources and implications of uncertainty among these global environmental threats, especially those associate with current and future human behavior. This describes the uncertainties associated with managing two global concerns: the nuclear (fission) fuel cycle and anthropogenic …

Canopy-Tree Influences Along A Soil Parent Material Gradient In Pinus-Ponderosa-Quercus Gambelii Forests, Northern Arizona, Scott R. Abella, Judith D. Springer

Public Policy and Leadership Faculty Publications

ABELLA, S. R. (Public Lands Institute and School of Life Sciences, University of Nevada, Las Vegas, Las Vegas, NV 89154-2040) AND J. D. SPRINGER (Ecological Restoration Institute, Northern Arizona University, Flagstaff, AZ 86011-5017). Canopy-tree influences along a soil parent material gradient in Pinus ponderosa- Quercus gambelii forests, northern Arizona. J. Torrey Bot. Soc. 135: 26–36. 2008.—The distribution of canopy trees can impose within-site patterns of soil properties and understory plant composition. At ten sites spanning a soil parent material gradient in northern Arizona Pinus ponderosa-Quercus gambelii forests, we compared soils and plant composition among five canopy types: openings, Pinus ponderosa …

Technical Risk Information: Decision Tool Or Rhetorical Ammunition? Undisputed Facts In The Yucca Mountain Debate, David M. Hassenzahl, Denise Tillery, Paulette Laidler

Public Policy and Leadership Faculty Publications

This paper examines how both opponents and proponents of the proposed high-level nuclear waste repository at Yucca mountain Nevada claim that uncontroversial information supports their conflicting positions. Four pieces of information in particular are claimed by both sides: the distance of the proposed site from Las Vegas, the volume of waste that has been produced, the threat of terrorism since 9/11/01, and the occurrence of an earthquake in early 2002. Possible explanations for the difference include naive positivism, social constructionism, persistent beliefs and implicit warrants. The latter two models better explain observed knowledge/preference states. If so, more or better information …

Microwave Backscatter Modeling Of Erg Surfaces In The Sahara Desert, Haroon Stephen, David G. Long

Public Policy and Leadership Faculty Publications

The Sahara Desert includes large expanses of sand dunes called ergs. These dunes are formed and constantly reshaped by prevailing winds. Previous study shows that Saharan ergs exhibit significant radar backscatter (σ°) modulation with azimuth angle (f). We use σ° measurements observed at various incidence angles and f from the NASA Scatterometer (NSCAT), the SeaWinds scatterometer, the ERS scatterometer (ESCAT), and the Tropical Rainfall Measuring Mission's Precipitation Radar to model the σ° response from sand dunes. Observations reveal a characteristic relationship between the backscatter modulation and the dune type, i.e., the number and orientation of the dune slopes. Sand dunes …

Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, Haroon Stephen, David G. Long

Public Policy and Leadership Faculty Publications

Sand seas (ergs) of the Sahara are the most dynamic parts of the desert. Aeolian erosion, transportation, and deposition continue to reshape the surface of the ergs. The large-scale features (dunes) of these bedforms reflect the characteristics of the sand and the long-term wind. Radiometric emissions from the ergs have strong dependence on the surface geometry. We model the erg surface as composed of tilted rough facets. Each facet is characterized by a tilt distribution dependent upon the surface roughness of the facet. The radiometric temperature (T(b)) of ergs is then the weighted sum of the T(b) from all the …

Converting Low-Level Mixed Waste Into Transuranic Waste For Geologic Disposal At Wipp: A Cost Analysis, Helen R. Neill, Robert H. Neill

Public Policy and Leadership Faculty Publications

The Department of Energy (DOE) has approximately 43,000 cubic meters of mixed-low-level waste (MLLW) with alpha emitting concentrations of 10 to 100 nanocuries per gram (nCi/g) generated from the nations defense programs requiring radioactive waste disposal [1]. DOE has decided to commingle MLLW containers with transuranic (TRU) waste containers in larger containers such that the average concentration in the larger container would qualify as TRU waste for deep geologic disposal at the Waste Isolation Pilot Plant (WIPP). Since Congress has exempted the WIPP mixed TRU waste from the Resource Conservation and Recovery Act (RCRA) [2] requirement to treat the waste …

Fifteen Years Of Plant Community Dynamics During A Northwest Ohio Oak Savanna Restoration, Scott R. Abella, John F. Jaeger, Lawrence G. Brewer

Public Policy and Leadership Faculty Publications

Midwest oak savanna communities are noted for their unusual plant assemblages, but these communities have been reduced by more than 98% because of changing land uses and conversion to closed-canopy forests. We initiated an ongoing 15-year experiment in 1988 to restore a 40-ha black oak (Quercus velutina) savanna by applying burn treatments that historically maintained this vegetation type. Groundlayer composition changed significantly for both the burn treatment and the control, with the burn treatment exhibiting slight increases in herbs such as wild lupine (Lupinus perennis) and hairy puccoon (Lithospermum caroliniense), both of which are species requiring greater insolation. Burn treatments …

Tree Thinning And Prescribed Burning Effects On Ground Flora In Arizona Ponderosa Pine Forests: A Review, Scott R. Abella

Public Policy and Leadership Faculty Publications

Ground flora is an important response variable to monitor after tree thinning and prescribed burning treatments designed to restore Arizona ponderosa pine (Pinus ponderosa P.& C. Lawson) forests. This paper reviews published literature on the effects of thinning and burning on ground flora in Arizona ponderosa pine forests in five main categories of research: ground flora biomass, species diversity, plant community composition, population processes, and individual species ecology. Research published to date suggests that thinning and burning generally increase ground flora biomass, whereas other categories of research such as community composition and population processes have been little studied in Arizona …

Ecology Of Eastern Prickly Pear Cactus (Opuntia Humifusa) In Oak Openings Preserve, Northwestern Ohio, Scott R. Abella, John F. Jaeger

Public Policy and Leadership Faculty Publications

Opuntia humifusa (eastern prickly pear cactus) is listed as potentially threatened in Ohio, and we examined the characteristics of O. humifusa sites in Oak Openings Preserve in northwestern Ohio’s Oak Openings region in an attempt to provide data that may help protect this species. Opuntia humifusa occurrences were associated with loose sands of the xeric Udipsamment Ottokee and Oakville soil series on sites that had been cleared before the 1940s during failed agricultural attempts. Shading by encroaching canopy trees is a threat to several O. humifusa populations in Oak Openings Preserve, and treatments that reduce canopy cover at these sites …

Ecological Species Groups Of South Carolina's Jocassee Gorges, Southern Appalachian Mountains, Scott R. Abella, Victor B. Shelburne

Public Policy and Leadership Faculty Publications

Ecological species groups, consisting of assemblages of co-occurring plant species exhibiting similar environmental affinities, were developed for ground-flora and tree strata in late- successional forests on a 13,000 ha southern Appalachian landscape. We distinguished 11 ground-flora groups that included 50 species and six tree groups comprised of 19 species. Ground-flora groups ranged from a xeric Vaccinium group (including Vaccinium pallidum, Euphorbia corollata, and Piptochaetium avenaceum) to a mesic Rhododendron group (typified by Rhododendron maximum, Mitchella repens, and Hexastylis heterophylla). Tree groups ranged from a Quercus coccinea group to a Tsuga canadensis group. Consistent with previous research, species groups exhibited a …

Public Education And Outreach On Radioactive Waste Management Issues At The Nevada Test Site, Helen R. Neill

Public Policy and Leadership Faculty Publications

No abstract provided.

A Monte Carlo Analysis Of Hedonic Models Using Traditional And Spatial Approaches, Helen R. Neill, David M. Hassenzahl, Djeto D. Assane

Public Policy and Leadership Faculty Publications

Hedonic regression analysis of single family homes typically includes structural variables, locational variables and neighborhood quality characteristics. When nearby properties are related, Dubin (1988) reports that error terms are spatially autocorrelated. Estimation methods for these spatially autocorrelated error terms or hereafter, spatial approaches, include maximum likelihood estimation (MLE) and kriging techniques such as kriged maximum likelihood estimation (KMLE). Unfortunately these spatial methods require massive computer resources and are limited to significantly fewer observations than traditional ordinary least squares (OLS). This paper investigates the combination of spatial approaches and Monte Carlo analysis, a method that approximates large data sets. A question …

Perspectives On Radioactive Waste Disposal: A Consideration Of Economic Efficiency And Intergenerational Equity, Helen R. Neill, Robert H. Neill

Public Policy and Leadership Faculty Publications

There are both internal and external pressures on the U.S. Department of Energy to reduce the estimated costs of isolating radioactive waste, $19 billion for transuranic waste at Waste Isolation Pilot Plant (WIPP) and $57 billion for high level waste at Yucca Mountain. The question arises whether economic analyses would add to the decision-making process to reduce costs yet maintain the same level of radiological protection. This paper examines the advantages and disadvantages of using cost-benefit analysis (CBA), a tool used to measure economic efficiency as an input for these decisions. Using a comparative research approach, we find that CBA …

Quantifying Ecosystem Geomorphology Of The Southern Appalachian Mountains, Scott R. Abella

Public Policy and Leadership Faculty Publications

Geomorphology is a dominant factor influencing vegetation distribution in the southern Appalachians, and quantifying landform characteristics is increasingly important for forest ecosystem classification. This study used slope gradient and two previously published geomorphic indices, terrain shape index and landform index that quantify landform shape and protection, to develop a field-based landform quantification system at four study areas in the southern Appalachians. Six major landform types (ridgetops, nose slopes, linear hillslopes, coves, stream ravines, and stream bottoms) exhibited quantitatively different characteristics, and these differences among landforms were not evident when using only categorical landform descriptions (e.g., convex, concave) that have been …

Perspectives On Economic Analyses For High Level Waste Disposal, Helen R. Neill, Robert H. Neill

Public Policy and Leadership Faculty Publications

There are both internal and external pressures on the U.S. Department of Energy (DOE) to reduce costs of disposal and still maintain radiation protection to both present and future generations. The question arises whether both of these goals are attainable.

Spatial And Temporal Patterns Of Eastern White Pine Regeneration In The Northwestern Ohio Oak Stand, Scott R. Abella, Neil W. Macdonald

Public Policy and Leadership Faculty Publications

Eastern white pine (Pinus strobus L.) was often associated with oaks (Quercus spp.) on upland sites in presettlement forests of the upper Great Lakes region, but widespread logging and subsequent fires in the late 1800s converted these upland sites to fire-tolerant oak forests. Although white pine regeneration is occurring in these second-growth oak forests, white pine regeneration patterns in oak forests of the Great Lakes region are not well documented. We examined white pine regeneration in the southern Great Lakes region in an oak stand within the Oak Openings region of northwestern Ohio, where white pine plantations established in the …

Bonytail (Gila Elegans) May Enhance Survival Of Razorback Suckers (Xyrauchen Texanus) In Rearing Ponds By Preying On Exotic Crayfish, Nathan Lenon, Krystyna Anne Stave, Tom Burke, James E. Deacon

Public Policy and Leadership Faculty Publications

This study examined the potential of bonytail (Gila elegans) to enhance survival of young razorback sucker (Xyrauchen texanus) in rearing ponds by serving as a biological control agent for young stages of Red Swamp Crayfish (Procambarus clarki). Large populations of crayfish in rearing ponds negatively affect the survival of razorback suckers, through predation and competition for food. Traps made with 6.34 mm (0.25 inch) mesh have been used in an effort to reduce crayfish populations, however crayfish less than 17 mm carapace length (CPL) are able to escape. Juvenile bonytail in experimental trials ate young crayfish ranging in size from …

What Does Smart Growth Mean For Housing?, Karen A. Danielsen, Robert E. Lang, William Fulton

Public Policy and Leadership Faculty Publications

Barely noticed amid the returns from the 1998 midterm elections was a quiet revolution that goes to the heart of how and where Americans live. While most news accounts focused on the high-profile candidate elections, voters across the nation-in Democratic and Republican areas alike-approved more than 160 state and local ballot measures intended to preserve open space and limit urban sprawl.

The coalition forming around the idea of limiting sprawl includes environmentalists, farmers, big-city mayors, and some developers. But perhaps most important, the so-called "smart growth" movement also includes many suburban voters who are fed up with growth. For example, …

Describing The Elephant: Multiple Perspectives In New York City's Watershed Protection Conflict, Krystyna Anne Stave

Public Policy and Leadership Faculty Publications

New York City's efforts to avoid filtration mandated by the 1986 Safe Drinking Water Act Amendments and the 1989 Surface Water Treatment Rule have generated considerable controversy. Since the conflict began in 1990, a spectrum of stakeholder groups has emerged, representing land owners, sport fishermen, businesses, environmental groups, developers, and watershed communities. What was originally defined by New York City water supply managers as a scientific problem--identifying sources of water quality degradation and preventing contaminants from entering the water supply system--now has broadened to include a diverse set of social and economic issues as well.

Resource Use Conflict In New York City's Catskill Watersheds: A Case For Expanding The Scope Of Water Resource Management, Krystyna Anne Stave

Public Policy and Leadership Faculty Publications

In New York City's water supply watersheds, controversy over water quality protection underscores both the need to expand the scope of water resource management and the challenges to doing so. This paper describes the response of watershed residents to !'Jew York City's efforts to avoid filtration mandated by the 1986 Safe Drinking Water Act Amendments and 1989 Surface Water Treatment Rule. The emergence of a spectrum of stakeholder groups representing land owners, sport fishermen, businesses, environmental groups and local communities has brought social and economic issues not previously part of the City's water management program to the center of the …

Using Gis To Identify Critical Areas For Water Quality Protection In New York City's Water Supply System, Paul K. Barten, Krystyna Anne Stave

Public Policy and Leadership Faculty Publications

The protection of water quality at its source — the watershed — recognizes that minimizing land use impacts and allowing natural processes to provide in situ biological treatment can complement conventional engineering methods. In contrast to the enormous costs projected for drinking water filtration, the judicious application of watershed management principles and practices is a way to balance the needs of people with the capacity of the natural resource base over time. This paper describes the development and initial application of a geographic information system (GIS) to a ortion of New York City's 2,000 square mile water supply system, the …