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University of Nevada, Las Vegas

Public Policy and Leadership Faculty Publications

Earth Sciences

Articles 1 - 13 of 13

Full-Text Articles in Physical Sciences and Mathematics

Evaluating Efficacy Of Restoration Techniques, Keys View Road Reconstruction, Joshua Tree National Park, California, U.S.A, Scott R. Abella, E. Cayenne Engel Jul 2010

Evaluating Efficacy Of Restoration Techniques, Keys View Road Reconstruction, Joshua Tree National Park, California, U.S.A, Scott R. Abella, E. Cayenne Engel

Public Policy and Leadership Faculty Publications

Keys View Road in Joshua Tree National Park (JOTR) was recently repaved, resulting in a buffer of vegetation and soil disturbance along the road corridor. In order to mitigate the effects of the repaving, JOTR designed an experimental framework to test various revegetation strategies. They outplanted salvaged and nursery grown native plant species in conjunction with vertical mulch in a fully crossed design (outplanting only, vertical mulch only, outplanting + vertical mulch, bare ground) to examine if any of the treatments most efficiently establish native plant communities.

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Land Surface Brightness Temperature Modeling Using Solar Insolation, Haroon Stephen, Sajjad Ahmad, Thomas C. Piechota Jan 2010

Land Surface Brightness Temperature Modeling Using Solar Insolation, Haroon Stephen, Sajjad Ahmad, Thomas C. Piechota

Public Policy and Leadership Faculty Publications

Retrieval of land surface emissivity and temperature from microwave brightness temperature data is a complex problem. The diurnal variation of temperature due to the diurnal cycle of solar radiation and weather conditions makes this problem even more challenging. In this paper, we use solar radiation in modeling the temporal variation of the brightness temperature state of the surface. Solar insolation modeling is used to estimate the diurnal variation of land surface brightness temperature. Solar radiation and brightness temperature are linked through temperature of the surface which is derived based on the radiation balance equation. The temperature state model behaves consistent …

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Heat And Smoke Effects On Red Brome Soil Seed Banks, Scott R. Abella, E. Cayenne Engel Oct 2009

Heat And Smoke Effects On Red Brome Soil Seed Banks, Scott R. Abella, E. Cayenne Engel

Public Policy and Leadership Faculty Publications

Management of exotic plants that are annuals entails understanding and managing their soil seed banks. We completed a study of the influences of heat and liquid smoke on red brome (Bromus rubens) soil seed banks collected from Red Rock Canyon in southern Nevada as part of a collaborative fire effects monitoring effort with Bureau of Land Management - Las Vegas. We collected the samples from the 2005 Loop Fire, where we observed in a monitoring field study that exotic grasses such as red brome were relatively sparse in the first 2-3 years (which were during a dry period) following the …

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Tree Canopy Types Constrain Plant Distributions In Ponderosa Pine- Gambel Oak Forests, Northern Arizona, Scott R. Abella Feb 2009

Tree Canopy Types Constrain Plant Distributions In Ponderosa Pine- Gambel Oak Forests, Northern Arizona, Scott R. Abella

Public Policy and Leadership Faculty Publications

Trees in many forests affect the soils and plants below their canopies. In current high-density southwestern ponderosa pine (Pinus ponderosa) forests, managers have opportunities to enhance multiple ecosystem values by manipulating tree density, distribution, and canopy cover through tree thinning. I performed a study in northern Arizona ponderosa pine-Gambel oak (Quercus gambelii) forests to measure the influences of tree canopy types on understory plant communities and soil properties. On ten 2.5-acre (1-ha) sites, I sampled five 43-ft2 (4-m2) plots below each of the following five canopy types: openings; single ponderosa pine; and Gambel oak single stems, dispersed clumps, and thickets. …

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Managing Gambel Oak In Southwestern Ponderosa Pine Forests: The Status Of Our Knowledge, Scott R. Abella Nov 2008

Managing Gambel Oak In Southwestern Ponderosa Pine Forests: The Status Of Our Knowledge, Scott R. Abella

Public Policy and Leadership Faculty Publications

Gambel oak (Quercus gambelii) is a key deciduous species in southwestern ponderosa pine (Pinus ponderosa) forests and is important for wildlife habitat, soil processes, and human values. This report (1) summarizes Gambel oak’s biological characteristics and importance in ponderosa pine forests, (2) synthesizes literature on changes in tree densities and fire frequencies since Euro-American settlement in pine-oak forests, (3) suggests management prescriptions for accomplishing various oak management objectives (for example, increasing diameter growth or acorn production), and (4) provides an appendix containing 203 Gambel oak literature citations organized by subject. Nine studies that reconstructed Gambel oak density changes since settlement …

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New Book Chapter Reviewing Mojave Desert Revegetation Practices Is Forthcoming, Scott R. Abella Oct 2008

New Book Chapter Reviewing Mojave Desert Revegetation Practices Is Forthcoming, Scott R. Abella

Public Policy and Leadership Faculty Publications

I was invited to write a chapter for a forthcoming book on Arid Environments to be published by Nova Science Publishers. This book is anticipated to appear in late 2008 or early 2009, and we will be able to provide additional details about the entire book at that time. I co-authored our chapter on revegetation with Alice Newton, Vegetation Manager at Lake Mead National Recreation Area. We systematically reviewed 23 published studies of planting or seeding native species in the Mojave Desert.

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Gambel Oak Growth Forms: Management Opportunities For Increasing Ecosystem Diversity, Scott R. Abella Sep 2008

Gambel Oak Growth Forms: Management Opportunities For Increasing Ecosystem Diversity, Scott R. Abella

Public Policy and Leadership Faculty Publications

Gambel oak (Quercus gambelii) clones have several different growth forms in southwestern ponderosa pine (Pinus ponderosa) forests, and these growth forms each provide unique wildlife habitat and resource values. The purposes of this note are to review published growth-form classifications for Gambel oak, provide examples of ecological effects of different growth forms, and summarize management strategies for promoting desired growth forms. Four different growth-form classifications have been published, which generally recognize variants of three basic forms: shrubby thickets of small-diameter stems, pole-sized clumps, and large trees. These growth forms exemplify ecological and management tradeoffs. For example, shrubby forms provide browse …

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Estimating Soil Seed Bank Characteristics In Ponderosa Pine Forests Using Vegetation And Forest-Floor Data, Scott R. Abella, Judith D. Springer Sep 2008

Estimating Soil Seed Bank Characteristics In Ponderosa Pine Forests Using Vegetation And Forest-Floor Data, Scott R. Abella, Judith D. Springer

Public Policy and Leadership Faculty Publications

Soil seed banks are important for vegetation management because they contain propagules of species that may be considered desirable or undesirable for site colonization after management and disturbance events. Knowledge of seed bank size and composition before planning management activities facilitates proactive management by providing early alerts of exotic species presence and of abilities of seed banks to promote colonization by desirable species. We developed models in ponderosa pine (Pinus ponderosa) forests in northern Arizona to estimate the size and richness of mineral soil seed banks using readily observable vegetation and forestfloor characteristics. Regression models using three or fewer predictors …

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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 Jan 2007

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 …

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Canopy-Tree Influences Along A Soil Parent Material Gradient In Pinus-Ponderosa-Quercus Gambelii Forests, Northern Arizona, Scott R. Abella, Judith D. Springer Jan 2006

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 …

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Microwave Backscatter Modeling Of Erg Surfaces In The Sahara Desert, Haroon Stephen, David G. Long Jan 2005

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 …

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Modeling Microwave Emissions Of Erg Surfaces In The Sahara Desert, Haroon Stephen, David G. Long Jan 2005

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 …

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Quantifying Ecosystem Geomorphology Of The Southern Appalachian Mountains, Scott R. Abella Jan 2003

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 …

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