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Physical Sciences and Mathematics Commons™

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University of Nevada, Las Vegas

Public Policy and Leadership Faculty Publications

Arizona

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

Survey Of Resource Managers Completed On Monitoring And Management Actions For Rare Plants In Arizona And Nevada, Scott R. Abella Jul 2010

Survey Of Resource Managers Completed On Monitoring And Management Actions For Rare Plants In Arizona And Nevada, Scott R. Abella

Public Policy and Leadership Faculty Publications

In a collaborative project with Northern Arizona University and more than 35 resource managers in Arizona and Nevada, we completed a survey of monitoring and management activities that are ongoing in these states for conserving populations of rare plants. We sent questionnaires consisting of 16 questions to as many resource managers as possible in these states and had follow-up conversations with several managers willing to share their perspective on ongoing conservation actions. The findings may be interesting for managers to see what issues and management strategies other managers in the same or different regions are grappling with. Results will be …

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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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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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Changes In Gambel Oak Densities In Southwestern Ponderosa Pine Forests Since Euro-American Settlement, Scott R. Abella, Peter Z. Fule Sep 2008

Changes In Gambel Oak Densities In Southwestern Ponderosa Pine Forests Since Euro-American Settlement, Scott R. Abella, Peter Z. Fule

Public Policy and Leadership Faculty Publications

Densities of small-diameter ponderosa pine (Pinus ponderosa) trees have increased in southwestern ponderosa pine forests during a period of fire exclusion since Euro-American settlement in the late 1800s. However, less well known are potential changes in Gambel oak (Quercus gambelii) densities during this period in these forests. We reviewed published literature to summarize changes in oak density in ponderosa pine forests over the past 140 years and evaluated the possibility that large-diameter oaks have decreased in density. All nine studies examining oak density changes found that densities of small-diameter oaks have escalated. Increases ranged from 4- to more than 63-fold. …

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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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Plant Recruitment In A Northern Arizona Ponderosa Pine Forest: Testing Seed- And Leaf Litter- Limitation Hypotheses, Scott R. Abella Aug 2008

Plant Recruitment In A Northern Arizona Ponderosa Pine Forest: Testing Seed- And Leaf Litter- Limitation Hypotheses, Scott R. Abella

Public Policy and Leadership Faculty Publications

Seed availability and leaf litter limit plant establishment in some ecosystems. To evaluate the hypothesis that these factors limit understory plant recruitment in Pinus ponderosa forests, I conducted a seeding and litter removal experiment at six thinned sites in the Fort Valley Experimental Forest, northern Arizona. Experimental seeding of four native species (Penstemon virgatus, Erigeron formosissimus, Elymus elymoides, and Festuca arizonica) and raking of litter occurred in 2005. Seeding resulted in a substantial recruitment of 14 to 103 seedlings/m2 (1 to 10/ft2) one month after seeding for two species (P. virgatus and E. elymoides), but these densities subsequently declined by …

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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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Forest-Floor Treatments In Arizona Ponderosa Pine Restoration Ecosystems: No Short-Term Effects On Plant Communities, Scott R. Abella, W. Wallace Covington Jan 2007

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 …

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Tree Thinning And Prescribed Burning Effects On Ground Flora In Arizona Ponderosa Pine Forests: A Review, Scott R. Abella Jan 2004

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 …

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