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Forest Landscape Dynamics: a Semi-Markov Modeling Approach

A transition model (MOSAIC) is used to describe forest dynamics at the landscape scale. The model uses a semi-Markov framework by considering transition probabilities and Erlang distributed holding times in each transition. Parameters for the transition model are derived from a gap model (ZELIG). This procedure ensures conceptual consistency of the landscape model with the fine scale ecological detail represented by the forest gap model. Spatial heterogeneity in the transition model is driven b… more

Date: August 1997

Creator: Ablan, Magdiel

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela

Light spectra distributions were measured in two different montane forests: temperate and tropical. Spectral light measurements were made in different sized canopy gaps in the conifer forest at H. J. Andrews Experimental Forest in Oregon, USA. Researchers at Oregon State University created these gaps of 20 m, 30 m, and 50 m in diameter. In the tropical cloud forest, spectral light measurements were made in two plots that were permanently established at La Mucuy Parque Nacional in Venezuela, in … more

Date: December 1997

Creator: Monteleone, Susan Elaine

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Assessment of the Efficacy of a Constructed Wetland to Reduce or Remove Wastewater Effluent Estrogenicity and Toxicity Using Biomarkers in Male Fathead Minnows (Pimephales Promelas Rafinesque, 1820)

Vitellogenin in Pimephales promelas was used to assess estrogenicity of a local municipal effluent. Vitellogenin induction in male P. promelas increased in frequency and magnitude with increased exposure duration and was greater ("=0.05) than controls after 2 and 3 weeks of exposure. The level of vitellogenesis induced by effluent exposure was high compared to similar studies. A spring season evaluation followed. Biomarkers in P. promelas were used to assess the efficacy of a treatment wetland … more

Date: December 2000

Creator: Hemming, Jon M.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Water Quality Aspects of an Intermittent Stream and Backwaters in an Urban North Texas Watershed

Pecan Creek flows southeast through the City of Denton, Texas. Characterized as an urban watershed, the basin covers approximately 63.5 km2. Pecan Creek is an intermittent stream that receives nonpoint runoff from urban landuses, and the City of Denton's wastewater treatment plant, Pecan Creek Water Reclamation Plant, discharges effluent to the stream. Downstream from the City of Denton and the wastewater treatment plant, Pecan Creek flows about 6,000 m through agricultural, pasture, and for… more

Date: August 2002

Creator: Taylor, Ritchie Don

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

A paleozoological perspective on predator extermination and white-tailed deer (Odocoileus virginianus Boddaert) overabundance in central Texas.

Archaeological and paleontological datasets are used in conservation to add time-depth to ecology. In central Texas several top carnivores including prehistoric Native American hunters have been extirpated or have had their historic ranges restricted, which has resulted in pest-level white-tailed deer (Odocoileus virginianus texana) populations in some areas. Predator extermination has dramatically reduced the average body size of members of the extant predator guild, and large carnivores most … more

Date: May 2007

Creator: Wolverton, Steven J.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

New Descriptions, Intraspecific Variation and Systematic Importance of Drumming Behavior in Selected North American Plecoptera

Drumming behavior is described for the first time in 33 North American Plecoptera species, and signals of an additional five species, Pteronarcys pictetii, Acroneuria abnormis, Paragnetina media, Clioperla clio and Isogenoides zionensis, are further detailed. An out-group comparison of behavioral characters in all 104 world species whose drumming is known showed that the behavior is more advanced in the Arctoperlaria Group Systellognatha than in the Group Euholognatha. In general, tapping, mono… more

Date: December 1986

Creator: Maketon, Monchan

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Biology and Production of Net-Spinning Caddisflies (Hydropsychidae And Philopotamidae) in a Regulated Portion Of The Brazos River, Texas

Four species of net-spinning caddisflies, Hydropsyche simulans Ross, Cheumatopsyche lasia Ross, Cheumatopsyche campyla Ross and Chimarra obscura (Walker) are common in the regulated portions of the Brazos River. Hydropsyche simulans spun capture nets with the largest meshdimensions; the two Cheumatopsyche species' nets had the next largest meshes, and Chimarra obscura spun nets with the smallest dimensions. Cheumatopsyche lasia and C. campyla constructed nets with similar sized meshes. The numb… more

Date: May 1984

Creator: Malas, Diane M. (Diane Mary)

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Development, Validation, and Evaluation of a Continuous, Real-time, Bivalve Biomonitoring System

A biological monitoring tool to assess water quality using bivalve gape behavior was developed and demonstrated. The purpose of this work was to develop methodologies for screening water quality appropriate to the goals of the watershed paradigm. A model of bivalve gape behavior based on prediction of behavior using autoregressive techniques was the foundation of the bivalve biomonitoring system. Current technology was used in developing the system to provide bivalve gape state data in a contin… more

Access: Restricted to UNT Community Members. Login required if off-campus.

Date: December 2002

Creator: Allen, H. Joel

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Response of Freshwater and Saltwater Toxicity Test Species to Calcium and Salinity Concentrations Encountered in Toxicity Tests

The responses of freshwater (Daphnia magna. Pimephales promelas) and saltwater (Mysidopsis bahia. Cyprinodon variegatus) toxicity test species to elevated calcium concentrations and changing salinity conditions were investigated. The use of salinity as a criterion for selection between saltwater and freshwater test species was investigated by conducting both calcium and salinity toxicity tests. Salinity was determined to be an inappropriate criterion under conditions encountered in this study.

Date: 1989

Creator: Price, Edmund E., 1954-

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Aqueous Solubilities and Water Induced Transformations of Halogenated Benzenes

Methods of determining the aqueous solubilities of twelve chlorinated benzenes were evaluated in pure and in different water matrices. In pure water, results were comparable with the calculated values. Higher chlorinated tetrachlorobenzenes (TeCBs), pentachlorobenzenes (PCBz), and hexachlorobenzenes (HCBs) gave better precision and accuracy than lower chlorinated monochlorobenzenes (MCBs), dichlorobenzenes (DCBs), or trichlorobenzenes (TCBs).

Date: August 1989

Creator: Kim, In-Young

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Spatial and Temporal Influences of Water Quality on Zooplankton in Lake Texoma

Seventy-one aquatic species including the copepodids and nauplii were identified from Lake Texoma from August 1996 to September 1997. Zooplankton community structure, abundance and spatial and temporal distributions were compared among five lake zones delineated a priori based on chloride concentration. The zones, in order of decreasing chloride concentration, are the Red River zone (RRZ), Red river Transition zone (RRTZ), Main Lake zone (MLZ), Washita River Transition zone (WRTZ) and Washita … more

Date: May 2000

Creator: Franks, Jessica L.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Remote Sensing of Landscape-Level Ecological Attributes at Ray Roberts Lake in North Texas

Biological diversity is a key component in assessing ecosystem health. Alteration, degradation and loss of habitat due to human influence is currently the primary stressor resulting in decreases in diversity. Reliable assessment of large areas in terms of biological integrity are needed for conservation and preservation efforts. Remotely sensed data provide an integrated view of reflected electromagnetic energy over large areas of the earth. These energy patterns provide unique spectral signatu… more

Date: December 1997

Creator: Smith, David P. (David Paul), 1956-

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Biogeographic Relationships of Pocket Gophers (Geomys breviceps and Geomys bursarius) in the Southeastern Portion of Their Ranges

This research utilized population genetic analyses (protein starch-gel electrophoresis and DNA sequencing of the cytochrome b mtDNA gene), host-parasite specificity (lice coevolution), remote sensing of satellite data, and geographic information systems (GIS) to characterize newly discovered populations of pocket gophers (genus: Geomys) in Arkansas. These populations are isolated and occur in seemingly unsuitable habitat in the Ozark Mountains of Arkansas. Analyses of electrophoretic and ectopa… more

Date: August 1998

Creator: Elrod, Douglas Allen

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Responses of Selected Texas Fishes to Abiotic Factors, and an Evaluation of the Mechanisms Controlling Thermal Tolerance of the Sheepshead Minnow

Low oxygen tolerances of ten fishes were estimated using an original nitrogen cascade design, and reciprocally transformed to express responses as ventilated volume necessary to satisfy minimal oxygen demand (L·mg O2^-1). Values ranged from 0.52 to 5.64 L·mg^-1 and were partitioned into three statistically distinct groups. Eight stream fishes showed moderately high tolerances reflecting metabolic adaptations associated with stream intermittency. Juvenile longear sunfish and two mollies comprise… more

Date: May 1994

Creator: Bennett, Wayne A. (Wayne Arden)

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Comparison of Risk Assessment-Predicted Ecologically Safe Concentrations of Azinphos-Methyl and Fenvalerate to Observed Effects on Estuarine Organisms in a South Carolina Tidal Stream Receiving Agricultural Runoff

A prospective ecological risk assessment method was developed evaluating the cumulative probabilistic impact of chemical stressors to aquatic organisms. This method was developed in response to the need to evaluate the magnitude, duration and episodic nature of chemical stressors on aquatic communities under environmental exposure scenarios. The method generates a probabilistic expression of the percent of an ecosystem's species at risk from a designated chemical exposure scenario.

Date: August 1997

Creator: Morton, Michael Gerard, 1957-

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

The Effects of Organic Surface Amendments on Soil Nutrients and Initial Tree Establishment

This study examined the effects of replicating woodland soil surface horizonation on the nutrient status of underlying soils and the initial establishment and growth of trees. A total of 283 container grown trees were planted in a bufferzone around a future landfill site. Control amendments consisted of an 8 cm layer (0.5 m3) of wood chips applied in a circular area of 4.6 m2 around the trees' planting pit. For the treatment, a 2.5 cm layer of composted biosolids (0.15 m3 or 80 Mg/ha) was appli… more

Date: May 1999

Creator: Thuesen, Kevin (Kevin Andrew)

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Analysis of Phytoplankton Responses to Water Chemistry Dynamics in a Moderately Eutrophic North Texas Reservoir

Canonical correspondence analysis (CCA) was used to explore relationships between measured environmental variables and in situ phytoplankton communities in a moderately eutrophic North Texas Reservoir.

Date: May 1998

Creator: Banks, Kenneth E. (Kenneth Edward)

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Effects of Methanol, Atrazine, and Copper on the Ultrastructure of Pseudokirchneriella Subcapitata (Selenastrum Capricornutum).

The toxicity of methanol, atrazine, and copper to Pseudokirchneriella subcapitata (Korshikov) Hindák historically referred to as Selenastrum capricornutum Printz were determined following 96 hrs growth in a modified Goram's growth media. Methanol and atrazine inhibited fluorescence readings in the cultures by 50% (IC50) at concentrations of 2% and 82 µg/l respectively. These toxicity values compared favorably to other published reports. The IC50 for copper was 160 µg/l which is substantially … more

Date: May 2004

Creator: Garrett, David C.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Spatial and temporal patterns exhibited by select physicochemical and biological water quality parameters in Lake Texoma, Oklahoma and Texas.

From August 1996 through September 1997 eleven fixed stations were sampled monthly in January, March , April , July, August, September, and November and fortnightly in May and June for the purposes of establishing baseline conditions present in Lake Texoma as related to U.S. Army Corps of Engineers chloride control activities in the upper Wichita River, Texas. Five reservoir zones were identified a priori using historical chloride concentration data and include the Red River Zone (RRZ), Red Riv… more

Date: August 2004

Creator: Clyde, Gerard A.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

On-Road Remote Sensing of Motor Vehicle Emissions: Associations between Exhaust Pollutant Levels and Vehicle Parameters for Arizona, California, Colorado, Illinois, Texas, and Utah

On-road remote sensing has the ability to operate in real-time, and under real world conditions, making it an ideal candidate for detecting gross polluters on major freeways and thoroughfares. In this study, remote sensing was employed to detect carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NO). On-road remote sensing data taken from measurements performed in six states, (Arizona, California, Colorado, Illinois, Texas, and Utah) were cleaned and analyzed. Data mining and explorat… more

Access: Restricted to the UNT Community Members at a UNT Libraries Location.

Date: May 2003

Creator: Dohanich, Francis Albert

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Geology as a Georegional Influence on Quercus Fagaceae Distribution in Denton and Coke Counties of Central and North Central Texas and Choctaw County of Southeastern Oklahoma, Using GIS as an Analytical Tool.

This study elucidates the underlying relationships for the distribution of oak landcover on bedrock and soil orders in two counties in Texas and one in Oklahoma. ESRI's ArcGis and ArcMap was used to create surface maps for Denton and Coke Counties, Texas and Choctaw County, Oklahoma. Attribute tables generated in GIS were exported into a spreadsheet software program and frequency tables were created for every formation and soil order in the tri-county research area. The results were both a vis… more

Date: December 2007

Creator: Maxey, George F.

Item Type: Thesis or Dissertation

Partner: UNT Libraries

Automated Low-cost Instrument for Measuring Total Column Ozone

Networks of ground-based and satellite borne instruments to measure ultraviolet (UV) sunlight and total column ozone have greatly contributed to an understanding of increased amounts of UV reaching the surface of the Earth caused by stratospheric ozone depletion. Increased UV radiation has important potential effects on human health, and agricultural and ecological systems. Observations from these networks make it possible to monitor total ozone decreases and to predict ozone recovery trends … more

Access: Restricted to UNT Community Members. Login required if off-campus.

Date: May 2006

Creator: Nebgen, Gilbert Bernard

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

Applications of GIS and Remote Sensing for the Characterization of Habitat for Threatened and Endangered Species

Geographic Information Systems (GIS) and remote sensing technologies were used to identify and describe potential habitat for three species endemic to the Southwestern United States; the Golden-cheeked Warbler (Dendroica chrysoparia), the Black-capped Vireo (Vireo atricapillus), and the Texas kangaroo rat (Dipodomys elator). For each species, the computerized classification of digital satellite imagery was integrated with ancillary spatial information (e.g. soils, geology, and land use) to con… more

Date: December 1989

Creator: Shaw, Denice Marie, 1958-

Item Type: Thesis or Dissertation

Partner: UNT Libraries

open access

A geospatial tool for assessing potential wildland fire risk in central Texas.

Wildland fires in the United States are not always confined to wilderness areas. The growth of population centers and housing developments in wilderness areas has blurred the boundaries between rural and urban. This merger of human development and natural landscape is known in the wildland fire community as the wildland urban interface or WUI, and it is within this interface that many wildland fires increasingly occur. As wildland fire intrusions in the WUI increase so too does the need for too… more

Date: August 2005

Creator: Hunter, Bruce Allan

Item Type: Thesis or Dissertation

Partner: UNT Libraries