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Forest Landscape Dynamics: a Semi-Markov Modeling Approach (open access)

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 by maps of terrain with characteristics contained in a Geographic Information System (GIS) database. The results of the transition model simulations, percent cover forest type maps, are exported to grid-maps in the GIS. These cover type maps can be classified and used to describe forest dynamics using landscape statistics metrics. The linkage model-GIS enhances the transition model spatial analytical capabilities. A parameterization algorithm was developed that takes as input gap model tracer files which contain the percent occupation of each cover type through time. As output, the algorithm produces a file that contains the parameter values needed for MOSAIC for each one of the possible transitions. Parameters for the holding time distribution were found by calculating an empirical estimate of the cumulative probability function and using a …
Date: August 1997
Creator: Ablan, Magdiel
System: The UNT Digital Library
Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela (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 collaboration with researchers at Universidad de Los Andes. In both studies, spectra and distributions of physiologically active light were analyzed: red, far-red, R/FR ratio, and blue light.
Date: December 1997
Creator: Monteleone, Susan Elaine
System: The UNT Digital Library
The Evolution, Applications, and Statistical Interpretations of DNA Typing in Forensic Science (open access)

The Evolution, Applications, and Statistical Interpretations of DNA Typing in Forensic Science

This thesis examines the evolution, applications, and statistical interpretations of DNA typing as a tool in the field of forensic science as well as in our criminal justice system. The most controversial aspect of DNA typing involves the determination of how likely it is that two people share the same DNA profile. This involves the use of population genetics and databases of allelic frequencies as well as some assumptions about population structuring.
Date: August 1997
Creator: Schober, Cassandra C. (Cassandra Carolyn)
System: The UNT Digital Library
Assessment of Changes in Aquatic Macrophyte Occurrence Following Introduction of Triploid Grass Carp in a North Texas Reservoir (open access)

Assessment of Changes in Aquatic Macrophyte Occurrence Following Introduction of Triploid Grass Carp in a North Texas Reservoir

The objectives of this project were to measure changes in frequency of occurrence of submerged macrophytes over the first two growing seasons following stocking with triploid grass carp at two fish per acre and to measure differences in macrophyte biomass between areas excluded from herbivory and adjacent control sites after 16 months following establishment of exclosures. The project also seeks to measure concentrations of fluridone following the herbicide treatment, and to compare two methods of aquatic vegetation sampling.
Date: August 1997
Creator: Bickel, Ken (Kenneth E.)
System: The UNT Digital Library
Remote Sensing of Landscape-Level Ecological Attributes at Ray Roberts Lake in North Texas (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 signatures which can be correlated to land cover and habitat. This research sought relationships between traditional ecological measures and information gathered from satellite digital imagery. Reliable interpretation of earth surface characteristics relies largely on accurate rectification to a map projection and subsequent thematic classification. Use of the Global Positioning System (GPS) for rectification was superior than digitizing topographical maps. Differentially corrected GPS locations provided optimum rectification with SPOT satellite imagery while marginally better rectifications were obtained for Landsat MSS imagery using uncorrected GPS positions. SPOT imagery provided more accurate land cover classifications than did MSS. Detection of temporal land cover change using MSS imagery was hampered by confusion among intermediate successional classes. Confusion between upland and bottomland forest classes occurred with both SPOT and MSS. Landscape analyses using thematic maps …
Date: December 1997
Creator: Smith, David P. (David Paul), 1956-
System: The UNT Digital Library