I quantified microhabitat conditions used by Yaqui chub (Gila purpurea), Yaqui topminnow (Poeciliopsis occidentalis sonoriensis), and beautiful shiner (Cyprinella lutrensis) on the San Bernardino National Wildlife Refuge, Arizona. Different species and different lifestages used different microhabitats. Smaller fish selected shallower water than adults. Yaqui topminnow and Yaqui chub showed seasonal variation in microhabitats used. Yaqui topminnows were found closer to cover when in the presence of beautiful shiners. Close proximity to cover may indicate a negative interaction. Yaqui chubs did not use microhabitats differently when in the presence of the other two species. Microhabitats used by Yaqui chubs in the ponds and Leslie Creek did not differ. Yaqui chub preferred pools with little or no flow. Management of aquatic environments on the refuge should focus on vegetative thinning. Stocking of beautiful shiner with Yaqui topminnow should be postponed until further research is conducted on the interactions between the two species.

Pandora moth (Coloradia pandora Blake) is a phytophagous insect, defoliating ponderosa pine trees in the western United States. However, long-term studies of this insect and its effects on the forest ecosystem have not been conducted. Using dendrochronological techniques, I examined past timing and intensity of defoliation through its effects on radial growth of trees in the forests of south central Oregon. Pandora moth leaves a distinctive ring-width "signature" that was easily identifiable in the wood. The growth for the first year of the signature was half the normal ring-width with narrow latewood. The following two years produced extremely narrow rings, with the entire suppression lasting from 4 to 18 years. Twenty-two individual outbreaks were reconstructed from this 620 year chronology. I found that pandora moth outbreaks were episodic on individual sites, with a return interval of 9 to 156 years. Conversely, on the regional scale of south central Oregon, outbreaks demonstrated a 37-year periodicity. On average, pandora moth defoliation caused a 29% mean periodic growth reduction in defoliated ponderosa pine trees. Spread maps of the first year that sites demonstrated suppression were plotted revealing an apparent annual spread of the outbreaks. Examination of a fire history on one pandora moth outbreak site suggested that pandora moth outbreaks delay fire by interrupting the needle fall needed for fire spread. Superposed epoch analysis showed that the year that the outbreak was first recorded was significantly dry and the fourth year prior was significantly wet. Therefore, climate may be a triggering factor in pandora moth outbreaks. The stem analysis demonstrated that the percent volume reduction was greatest at the base of the tree and declined further up the bole. The percent volume reduction in the canopy of the trees was variable with outlying high and low values. The mean volume reduction per outbreak was .053 m³ per tree. Although this insect is considered a forest pest and causes inconvenience for people living nearby, pandora moth is not as widespread and damaging as some other phytophagous insects. However, its very distinctive ring-width signature and the length of the ponderosa pine record enables reconstruction of very long outbreak histories, which may deepen our understanding of the interaction between defoliating insects and their ecosystem.

Sap flow, leaf gas exchange, and micrometeorological parameters were evaluated during 1997 in riparian forest at perennial and ephemeral stream sites on the San Pedro River in southeastern Arizona, USA. At the perennial stream site, measurements of sapwood area based transpiration and sapwood area/canopy area of clusters of Populus fremontii and Salix goodingii were used to estimate transpiration across the stand. Stand structural heterogeneity resulted in as much as 30% variation in mean transpiration across the stand. Transpiration of cottonwood was more dependent upon vapor pressure deficit at the ephemeral stream site which had an open, less dense canopy compared to that at the perennial stream site. This may be due to differences in advection properties and canopy feedback processes between sites. Conversely, transpiration in willow was less dependent upon vapor pressure at the ephemeral stream site than that at the perennial stream site. This may be due to water stress associated with deeper depth to groundwater.

The Endangered Species Act of 1973 (ESA) reflects society's concern over the rate of species extinction and aims to halt or reverse this trend. Several policies of the ESA protect listed species over resource development projects. Due to this protection, several listed species have recently experienced a recovery. Two have been removed, or delisted, from the federal Endangered Species list. Once a recovered species becomes delisted, the majority of these protections are removed. This paper analyzes the political implications of such delistings utilizing formal interviews, personal experiences, and a literature search. Through analysis, it is found that two specific policies seem to protect delisted species. It is concluded that a quantitative analysis may be premature at this time due to the small number of recovered species and that these policies must be effected to their fullest potential to ensure the long-term success of the federal endangered species program.

With recent advances in artificial intelligence, new methods are being developed that provide faster, and more consistent predictions for data in complex environments. In the field of landscape assessment, where an array of physical variables effect environmental perception, natural resource managers need tools to assist them in isolating the significant predictors critical for the protection and management of these resources. Recent studies that have utilized neural networks to assist in developing predictive models of scenic beauty that have typically utilized linear regression techniques have found limited success. The goal of this research is to compare NN's with linear regression models to determine their efficiency predictive capability for assessing near view scenic beauty in the Cedar City District of the Dixie National forest (DNF). Results of this study strongly conclude that neural networks are consistently better predictors of near view scenic beauty in spruce/fir dominated forests than hierarchical linear regression models.

In some cases, preservation priorities and recommendations are based on specific vegetation communities. One example is Fremont Cottonwood-Goodding Willow forests within Pima County, Arizona, which are regarded as critical habitat and protected by the Sonoran Desert Conservation Plan. However, a prioritized system based on conditions within Fremont Cottonwood-Goodding Willow patches may afford greater flexibility to land managers, including selective or incremental preservation, which could accommodate funding challenges. This investigation assessed patches in three watercourses within Tucson, Arizona, and addressed the following questions: Are Fremont Cottonwood-Goodding Willow patches exhibiting characteristics related to vigor or decline? Are there significant relationships between patch vigor and channel variables? On-site assessment addressed Fremont Cottonwood-Goodding Willow patch characteristics and channel variables. Significant relationships were found between vigor and proximity of primary flow, channel width, and bank treatment. Vigor results were employed to develop recommendations designed to facilitate preservation decisions.

<p> Hybrid poplars are a short rotation woody crop grown for a variety of target markets including paper pulp, saw timber, and biofuels in the Pacific Northwest. Development of pest control strategies within hybrid poplar plantations over the last several decades has focused on controlling foliar feeding herbivores and wood boring pests, and has overlooked the epigeal arthropod community. Understanding this unstudied suite of organisms would allow pest managers to better evaluate the impact their management strategies have on the poplar agroecosystem. Qualitative surveys of the arthropod communities in hybrid poplar plantations and nearby native habitats demonstrated that a greater arthropod diversity persists in the surrounding native areas. Additionally, the poplar plantation's epigeal arthropod community was composed of species found within sampled native areas. </p><p> Historically poplar research focused on protecting trees in the years following establishment through harvest from emerging pests while discounting cutting mortality by replanting areas of failure. Describing unrooted cutting transplant morality and distribution within newly established planting block could provide a risk assessment tool that growers could utilize to evaluate their potential crop loss. It was determined through the examination of damaged cuttings that several pests were responsible for diminishing establishment success. Identification of these risks led to the development of a management strategy to reduce mortality in newly planted areas. Soaking cuttings in imidacloprid for 48 hrs provided superior herbivore protection for unrooted cuttings until root formation allowed for uptake from chemigation treatments. </p><p> An additional study was motivated by the increased concern in growing `clear wood' as poplar has migrated from pulp to saw timber. The accompanying renewed interest in reducing insect galleries in mature trees led to the exploration of deploying a mass trapping, or trap out, effort to reduce populations of <i> Prionoxystus robiniae</i> (Lepidoptera Cossidae) in specific areas of a hybrid poplar plantation. We show that a trap out effort of roughly 5 pheromone-baited traps/ha decimated <i>P. robiniae</i> populations in treated areas throughout the trap out effort and three years post application.</p>

Increasing levels of atmospheric CO2 threaten to change the earth's climate and diversity in numerous adverse ways. This thesis explores aspects of two potential types of terrestrial sinks in East Texas, plantation rotation management and reforestation. I used a simple method of employing government GIS and tabular data for calculating and visualizing the size of those sinks, which could store an additional 2.3 to 98 million Mg C aboveground. The uncertainty of these values is high because of data inadequacies and also uncertainty about future land use trends. The mitigative powers of these sinks are discussed, as is their potential application in newly forming carbon credit programs such as the Chicago Climate Exchange.

<p> Butternut (<i>Juglans cinerea</i> L.), or white walnut, has suffered large population declines in the past half-century due to poor regeneration and mortality caused by an introduced fungus, <i>Ophiognomonia clavigignenti-juglandacearum </i> (Nair, Kostichka &amp; Kuntz) Broders &amp; Boland. This fungus causes branch and trunk cankers that can coalesce to girdle adult trees. Chapter 1 provides background information on butternut and butternut canker. We used next-generation sequencing to identify new nuclear DNA markers for butternut and Japanese walnut, a congener with which butternut readily hybridizes. We also examined the alignment of SSR repeat sequences in butternut and Japanese walnut with similar sequences from other angiosperms in public sequence databases. The methods used and results obtained in this process are detailed in Chapter 2. Chapter 3 summarizes an investigation of the environmental and genetic factors contributing to canker disease incidence, severity, and mortality in a large (n=113) population of butternut in southern Wisconsin and two other populations of butternut, one near the main study site in southern Wisconsin and another in the Great Smoky Mountains National Park. We present evidence for weak correlations of genetic similarity and phenotypic similarity for several disease traits, parentage analysis of regeneration in the smaller Wisconsin population, and evidence for significant microsite influences on butternut mortality over an 11-year period in the large Slocum's Woods butternut population.</p>

<p> What drives invasive species success? My research consists of four studies aiming to answer this question for <i>Ligustrum sinense</i>. The four projects are: (1) Synthesis of invasion literature within passenger-driver-backseat driver frameworks; (2) hydrochory investigation of water as a dispersal mechanism for invasion; (3) ecohydrology investigation of inundation effects on seed viability of <i>L. sinense</i>; (4) dendrochronology study of the effects of stream channelization and <i>L. sinense</i> invasion on bottomland oak tree growth. Results suggest that <i>L. sinense</i> initially invaded habitats that were hydrologically altered, resulting in drier conditions and a "novel niche." Dispersal <i>via</i> hydrochory allowed <i>L. sinense</i> to quickly colonize the novel niches. Once established, <i>L. sinense</i> competed with native oak species contributing to reduced growth rates, an "invasion meltdown." Control strategies should aim to remove <i>L. sinense</i> and return natural hydrologic regimes, or should consist of human-assisted re-establishment of native species that can thrive in altered conditions.</p>